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diff --git a/old/53363-0.txt b/old/53363-0.txt deleted file mode 100644 index 2e09883..0000000 --- a/old/53363-0.txt +++ /dev/null @@ -1,11897 +0,0 @@ -The Project Gutenberg EBook of Glue, Gelatine, Animal Charcoal, -Phosphorous, Cements, Pastes and, by F. Dawidowsky - -This eBook is for the use of anyone anywhere in the United States and most -other parts of the world at no cost and with almost no restrictions -whatsoever. You may copy it, give it away or re-use it under the terms of -the Project Gutenberg License included with this eBook or online at -www.gutenberg.org. If you are not located in the United States, you'll have -to check the laws of the country where you are located before using this ebook. - - - -Title: Glue, Gelatine, Animal Charcoal, Phosphorous, Cements, Pastes and Mucilages - -Author: F. Dawidowsky - -Editor: William T. Brannt - -Release Date: October 25, 2016 [EBook #53363] - -Language: English - -Character set encoding: UTF-8 - -*** START OF THIS PROJECT GUTENBERG EBOOK GLUE *** - - - - -Produced by deaurider, Les Galloway and the Online -Distributed Proofreading Team at http://www.pgdp.net - - - - - - - GLUE, GELATINE, ANIMAL CHARCOAL, - PHOSPHORUS, CEMENTS, PASTES, - AND MUCILAGES, - - COMPRISING - - THE RAW MATERIALS AND MANUFACTURE OF SKIN AND BONE GLUE, - DIFFERENT VARIETIES OF GLUE, ANIMAL CHARCOAL, PHOSPHORUS, - GELATINE AND PRODUCTS PREPARED FROM IT; ISINGLASS AND - FISH-GLUE, METHODS OF TESTING GLUE AND GELATINE, - AND THE PREPARATION AND APPLICATION OF - CEMENTS, PASTES AND MUCILAGES FOR USE - IN THE WORKSHOP, LABORATORY, - AND OFFICE. - - - BY - F. DAWIDOWSKY, - TECHNICAL CHEMIST. - - - EDITED FROM THE GERMAN, WITH EXTENSIVE ADDITIONS, INCLUDING - A DESCRIPTION OF THE MOST RECENT PROCESSES. - - BY - WILLIAM T. BRANNT, - EDITOR OF “THE TECHNO-CHEMICAL RECEIPT BOOK.” - - ILLUSTRATED BY FIFTY-NINE ENGRAVINGS. - - SECOND EDITION, REVISED AND LARGELY RE-WRITTEN. - - - PHILADELPHIA: - HENRY CAREY BAIRD & CO., - INDUSTRIAL PUBLISHERS, BOOKSELLERS AND IMPORTERS, - 810 WALNUT STREET. - 1905. - - - - - COPYRIGHT, BY - HENRY CAREY BAIRD & CO., - 1905. - - - PRINTED BY THE - WICKERSHAM PRINTING CO., - 53 and 55 North Queen Street, - LANCASTER, PA., U. S. A. - - - - -PREFACE TO THE SECOND EDITION. - - -The first edition of this work has been out of print for some years, -but nevertheless there is a constant demand for it, and this together -with the fact that frequent inquiries are received for information in -this department of industry, are the inducements which have led to the -preparation of the present treatise. - -The book is arranged in two parts, Part I. comprising Glue, Gelatine -and Allied Products, and Part II. Cements, Pastes and Mucilages, and it -is fully illustrated with engravings of various types of apparatus. - -Since the appearance of the first edition much progress has been made -in the manufacture of glue and allied products. Old and wasteful -methods of working have been replaced by more approved processes, and -in the present volume it has been endeavored to place before those -interested in these industries, a practical and comprehensive account -of modern methods of operation. - -In order adequately to represent this advancement and development, the -best authorities have been freely consulted and drawn upon, special -acknowledgments being due to the following works: “Bone Products and -Manures,” by Thomas Lambert, and “Glue and Glue Testing,” by Samuel -Rideal. - -As the demand for phosphorus is steadily increasing, and the -manufacture of this product from bones and bone-ash forms an important -branch of the utilization of bones, it has been deemed advisable to -devote a chapter to this subject. - -The receipts for cements, pastes, and mucilages given in Part II. -have been gathered from numerous sources. They have been critically -examined, and are offered, with the full conviction, that they will not -be found wanting in efficacy. - -The Table of Contents and Index have both been carefully prepared, and -being very full, will make reference to any subject in the volume easy -and satisfactory. - - W. T. B. - - PHILADELPHIA, PA., AUGUST 10, 1905. - - - - -CONTENTS. - - - PART I. - - GLUE AND GELATINE. - - - CHAPTER I. - - NATURE of GLUE. - - PAGE - - Sources of glue; Change in the animal tissues by continued boiling; - Definition of what is known as glue; Most important glue-yielding - substances 1 - - Transformations of which glue and gelatine are the products; - Transition stages of glue; Production of the glue-yielding substance - of the animal body 2 - - Crude glue and jelly; Constitution of glue; Combinations of which glue - consists 3 - - Preparation of pure glutin; Properties of glutin 4 - - Preparation and properties of chondrin 5 - - Adhesive power of glutin and of chondrin; Properties of glue and its - behavior towards other substances; Quantity of glutin in glue 6 - - Properties of jelly before drying to glue; Absorption of ozone by the - jelly; Behavior of glue solution towards different salts; Effect of - acids upon glue; Meta-gelatin 7 - - Combinations of tannin with the jelly; Effects of dry heat upon glue; - Chemical composition of glue and glue-yielding substance 8 - - - CHAPTER II. - - USES of GLUE. - - Glue as a joining medium, and requirements for this purpose 10 - - Glue as a binding agent; Consumption of glue in the manufacture of - matches 11 - - Quality of glue required by bookbinders; Glue in sizing; Glue for - culinary and medicinal purposes 12 - - Glue for clarifying and fining beer, wine and other liquids; Bouillon - tablets; Glue as a healing agent 13 - - Glue for elastic masses and a partial substitute for rubber; Use of - glue in photolithography; Hectograph mass; Glue for fancy articles 14 - - Gelatine veneers and their uses 15 - - - CHAPTER III. - - RAW MATERIALS AND THEIR PREPARATION FOR THE MANUFACTURE OF GLUE. - - Principal substances employed for the manufacture of glue; Division of - raw materials into groups 16 - - Animal skin and its constitution 17 - - Portion of the skin of value for the manufacture of leather and glue; - Yield of glue from tannery waste; Influence of the age of the animals - from which the skins have been derived upon the quality of the - glue 18 - - Notes in reference to judging glue-stock 19 - - Liming of waste 20 - - Precaution and care required when buying glue leather; Arrangements - required for the preparation of glue stock; Location of the glue - factory; Lime pits; Contrivances for washing the limed stock 21 - - Washing drums; Pits or vats with proper arrangements for stirring, - draining and inspection; Glue stock washer invented by W. A. - Hoeveller, described and illustrated 22 - - Sheds for storing and sorting; Mode of carrying on the work in the - factory; Liming; Preparation of milk of lime 26 - - Importance of the quality of the lime used; Testing the value of a - lime by determining the amount of real calcium hydroxide contained in - it; Mode of conducting the operation 27 - - Washing the material after removal from the lime pit; Washing and - drying 28 - - Preservation of the glue-stock by means of carbolic acid; Preparation - of carbolic acid solution for this purpose 29 - - Use of other antiseptics for the purpose of preventing putrefaction; - Formaldehyde and boric acid; Classification of the principal varieties - of hides and leather for glue-stock 30 - - Bones and cartilages 31 - - Constitution of bones; Composition of bone cartilage; Value of bones - for the manufacture of glue; Necessity of exercising care in buying - bones 32 - - Sorting the bones; Crushing or grinding the bones 33 - - Stamping mill for crushing bones, described and illustrated 34 - - Bone crusher, described and illustrated; Crosskill bone mill, - described and illustrated; Sieve for sorting the crushed bones, - described and illustrated 36 - - Lime bath for bones; Treatment of the bones with hydrochloric - acid 37 - - Washing the stock; Use of dilute sulphurous acid in place of - hydrochloric acid as suggested by Gerland; Jullion and Pirie’s process - for the preparation of gelatine from bones 38 - - Leather waste; Mechanical manipulation of the waste; Comminution of - the waste and use of a rag-engine or hollander for this - purpose 39 - - Various methods of extracting tannin from leather waste 40 - - Raw materials for fish glue; Difference between isinglass and glue - manufactured from entire fishes; Principal points to be observed in - the manufacture of fish glue 41 - - Utilization of scales of large fishes 42 - - - CHAPTER IV. - - MANUFACTURE OF SKIN GLUE. - - Classification of operations; Definition of crude glue; Derivation of - the bulk of this stock 43 - - Cooking or boiling glue-stock; Boiler for this purpose, and manner of - using it 44 - - Duration of boiling 45 - - Mode of ascertaining the progress of the operation; Convenient - apparatus for glue-boiling with water, described and - illustrated 46 - - Extracting the glue stock by the use of steam 47 - - Boiler for this purpose, described and illustrated; Use of - open-jacketed pans heated by steam, described and illustrated 49 - - Process of cooking as described by Mr. Thomas Lambert; Terne’s glue - boiler, described and illustrated 51 - - Clarifying the glue-liquor 52 - - Distinction between clearness and color; Clarifying vats; Prevention - of putrefaction of the liquor 53 - - Use of alum and other chemicals for clarifying; Freeing the liquor - from coloring substances 54 - - Use of animal charcoal for this purpose; Bleaching the raw materials - previous to boiling them to glue; Use of chloride of lime or of - sulphurous acid for this purpose 55 - - Forming or moulding the glue; Moulds for this purpose 56 - - Detaching the glue from the sides of the moulding boxes; Cutting the - cubes of glue into commercial cakes or sheets; On what the shape of - the cakes depends 57 - - Use of stone-slabs in place of cooling boxes; Use of glass or zinc - plates for liquors which in gelatinizing do not become very - solid 58 - - Tools for cutting the jelly into cakes, described and - illustrated 59 - - Machine for slicing and spreading glue-jelly preparatory to drying - invented by Mr. J. Schneible, described and illustrated 60 - - Cutting apparatus patented by M. Devoulx, described and - illustrated 62 - - Drying the cakes of glue; Drying in the open air; Mode of conducting - the operation in a drying room 64 - - Size of the drying room; Circulation and change of air in the drying - room 65 - - Nets and frames for drying the glue; Objections to twine - netting 66 - - Metallic netting and its advantages; Regulation of the temperature of - the drying room; Means of promoting the dryness of the air 67 - - Use of long drying galleries; Apparatus for drying glue, invented by - W. A. Hoeveller, described and illustrated 68 - - Modern drying house, described and illustrated 71 - - Method to accelerate the drying of glue, proposed by Fleck 72 - - Mode of giving the dry cakes a good lustrous appearance 73 - - - CHAPTER V. - - MANUFACTURE OF BONE GLUE. - - Comminution of the bones; Various methods of extracting the fat; - Boiling bones 74 - - Steaming bones and apparatus for this purpose 75 - - Extraction of bones with benzine or carbon disulphide; Apparatus for - the use of benzine invented by Messrs. Wm. Adamson and Charles F. A. - Simonis of Philadelphia, Pa., described and illustrated 76 - - Adamson’s method for treating substances with hydrocarbon vapor for - the purpose of extracting oils, fats, etc., described and - illustrated 79 - - Adamson’s method for treating substances with liquid hydrocarbon for - the purpose of extracting oils, fats, etc., described and - illustrated 82 - - Adamson’s process for removing hydrocarbons from substances which - have been treated therewith, described and illustrated 84 - - F. Seltsam’s apparatus, described and illustrated 86 - - F. Seltsam’s apparatus as improved by Th. Richter, described and - illustrated 88 - - Alfred Leuner’s apparatus, described and illustrated 90 - - Extraction with hydrochloric acid 91 - - Sulphurous acid process 92 - - Generation of sulphurous acid 93 - - Apparatus for the generation of sulphurous acid constructed by Dr. - Bruno Terne, described and illustrated; Conversion of cartilage into - glue; Wm. Friedberg’s apparatus for this purpose, described and - illustrated 94 - - Mode of operation with this apparatus 95 - - Construction of the filter used in connection with the - apparatus 96 - - Settling tank, described and illustrated; Arrangement of an open - evaporating pan, described and illustrated 98 - - Cooling the glue liquor; Use of refrigerating machines for that - purpose; Spiral evaporators 100 - - Vacuum pan for evaporating glue and gelatine liquors, described and - illustrated 101 - - Instrument which indicates the amount of dry glue in the solution, - described and illustrated 103 - - Process for the simultaneous utilization of bones for fat, bone-meal - and glue 104 - - Crushing the bones; Apparatus for subjecting the crushed bones to the - action of high-pressure steam, described and illustrated 105 - - Mode of operation with this apparatus 106 - - Duration of steaming the bones for the manufacture of animal - charcoal 107 - - Sorting the bones for the manufacture of animal charcoal; Former - method of carbonization 108 - - Arrangement of a Belgian retort-furnace, described and - illustrated 109 - - Products evolved in the destructive distillation of bones; Mode of - operation with Belgian retort-furnaces 112 - - Products obtained in making animal charcoal on a large scale; Process - for the simultaneous utilization of the bones for fat, glue and - calcium phosphate; Degreasing the bones 113 - - Treatment of the bones with hydrochloric acid; Preservation of the - resulting cartilage; Boiling the cartilage in open vessels 114 - - Mode of extracting the phosphates from bones; Yield of glue obtained - from cartilage after extraction of the mineral constituents; - Constituents of the liquor obtained by treating the bones 115 - - Utilization of the liquor in the manufacture of fertilizers 116 - - - CHAPTER VI. - - MANUFACTURE OF PHOSPHORUS. - - Operations included in the ordinary method of preparing phosphorus; - Burning the bones to ash; Kiln used for this purpose 117 - - Improved form of kiln proposed by Fleck; Mode of operation with a kiln - of this construction 118 - - Quantity of substance which remains after burning the bones; - Composition of bone ash; Conversion of the bone ash into a coarse - powder; Decomposition of the bone ash by sulphuric acid 119 - - Separate processes which have to be distinguished; Embodiment of these - processes in equations 120 - - Actual yield of phosphorus; Methods by which the formation of calcium - phosphate may be effected; Process without the assistance of - heat 121 - - Decomposition of the bone ash in the warm way 122 - - Apparatus for hot lixiviation 123 - - Evaporation of the liquor; Mixing the fluid with charcoal 124 - - Yield of so-called distilling mass; Utilization of the liquor obtained - in treating bones for the manufacture of glue with hydrochloric acid; - Concentration of the liquor for crystallization 125 - - Mode of obtaining the calcium phosphate contained in the - mother-liquor; Drying the crystals 126 - - Mixing the crystals with charcoal; Evaporating pans; Treatment of - the residue of basic calcium phosphate left in the manufacture of - phosphorus; Distillation of the phosphorus; Conversion of the acid - calcium phosphate into calcium metaphosphate and reduction of the - latter; Retorts and furnace for distilling the mixture of acid - calcium phosphate and charcoal; The galley-furnace 127 - - Modification of the galley-furnace, described and - illustrated 128 - - Furnaces for the use of coke as fuel; Receivers for collecting the - phosphorus distilling over 129 - - Process of distillation; Indication of the commencement of - distillation 130 - - Removing the phosphorus from the receivers; Regaining the phosphoric - acid contained in the water from the receivers; Constitution of crude - phosphorus 131 - - Refining and purifying the phosphorus; Various methods of - purification; Percentage of loss of phosphorus 132 - - Distillation of the crude product in order to obtain pure phosphorus; - Retorts and distilling apparatus for this purpose, described and - illustrated 133 - - Process of distillation; Different qualities of the phosphorus - passing over in the various stages of distillation; Separation of the - phosphorus passing over according to quality 134 - - Moulding the refined phosphorus; Seubert’s apparatus for this - purpose 135 - - Disadvantages of Seubert’s apparatus; Improved apparatus by which - the operation is rendered perfectly free from danger, described and - illustrated 136 - - Moulding the phosphorus in wedge-shaped sheet-metal boxes 137 - - Mode of storing and shipping phosphorus; Manufacture of phosphorus - with the assistance of electricity; Mixture used for the - operation 138 - - Furnace employed for the electrolytic manufacture of phosphorus, - described and illustrated 139 - - Mode of operating the furnace 140 - - - CHAPTER VII. - - METHODS OF BLEACHING GLUE. - - Bleaching in the air; Bleaching with chlorine 141 - - Bleaching with animal charcoal 142 - - Bleaching with sulphurous acid; Apparatus for the production of the - acid solution, described and illustrated 143 - - - CHAPTER VIII. - - DIFFERENT VARIETIES OF GLUE AND THEIR PREPARATION. - - Joiner’s glue; Material for the best variety of joiner’s glue 146 - - How to make and use glue; Holding power of glue 147 - - Cologne glue 148 - - Russian glue; Additions by means of which the color and opaqueness are - imparted to this variety of glue 149 - - Patent glue; Gilder’s glue; Superior article of gilder’s glue; Size - glue and parchment glue; Paris glue 150 - - Liquid glues; Receipts for liquid glues 151 - - Preparation of saccharate of lime; Steam-glue; Russian steam-glue; - Pale steam-glue; Dark steam-glue 152 - - Chrome glue; Glue for attaching leather to metal; Glue for leather, - paper, etc. 153 - - Glue for parchment paper in making sausage skins 154 - - Tungstic glue; Indestructible mass for the manufacture of ornaments, - toys, etc.; Compound for billiard balls 155 - - Coloring glue; Process for this purpose invented by G. J. Lesser 156 - - Composition for printing rollers; Size 157 - - Process used in an English factory for making tub-size 158 - - Preparation of bone-size; Composition of the different grades - of size 159 - - Concentrated size; Bookbinder’s size; Water-proof glue; Glue solution - for rendering wrapping paper water-proof 160 - - Water-proofing fabrics with glue and tannin 161 - - Muratori and Landry’s process of water-proofing fabrics 162 - - Muzmann and Krakowitzer’s process of water-proofing fabrics; Glue for - joints in leather driving belts; Hectograph mass 163 - - Formulas for hectograph masses 164 - - - CHAPTER IX. - - MANUFACTURE OF GELATINE, AND PRODUCTS PREPARED FROM IT. - - Properties of gelatine; Change in the chemical constitution of - gelatine produced by concentrated sulphuric or nitric acid; Tannin as - a test for the presence of gelatine; Use of gelatine for culinary and - medicinal purposes 165 - - Skin gelatine; Method of manufacture introduced and patented, in 1839, - by George Nelson; Process patented, in 1844, by Messrs. J. & G. - Cox of Edinburgh 166 - - G. P. Swinborn’s improved patented process for the preparation - of gelatine from hides, skins and glue pieces; Modern process of - preparing skin gelatine; “Steeping” the skins 167 - - Washing and bleaching the skins 168 - - Digesting the skins; Clarifying the liquors 169 - - Evaporation of the liquors in vacuo; Drying the cut cakes; Bone - gelatine; Materials for this purpose; Crushing the bones; Solution of - the glue cartilage 170 - - Apparatus and improved manner of manufacture employed in the factory - of D. J. Briers, described and illustrated 171 - - Modern process of preparing bone gelatine 179 - - Colored gelatine; Uses of colored gelatine; Harmless coloring matters; - Colors for coloring leaves of gelatine with aniline colors for - technical purposes 181 - - Gelatine for fining purposes; _Gelatine Lainée_; Fining powder for - wine and beer; Liquid fining gelatine; Preparation of gelatine from - ordinary glue 182 - - Preparation of gelatine for photographic printing and for photographic - purposes in general; Removal of the salts from the gelatine 183 - - Gelatine capsules for medicinal purposes; Court plaster 184 - - Gelatine foils; Mode of coloring the foils 185 - - Gelatine veneers; Principal operations in the manufacture of gelatine - veneers 186 - - Preparation of the plates; Preparation of the glue solutions; - Proportions by weight of the mixtures for ten different varieties of - imitations of marble and enamel 187 - - Imitation of mother-of-pearl veneers 188 - - Pouring the colored solutions of glue upon the plates 189 - - Preparation of imitations of malachite 190 - - Transferring the layer of glue to a layer of gelatine 191 - - Drying and detaching the veneers 192 - - Water-proofing gelatine veneers; Uses of gelatine veneers; - Formo-gelatine and its uses 193 - - Use of gelatine in bacteriology 194 - - Artificial silk from gelatine 195 - - - CHAPTER X. - - ISINGLASS AND ITS SUBSTITUTES. - - Sources of isinglass; Properties of a good quality of isinglass; - Imitations of isinglass and their detection; Adulteration of isinglass - and its detection 196 - - Russian isinglass; Siberian purse isinglass; Preparation of isinglass - in Russia 197 - - North American or New York isinglass 198 - - East India isinglass; Hudson Bay isinglass; Brazilian isinglass 199 - - German isinglass; Isinglass from the scales of shad and herring; - Bleaching inferior qualities of isinglass; Ichthycolle - Française 200 - - Isinglassine; Chinese isinglass 201 - - Irish moss; Fish glue; Jennings’ process for the preparation of fish - glue 203 - - Treatment of fish scales; Production of fish glue on the Norwegian - coast; Substitute for isinglass according to C. A. Sahlström’s - process 203 - - Whale glue 204 - - - CHAPTER XI. - - TESTING GLUE AND GELATINE. - - Determination of moisture; Determination of ash; Determination of - acidity 205 - - Determination of glutin; Bisler-Beumat’s method 206 - - Analysis of samples of American glue by S. Dana Hayes; Deduction of - the quality of glue from indirect properties 207 - - Lipowitz’s method of testing the strength of a glue, described and - illustrated 208 - - Results obtained by comparative experiments 209 - - Facts shown by the results 210 - - Weidenbusch’s method of testing glue 211 - - Preparation of the plaster of Paris stick and of the glue solution - used in this test 212 - - Apparatus for testing the strength of the plaster of Paris sticks, - described and illustrated; Test adopted by the “Artillerie Werkstätte” - at Spandau 213 - - Determination of adulterations 214 - - Kissling’s results in testing a large number of samples of glue 215 - - Practical tests of glue 216 - - - PART II. - - CEMENTS, PASTES, MUCILAGES. - - - CHAPTER XII. - - CLASSIFICATION OF CEMENTS. - - Stohmann’s division of cements and pastes; Groups of cements 218 - - Chemical nature of cements; Oil cements 219 - - Resinous cements; Definition of resins 220 - - Properties of resinous cements 221 - - Rubber and gutta-percha cements; Glue and starch cements 222 - - Lime cements 223 - - - CHAPTER XIII. - - PREPARATION OF CEMENTS, PASTES, AND MUCILAGES. - - Oil cements; Putty and its preparation 224 - - French putty; Soft putty; Litharge cement; Red lead cement; Cement - for wash basins 225 - - Zinc-white cement; Mastic cement, mastic or _pierres de mastic_ 226 - - French mastic; Paget’s mastic; Water-proof cement; Serbat’s - mastic 227 - - Stephen’s oil cement; Oil cement for glass; Oil cement free from lead - for steam pipes; Oil cements for steam pipes; Oil cement for - marble 228 - - Oil cement for porcelain; Diamond cement; Hager’s diamond cement; - Resinous cements; Resinous cement for amber; Cement for - turners 229 - - Cement for ivory and bone; Cement for white enameled clock faces; - Cements for glass; Cement for glass upon glass; Cement for glass upon - metal; Cement for metal letters upon glass; Cement for wood 230 - - Cement for knife handles; Cement for petroleum lamps; Cement for - porcelain; Cement for porcelain which is to be heated; Cement to - withstand the action of petroleum; Cement for mica 231 - - Cement for horn, whalebone and tortoise shell; Cement for terra cotta - articles; Mastic cement for glass; Stick mastic cement; Sulphur cement - for porcelain 232 - - Insoluble cement for wooden vessels; Rubber cements; Cements for glass; - Soft rubber cement 233 - - Hard rubber cement; Elastic cement; Marine glue 234 - - Jeffrey’s marine glue; Marine glue for damp walls; Gutta-percha - cements; Cement for leather 235 - - Cement for hard rubber combs; Elastic gutta-percha cement; Cement for - horses’ hoofs; Cement for crockery 236 - - Cement for leather; Caseine cements; Preparation of pure caseine 237 - - Preparation of ordinary technical caseine; John A. Just’s method for - obtaining a purer technical caseine 238 - - Caseine cement which can be kept for a long time; Cement for glass; - Cement for metals; Cement for porcelain; Cement for meerschaum; - Cement for wood, etc. 239 - - Cement for porcelain; Water-glass and water-glass cements; Water-glass - and its properties; Cement for cracked bottles 240 - - Cement for glass and porcelain; Cement for hydraulic works; Cement for - uniting metals; Cement for tightening joints of pipes exposed to a red - heat 241 - - Cement for marble and alabaster; Glycerine and glycerine cements; - Properties of commercial glycerine; Glycerine and litharge cement 242 - - Lime cements; Properties of lime and chalk; Cement for glass; Cement - for joiners; Cement for cracked clay crucibles and porcelain 243 - - Lime and glue cement; Gypsum cements; Preparation of plaster of Paris; - Cement for plaster of Paris statues 244 - - Cement for glass and porcelain; Cement for iron and stone; Cements - for porcelain; Universal plaster of Paris cement; Iron cements; - Heat-resisting cement; Water and steam-proof cement; Cement for - iron 245 - - Fire-proof cement for iron pipes; Cements resisting high temperatures; - Cement for filling in defects in castings; Cement for cracked - stove-plates, etc.; Cement for iron water-tanks; Cement for cracked - iron pots 246 - - Black cement for stoves; Cements for chemical apparatus; Requirements - of such cements; Cement for small apparatus to be used for the - development of fluoric acid 247 - - Linseed oil and clay cement; Linseed oil and manganese cement; Cements - resisting very high temperatures; Cement resisting acids; Rubber - cement for chemical apparatus 248 - - Scheibler’s cement for chemical apparatus; Cements for special purposes; - Cement for attaching metal letters to glass, marble, wood, etc.; Cement - for joints of iron pipes 249 - - Steam boiler cement; Cement for rubber; Cement for tires; Cement for - steam pipes, etc. 250 - - Cement for marble; Cement for attaching wood, glass, etc., to metal; - Brushmaker’s cement; Cement for electrical apparatus 251 - - Jeweler’s cement; American cement for jewelers; Cement for celluloid; - Stratena; Cement for cloth; How to use cements 252 - - Importance of bringing the cement into intimate contact with the - surface to be united 253 - - Obstacles to the junction of any two surfaces; Importance of using as - little cement as possible 254 - - Cleansing surfaces to be joined from grease and dirt; Paste and - mucilages; Starch paste 255 - - Rules for preparing paste; Flour paste 256 - - Means to prevent the spoiling of paste 257 - - Shoemakers’ paste 258 - - Gum arabic and its properties; Dextrine and its use in place of gum - arabic; Properties of commercial dextrine 259 - - Preparation of dextrine; Blumenthal’s method 260 - - Heuzé’s method; Tragacanth, or gum tragacanth; Pastes and mucilages - for special purposes; Starch paste; Flour paste 261 - - Strong adhesive paste; Paste that will not sour; Venetian paste 262 - - Label paste; Elastic or pliable paste; Mucilage for labels; - Mucilage 263 - - Mucilage for postage stamps; Caseine mucilage; Tragacanth mucilage; - Adhesive paste; Fluid pastes 264 - - Sugar and lime paste; Liquid sugar and lime paste; Pastes for paper and - fine fancy articles; Albumen paste 265 - - Glycerine paste; Paste for fixing labels on machines; Paste for - mounting maps; Paste for fastening paper on tin-foil; Paste for paper - bags; Caseine mucilage for photographer’s use; Paste for scrap - books 266 - - Paste for skins; Strong mucilage capable of fastening wood on china - and glass; Dextrine mucilage; Paste for joining leather to - pasteboard 267 - - Paste for attaching labels to polished nickel; Mucilage for attaching - labels to tin; Mucilage for office use; Glycerine paste for office - use; Clean and durable paste 268 - - Banknote or mouth glue; Paste for cardboard; Paste for attaching cloth - or leather to table tops; Caseine mucilage; Very adhesive paste which - may be used for wood and parchment 269 - - Paste for pads; Paste for fastening paper on tin-foil; Paste for - attaching labels to glass, porcelain and metal; Preparation of - arabol-gum; Preparation of an adhesive substance from desaccharized - beet-root slices 270 - - Index 273 - - - - -GLUE, GELATINE, CEMENTS, PASTES. - - - - -PART I. - -GLUE AND GELATINE. - - - - -CHAPTER I. - -NATURE OF GLUE. - - -1. SOURCES OF GLUE. - -The organisms of all animals, but more especially of the higher -classes, contain tissues which are insoluble in cold, as well as in -hot, water. However, by continued boiling they become dissolved, and -yield on evaporation of the solution a glutinous, gelatinizing mass. By -further drying this mass exhibits, according to the degree of purity -of the material, a more or less transparent and brittle substance, -which in its pure state is devoid of color as well as of smell; it -swells up in cold water and dissolves by boiling in that liquid. This -substance, _i. e._, the product of the conversion of the so-called glue -or gelatine-yielding tissue, is what is known in the trade as _glue_. - -Among the glue-yielding tissues, the following are the most important: -Cellular tissue, the corium, tendons or sinews, the middle membrane of -the vasa lymphatica and veins, the ossein or organic matter of bones, -hartshorn, cartilage, the air bladders of many kinds of fishes, etc. - -Neither glue nor gelatine exists ready formed in the animal organism, -except under abnormal conditions as a phenomenon of disease, but they -are the products of various transformations. The first of these -transformations evidently takes place in drying the hide, since the -result of boiling to glue a green hide prepared in the usual manner by -liming, etc., but not previously dried, will be an entirely different -product of less consistency than that obtained by drying the hide after -liming and then boiling. A second transformation seems to take place -in boiling the material, and a third in drying the jelly obtained, and -this may explain the fact that the latter, which is not converted into -actual glue, differs in its behavior from glue solution. The series -of transformation does not end even with the actual glue, for it is a -well-known fact that glue dissolved in water and boiled for some time -does not gelatinize on cooling, but remains liquid. We have here to -deal with organic combinations which are distinguished from the more -solid organic compounds by passing more readily into decomposition. -However, it is an established fact that glue is an organic combination -presenting itself in different modifications. In the animal organism -it occurs ready formed only under abnormal conditions as a phenomenon -of disease, and hence it is only produced by first drying and then -by continued boiling of the glue-yielding substance, and finally by -evaporating and further drying the gelatinous mass obtained by boiling. - - -2. TRANSITION STAGES OF GLUE. - -We therefore distinguish: - -_a._ Glue-yielding substance. - -_b._ Crude glue. - -_c._ Jelly. - -_d._ Glue. - -_a._ The glue-yielding substance of the animal body is produced from -proteïne substances, albumen, fibrine and caseïne, in a manner similar -to that in which new substances are formed in the ripening fruit by -the transformation and disintegration into constituent parts of others -previously present. - -_b._ By _crude glue_ are understood glue-yielding materials free from -all foreign matter and physically prepared by drying. It forms an -intermediate link between glue-yielding substance and jelly. - -This distinction between glue-yielding substance and crude glue is -justified by experience. If, for instance, fresh calves’ heads, such as -the tanner cuts off after swelling the skins, be carefully limed and -then boiled without previous drying, the result will be a turbid liquor -containing, though everything be dissolved, no jelly whatever, or at -least, very little. - -_c._ _Jelly_ is obtained by boiling the crude glue. Its adhesive power -is far less than that of solution of finished glue, and it will become -more quickly putrid than the latter. - -_d._ The finished product _glue_ is, in most cases, not a definite -chemical compound, but a mixture of substances, with two of which -scientific research has made us thoroughly acquainted. - - -3. CONSTITUTION OF GLUE. - -Independent of impurities and accidental constituents, glue consists -of two distinctly distinguishable combinations, namely, _glutin or -gelatin_ and _chondrin_, the former being formed from the hide and -osseous parts, and the latter from young bones while still in a soft -state, and the “permanent” cartilages, such as those of the ribs and -joints. - -The manufacturer has it, of course, in his power to allow either of -these substances to predominate in his product, but since experiments -have shown glutin or gelatin to possess much greater adhesive power -than chondrin, it is advisable to separate as much as possible the -cartilaginous matter from other glue-yielding material. - -As an accurate knowledge of these constituents of glue is of great -importance to the manufacturer, brief reference will here be made to -what scientific research has made known to us in regard to them. - -Pure glutin or gelatin is obtained by treating buckshorn, etc., with -water containing hydrochloric acid, until the phosphate of lime which -serves, so to say, as a frame for the glue-yielding substance, is -dissolved, and the organic tissue called _collagen_ or _ossein_, -remains behind. After freeing the latter from fat by steeping in milk -of lime and careful washing, it is boiled, and the resulting jelly, -when cold, mechanically distributed in cold water, in which it softens -but does not dissolve. By thoroughly stirring the mass the glutin -yields its coloring matter to the water, the latter being replaced -by fresh water until all the coloring matter is extracted. Then pour -off the water and after dissolving the jelly in hot water, filter the -solution through a cloth. By mixing the filtered solution with an -equal volume of alcohol, a precipitate of pure glutin is obtained. By -the precipitation with alcohol, the separating glutin carries down -inorganic salts, especially phosphates, which may be present in the -solution. To free it from them, dissolve it in a small quantity of -lukewarm water, acidulate the solution with hydrochloric acid and bring -it into a dialyser. The salts and the acids diffuse in the water which -has from time to time to be renewed, and finally a jelly of pure glutin -remains behind; this is evaporated to dryness in shallow vessels. - -Pure glutin, in a dry state forms a glassy substance, almost colorless, -transparent to translucent, brittle or slightly elastic, free from odor -and taste, and remains unchanged in the air. Its specific gravity is -greater than that of water. It is neutral, exerts no influence whatever -upon vegetable colors and is insoluble in alcohol, ether, hydrocarbons -or oils. In cold water it swells up, absorbing as much as 40 per cent., -and becomes opaque, but does not dissolve. It dissolves in hot water -and on cooling forms a jelly even if the solution contains only 1 per -cent. of glutin. It gelatinizes at a lower temperature than chondrin. - -An aqueous solution of glutin is precipitated by chlorine, platinic -chloride, tannin and alcohol, but not by hydrochloric acid, -acetic acid, lead acetate, alum and ferric sulphate. Concentrated -sulphuric acid decomposes glutin, forming, besides other products of -decomposition, chiefly glycocoll and leucine. - -When heated, glutin softens, swells and diffuses an odor of burnt -hartshorn. In the air, it takes fire with difficulty, smokes, flames -only for a few minutes, and leaves a bulky charcoal difficult to -incinerate, the ashes of which consist principally of calcium phosphate. - -Glutin, when in the jellied state, and treated with alcohol, undergoes -dehydration, under the influence of which it contracts greatly. It was -by this means that Gonnor succeeded in reducing in a remarkable degree -the size of a print obtained in a very hydrated film of glutin, and -transferring it, so reduced, to stone, from which he obtained a new -impression, quite similar to the first, but more or less diminished. - -By taking these prints, on the contrary, with glutin very little -hydrated, and afterwards steeping them in water, a dilatation of the -plate is obtained, which enlarges the figures with the same regularity. - -Pure _chondrin_ is prepared by boiling for from 24 to 48 hours the -cartilages of the ribs, of the larynx with the exception of those of -the epiglot, or of the windpipe and the bronchi. - -Chondrin is precipitated from its solution by alcohol. The precipitate -is redissolved in warm water, evaporated, and dried. It forms a -semi-translucent mass of a slightly yellow color and resembles glutin -as regards fracture and all external properties, but differs from it in -being precipitated from its aqueous solution by mineral acids, acetate -of lead, alum and ferric sulphate, and also by organic acids such as -vinegar, citric and oxalic acids, none of which precipitate glutin. - -As regards its chemical composition, chondrin is poorer in nitrogen -than glutin, and contains more sulphur. Its formula approaches more -closely that of albumen, which corresponds also with the origin of -chondrin, for cartilages may be considered as transition-links between -the proteïne and glue-yielding substances. - -By the action of concentrated sulphuric acid upon chondrin, leucine -is only produced but no glycocoll. By potassium hydrate chondrin is -converted into glutin and yields then, like the latter, leucine and -glycocoll. By boiling with concentrated hydrochloric acid chondrin is -decomposed; a peculiar variety of fermentable sugar, to which the term -chondroglucose has been applied, being formed. - -It may finally be remarked that chondrin possesses less adhesive power -than glutin and its presence in glue may be considered detrimental. To -avoid its formation, the glue manufacturer should separate as much as -possible cartilages from bones. Chondrin, however, is useful for size. - - -4. PROPERTIES OF GLUE AND ITS BEHAVIOR TOWARDS OTHER SUBSTANCES. - -The product designated by the general term glue, is always a mixture of -glutin, chondrin and other substances not yet accurately determined. -Glue is formed by evaporating and further drying the jelly, and its -properties depend on the crude glue and glue-yielding material used for -the production of the jelly. - -It may here be remarked that even if the quantity of glutin contained -in the different products could not be determined by scientific means, -the glue obtained from various materials can be readily distinguished -by external characteristics. Every manufacturer knows that hides and -bones yield a distinct quality of glue as regards adhesive power, -elasticity and fracture, and that the jelly from glue-yielding -substances of older animals is more solid and gives a larger yield than -that obtained from the tissues of younger and weaker animals. Glue from -the bladders and scales of fishes, though consisting mainly of glutin, -differs materially from hide or bone glue. - -Generally speaking, the jelly, no matter whether consisting of glutin -or chondrin, possesses, before drying to glue, different properties -from glue solution. It has less adhesive power and spoils more quickly. -At a temperature of 68° to 72.5° F., jelly putrefies inside of 24 -hours, smells of ammonia, and decomposes, while glue solution can be -kept much longer without suffering deterioration. - -The jelly absorbs ozone with avidity and is decomposed by it, this -being the reason why an approaching thunderstorm may cause great damage -by destroying the coagulating power of the glue liquors, or causing the -glue to turn on the nets, _i. e._, to lose its consistency and become -liquid and foul. - -The behavior of glue solution towards different salts also deserves -attention. - -By adding potassium or sodium carbonate, neutral potassium tartrate, -Rochelle or Epsom salts to a lukewarm fluid containing 15 to 20 per -cent. of glue, the latter coagulates by the salt withdrawing the water -from it. A lukewarm solution saturated with common salt, sal ammoniac, -saltpetre, or barium chloride does not gelatinize. - -By adding to glue solution a large quantity of alum, the glue is -precipitated as a transparent mass. - -Glue compounded at a high temperature with dilute acids, does not -gelatinize by itself, but will do so on adding common salt. - -Boiling with slaked lime deprives glue solution of its power of -gelatinizing, and, on evaporation, changes it into a colorless gummy -mass which is soluble in cold water and in saturated solution of common -salt. - -From a glutin solution compounded with oxalic acid, the latter can -after some time be again separated by the addition of lime, the result -being a non-gelatinizing fluid which, however, possesses great adhesive -power. This is the so-called _meta-gelatin_. - -Glue solution also loses its property of gelatinizing by repeated -boiling and cooling (for about six days). - -Tannin enters with the jelly, as well as with glue solution, into -characteristic combinations which are formed even in solutions -containing only 0.005 per cent. of jelly or glue. Glue is, therefore, -an excellent agent for the detection of tannin. - -When quite concentrated glue solution is treated with tannin, a heavy, -flocculent precipitate of a dirty-yellow, caseous character is formed, -which turns brown on exposure to the air and, after drying, constitutes -a hard brittle mass, easily reduced to powder and soluble in hot potash -lye, but insoluble in water, ether and alcohol. This precipitate, if -not identical with, is closely allied to the combination of tannin with -skin, called leather. - -Glue exposed to a dry heat melts, diffuses a strong disagreeable odor -of burned horn and leaves behind a charcoal which has a powerful -discoloring effect like animal charcoal. When subjected to destructive -distillation, glue yields an aqueous solution of ammonium carbonate -and a thick brown oil consisting of a mixture of ammonium carbonate, -sulphur, ammonium cyanide, etc. - -The chemical composition of glue is such as to bring to mind that of -starch and cellulose derived from the vegetable kingdom. It contains: - - Carbon 49.1 per cent. - Hydrogen 6.5 per cent. - Nitrogen 18.3 per cent. - Oxygen and sulphur 26.1 per cent. - -which may be represented by the formula: C_{12}H_{10}N_{2}O_{4}. - -The composition of glue differs but little from that of the -glue-yielding substance. Isinglass is composed of: - - Carbon 49.5 per cent. - Hydrogen 6.9 per cent. - Nitrogen 18.8 per cent. - Oxygen 24.8 per cent. - -This justifies the assumption that glue in its various transition -stages does not represent different chemical combinations, but only -modifications of one and the same combination distinguishable from each -other by physical characteristics, as is the case with starch, which -without suffering an alteration in its composition, appears as dextrine -and grape-sugar, or as with cellulose, which, without altering its -composition, can be transformed into amyloid and grape-sugar. - - - - -CHAPTER II. - -USES OF GLUE. - - -An inquiry into the various technical uses of glue must be of interest -to the manufacturer so as to enable him, when acting, as is frequently -the case, as salesman, to know to whom to offer his product; and also -to learn what special demands he has to satisfy, as not every glue -is adapted to every purpose, different qualities being required for -special uses. - -_Glue as a joining medium._ In Chapter I, treating of the nature of -glue, special attention has been drawn to the fact, that the adhesive -power of glutin is greater than that of chondrin; and that glutin -obtained from skin and tendons possesses still greater adhesive power -than the product from bones. This is the reason why good sound glue -made from scraps of skin is preferred by those artisans who may be -considered the principal consumers, such as cabinet-makers, carpenters, -turners, instrument-makers, wood-carvers, carriage-builders, -brush-manufacturers, bookbinders, paper-manufacturers, etc., all -of them requiring glue of the greatest possible adhesive power. It -must, however, by no means be understood that a good quality of bone -glue cannot be used for the same purposes; because much bone glue of -excellent quality and at a low price is brought into the market by -manufacturers of animal charcoal and bone meal, and is used in glueing -wood, etc. - -Glue suitable as a joining medium for the above purposes should be of -an amber or brown-yellow color, transparent or translucent, clear, dry -and hard, and show a glassy fracture which should not be brittle, but -somewhat elastic. Placed in cold water it should swell up and absorb -as much of it as possible without actually dissolving, even if it -remains there for 48 hours. The supernatant water should be free from -a putrid odor and contain but a small quantity of foreign substances -in solution. Such glue passes into solution at 122° F., and dissolves -entirely on heating to 144.5° F. Heating to a higher temperature should -be avoided. - -_Glue as a binding agent._ Glue solution is used for bind-together -pulverulent substances, such as mineral colors in the manufacture of -colored paper and paper-hangings, in painting in distemper, in the -size of the gilder; or it is mixed with plaster of Paris or chalk for -the manufacture of plastic masses which become hard on drying, such -as stucco-work, papier-maché, etc. Generally speaking, it is best to -use only good sound glue for these purposes, though it may sometimes -be possible to utilize defective and cheap qualities without injurious -consequences. For color mixtures, the glue should at all events be -free from acids and alkalies, as they exert a decomposing and altering -effect upon the colors. The gilder should always use the best quality -of glue, as otherwise the work he applies later on to the size will -spoil. - -A very large quantity of glue is consumed _in the manufacture of -matches_, and much depends on its quality and drying properties. The -dipping composition for matches containing phosphorus is a bath of -glue of 25 to 50 per cent. strength to which the requisite amount of -an oxidizing agent, like potassium nitrate or chlorate has been added, -kept at a temperature of 100.4° F. The phosphorus is cautiously put -in; it melts, and is stirred to an emulsion, when the sand, glass or -other friction-agent is incorporated. The object of the glue is to -protect from oxidation, without diminishing the sensitiveness. Glue is -also used as the binding material in the heads and rubbers of safety -matches. - -_Book binders_ require for the better classes of work a glue which -should naturally be pale and strong, and without marked odor. Some -inferior glues which have been chemically bleached turn almost black in -the pot, owing to the bleaching agent not having been properly removed -or neutralized. - -Sand, glass and emery papers and cloths are made by coating the surface -with a thin uniform layer of strong glue, and sifting the powder evenly -on. - -_Glue in sizing._ The principal object of sizing goods is to impart to -them a certain degree of stiffness, to give them a nice appearance and -a good feel. - -As glue would injure the color of white goods, it cannot be used for -sizing them, but, on the other hand, much is employed for preparing -size for the use of hat and cloth manufacturers, weavers, etc. Before -the introduction of the paper machine and invention of rosin glue, -animal glue was exclusively used for sizing paper, but at the present -it is only used for sizing paper manufactured from rags, and for -pasteboard, and also by manufacturers producing drawing paper sized -with animal substances. The paper, after leaving the machine, is passed -through a glue solution and then dried in the air. - -For actual sizing purposes good and fine varieties of glue are only -used, or sometimes the manufacturers prepare their own size by boiling -to glue dried calves’ heads, or rabbit skins deprived of their fur, -scraps of parchment, etc. For cheap woollen hats, glue is used in place -of shellac. The cloth manufacturer procures his glue mostly in the form -of a jelly. This variety of glue deserves special attention and the -mode of preparing it will be referred to later on. - -_Glue for culinary and medicinal purposes._ The use of glue for these -purposes is based upon three properties: - -1: Upon its power of coagulating and inclosing while in this state, -substances mechanically dissolved and finely divided in a fluid, which, -being specifically as heavy as the fluid itself, render the latter -turbid and cannot be got rid off by settling. The glue in this case -acts as a clarifier. - -Large quantities of isinglass and gelatine, specially prepared for -the purpose, are used for clarifying and fining beer, wine and other -liquids, as well as for preparing jellies. The material to be used for -jellies and other culinary purposes must, of course, be colorless and -entirely free from odor. Jellies are made palatable by flavoring with -spices, sugar, essences, etc., before congealing, A vegetable gelatine, -Agar-Agar, which will be referred to later on is now brought from -China, and being cheaper and perfectly free from odor, has become quite -a competitor with isinglass and gelatine. - -Prior to the introduction of Liebig’s and other beef extracts, bouillon -tablets, consisting of a mixture of bone-jelly, meat broth, extract -of pot herbs and flour, were largely used. One hundred and ten pounds -of meat repeatedly boiled yield five pounds of bouillon tablets. A -good meat broth, though not equal to that from Liebig’s or other meat -extracts, is obtained from these tablets by the addition of thirty -times their weight of water. - -If glue be dissolved in water, it gelatinizes at the ordinary -temperature, and if the solution be mixed with other fluids, for -instance, meat broth, fruit juices and essences, which in the form of -jelly are to serve as food, it effects their solidification. - -Glue acts as a healing agent by preventing the access of air to -wounds. Court plaster is prepared from gelatine. When cabinet-makers -cut themselves, they apply glue to the wound with the best success. -In hospitals a compound of gelatine and glycerine is used as the -best means of closing wounds, the same compound having also been -successfully used for preserving articles of food such as eggs, fruit, -and even meat. - -Every good quality of glue can be used for the above purposes. - -Medicines of a disagreeable taste are frequently inclosed in gelatine -capsules, so that they can be taken without causing inconvenience to -the patient. The use of these capsules has grown to such an extent as -to form a special branch of industry. The mode of manufacturing them -will be described later on. - -_Glue for elastic masses and as a partial substitute for rubber._ Glue -mixed with glycerine forms an elastic mass resembling rubber. The -same effect can be produced by an addition of molasses. This elastic -mass, the preparation of which will be described later on, is of great -importance for the manufacture of printers’ rollers, for moulds, etc. -Some manufacturers prepare the mass ready for use, so that the printer -or lithographer need only remelt it, and cast it in a mould. - -Glue is of great importance in photolithography as, mixed with chromium -salts, it is the only known means of transferring a photographic -negative to the stone. In photography, gelatine is used for negative -pictures upon glass. For the manufacturer of casts of plaster of Paris -or cement, this glue mass, which is generally used without an addition -of glycerine, is indispensable for making moulds which are much -undercut. - -Glue mixed with glycerine may be used as a substitute for rubber in -manufacturing elastic toys, such as dolls’ heads, animals, etc. For -these purposes it is advisable to select glue which forms a very solid -jelly, even if it possesses but little adhesive power, pure bone-glue -being the best. - -Glue mixed with glycerine (1 part glue, 1 part glycerine) is used as -hectograph mass for the transfer of matter written with concentrated -solution of aniline color. - -_Glue for fancy articles._ Great progress has been made in the use of -glue and gelatine in the manufacture of fancy articles. - -The best known of all these products are perhaps the gelatine foils. -They form thin, transparent sheets, brilliantly colored, and are used -for printing sacred images, visiting cards, labels, etc. - -Gelatine veneers were first shown at one of the Paris International -Exhibitions. They consist of sheets varying in thickness, which -have been deprived of their translucency by an admixture of colors -in imitation of various crystallization of salts, and such stones -as lazulite, malachite and avanturine. Glue imitations of mother of -pearl, tortoise shell, and ivory were shown which closely resembled the -genuine articles. These veneers have been largely introduced in the -manufacture of fancy articles, cabinet ware, buttons, etc. The most -brilliant use to which they have been put is in the manufacture of -fans, for which ivory and tortoise shell were formerly used, and there -are perhaps few ladies that are aware that these glittering toys are -manufactured from horse bones from the knacker’s yard. - -The successful introduction of gelatine veneers was soon followed by a -substitute for horn in general, and combs, buttons, snuff-boxes, and -hundreds of other fancy articles have been manufactured from these -imitations. - -In the foregoing statement only some of the principal uses of glue have -been enumerated, and there can be no doubt that with an increase in the -knowledge of its nature and properties, a wide field is still open for -progress in this industry. - - - - -CHAPTER III. - -RAW MATERIALS AND THEIR PREPARATION FOR THE MANUFACTURE OF GLUE. - - -The raw materials used for the manufacture of glue consist of a variety -of animal offal. The principal substances employed are refuse from -tanyards, such as scraps of ox and other thick hides, the waste of the -workshops of leather dressers, morocco leather manufacturers, etc. The -tendons and intestines of many animals, rabbit and hare skins deprived -of their fur, cat and dog skins, scraps of parchment, waste of turners -and button makers, and offal from butcher shops and households, help to -swell the series of materials used for the manufacture of glue. - -The materials are collected and sold either directly to the glue -boiler, or to dealers making a specialty of glue stock. - -As a thorough knowledge of these waste products is of importance to -the manufacturer, this chapter will be devoted to their detailed -description, the success of the enterprise depending largely on -the selection of the raw materials and their careful sorting and -preparation. By bearing in mind the varied products—from the most -ordinary black glue to the colorless glassy gelatine for photographic -and culinary purposes—it will be understood that entirely different -raw materials have to be employed for the finer products than for the -ordinary qualities of glue. - -According to their derivation the raw materials may be divided into -three groups, namely: - -1. Skin-like raw materials: Skin, leather, tissues. - -2. Bone raw materials. - -3. Materials obtained from fishes: Air bladders, scales, etc. - - -1. ANIMAL SKIN. - -[Illustration: FIG. 1.] - -This consists of three layers, namely: 1. The thin upper-skin—the -epidermis—which consists only of cellular tissue, and is of no special -importance for the manufacture of glue. 2. The actual leather-skin, or -corium, which consists of fibres of connective tissue and forms the -actual object of the tanner as well as of the glue boiler. Underneath -the corium lies the under-skin, which consists only of cellular tissue -contaminated with particles of flesh and fat, which are detrimental -to the manufacture of glue. Fig. 1 represents a section of the animal -skin. _O_, is the epidermis, _L_, the corium, _U_, the under-skin. The -epidermis consists of two layers. The first, superficial one, _H_, is -known as the cuticle or lamellar layer, and the other deeper layer, -_S_, as the mucous or malpighian layer. The corium also consists of -two layers, the upper one _C_, and the lower one _C_{1}_, which is -the actual leather-skin. The under-skin, _U_, is an elastic tissue -containing many deposits of fat, _F_, and perspiratory glands, _D_, -which are connected with ducts, _D_{1}_, with the surface of the skin. - -For the manufacturer of leather and glue, the corium is the only -material of value. - -The tanner trims the skins before steeping them in the ooze. From sheep -and calf skins he removes the head portions, it being more advantageous -to use them for glue stock. He also cuts off the skin covering the -lower part of the thighs, and, to give the skin a neat finish, the -ragged edges of the belly part. Of bullock hides, the ears, tails and -foot pieces are utilized for glue stock, while the head parts are -tanned. Such tannery waste may yield 44 to 46 per cent. of glue. Scarf -skin of bullocks’ hides and waste in fleshing the hide, tendons and -hinder parts of cattle yield from 30 to 35 per cent.; horse sinews from -15 to 18 per cent. - -Scraps of parchment and bullocks’ feet are highly valued as glue -stock, since they are in fit condition for boiling without further -preparation. They may yield up to 62 per cent. of their weight in glue. - -Calf and sheep skins yield a superior glue; that from horse hides is -usually dark and poor in quality, although with careful working a -strong product can be obtained from the latter. - -Of great value to the glue boiler are the so-called calves’ heads, -which, after liming and drying, form a special article of commerce. - -Skins of hogs, hares and rabbits yield a light-colored glue of little -consistency. It is, therefore, best to use these last-named raw -materials for the preparation of jelly, such as is used in sizing, in -the manufacture of paper, etc. - -The older the animals from which the skins have been derived, the more -solid the glue will be. In many cases, especially where a certain -quality of glue is to be produced, it may be recommended to separate -the different kinds of skin refuse into lots, provided there is enough -of each kind to boil it separately. - -A considerable number of skins used for packing various articles, such -as indigo from South Africa, have been so much damaged in transit as to -render them useless for tanning, but they form good material for glue, -frequently yielding 50 to 55 per cent. - -In reference to judging glue stock some valuable notes are given in -an article on glue, published by the American Provision Co., Chicago, -Ills.: - -“Dry, uncured or salted stock, such as raw hide or South American, if -soaked for twelve hours in cold water, gains about 50 per cent. in -weight, and still remains tough, and the water sweet. The moisture, -dirt, and salt should not be over 10 per cent. - -“Green salted stock, such as hide pieces, sinews, calf heads and pates, -should have no excess of salt, nor be foul, discolored or heated; -should be tough, with the hair not loose, and have a mild animal odor. -Moisture and salt not over 40 per cent. - -“Dry limed stock soaked twelve hours develops a characteristic odor, -and should be firm, fibrous, and have no slimy pieces. The water should -not be dark. Lime, sand and dirt, not over 5 per cent. - -“Green limed stock should be smooth and soft, any remaining hair being -easily detachable, while the liquor should be fairly clean, sweet, and -not too alkaline. - -“A large quantity of waste bones accumulates in the preparation of -tinned provisions. If these have not been overheated and are in good -condition, a considerable amount of glue can be obtained from them, the -bones of the head, ribs, and feet giving a better yield than those of -the thighs and legs. - -“Horn piths should not contain over 12 per cent. moisture, and should -not have been overheated in drying; they should have been cleansed from -skin and hair, which are of little value to the glue-maker. - -“The age of the animals yielding glue stock has an important influence -on the product. While from younger animals the product, as a rule, is -of lighter color, more abundant and more easily obtained, it contains -more chondrin, so that from solutions of equal strengths, those from -mature animals will be found to be of greater consistence and the glue -more solid. - -“Abroad, dry hides are often, for weighing, soaked in chlorbarium, a -solution of barium chloride, and then in a bath of dilute sulphuric -acid, 1½ per cent., which readily soaks in, combines with the barium -to form the white insoluble powder of barium sulphate, leaving weak -hydrochloric acid in the fibre, to be afterwards neutralized in -liming, the chloride of calcium dissolving out. This treatment affects -considerably the subsequent making of glue, as, beside the effects of -the acids, the sulphate of barium will render the liquors cloudy and -difficult to clarify. Of course if colored glues are to be made this -will be no detriment.” - -To prevent putrefaction, which is always accompanied by decomposition -of glue-yielding substance and consequent loss, the scraps must be -carefully preserved, especially in summer. - -The tanner prepares the waste by liming, _i. e._, steeping it during -fifteen to twenty days in milk of lime which is frequently renewed. -By the action of the lime, adhering particles of blood and flesh are -dissolved and the fatty matter is saponified. After this treatment the -glue-stock is dried. - -In case this work is not done carefully in the tanyard, as is only -too frequently the case, the stock is of but little value to the -glue-boiler. - -By allowing the refuse to lie too long in a heap, as is sometimes done, -putrid fermentation sets in, the injurious effects of which cannot be -remedied by subsequent liming, or the lime bath has not yet been strong -enough, or has not acted sufficiently long upon the scraps to destroy -the adhering particles of blood and flesh. The lime bath, on the other -hand, may have been too strong, so as to attack the glue-yielding -substance. Frequently it is also the case that the scraps having been -dried under unfavorable circumstances, mould has commenced to form, -and finally they may be spoiled in winter by allowing them to freeze. -Frozen glue leather yields glue of very little consistency. - -It will be seen from the foregoing that great precaution and care are -required when buying glue leather. The manufacturer should especially -see that it is dry and tough, free from mould and all organic and -inorganic substances, and not too strongly limed. - -The glue-boiler should, in all cases, be prepared to undertake the -preparation of the glue stock himself. The following arrangements are -required for the purpose: - -Let us assume that the glue factory is located on a stream of water. In -the immediate neighborhood of the stream a sufficient number of pits -to prepare all the glue stock used, each about 6½ feet deep and 6½ to -10 feet in diameter, and lined with cement, are so arranged that their -bottoms are about 3 to 3½ feet above the level of the water. They are -supplied with water by means of a pipe line connecting one with the -other. Each pit is provided with a discharge pipe to draw off the dirty -water. - -As the glue-stock, before undergoing other operations, has to be -freed from the lime by washing with water, the simplest plan is to -place the limed stock in nets or wicker baskets suspended in running -water by means of a traveling crane or other contrivance erected on -the bank of the stream. This elementary method, however, is open to -several disadvantages, as it fouls a large volume of water and may -lead to legal interference, and its very simplicity is apt to lead to -neglect of precautions, such as brushing away solid particles of lime -or softened animal matters. Further, the great quantities of water -carry off small pieces of glue-stock and fat, if catch-basins are not -provided sufficiently large to allow fat, glue-stock, hair and lime to -separate from the water. - -The object is better accomplished and in a shorter time by the use of a -washing drum. This consists of a perforated iron cylinder about 6 feet -in diameter and 4 feet in length, and open on both ends. Around the -inside of the cylinder are fixed a number of wooden shelves 6 inches -broad, which, as the cylinder revolves, carry the glue-stock partly -round, ultimately falling to the bottom again, the movement dashing -it about under a spray of water. In the cylinder is also arranged an -iron plate supported by stays from the outside. While the washing -is in operation the plate is turned perpendicular; on completion it -is brought to a horizontal position, forming a table, on which the -glue-stock falls, and the latter is then removed to a hand-press to -squeeze out the water. The washed stock is then removed to the drying -ground, which should be in a sunny and airy location, and provided with -an inclined floor of planks or cement so arranged as to allow of the -admittance of air from beneath. - -As it is well known that small quantities of liquid, frequently renewed -and thoroughly drained off each time, effect the most complete and -economical washing, and in the shortest time, S. Rideal recommends the -use of pits or vats with proper arrangements for stirring, draining and -inspection. The lime scum from the pits can be used in the manufacture -of fertilizers. - -The glue-stock washer shown in Figs. 2 to 5, is the invention of W. -A. Hoeveler (American patent), and it relates to the construction of -apparatus for washing glue-stock. - -In apparatus for this purpose the stock is very commonly damaged by -being broken up too much, and considerable loss results, besides, -from the fact that the small particles are allowed to escape with the -wash-water. By the present construction and arrangement these defects -are remedied and other advantages derived. - -Fig. 2 is a transverse vertical section on line x-x of Fig. 3 of this -apparatus; - -[Illustration: FIG. 2.] - -Fig. 3 is a longitudinal vertical section of the same; - -[Illustration: FIG. 3.] - -Fig. 4 is an enlarged plan illustrating the screen and hinged covers, -one being opened and one closed; and - -[Illustration: FIG. 4.] - -Fig. 5 is a detail of the hub, stems and part of one paddle. - -[Illustration: FIG. 5.] - -The apparatus is constructed in the form of a rectangular trough-like -structure, with its sides and ends, _A_, substantially water-tight by -means of the double walls, _a a_. The upper portion of the interior is -occupied by the swinging wash-box, _B_, semicircular in shape, with -flat sides and rounded bottom throughout, the bottom being perforated. - -Upon a transverse shaft, _c_, journaled at the axis of box, _B_, is set -a paddle-wheel composed of a suitable hub, _d_, and adjustable paddles, -each composed of the radial stem, _e_, and the blade, _f_, or spoon. -The spoons, _f_ are set on the stems, _e_, so as to be capable of being -reversed or turned half-way round, more or less. One side of the spoon, -_f_, is rounded off, so that while passing through the stock the latter -will not cling to or remain upon it. The other side of the spoon is -flat, but slightly skewed or bevelled, so that when turned to face -with the direction of motion of the wheel it not only gathers up the -stock and holds it till out of the box, _B_, but upon further elevation -causes it to roll or slide along the paddle to a predetermined point, -where it falls off gently into a discharge-spout, _g_, which carries it -off for further treatment practically undamaged. During the operation -the box, _B_, and the body, _A_, are kept supplied by a stream of clean -or chemically-prepared water, and the wheel, _e f_, revolves slowly -in the box, the edges of the paddles sweeping around, while the box, -_B_, or its bottom, is kept oscillating, thus preventing an injurious -clogging of the perforations in the box-bottom. After the stock is -placed in the box, _B_, and the latter filled with sufficient water, -the wheel, _e f_, is caused to slowly revolve (by motive or hand -power), with the rounded sides of the spoons, _f_, presented forward. -This operation thoroughly agitates and cleanses the stock, while the -rounded form of the spoons prevents the breaking up of the natural -condition of the stock. The inventor gathers the finer particles as -follows, after they have escaped through the perforated bottom of -the wash-box, _B_. At the lower part of the trough, _A_, elevated on -crossbars or blocks, _h_, he places two parallel strips, _i_, and -between these, which are grooved to form ways, _k_, inside, is set a -long screen, _l_, placed on rollers, _m_, and movable thereby on the -rails or ways, _k_. To give movement to the screen, _l_, the inventor -attaches to its end a rod, _n_, which projects outwardly through the -walls, _a a_, by means of the packing-box, _p_, and cap or door, _q_, -which, when opened, allows the withdrawal of the screen, _l_, and -its burden. The shaking of the screen is accomplished by a suitable -motor applied to rod, _n_, and is kept going during the operation as -required. To the strips, _i_, which are placed at a little distance -from the side walls, _a_ (to leave a passage for the water and refuse -to go through), are hinged the two doors, _r_, which shut down upon -the rod, _s_, as a support, in which case nothing can fall upon the -screen, or which open up and rest against the sides, _a a_, in which -case the screen is exposed and the side passages closed by the doors, -_r_. During the initial or rough-washing stage the doors, _r_, are -kept closed, and the dirty water and refuse pass freely down the side -passages and out at a suitable opening at the bottom. After this stage -it becomes desirable to catch the particles which get detached from the -stock in box, _B_, and come through the perforations therein. Then open -up the doors, _r_, thus closing the side passages and compelling all -the water and small stock to go to the screen, _l_, which catches the -remaining stock. When sufficiently accumulated the screen may be drawn -out and the stock thereon removed. When the main body of stock in box, -_B_, has been cleansed, the paddles or spoons, _f_, are reversed, so as -to present their flat, skewed faces to the stock, and in revolving the -paddles now gently lift the stock and discharge it into the spout or -hopper, _g_. The washing and removal of the stock when washed are thus -accomplished without further manipulation than to reverse the paddles, -which obviously could be done by a reversing-gear on the motor, thereby -reversing the direction of movement of the paddle-wheel. - -Instead of the whole box _B_ being oscillated back and forth, its -bottom may be set on slides or rollers and oscillated, while the sides -remain stationary. - -In the drawings the box _B_ is shown as hung upon the shaft _c_ as a -centre; but as the provision of means of reciprocating or oscillating -the box or its bottom is within the skill of any machinist, it is not -necessary to describe any specific form. As the box with its contents -will be very heavy, the inventor prefers a special motor for it, which -may also be geared up to reciprocate the screen _l_. - -Instead of the door _q_, as located in Fig. 2, it can be located as at -_q’_, same figure. - -The entire plant must of course be arranged according to sanitary -regulations, especially as regards river pollution, etc. - -The sheds for sorting and storing the glue-stock should, if possible, -be in close proximity to the pits and washing drums, and be dry and -airy. In arranging his plant, the glue manufacturer must, in short, -exercise his ingenuity with a view to carrying on the business with -as little loss of material, and as much saving of time and labor as -possible. - -The work in a factory arranged in the above manner, is carried on as -follows: - -The raw materials brought by the dealer are weighed, and if in green -state, the customary percentage—generally 50 per cent.—taken off. To -facilitate future operations, and to enable the manufacturer to produce -different varieties of glue, the dry materials are sorted and stored in -different compartments of the store-shed. - -Green waste, _i. e._, such as has not been limed must be taken in hand -at once, as otherwise it would taint the air, be attacked by rats and -other animals, and suffer injurious alterations by decomposition. The -manner of operation is as follows: - -_Liming._ Prepare “milk of lime” by filling the pits, which are to -serve for the reception of the skin waste, with the required quantity -of water and dissolve in it 2 per cent. of calcium hydrate obtained by -slaking a good quality of quick lime. Stir thoroughly, and in order -that the water may become thoroughly saturated with the lime, let the -liquor stand for 8 or 10 days before placing the waste in it. The -liquor should stand about 9 inches deep over the waste in the pits. -The length of time the waste has to remain in the milk of lime varies -according to the material; calf skins requiring 15 to 20 days, sheep -skins 20 to 30 days, and heavy ox hides 30 to 40 days. The milk of lime -should be renewed once or twice a week, and thoroughly stirred. - -For the purpose of liming, the quality of the lime used is of the -utmost importance, the milk of lime being frequently quite valueless -by reason of having become carbonated or a bad quality of quick lime -having been originally employed. It should be borne in mind that only -the hydrate of lime which is present in solution in lime water is of -use, whereas in milk of lime so much carbonate and other impurities -may be present that the liquid, though thick, may be quite useless. -The value of a lime should always be tested by determining the amount -of real calcium hydroxide, Ca(OH)_{2}, contained in it. The operation -according to S. Rideal, is conducted as follows: Water free from -carbonic acid is first prepared by boiling distilled water for half an -hour in a strong, round-bottomed Bohemian or Jena flask. While steam -is still issuing, the flask is removed for an instant, closed by a -well-fitting greased cork or a rubber stopper, and allowed to cool. -When the temperature has somewhat fallen, the cooling may be cautiously -accelerated by dipping into a pail of warm water, then transferring to -the cold stream from a tap. The water may be preserved in the flask -or, preferably, a number of bottles with vase-lined stoppers should be -filled quite full and retained for use. - -From the sample of lime, well mixed, a small portion (about 0.25 -gramme) should be accurately and rapidly weighed, placed in a -wide-mouthed, stoppered bottle holding about 300 cubic centimeters, 250 -Cc. of the boiled water added, and then allowed to settle. The whole of -the calcium hydrate will now have dissolved. Fifty cubic centimeters -of the clear liquid should now be withdrawn by a pipette, transferred -to a flask, colored with an indicator—either phenol-phthalein, -methyl-orange, or litmus may be used—and its alkalinity determined by -running in decinormal hydrochloric or sulphuric acid from a burette -till the change of color occurs. Each cubic centimeter of the acid -corresponds to 0.0028 gramme of calcium oxide, or 0.0037 gramme of the -hydrate, Ca(OH)_{2}. The amount by calculation will give the percentage -of real lime present in the sample. It is well to notice that any soda -or potash present will equally neutralize the acid, and be returned -as lime, but as these are of almost equal efficiency their presence -in _small quantity_ has no disadvantage. For special work it will be -necessary to have a full analysis. As a rule the product made from -limestone, or “stone lime,” is the best article in commerce, and is -much more free from stones and clay than “gray lime” or “shell lime.” -The best stone lime contains sometimes only ½ per cent. of impurities, -and seldom more than 5 per cent., while inferior kinds of gray lime -may contain as much as 50 per cent., and would be of little use in -glue-making. - -After removal from the lime pit, the material is placed in willow -baskets or nets, and immersed in the stream to remove the greater -portion of the lime, which is generally effected in a few days. It -is still more effectively accomplished by placing the waste, after -soaking in the willow baskets, in the wash drums. After taking it from -the baskets or wash drums it is spread in the drying yard to drain and -dry, the desiccation being accelerated by turning it over with a fork -several times a day. While drying, the quick-lime is converted into -carbonate, the latter exerting no disturbing effect in the manufacture -of glue. When sufficiently dried, the material is ready for boiling, -and the crude glue thus obtained can be stored for any length of time, -until wanted for further manipulation. - -In summer it is scarcely possible to cleanse the raw material as -rapidly as it is brought to the factory, and to work it immediately -without putrefaction setting in, and for this reason it would -frequently be risky to purchase larger quantities of it, even if -offered at very favorable terms. During the colder season of the year, -drying of the cleansed raw material is such a slow operation, that -in order to prevent putrefaction, recourse would have to be had to -artificial heat. - -These drawbacks can, however, be overcome by the use of carbolic -acid, which possesses in a high degree the property of preventing -putrefaction. It is quite cheap, and as but a comparatively small -quantity of it is required, the additional cost need scarcely be taken -into consideration, since the value of glue-stock annually destroyed by -putrefaction is considerably greater than the expense for carbolic acid. - -The raw material is thoroughly cleansed, and while in a moist state -is gradually brought into a brick cistern or large vat, carbolic acid -solution being poured over each layer, so that, when the cistern or vat -is filled, it stands about an inch or two deep over the material. The -latter may be left in this state until wanted. - -The carbolic acid solution is prepared by dissolving 2 lbs. of carbolic -acid in 1000 quarts of water; the fluid thus obtained possessing a -slight odor of smoke. The washed glue-stock treated as above described -with carbolic acid remains absolutely unchanged, and when wanted needs -only be taken from the cistern and worked like fresh material. - -In plants having no running water at their disposal and depending -entirely on well water, and where the waste water has to be discharged -into rivers or creeks, water containing carbolic acid should be used -for all the washing operations, a fluid containing 1 to 2 parts of -carbolic acid in 10,000 parts of water being sufficient for this -purpose. Such an addition of carbolic acid prevents the wash-water from -becoming foul. - -Carbolic acid has the tendency of hardening the glue-stock and -imparting its odor to the glue, and among other antiseptics, -formaldehyde and boric acid have been recommended for the purpose of -preventing putrefaction for a reasonable time. Formaldehyde in weak -solution (1 part in 10,000 to 100,000 parts water) has been found -beneficial. In this small quantity it does not harden the stock nor -affect the subsequent boiling, as it is dissipated by the heat. Boric -acid and its preparations, notwithstanding their low antiseptic power, -are much in favor. A fluid containing 1 part boric acid in 200 parts -water will have to be used. - -The principal varieties of hides and leather for glue-stock may be -classed as follows: - -1. Bullock leather from old animals, highly limed, mixed with rump -pieces, also with horse leather, the latter being thin, of a dark color -and soft, and is of less value than bullock leather, because it yields -a dark glue. Fat leather is bullock’s leather from fat, stall-fed -cattle, and before use has to be freed from fat (by means of benzine). - -2. Pieces of hide from the lower parts of the limbs of cattle, not -limed and with the hair; they form excellent glue-stock, yielding a -very adhesive glue. - -3. Worn-out hinges from weavers’ looms, consisting of strongest -untanned bullock’s hide. When treated with lime they yield a very -strong glue, but are worked with difficulty. - -4. Whip leather. This is waste in the manufacture of whips, and -is derived from thick tawed bullock hide. It yields an excellent, -light-colored glue. - -5. Calf leather. Broad, thin, translucent strips, slightly limed, -yields glue of a very light color. - -6. Calves’ heads. The skin of calves’ heads, limed, without hair. They -constitute the best material for gelatine, and form a special article -of commerce. - -7. Calves’ feet. The skin from the last but one leg-joint which is cut -off from dry, unlimed, haired skins. It is the best material next to -calves’ heads. - -8. Knapsack leather. Old knapsacks of calf skin and waste in the -manufacture of new ones, tawed with the hair on with alum and common -salt. When suitably washed this yields good glue-stock. The alum and -common salt have to be completely removed by washing. The hair is no -detriment to the process of boiling, it serving as a filter for the -glue running off. To this class belong also all kinds of fur waste, -especially remnants of old fur coats (sheep skin coats), from which the -wool is removed and the skin used as glue-stock. All these materials -having been treated with alum and common salt have to be freed from -them by suitable manipulation. - -9. Hare and rabbit skins freed from their fur. They yield a -light-colored glue of little consistency. - -10. Cut rabbit skins. In depriving these skins of their fur, they are -cut by a machine into fine threads of even size. In France they are -worked into size for gilders’ use which is highly valued. - -11. Sheep and lamb leather (goat leather) limed, thin and very light, -yields but a small quantity of glue of little consistency. To this -class belongs the waste in the manufacture of kid gloves. Waste of -morocco and other varieties of similar leather, pressed into bales and -secured with wire, comes into commerce under the name of Levant leather. - -12. Waste obtained in paring kid leather and in the manufacture of -gloves. It constitutes a flocculent powder and yields very thin glue -liquor with slight adhesive power. Before boiling, the substances used -in tanning must be completely removed by washing. - -13. Surrons. These are untanned, unlimed skins of various wild animals -(antelopes, gazelles) which have been used for packing leaf tobacco and -various drugs. They form good glue stock. - - -2. BONES AND CARTILAGES. - -In addition to hides, bones are a material highly valued by the glue -boiler. Chemically speaking, the framework supporting the fleshy -tissues of the animal order, and which we call bones, is a combination -of phosphates of lime and magnesia, carbonate of lime, and alkaline -salts, united with fatty and cartilaginous matter. To the latter we -look for our yield of glue; to the fatty matter for the fat, and to the -phosphates for the basis of fertilizers. - -Bone cartilage is composed of carbon, hydrogen, oxygen and nitrogen, -the percentage composition being practically constant, whether the -cartilage be from an old or a young animal. The bones of the young -are, however, much richer in cartilage than those of the old. This is -reversed in the case of the inorganic or mineral matter, the old having -the greatest yield of phosphates. - -Then again, the fatty matters are more in evidence in full-grown -animals than in youth or age; also in the thigh and leg bones the -yield is higher than in the heads, ribs or shoulder blades, the latter -averaging 12 to 13 per cent., whilst the former runs 18 to 19 per -cent.[1] - -[1] Bone Products and Manures. By Thomas Lambert. London, 1901. - -Bones being less subject to putrefaction than skin-stock, they are -not brought into commerce in a prepared state. They are mainly bought -by contract from various dealers within easy access to the works. The -rates are generally fixed for a certain period, and cover all classes -of common bones, whether fresh butchers’ or a mixture with partly -boiled bones. Bones differ considerably in their value. A fresh bone -will yield the highest percentage of fat and glue. On the other hand, -partly boiled bones may contain only 6 per cent. fat with 30 per cent. -water. In buying bones the manufacturer should exercise great care, as -the dealer sometimes finds ways and means of including hoofs, horns, -iron, beefy matter, and even pieces of brick. Naturally they form -weight, but, excepting the horns, have no value. - -To separate the different classes of bone coming into the works, and -arrange them according to the amounts they would produce of fat and -glue, is no doubt a desirable object, but in practice it is seldom -carried out. However, if the manufacturer wishes to undertake this -tedious work, it is recommended to make the following distinctions: - -1. Bones of young animals, sheep, calves, dogs, cats, etc., being -readily disintegrated, are thrown into one pile, and also the light -bones of oxen, such as skull bones, shoulder bones, the vertebra of the -tail, etc. - -2. A second pile is made of the foot bones of goats, sheep and cattle, -provided they can be had, as is the case in the United States and -England, in sufficiently large quantities. - -3. Scraps and shavings from bucks’-horn from turners and button-makers. - -4. Thick bones of oxen, horses, etc., which must remain longer in the -lime-bath, together with waste of hard bones from turners. - -5. Where large quantities of bones are handled it is advisable to sort -out the bones of the upper thigh, as they can be more advantageously -used for the manufacture of piano-keys, handles for tooth-brushes, etc. -Hoofs, which are frequently found, should be thrown out, as they yield -no glue and can be utilized for other purposes. - -The further manipulation of the bones for the manufacture of glue -requires first of all their crushing or grinding in a stamper or mill. -By this crushing or grinding of the bones two objects are attained, -namely, they are more readily deprived of their fat and present more -points of attack to the corrosive agents to be used later on. The -crushed bones are put in a large boiler, and for a few hours subjected -to the action of steam. Leg bones, as well as horns, should not be -boiled, as they contain no fat, and would lose too much glue-yielding -substance. After boiling, the bones are placed in a lime vat for 8 to -14 days. The water used for boiling the first portion of bones may be -used for a second one. - -The extracted fat amounting to 4 or 5 per cent. of the quantity of -bones used, is taken off the surface of the cold liquor and the latter -may be utilized as a fertilizer, or fed to cattle. - -For crushing the bones, a stamping mill is generally used, it yielding, -when properly constructed, material for the manufacture of glue, as -well as granulated bones which form an excellent product for the -preparation of animal charcoal. - -Since animal charcoal in pieces of quite even size is now in -general demand, it is recommended to manipulate the bones in the -above-described manner, to sell the granules to the manufacturer of -animal charcoal, and use for boiling glue only the completely-crushed -portions and the porous bones which are not at all suitable for the -manufacture of animal charcoal. - -[Illustration: FIG. 6.] - -Fig. 6 shows a stamping mill very suitable for the crushing of bones, -the illustration showing the mill open on the left side and closed -on the right. It is furnished with 16 stamps, _D_, each stamp being -provided with a cast-iron shoe. The stamps are lifted by means of a cam -shaft in such a manner, that the height of fall of the outermost pairs -of stamps is least and that of those in the centre greatest. Between -the inner stamps is a sieve _H_ with meshes of sufficient size to allow -the largest pieces, which can be produced by granulation, to fall -through. - -Underneath the sieve is an Archimedean screw _K_ for carrying off the -pieces of bone passing through the sieve. - -[Illustration: FIG. 7.] - -[Illustration: FIG. 8.] - -The base of the stamping mill consists of iron plates so arranged -as to form steps, the plates lying towards the center of the mill -constituting the lowest steps. Every two stamps standing alongside one -another rest upon such a step. When the mill is set in motion, the -bones reaching the stamping trough from the right and left fall upon -the steps, and are crushed by the descending stamps. - -As a rule, the bones to be stamped are not brought directly into the -stamping trough, but are first passed through a crushing mill and -the coarser pieces thus obtained are subjected to the action of the -stamping mill. - -Figs. 7 and 8 show a well-constructed bone crusher. It consists -essentially of two cast-iron rollers _A_ and _B_, furnished with -case-hardened cutters. The bones are introduced through the hopper _B_, -and the rolls set in motion by means of cog-wheels _a_ and _b_. The -bearings of the roll _B_ run in a carriage which can be shifted by the -lever-construction _f i_. The object of this contrivance is to allow -of the roll _B_ giving way in case a harder material than bones, for -instance, a stone, passes between the rolls. - -[Illustration: FIG. 9.] - -The Crosskill bone mill, Fig. 9, as described by S. Rideal, is intended -to be driven by a strap from the fly wheel of a common portable -engine. It consists of a pair of strong rollers made of wrought-iron -with case-hardened cutters, and a revolving or oscillating riddle for -separation of the ground bones as they fall from the cutters; the whole -carried by a substantial cast-iron frame. The mill will grind from 6 to -16 hundred-weight per hour with a three to eight horse-power engine. - -For sorting the crushed bones into pieces of equal size, a sieve, Fig. -10, is used consisting of a drum constructed of narrow boards covered -with wire-netting of different degrees of fineness. The upper portion -_A_ of the drum consists of narrow-meshed net and through this falls -the fine meal which is conveyed by the Archimedean screw _F_ over the -frame _F G H_ into vessels serving for its reception. - -The lower section, _B_, of the drum is furnished with netting, the -meshes of which become gradually wider towards the lower end, and, -hence, the smallest particles of bone fall through the funnel, _D_, the -medium-sized ones through _E_, and the largest ones through _F_. Pieces -which cannot pass through _F_, leave the drum at _G_. - -In factories manufacturing glue as well as animal charcoal, the larger -pieces are steamed by themselves to obtain their fat, and then charred, -while the small pieces and the meal are utilized for glue. - -[Illustration: FIG. 10.] - -The lime-bath used for bones should be of the same strength as that -for skin-stock. After removal from the lime vat and washing, the bones -are put in a tank of stone or wood (brick pits should not be used) -containing cold hydrochloric acid of 70° Bé. or 1.05 specific gravity -(= 10.6 per cent. HCl) for thick bones, or half that strength for thin -bones, and are thus left to digest for 8 to 14 days, being frequently -stirred and fresh acid added. By the action of the acid the calcium -phosphate is dissolved and the bones become cartilaginous, flexible -and transparent. The phosphates can be precipitated by ammonia, or -the whole evaporated with charcoal or silica, and distilled to make -phosphorus. - -When sufficiently softened, the stock is washed in wicker baskets or a -washing drum to remove adhering acid. They are then placed for one day -in the lime liquor, again washed, and then either dried or stored away -for future use, or boiled at once to glue, while in a moist state. - -Leg bones, horns, and other soft bones which contain scarcely any fatty -matter are not steamed for the reason previously stated, but in all -other respects are treated like steamed bones. - -It is of the greatest importance that the bones should be thoroughly -freed from acid, since even the smallest quantity remaining behind -exerts an injurious effect upon the finished glue. It is therefore -recommended to test the water draining off, or the bones themselves, -with litmus. If the tincture turns red, it is a sure indication of the -presence of free acid, and the washing must be continued until the blue -color of the tincture remains constant. - -Gerland’s suggestion, to use dilute sulphurous acid in place of -hydrochloric acid for dissolving the phosphates of the bones, and -to evaporate the sulphurous acid by heating, whereby the phosphates -are precipitated in an insoluble state, has now been quite generally -introduced. - -For the preparation of gelatine from bones, Jullion and Pirie’s -process may be recommended. It requires a somewhat expensive plant, -but saves hydrochloric acid and time. The process consists essentially -in dissolving the phosphates of the bones in vacuum. A box of wood, -or better of granite, which can be closed air-tight, is required -for this purpose. The box is filled with bones, and acid of the -previously-mentioned strength poured over them. The box is then closed -and the air pumped out by water or steam power. The smallest cracks -and pores of the bones are thus freed from air, and the latter is -replaced by hydrochloric acid, which in this manner acts rapidly and is -completely exhausted. The remaining crude glue is then further worked -in the usual way. - -Bones honey-combed by putrefaction, exposure to the weather, or burial -in the ground are of little or no value to the glue-boiler, as nearly -all the glue-yielding substance has been destroyed; they should -therefore be thrown out in buying stock. The ammonia which is formed -when putrefaction sets in, colors the glue dark. - - -3. LEATHER WASTE. - -Leather tanned with a substance insoluble in water is not directly -suitable for manufacturing glue, but can be made so by a special -process, which, though somewhat tedious, nevertheless pays for the -trouble. - -In using such stock the manufacturer should make a distinction -between old and new leather. The principal materials of this kind, -large quantities of which contribute their quota to the glue-boiler’s -stock, are old shoes, straps, harness, etc., and further, waste from -shoemakers, trunk-makers, and in fact from the shops of all workers in -leather except those using alumed leather. - -Before boiling the leather waste to glue, the removal of all traces -of tannin becomes absolutely necessary, since the retention of the -smallest quantity prevents the animal tissue from dissolving in water. - -The various methods proposed for the preparation of the leather waste -differ either in the chemical solvent used, or in the mechanical -manipulation of the waste. - -The principal point in all methods is to comminute the waste as -uniformly as possible to facilitate the complete removal of the tannin. - -Various machines, some very complicated, have been proposed for the -comminution of the waste, but a rag engine or “hollander” such as is -used by paper-makers deserves preference for the purpose, as it not -only comminutes, washes and prepares the waste in a suitable manner for -the manufacture of glue, but the leather pulp when mixed with rags or -woody fibre gives a substitute for leather which is very tough and of -good appearance, and can be worked into many articles. - -After the preparation in the hollander and careful washing the waste is -treated, according to Stenhouse, under a pressure of two atmospheres in -a boiler with water to which is added 15 per cent. of the quantity of -waste to be treated at one time of slaked lime. - -By another method the extraction of the tannin is effected by boiling -the leather pulp with caustic soda of 1.025 specific gravity for from -six to twelve hours. After drawing off the water and pressing out, the -pulp is again boiled with caustic soda of the same concentration. The -next process is to carefully wash out the soda, which is best effected -in the hollander. - -By neutralizing the soda lye in the fluid drawn off after the first -boiling, it can be re-used for tanning or purposes for which tannin is -required. - -According to another method, the _modus operandi_ is as follows: - -Dissolve 1½ lbs. of oxalic acid in 3 gallons of water, pour the boiling -solution over 110 lbs. of waste, and keep the mixture in a water-bath -at a temperature of 176° to 212° F. This effects the solution of the -pulp. Then dilute the solution by adding gradually 4 gallons of water -until a uniform mass is formed. Now add 5 lbs. of lime slaked to a -thin paste, and mix the whole thoroughly. The mass becomes friable and -pulverulent. It is passed through a wire sieve and then exposed to the -air. In three to four weeks the tannin is entirely destroyed, which -is recognized by the mass assuming a lighter color. The lime is then -removed by washing with water and hydrochloric acid. If the tannin -has not been entirely destroyed by exposure to the air, add 1 lb. of -liquid ammonia and a like quantity of pyrolusite to every 110 lbs. of -leather substance when boiling it to glue. The oxygen yielded up by -the pyrolusite, which, in the presence of ammonia, exerts no injurious -effect upon the glue, destroys the last traces of tannin. Frequent -stirring with a shovel while the material is exposed to the air and -moderate heating, facilitates the destruction of the tannin. - - -4. RAW MATERIALS FOR FISH GLUE. - -The air-bladders or sounds of various fishes contain much glue-yielding -substance and on account of its purity, the product known as isinglass -obtained from them is preferably used for culinary and medicinal -purposes. The high price of the raw material excludes it from being -used by the glue-boiler, but as he manufactures substitutes for -isinglass, and should therefore have a thorough knowledge of the -article with which he has to compete, its manufacture will be included -in this treatise. Since, however, the work of the manufacturer is -finished with the preparation of the raw material, _i. e._, of the -air-bladders into crude glue, isinglass and its substitutes will be -referred to later on. - -There is a material difference between isinglass and glue manufactured -from entire fishes. The raw material is, of course, limited to certain -localities. The principal point to be observed in the manufacture of -fish-glue is the removal of the skin, which is effected by means of -dilute sulphuric acid. - -After removal of the last traces of acid, the fatty matter of the -fishes is saponified by a treatment with milk of lime frequently -renewed. After washing out the lime, the pulpy mass is placed in a -solution of sodium hyposulphite, alum, and common salt, where it -remains for a few days. The liquor is then drawn off and replaced by -a mixture of solution of alum, dilute sulphuric acid and nitric acid. -After macerating in this mixture for a few days, the mass is thoroughly -washed and boiled to glue, and the resulting product clarified with -sulphurous acid or alum solution. As will be seen, the entire process -is tedious, requires many chemicals, and besides the yield of glue, -which has no specially good qualities, is small. It is used as a -substitute for isinglass for clarifying liquids. The best proof that -the business is of but little importance is found in the fact that -no fish-glue has been exhibited at any of the late international -exhibitions. - -The scales of large fishes, such as carp, give more favorable results. -They are treated with hydrochloric acid in a similar manner to bones. -The scales do not dissolve entirely, a horny insoluble mass, giving -no glue, remaining behind after the solution of the glue-yielding -substance. - - - - -CHAPTER IV. - -MANUFACTURE OF SKIN GLUE. - - -The thorough preparation of the raw materials will materially -facilitate all succeeding operations, which may be classified as -follows: - -1. Boiling the glue. - -2. Clarifying the glue-liquor. - -3. Forming or moulding the glue. - -4. Drying the glue. - -However, before entering into the description of these operations, it -will be necessary to refer to an intermediate product, which has been -previously mentioned under the name of crude glue, and is prepared, for -instance, by tanners and manufacturers of parchment, but also forms in -some localities a special branch of industry. - -This crude glue is actually not glue, but a glue-yielding substance in -such a state of preparation that it can be directly used for the first -operation, namely, boiling. It consists of waste of skins and leather -of all kinds, completely cleansed, dried and limed, and in the case -of leather treated with agents for the extraction of the substances -used in the tanning. As will be readily understood, the operations -required for the preparation of this stock are virtually the same as -those described in the previous chapter for raw materials and need not -further be here referred to. - -The bulk of such stock is prepared by tawers and manufacturers of -parchment, though a considerable quantity of it is also derived from -waste in the manufacture of gloves. The product from the latter source -is also found in commerce under the French names _Colle franche_ or -_Brochette_. However, if such stock is used, it is best to again -immerse it in lime water, after which it should be thoroughly washed. - -The manufacture of glue from hide and leather waste differs materially -in many respects from that of bone glue, it being the more simple -process, as no other preliminary operations than the preparation of the -glue-stock are required. The first operation is - - -1. COOKING OR BOILING. - -For this operation any kind of boiler may be used, but the materials -should be supported on a perforated grid a little distance above the -bottom, so as to save them from risk of scorching. In the centre of -the grid stands a conical pipe 2 to 3¼ feet long, perforated like the -grid and communicating with the space between the grid and the bottom -of the boiler. The height of the boiler can be increased 1 to 1½ feet -by placing an annular piece upon the rim which is bent upwards for its -reception. - -The size of the boiler depends on the quantity of raw material to be -worked at one time. It is best to choose boilers holding from 110 to -440 lbs. of glue-stock, and to place two, four or more of such boilers -in one hearth. - -The manner of using such a boiler is very simple. Straw is placed upon -the false bottom in such a manner as to cover its entire surface, and -extend up the sides of the boiler at least as far as it is touched by -the flame. The object of the straw is to serve as a filter, and protect -the materials from injury by the flame. But for the production of -entirely pure gelatine or glue, straw cannot be used, as, by boiling, -it yields a yellow coloring matter, which passes into the glue. Barley -straw gives a less intense coloring matter than rye straw. - -In case straw cannot be used, the material is placed in a large bag, -previously thoroughly boiled, and suspended in the boiler so as not to -touch the sides. By this means scorching is prevented even if the fire -touches the bottom as well as the sides of the boiler. - -The boiler having been heaped with material so high as to overflow the -brim and fill the annular piece placed upon it, is filled with water -as far as touched by the fire. The fire may now be started. The hearth -in which the boiler is placed should, of course, be so constructed -that the gases are uniformly distributed and the water quickly brought -to the boiling-point. When the water commences to boil, bubbles of -steam ascend from the space beneath the grid and, passing through the -perforations of the conical pipe, penetrate the glue-stock. Thus the -first formation of glue takes place, and the stock begins to settle -down gradually as it goes into solution. The stock heaped up in the -annular piece also sinks down gradually, and being partly heated by the -hot vapors and thus prepared for solution, is finally submerged in the -boiling solution and becomes soon entirely dissolved. - -Waste of hide and horn piths are completely dissolved in five to seven -hours. No more water should be used than is absolutely required for -cooking the entire quantity of stock, because too much water renders -the solution too thin and gives a jelly of little consistency and -difficult to dry. Concentrating the glue solution by continued boiling -is bad practice, as it is detrimental to the resulting product by -reason of the glutin undergoing a gradual transformation. - -It is best to start with a slow fire to give the stock time to soften -and thus prepare it for solution. When somewhat softened, the mass is -brought to boiling and the latter kept up, gently and uniformly, until -solution is complete. Solution is promoted by careful stirring, but -care should be had not to disarrange the straw upon the grid and on the -sides of the boiler as this would interfere with proper filtration of -the glue solution. - -The duration of cooking depends on the nature of the raw materials. -Scraps of skin from young animals, antlers, sheep trotters, etc., -dissolve in three to four hours, while waste from ox and horse hides, -or bones from old animals, require six to eight hours. - -The progress of the operation is readily ascertained by pouring a -small sample of the gelatinous fluid in half an eggshell, and setting -it aside for a few minutes to cool. If a clear and consistent jelly -be obtained, boiling has been carried on to a sufficient extent, and -the liquid is drawn off. Any undissolved glue-stock remaining upon the -straw filter can be boiled by itself, and the resulting gelatinous -liquor utilized in the next boiling. - -It is evident that quick and uniform solution of the materials, which -enhances the quality of the glue, is promoted by comminuting the -glue-stock either by grinding, stamping, or mechanical means. - -The succeeding clarification of the glue is much facilitated by -removing while boiling the scum, consisting of fat, coagulated albumen, -lime-soap, accidental admixtures, and other impurities. Before drawing -off the gelatinous liquor it is advisable to withdraw the fire and -allow the contents of the boiler to rest for fifteen minutes. - -The residue remaining upon the straw filter consists of hair, -lime-soap, undissolved particles of hide and bones, lime, etc., and is -utilized, after repeated boiling, as fertilizer or for the manufacture -of gas. - -The mode of glue boiling above described is the oldest and at present -is only in use in small establishments. Fig. 11 represents a convenient -apparatus for the purpose. It consists of three boilers upon as many -different levels. The lower boiler, _b_, serves for the settling and -clarification of the glue. It communicates with the second boiler, _a_, -which contains the material to be acted on, by means of a pipe provided -with a stopcock, and is sufficiently heated by a small fire to keep -the glue liquid without allowing it to reach ebullition. The upper -boiler, _c_, which is heated by the waste heat of the chimney, serves -as an economical reservoir for hot water. The end of the discharge-pipe -of the settling boiler is provided with a filter of woven wire. As -the sides and bottom of the second boiler are lined with straw, which -acts as a preliminary filter, the glue runs off quite clear from the -settling boiler. - -When this mode of manufacture is adopted, two boilings can be made -per day, under favorable circumstances, so that, if the boiler has a -capacity of 220 lbs. of stock, which will yield from 110 to 132 lbs. -of dry glue, the daily fabrication will be about 220 lbs. of finished -product. - -[Illustration: FIG. 11.] - -In larger plants, the above described mode of extracting the glue-stock -with water has been superseded by the use of steam in a cylindrical -wrought-iron boiler, twice as high as wide, and capable of withstanding -a pressure of three atmospheres. The boiler is furnished with a -perforated false bottom underneath which terminates a steam pipe. It is -filled from above with previously softened glue-stock and the charging -hole hermetically closed. Steam is then gradually admitted and exerts -at once a dissolving influence upon the stock. A portion of the steam -condenses and forms with the dissolved glue-stock a concentrated jelly -which collects between the true and false bottoms. - -For the escape of air a cock is provided which is closed as soon as -steam commences to escape from it. - -[Illustration: FIG. 12.] - -The advantages of this process are obvious. A larger quantity of -glue-stock can be extracted than in the boiler previously described, -and there is no danger of injury by scorching and consequent damage to -the color of the glue. More highly concentrated solutions are obtained -in a shorter time, and the spoiling of the glue solution by too long -continued cooking is prevented by drawing off the solution as quickly -as formed. The escaping hot vapors may be utilized for drying the glue, -softening the raw material, etc., the entire quantity of heat being -thus utilized. A further great advantage of this method is that there -is less annoyance from badly-smelling vapors than when boiling is done -over an open fire. A number of such boilers can be arranged in one -room and supplied from a common steam boiler. - -Fig. 12 represents a boiler for extracting glue-stock with the use of -steam. It is provided with a lid, _D_, which is removed for charging -the boiler. The aperture, _E_, in front, serves for the removal of -the residue. Above the true bottom there is another false bottom, -perforated and movable, which can be covered with straw for preliminary -filtration. The steam reaches the glue-stock through a pipe which -passes through the actual and false bottoms, and is perforated above -the latter. The resulting jelly collects between the true and false -bottoms, where it is less exposed to the action of hot steam. The -escaping steam passes through the pipe, _F_, which is provided with a -stock-cock. The pressure in the boiler is indicated by the manometer, -_K_. After throwing the materials into the boiler they can be covered -with warm water, or, after the lid is closed, warm water is introduced -from a reservoir through a special pipe and distributed over the -material through a rose. - -The boiler stands upon a frame sufficiently high to allow of -conveniently placing a vessel under the pipe _G_, through which the -jelly is discharged. The vessel, when full, is conveyed to the settling -vat, or the arrangement may be such that the jelly is directly run into -the settling vat. - -In many large plants open jacketed pans heated by steam are still used -for treating the material. Fig. 13 shows an arrangement with two of -such pans; of course one, or a larger number may be used, according -to requirement. In the illustration the pan _I_ on the left is shown -in front view, and the pan _II_ on the right, in section. _K_{1}_ is -the actual pan enclosed by the jacket _K_. Steam circulates in the -space between pan and jacket, whereby the stock in the pan is heated. -_K_{1}_, in addition, is furnished with a steam coil _S_, which may, -however, be omitted. - -The steam enters through the pipe _D_, the space between pan and -jacket, passes into the coil _S_, and escapes at _b_. The water formed -by the condensation of steam in the space between pan and jacket, as -well as that which runs off at _b_ from the coil _S_, is carried away -by the pipe _A_. - -The pipe _L_ serves for conveying hot water to the pans, and the pipe -_F_ for the discharge of the finished glue liquor. The stirrer _R_, is -furnished with two paddles, and is set in motion by a transmission on -the ceiling of the room. It serves for keeping the stock in the pans -constantly agitated, solution being thus very much promoted. - -[Illustration: FIG. 13.] - -The mode of working with this apparatus is very simple. Water being -admitted into the pan through _L_, the glue-stock is introduced and the -mass brought to boiling by admitting steam. The finished glue-liquor -is from time to time drawn off through the pipe _F_ into the settling -vessel. - -It is generally preferred not to concentrate the glue-liquor in the -pans to such a degree as required to obtain a jelly, which after -cooling, can be immediately moulded, experience having shown that less -concentrated liquors can be more readily and better clarified, and -yield a lighter and more transparent glue. - -Mr. Thomas Lambert gives the following process of cooking: The skins -are taken to the glue-boiler, which is an open vessel, 8 feet in -diameter at the top and 7 feet deep, and provided with a perforated -false bottom, through the center of which passes a two-inch pipe, one -end dipping below a layer of water at the bottom, the other projecting -about half the height of the boiler, this part being covered with a -perforated hood to spray the liquor through the mass. The skins are -placed on the false bottom and the added water at the bottom of the -boiler is brought to the boil by means of a steam pipe. The steam not -being able to escape quickly through the dense mass of glue-stock -above, exerts a pressure on the water, forces it through the pipe, to -be sprayed through the mass, and ultimately works its way to the bottom -of the boiler to be forced up again. This continual circulation of the -hot liquor rapidly dissolves the gelatinous matter, and when a strength -of 18 per cent. dry glue is reached, the first run is made to the -evaporating pan, the liquor passing through a filter of fine shavings, -to remove any suspended matter. Fresh water is added to the boiler, and -the boiling renewed. Three extractions are usually made, the last being -used for size. - -In order to avoid annoyance to the neighborhood from foul odors, -Terne’s glue-boiler shown in Fig. 14 may be recommended. The lead-lined -iron boiler _A_, with manholes _B_ and _C_, on top and side, is -furnished with a false perforated bottom upon which the glue-stock is -placed. Underneath the false bottom lies the coil _E_ with valve-box -_e_. The boiler is filled through the upper manhole with glue-stock and -water admitted, steam being at the same time introduced in the coil -and in order to quickly heat the water, direct steam is also admitted -to the boiler through the pipe _F_ and cock _G_. When the water is -boiling the cocks _G_ and _F_ are closed, the coil furnishing now -sufficient heat. During boiling some steam is allowed to escape through -the partly-opened cock _L_, all badly-smelling gases being thereby -carried to the fire-box of a boiler where they are burned. When boiling -is finished, the glue liquor remains for a short time in the boiler to -allow the melted fat to separate on the surface, the cocks _K_{1}_ and -_K_{5}_ and serving for drawing off the fat. The insoluble residues of -the glue-stock remain upon the false bottom and are taken out through -the manhole _C_. - -[Illustration: FIG. 14.] - - -2. CLARIFYING THE GLUE-LIQUOR. - -The clearness of glue, _i. e._, its freedom from undissolved -substances, is by no means a criterion of its value as an agglutinant, -since pulverulent inorganic substances (white lead) are frequently -intentionally introduced into some varieties, for instance into -Russian glue, without injury to their adhesive power. But as a turbid -appearance may also be an indication of unsoundness and decomposition, -the manufacturer endeavors by all means to obtain a clear product. - -A strict distinction should be made between clearness and color. -Very dark-colored glue may be very clear, and a very pale variety -the reverse, yet both possess excellent qualities. Both properties, -clearness and light color, cannot be obtained by the same process. - -Clearness will be first referred to. If the glue-stock has been -properly prepared by rendering adhering particles of blood and fat -innoxious by liming and subsequent careful washing, the separation of -the few remaining impurities, which may have passed through the straw -filter, is readily effected by allowing the liquor to stand, care -being had to keep it liquid as long as possible to give the grease -time to rise and the flocculent and fibrous impurities to settle. This -is best effected in a wooden vat surrounded by a wooden or sheet-iron -jacket, the intermediate space between jacket and vat being filled -with a non-conductor of heat, or, if required, it may be heated by the -introduction of steam. The grease is skimmed off as it rises, and when -the solid particles have settled the liquor is drawn off through a pipe -placed a short distance above the bottom of the vat. - -The size of the clarifying vat depends on the size of the boiler. -It is, however, best to have two vats for each boiler, in order to -keep the first liquor, which is always clearer and more concentrated, -separate from the last run. To be able to draw the upper layers of -purer liquor into cooling boxes by themselves, the vats are provided -with faucets at different heights. - -To prevent putrefaction of the liquor which readily sets in during -settling at a higher temperature, the vats should be kept scrupulously -clean, and from time to time rinsed with clean, hot water. It is also -advisable to line them with sheet-iron. - -Should the above-described mechanical separation not prove sufficient, -recourse must be had to other means. Alum and sulphate of alumina have -long been used for clarifying, 1 lb. of either of them, pulverized, -added to every 300 gallons of liquor, being as a rule sufficient. -Either of these chemicals removes the albuminous and extractive -constituents of the solution, and converts the dissolved free lime into -sulphate of lime, which settles readily, and prevents putrefaction of -the glue solution while drying under unfavorable circumstances. The -quantity of alum mentioned above does not impair the quality of the -glue. - -Albumen is sometimes used for the better qualities of glue, and -generally for gelatine, but a cheaper substitute is fresh blood, which -contains albumen and fibrin. Dry albumen is dissolved in cold water, -or white of egg is used direct, if procurable. Before adding either of -these substances, the liquor is cooled to 130° F., and the clarifier -well stirred in; then the temperature is raised to about 200° F., when -coagulation occurs, and the precipitate entangles the impurities and -falls to the bottom, requiring, however, from twelve to twenty-four -hours to clear. It is said that glues clarified with albumen have a -characteristic soapy smell and show a tendency to foam. - -The precipitation of the lime might be better effected by oxalic acid, -and the organic substances removed as scum by adding to the boiling -mass some astringent matter, such as a decoction of oak bark or hops; -but the purification has, in either case, to be done at the expense of -glutin. - -A glue liquor, which does not clarify by these means, is not sound, and -is derived either from spoiled raw materials, or such as have not been -thoroughly prepared, or has been injured in boiling. - -A far more difficult matter than the removal of mechanical admixtures -is to free the liquor from the coloring substances from which -it derives its color, and to discolor it without injury to the -characteristic qualities of the glue. - -The use of animal charcoal for such large quantities of somewhat -thickly-fluid solutions, which are liable to spoil at the high -temperature at which they would have to be filtered, is very -difficult, and the result not favorable, except the solutions could be -successfully deprived of their tendency to putrefy. The use of carbolic -acid is also in this case the only means of removing the great tendency -of the liquor to putrefy, and hence, if the liquor is to be discolored -by treatment with animal charcoal, it can only be done without danger -to the glue, by mixing it with carbolic acid. - -The object is more easily effected by bleaching the raw materials -previous to boiling them to glue. - -This is accomplished by placing the glue-stock, thoroughly limed and -while still moist, in a bath of chloride of lime, not too strong, as -otherwise the solution of the materials becomes difficult. A bath of -the proper concentration is made by dissolving about 9 ozs. of chloride -of lime in sufficient water to cover 110 lbs. of glue-stock. After one -hour add sufficient hydrochloric acid to obtain an acid reaction, which -is recognized by litmus-paper dipped in the bath turning red. - -Although the glue-stock is not bleached entirely through by this -process, the thin portions and outsides of the thick material acquire -a lighter color, and the first run of glue solution will have a light -color and can then be treated further without much difficulty. - -Sulphurous acid has been successfully used for the production of -colorless glue without the necessity of boiling. - -Waste of hides and skins is the only available material for this -process. Place the waste in water until putrefaction sets in. When this -is the case wash the material in a bag or wicker basket in running -water. Then pour 2½ parts of sulphurous acid over 12 parts of wet -material, mix the whole thoroughly and let it stand in a hermetically -closed vessel for 24 hours. Now draw off the acid, and after washing -the material thoroughly repeat the operation. When the vessel -containing the mixture of material and sulphurous acid is opened for -the second time the foul odor should be entirely superseded by that of -sulphurous acid, this being a sure indication of the correct execution -of the process. Wash the material, and, after squeezing, throw it -into a vat large enough not to be filled by it more than two-thirds -full. After filling the vat with water allow the mass to digest at a -temperature of 109.4° F. for 24 hours. The result will be a gelatinous -solution, which is drawn off and converted into glue. The undissolved -residue is transformed into gelatinous solution by pouring water over -it and allowing it to stand at a somewhat higher temperature. - -For carrying out this process and that of bleaching with chloride -of lime it is best to use a vat provided with a stirring apparatus, -somewhat like a hollander used by pape-rmakers, as being most suitable -for washing, disintegrating and mixing the material. - -Glue-liquor may also be successfully bleached with sulphurous acid, and -in speaking later on of the manufacture of bone glue, a very practical -apparatus for this purpose will be described. - -Glue-liquor bleached by sulphurous acid clarifies very readily and -is protected from spoiling. The resulting glue remains, however, -quite acid, and cannot be used for all purposes, especially not in -combination with colors, chemicals, etc., upon which the acid has a -destructive effect. - - -3. FORMING OR MOULDING THE GLUE. - -After clarifying, the liquor is run into moulds of deal wood or sheet -iron, lightly joined and of a rectangular form, slightly converging -towards the bottom so as to allow the more ready detachment of their -contents. They are about 3.25 feet long, 10 inches wide at the top, and -7¾ inches at the bottom, and 5 inches deep. When very regular cakes of -glue are desired, cross grooves of the required shape are cut in the -bottoms. After being well cleansed and ranged upon a level the boxes -are filled to the brim through large funnels with strainer cloths -affixed to their barrels. It is best to place them upon perfectly clean -stone flagging slightly inclined towards a reservoir for the reception -of such portions of their contents as may run over. The apartment in -which the work is performed should be clean and airy, a dry cellar -being the best for the purpose. In place of a large number of boxes, a -shallow vessel lined with sheet-iron and capable of holding the entire -quantity of liquor is sometimes used, from which the solid jelly is cut -out in cubic masses, which are further divided. - -This arrangement can only be recommended for establishments where -but one variety of glue is produced, and the different layers in the -clarifying vat are not separated according to their clearness. Before -running the liquor into the boxes the latter should be moistened with -water, or, if made of wood, coated with oil, stearine, or paraffin to -prevent the liquor from penetrating the wood and the solidifying glue -from adhering to the sides. - -After the solidification of the glue, which generally takes place in -twelve to eighteen hours, the boxes are inverted upon a table with a -smooth top of wood or stone previously wetted, so as to prevent the -adherence of the gelatinous cake to its surface. To detach it from the -sides of the boxes the moistened blade of a large knife is generally -used. - -Cutting the cubes of glue into commercial cakes or sheets is readily -accomplished by observing the following instructions:— - -The shape of the cakes depends principally on custom. The consumer is -used to a certain variety of glue, and if it is not offered to him in -the customary shape, he might refuse it and take his custom elsewhere. -The quality of the glue is the next point to be considered. If very -dark, it is advisable to cut the glue into thin cakes, and if turbid, -into thick ones, in order to make this defect the less apparent. -Thicker cakes can also be cut if the conditions for drying them are -favorable, and thinner ones if the reverse is the case. - -The mass is first divided by a steel or brass wire stretched over a -frame, like a bow saw, into horizontal layers. The size of these layers -is regulated by guides which are placed at distances corresponding with -the desired thickness of the cake of glue. Instead of one wire, as many -as the cakes of glue to be cut, can be stretched over the frame, which -is best made of iron and provided with conical pins by means of which -the wires can be tightened, in the same manner as piano strings, when -they have become slack by use. - -The width and thickness of the cakes of glue are regulated by the -distance of the wires from each other, and the length by the width of -the box. The cakes thus formed are dexterously lifted from the block -with the moist blade of a large knife and placed upon nets. - -Instead of using wooden or sheet-iron cooling-boxes, it is recommended -to pour a layer of liquor of the desired thickness of the glue cakes -upon large polished stone slabs, and when congealed, cut it into -sheets, which are placed upon the nets to dry. The advantages of this -method are obvious. The liquor cools more quickly by being exposed in a -thin layer upon a large surface, which reduces the danger of spoiling, -and a strong evaporation of water and consequent concentration take -place. Besides, the cakes show the smooth surface of the polished -stone, and become in a short time so hard, that when placed upon the -nets, the twine will make no impression upon them. - -Liquors which in gelatinizing do not become very solid, are not run -into forming boxes, but upon glass or zinc plates, and thus spread out -in a thin layer, acquire sufficient solidity to be removed cake by cake -after being cut. The plates upon which the glue is run are placed in -frames and laid upon a table furnished with a rim about 1 inch deep. -To accelerate gelatinization of the liquor, the table is flooded with -water before placing the plates upon it. - -Where cooling-boxes are used, the jelly when completely congealed is -placed upon a table with a stone plate, by inverting the boxes, and -then cut into cakes. Figs. 15 and 16 represent the tools for cutting -the jelly into cakes. The block of glue is laid upon the surface _A_, -Fig. 15, and the frame, _B_, is gently drawn along in the grooves, _a_. -In the upright portion of the frame are fixed wires at such a distance -from each other as required for the thickness of the cakes to be cut. - -[Illustration: FIG. 15.] - -[Illustration: FIG. 16.] - -When the block of glue has been cut in this direction, it is divided -by cuts perpendicular to the former, into cakes of a size in which the -finished product is to be brought into commerce. The apparatus shown in -Fig. 16 serves for this purpose. The vertical bars, _a_, furnished with -the wire, _b b_, serve as guides. The sheets thus formed are lifted -from the block with the moist blade of a large knife, and laid upon -nets. - -The machine shown in Figs. 17 and 18 is the invention of Mr. J. -Schneible, and it is for slicing and spreading glue-jelly preparatory -to drying, and it consists in the combination of a reciprocating cutter -with the jelly-box and a traveling belt-carrying frame for receiving -the slices as cut by the knife. - -Fig. 17 is a partly sectional side view of the machine, and Fig. 18 is -a cross-section of the same. - -[Illustration: FIG. 17.] - -_A A_ are side bars of the supporting frame, fitted at the ends with -cross-shafts, _a´_, carrying pulleys, _a a_, around which are endless -belts, _b b_. _c c_ are slide-ways upon the bars, _A_, and _d d_ are -slides carrying a cross-plate, _e_, and also a plate, _f_, to which -plate _e_ is attached a knife or cutter, _g_, the cutting edge of which -is at the edge of the plate, _f_, and about the same thickness as the -slices to be cut. The cross-shaft, _h_, is fitted in boxes on bars, -_A_, and near one end thereof it is provided with cranks at its ends, -which connect by rods, _i_, to the slides, _d_. - -[Illustration: FIG. 18.] - -From the opposite ends of the slides, rods, _k_, pass to loose arms, -_l_, on the shaft at the opposite end of the machine, and the arms, -_l_, carry pawls, _l´_, that engage ratchet-wheels, _m_, fixed on -the shaft, so that the shaft, _h_, being revolved, the slides, with -plates, _e f_, are reciprocated, and at the backward movement of the -cutter the pawls engage the ratchet-wheels, and belts, _b_, are moved a -distance equal to the movement of the knife. - -The jelly-box, _n_, is fixed to side bars, _A_, by brackets at its -ends, as shown in Fig. 18, and is placed above the cutter and the -plate, _e_, so that when the plate, _f_, is drawn out from beneath the -box the plate, _e_, takes its place for holding up the block of jelly. - -In operation the block of jelly is placed in box _n_, resting on plate -_e_. A frame provided with netting—such as is used for drying glue—is -placed on belts, _b_, beneath the box, and the shaft, _h_, being -rotated by power, the cutter moves forward and cuts a slice from the -jelly. The plate, _f_, at the same time moving away, the slice passes -upon the frame, and the return movement taking place, plate _f_ is -carried beneath the jelly-block, and the belts being at the same time -moved, the frame is carried forward in position for receiving the next -slice apart from the first one. In this manner, as slice after slice -is cut, they are spread on the frame, and the frames, when filled, -are carried to the end of the machine for removal. The plate, _f_, is -adjustable, so as to vary the thickness of the slices cut. - -The box may be divided into cells of any size desired, so that each -movement of the knife will cut a slice from the bottom of each cell, -and the box extending the full width of the drying frames, all the -slices cut at once will be properly spread. - -In order to keep the plates, _e f_, moist, so as to prevent the -glue-jelly from sticking thereto, there are fitted at the sides of the -jelly-box, _n_, open-bottomed boxes, _o_, containing fibrous material -soaked with water, which, resting on plates, _e f_, keeps their -surfaces moist. - -The machine saves the troublesome and expensive work of spreading the -jelly by hand, as has been heretofore practiced. - -The knife is to be attached to plate, _e_, in any suitable manner, and -the surface of plate, _f_, may be corrugated, so as to slide on the -jelly more readily. - -[Illustration: FIG. 19.] - -The cutting apparatus patented by M. Devoulx, of Marseilles, is much -used in France. The machine stands upon a board or table, upon which -are fastened two uprights, far enough apart to allow of the passage of -a truck carrying the glue, which is cut into cakes by blades or wires -stretched between the uprights. - -[Illustration: FIG. 20.] - -Fig. 19 shows the perspective elevation of the machine with its truck. -The upper part is filled up for the reception of the glue to be cut up -into cakes. The sides are omitted in this figure in order to admit of -a better explanation of the separate parts. - -Fig. 20 gives the same view, except that the truck, the upper part of -which is closed, is between the uprights, and contains the glue to be -cut. - -Fig. 21 represents the moment the wires have passed through the glue -and cut it into cakes. In all the figures, _a_ is the wooden frame upon -which the machine rests, _b_ the table-plate fastened to the frame, -_c_ and _d_ are the uprights, between which the cutting wires are -stretched, and _f_ the truck carrying the glue. - -[Illustration: FIG. 21.] - -[Illustration: FIG. 22.] - -Figs. 22 and 23 show the truck by itself, _g_ representing the bottom, -and _h_ the back, which is provided with slight grooves, into which -the wires catch to assure the entire cutting through of the block of -jelly; _i_ is the upper part of the truck, which opens by means of a -hinge, and when closed is fastened with the pin, _k_. This upper part -of the truck is fastened to the back part of the truck by means of a -screw, which allows it to be set higher or lower, according to the size -of the block of jelly to be cut; _m_ is the bar of a rack fastened to -the truck, and serves for moving the latter. The driving gear, _n_, the -shaft of which carries a crank, _o_, catches into the rack. - -[Illustration: FIG. 23.] - -Two boards, one on each side of the truck, serve to keep the block of -jelly in position, and guide the truck. - -With this machine 120,000 to 130,000 cakes can be cut in five or six -hours. - - -3. DRYING THE CAKES OF GLUE. - -Drying the cakes is without doubt the most precarious part of the -manufacture. The jelly contains a large quantity of water which, to -prevent decomposition of the jelly before it is converted into glue, -must be evaporated as quickly as possible. In favorable weather, drying -may be accomplished either in the open air or in covered sheds. - -Drying in the open air is connected with many inconveniences, for if -the sun strikes the cakes of jelly when they still contain a large -quantity of water, they may become soft so as to run through the -meshes of the net, or they may dry so quickly as to prevent them from -contracting to their proper size without numerous cracks and fissures. -If frost supervenes, numerous cracks may be formed in the cakes from -the congelation of their water, or a shower of rain may cause much work -and damage. In consideration of all these inconveniences, it is best to -conduct the operation in a drying-room. - -To insure a constant circulation of air, which is absolutely necessary -for the expulsion of the aqueous vapor caused by the evaporation of -such a large quantity of water, the drying-room should be at least 10 -feet high, even if intended for summer use only, and the windows be -provided with Venetian blinds so as to shut out the sun, if necessary, -without disturbing the circulation of air. - -To dry the cakes in heated rooms in winter is a more difficult matter, -as provision has to be made for the removal of the aqueous vapor, and -a current of warm dry air has to be kept up at the same time. But such -a room is an absolute necessity for the manufacturer on a large scale, -who, in order to carry on his business without interruption throughout -the entire year, must be independent of the changes of wind and weather. - -[Illustration: FIG. 24.] - -The size of the drying-room should be proportional to the daily -production. Constructions are fitted up with the requisite frames for -the reception of the glue cakes, and are heated by steam pipes arranged -along the walls. In the floor in the immediate neighborhood of the -steam pipes are openings, which can be opened and shut at pleasure, -for the admission of fresh dry air. The latter on entering the room -is heated, and after passing over the frames and absorbing water from -the glue cakes, escapes through openings in the ceiling to a space -above it from which it is withdrawn by means of ventilators in the -roof. A constant change of air must be kept up. The quick drying of -the glue is of the utmost importance, as otherwise the jelly putrefies -either entirely or partially, and the glue acquires a turbid and mean -appearance. Too much heat causes the cakes to bend and crack. The -cakes are laid upon widemeshed nets of twine stretched in frames 6½ -to 8 feet long and 3¼ feet wide. Fig. 24 represents the form of nets -commonly used. The nets are placed upon frames, such as shown in Fig. -25, arranged around the drying-room in the neighborhood of the steam -pipes and air flues. As the cakes have to be occasionally turned upside -down upon the nets, the latter must be placed at convenient distances, -one above the other in the frames. - -[Illustration: FIG. 25.] - -The use of twine netting has been found to be attended with many -disadvantages, the principal ones of which are given by S. Rideal as -follows: - -1. “Being freely handled in the making, the netting is almost always -impregnated with dangerous organisms which penetrate the moist glue -cakes, and cause moulding or putrefaction. When this occurs, it is -usually attributed to a state of the atmosphere, but if the cakes are -examined, the alteration will generally be found to originate along -the lines made by the netting. The fault could be cured by sterilizing -the net for an hour at 212° to 248° F. in a hot oven, but besides the -expense, the fibre is thereby weakened. Moreover, the spores of a few -bacteria, such as _Bacillus subtilis_, which is widely distributed and -has the power of liquefying gelatine, will bear a heat of 248° F. for -over an hour, and still be capable of growing. - -2. “However smooth the fibre, the glue will stick in places, leaving -small remains, which being hygroscopic, become ’sour,’ and set up the -objectionable bacterial changes in the subsequent batches. - -3. “Owing to sagging, rotting, scouring, or wearing into holes, the -life of cotton or hemp netting is so short that the constant renewal is -a considerable item. A whole batch is frequently spoilt by the fault -of a net. In some works, heaps of old netting are found, which become -very putrid in the rain and sun, and give rise to mysterious bacterial -inroads in the factory. In others they are regularly burnt under the -boilers. - -4. “The considerable overlap or selvedge required for securing the -edges of the net involves a waste of the area, and also some difficulty -in refixing.” - -For this reason metallic netting has been largely adopted. The best -material has proved to be a heavily galvanized iron-wire netting having -no less than 15 to 25 per cent. of its weight of zinc. It can be -strengthened by longitudinal and transverse wires or ribs. It must be -examined by the microscope to see that it is perfectly free from holes -or cracks, and should last at least two years in constant use. - -The temperature of the drying-room requires careful regulation, and -should never be allowed to rise above 68° to 77° F., as otherwise the -glue would soften and run through the meshes of the net, or adhere so -firmly to the twine as to require the nets to be put in hot water for -its separation. Dryness of air is of far greater importance in the -drying process than a high temperature. To promote this dryness of air -and prevent the aqueous vapor from condensing, evaporating, and again -condensing upon the cold walls of the room, they are wainscoted. Thus -protected by a bad conductor, they acquire a higher temperature, and -the aqueous vapor, instead of being precipitated upon them, is carried -off by the air-currents. - -As the cakes placed in the immediate neighborhood of the steam pipes -and near the floor where the dry air enters, dry quickest, the nets -containing them are shifted after some time to a higher part of the -drying-room and their former places filled with cakes still wet. When -the cakes are dry, they are finally desiccated in a room at a higher -temperature, which serves to harden and improve them. - -In modern times drying-rooms have been almost entirely abandoned and -in this country long drying galleries are used, sometimes 250 feet -in length and 6 to 8 feet square, with traveling platforms on rails -carrying the sheets of glue on stout galvanized netting. Wood is found -to be a better material for the galleries than stone or brick. - -Figs. 26 to 28 show an apparatus for drying glue which is the invention -of W. A. Hoeveller. - -Fig. 26 is a plan section, and Fig. 27 a side elevation in section, of -this improved drying-alley. Fig. 28 is an end view in section. - -The form and arrangement are as follows:— - -_A B_ represent the two parts of the alley, separated by the partition -_C_, which is shorter than the alley, so as to leave a communicating -space at both ends. - -At the front of section _A_, is located a blower, _D_, actuated by a -steam-engine or other motor, _E_, also located within the walls of the -alley. The whole current from blower _D_, is directed through section -_A_ of the alley, whence it turns into section _B_, and comes back -through it, to be again drawn into and forced out of the blower into -section _A_. By this means the contained air of the alley is set in -continuous motion through the two sections successively, and as the -structure is made as air-tight as practicable in such cases, the air -remains unchanged until the doors _F_, or either of them, are opened to -discharge the vitiated air and let in the fresh. - -In sections _A_ and _B_, is placed the railway _a a_, to admit of the -convenient movement of the contents in process of drying, which are -generally set on cars or buggies. - -[Illustration: FIG. 26.] - -[Illustration: FIG. 27.] - -[Illustration: FIG. 28.] - -In section _A_, in front of blower _D_, is placed a steam or other -heating device, _G_, which may be of any form or design adapted to -allow the air from blower _D_ to pass through it and to heat such air -while passing therethrough. The inventor prefers the radiating coil -for such purpose, the steam entering at _b_, and emerging at _c_. At -the other end of the alley, which by the double construction is in -section _B_, just back of the blower and heating-coil, there is placed -a condensing-coil, _H_, of a construction similar to coil _G_, and -having inlet _d_, and outlet _e_. Through this condenser there is kept -flowing a refrigerating liquid or brine, which renders the condenser -very cold. The continuous current of air from the blower passes over -the contents of the cars or trays in the alley and takes up moisture in -its passage. After such passage the air is charged with moisture and -comes in contact with the coils of the condenser _H_, upon which the -charge of moisture is condensed, and the air emerges dry again, enters -the blower, and is again made the vehicle by which the moisture of the -glue or other contents is transported to and deposited on the condenser. - -In drying glue by this method do not use the steam-coil at the first -stage of drying a charge, as the drying should not be effected too -rapidly; but as soon as the product begins to stiffen properly, admit -the steam to the coil _G_, and thereafter the operation is continuous, -as above described. - -By doubling up the alley into two sections, as shown, the inventor is -enabled to erect the alley in a more contracted space. In a length of -ninety feet he obtains the benefit of a single alley one hundred and -eighty feet long. Section _B_ may, if desired, be located on top of -section _A_. Doors may be located wherever desired, to facilitate the -movement of the trays or cars and the placing of them in and their -removal from the alley. - -[Illustration: FIG. 29.] - -By the above apparatus the drying can be perfected in a very much -shorter time than can be done by the old alleys, and operations can be -conducted in hot weather without hindrance from the condition of the -atmosphere. - -In cases where the atmosphere is dry enough to dispense with the -heater and the condenser, the inventor can throw the doors _F_ wide -open, extend the partition _C_ out to that end of the alley, and then -preserve a continuous forced draft of sufficiently dry air in both -alleys for the purpose. As there are many days during the year fine -enough to give reasonably dry air, operations can be conducted with -the blower alone in this way, and thus economize the steam and the -refrigerating-brine. - -[Illustration: FIG. 30.] - -Figs. 29 and 30 show a longitudinal section, with upper and ground -floor plans of a modern drying-house, as given by Thomas Lambert. In -the ground floor the whole of the liquors are jellied in coolers, -and then cut into cakes by the two cutting machines in the centre. -Here a hoist, _E_, Fig. 30, is placed which carries the cut cakes on -“glasses” to the floor above. This forms the drying-floor, and is -partitioned off in three divisions, running nearly the length of the -building. The two outer divisions form the tunnels proper, and at the -ends are fixed two powerful revolving fans, driven at high speed and -drawing the air through the tunnels at a high rate. At the opposite -ends of the fans are fixed a series of 6-inch pipes, heated up by -waste steam, and the air passing between is warmed up to any desired -temperature, of necessity below 78° F. In the center passage a number -of girls are employed in transferring the cut cakes to the nets, which -are built upon a carriage running on a small railway. The carriage -with the complement of filled nets is run to the end of the division, -transferred to the lower railway, _C_, by which it is carried either -to the right or left hand tunnels as desired; the glue when dried on -the nets is run to the other end and by another lower railway brought -to the middle division, and ultimately by the hoist raised to a large -store-room, seen in section, where the glue is sorted and bagged. At -the end of the store-room is placed a grinding machine, and all the -off-color and twisted cakes are ground to a powder and sold as powdered -glue. The manufacturer by varying the size of the cake, its thickness, -and its color, may make any number of grades from the same boiling. - -Fleck proposes to accelerate the drying of glue by utilizing the -water-absorbing power of some salts, such as Epsom and Glauber’s salts, -ammonium sulphate, crystallized acid sodium sulphate, etc., for the -purpose of withdrawing water from the glue cakes. For the practical -application of this principal a shallow, water-tight, wooden box is -required. The bottom of the box is sprinkled with a layer of the -water-absorbing salt about half an inch deep, and covered with a moist -linen cloth. Upon this is placed the jelly cut into sheets and also -covered with a moist cloth, a layer of salt being finally scattered -over it. After standing for a few hours, the box is slightly inclined -and the salt solution allowed to drain off through a hole in the -bottom, the dropping ceasing in from 12 to 18 hours. If now the upper -cloth is taken off with its layer of salt, the glue beneath it will be -found so far deprived of its moisture that when placed in the sun or -exposed to other heat, it will become completely dry in a short time -without either melting or spoiling, and in winter may be laid upon -drying-floors with the same result. The salt-solution formed may be -evaporated to crystallization and the salt thus obtained be again used. - -After the treatment with the salt, the jelly contains 70 to 75 per -cent. of anhydrous glue, while the content in jelly not thus treated -varies between 7 and 28 per cent. according to the concentration of the -liquor from which it has been derived. It is claimed that the adhesive -power of the glue is not injured by this treatment. - -Commercial glue must not only be thoroughly dry, but should also -present a good appearance, showing especially lustre. However, after -drying, the glue is dull, spotted, dusty and sometimes even mouldy. To -give a good lustrous appearance the dry cakes are dipped in warm water -and replaced upon the nets to dry. - - - - -CHAPTER V. - -MANUFACTURE OF BONE-GLUE. - - -The manufacture of bone-glue differs chiefly from that of skin-glue in -the processes employed for the conversion of the glue-yielding tissues. -This conversion may be effected by boiling the bones with water, or -subjecting them to the action of steam, or by first extracting their -mineral constituents with acid, and boiling the remaining cartilaginous -mass with water until dissolved. - -When the finest quality of all varieties of glue, namely, colorless -gelatine, is to be manufactured, the bones should not be comminuted in -a stamping mill, because in consequence of the unavoidable development -of heat, they acquire a slightly empyreumatic odor which adheres to the -gelatine prepared from them, and cannot be removed. - -In factories working on a small scale, the bones are comminuted by -hand, being placed upon a grate-like support of heavy iron rods -and crushed with a wooden hammer, the face of which is studded -with big-headed nails. In larger establishments the crushing rolls -previously described are used, and in order to lessen the effect of -heating as much as possible, the crushed bones are allowed to fall -directly into a vessel filled with water. - -Fat being a very valuable constituent of bones, it should be gained -as completely as possible, by boiling or steaming the bones, or by -extracting them by means of a solvent, such as benzine or carbon -disulphide. - - -1. BOILING BONES. - -This is the older and more incomplete process of extracting the fat. -The bones are placed in a boiler, covered with water so that it -stands a few inches deep over them, and the whole is boiled over an -open fire. The melted fat collecting on the surface of the water is -skimmed off. By boiling, a portion of the glue-yielding substance is, -of course, converted into glue, and passes into the water. In order not -to lose this glue, the same water is repeatedly used for boiling fresh -quantities of bones, and is finally used for feeding pigs. By this -method 4 to 5 per cent. of fat is at the utmost obtained. - -The bone fat obtained by direct boiling of the bones, is, if entirely -fresh material has not been used, of very inferior quality. It is dark -yellow to deep brown and of a disagreeable odor. It is only fit for -certain purposes, and to be utilized in the manufacture of soap has to -undergo a special process of purification, whereby it is rendered white -and odorless. - - -2. STEAMING BONES. - -In order to obtain a larger quantity of fat than is possible by -boiling, the bones are preferably steamed, _i. e._, subjected to the -action of high-pressure steam. This is effected in a closed cylinder -of thick boiler-plate, into which steam of ½ to 1 atmosphere pressure -is admitted. The cylinder is provided with a perforated false bottom -upon which the bones are placed. By steaming for two or three hours, -all the fat is extracted from the bones and collects, together with -the condensed water formed by the steam coming in contact with the -cold bones, underneath the false bottom. However, by the continued -action of high-pressure steam upon the bones, a considerable portion -of the glue-yielding tissue is converted into glue, which passes into -the resulting liquor. This, however, is no drawback if only fat and -glue are to be obtained from the bones, since by continued steaming, a -liquor still richer in glue results, and need only be evaporated. But, -as a rule, the greater portion of the bones, especially the granulated -parts, are to be utilized in the manufacture of animal charcoal, and, -hence, great care has to be observed in steaming. - -Animal charcoal is produced by calcining bones in vessels from which -the air is excluded, whereby the glue-yielding tissue is converted -into carbon, which is distributed upon the bone-earth. Since the value -of animal charcoal depends on the quantity of carbon it contains, a -product prepared from bones highly steamed, will evidently be of little -value, as a considerable portion of the glue-yielding substance has -been converted into glue. - -If the bones are to be used for the production of animal charcoal they -should be subjected to the action of high-pressure steam only long -enough to extract the fat, but the resulting glue-liquor is very thin -and difficult to work. The watery glue-liquor is first drawn off, and -the fat which comes last is caught by itself. The thin glue-liquor is -evaporated in vacuum. - - -3. EXTRACTION OF BONES. - -To avoid the loss of glue-yielding substance which is unavoidable in -steaming bones, even if only for a short time, in many plants the -fat is now extracted by treating the bones with benzine or carbon -disulphide. No loss of glue-yielding substance being involved by this -process, bones thus treated yield the best quality of animal charcoal. - -The fat obtained by extraction with carbon disulphide has such a -disagreeable odor as to render it almost worthless. In addition this -solvent is very volatile, consequently very inflammable, and is also -very poisonous. For these reasons its use for the extraction of fat has -been almost entirely abandoned. - -Figs. 31 and 32 show an apparatus for the use of benzine which is -the invention of Messrs. Wm. Adamson and Charles F. A. Simonis, -of Philadelphia, Pa. It is for the purpose of treating animal and -vegetable substances with hydrocarbons for extracting therefrom oily, -fatty and resinous matter; and the object of this invention is to -cause hydrocarbons to trickle through such substances instead of -flooding the same, so that it will take up the oily, fatty and resinous -matter without any of the albuminous or gelatinous ingredients. - -Fig. 31 is a vertical section of apparatus wherewith this invention may -be carried into effect; Fig. 32, an inverted plan view of part of Fig. -31. - -[Illustration: FIG. 31.] - -[Illustration: FIG. 32.] - -_A_ is a vessel, preferably of cylindrical form, and containing an -upper perforated diaphragm, _a_, and lower perforated diaphragm, _b_, -the former having a central opening, through which the material to be -treated may be introduced between the two diaphragms, and this opening -having a detachable perforated cover, _d_. - -On the top of the vessel there is an opening, _e_, furnished with a -detachable cover, _f_, and at the bottom of the vessel there is an -outlet-pipe, _h_, furnished with a suitable cock or valve, _i_. - -Liquid hydrocarbon, preferable such as is of a volatile -character—benzine, benzole, or gasoline, for instance—is introduced -into the vessel above the diaphragm _a_ through a pipe, _H_, and -perforated ring, _I_, or otherwise, the hydrocarbon passing through -the diaphragm and falls in a shower on the substance contained in the -vessel. - -The hydrocarbon will trickle through the mass, taking up whatever oily, -resinous, or fatty matter it comes in contact with until it falls -through the lower diaphragm into the space _D_, whence it may be drawn -off from time to time through the outlet-pipe, _h_. - -In extracting oily, fatty, or resinous matter from vegetable or animal -substances by hydrocarbons, it has been the practice either to subject -them to hydrocarbon vapors, or to immerse or steep the substances in -hydrocarbon until the latter takes up the oily, fatty, or resinous -matter. - -The vapor plan is preferable in treating wet animal substances, such as -offal; but for dry vegetable or animal matter—seeds, for instance, or -the residuum resulting from the rendering of tallow—we prefer the plan -before described. - -The flooding or steeping of animal or vegetable matter in liquid -hydrocarbon results in a mixture or emulsion of gelatinous, albuminous, -and fatty or oily matter, combined with animal or vegetable tissues, -the whole forming an amalgamated mass; hence, whatever fatty or oily -matter is extracted is accompanied by more or less of the suspended -gelatine or albumen, either of which is more difficult to remove from -the oil or fat, and has a tendency to discolor the same. - -This difficulty, it has been found, can be obviated by preventing the -hydrocarbon from remaining in a quiescent state in contact with the -material; in other words, by causing it to trickle through the mass, -which, by this plan, retains its granular condition, and gives out its -oil or fat to the hydrocarbon without the albuminous or gelatinous -matter. - -In the apparatus before described, for instance, an occurrence of the -objectionable flooding of the material, tending to bring about the -results previously mentioned, is obviated by never permitting the -extract in the lower portion of the vessel _A_ to reach the lower -diaphragm _b_. By drawing off the extract from time to time, any -impediment to the free discharge of the hydrocarbon with such oily and -resinous matter as it has taken up, through the lower diaphragm, is -prevented, and a continuous dripping of the hydrocarbon through the -mass secured. - -The extract obtained by the trickling or filtering process is much more -concentrated than that obtained by the steeping and flooding process. - -_Adamson’s Method for Treating Substances with Hydrocarbon Vapor -for the Purpose of Extracting Oils, Fats, etc._ This improvement is -intended to prevent the fetid or other odors imparted to the vapor -from the substances treated from being recommunicated to the said -substances, and to the extracts obtained therefrom through the medium -of the vapor from the re-used hydrocarbon. The vapor is obtained from -benzine, benzole, etc. - -Fig. 33 represents, partly in section, the apparatus whereby the -invention may be carried into effect. - -_A_ is a vessel in which the substances have to be treated by -hydrocarbon vapor, the said substances being introduced into the vessel -through a manhole, _x_, and deposited on a perforated diaphragm, -_B_, the manhole being provided with a suitable cover. A steam-coil, -_D_, is placed in the vessel in a space beneath the diaphragm, and -liquid hydrocarbon is introduced into the said space, and is there -vaporized by the steam-coil. The vapor rising through the perforated -diaphragm permeates the substance upon the same, so as to extract -therefrom the oily, fatty, or resinous matter, which passes downward -through the diaphragm into the space below the same, whence it may be -drawn off from time to time through the discharge-pipe _j_. Liquid -hydrocarbon may be introduced from a tank, or from a source explained -hereafter, into the top of the vessel _A_, so that it will pass through -the material and be vaporized when it reaches the coil; the said -material being in this case subjected to a downward current of liquid -hydrocarbon and an upward current of vapor. - -Previous to this invention it was Mr. Adamson’s practice to cause the -vapor, after acting upon the substances in the vessel, to pass through -a worm in a condenser, the lower end of the worm communicating with the -vessel, _A_, beneath the diaphragm, as shown in Fig. 35, p. 85, so that -the hydrocarbon was used over and over again. But in practice this has -been found objectionable in many cases for the following reason:— - -In treating animal offal, for instance, for the extraction of fats, -fetid odors are imparted to the hydrocarbon vapor, and remain, to a -considerable extent, in the condensed vapor when the latter is restored -to the vessel _A_; hence, the fetid odors were recommunicated both to -the fatty extracts and to the material. The same objections have been -experienced in treating meat for preservation and vegetable matter for -the extraction of oil by hydrocarbon vapor. - -This difficulty is obviated in the following manner: The vapor-pipe -_D´_ communicates with a vessel _H_ at the top of the same, and the -vapor is met by numerous small jets of cold water—in the present -instance, from a perforated tubular ring, _m_, into which the water is -forced through a pipe _n_. - -Many different appliances may be used, such as roses, revolving jets, -etc., for causing a spray through which the vapor must pass, and by -which it must be condensed. The result of this will be a supply, _I_, -of tainted water on the bottom of the vessel, _H_, and a quantity, _J_, -of washed and purified hydrocarbon above the water, the latter having -taken up the fetid odors. - -The washed hydrocarbon may be drawn off through a pipe, _g_, into any -suitable vessel, and thence introduced through the pipe _h_ into the -vessel _A_, or may pass directly into the latter to be again vaporized -therein, the vapor after permeating the material and passing through -the pipe _D´_ being simultaneously condensed and washed in the vessel -_H_, preparatory to being returned in the condition of purified liquid -hydrocarbon to the vessel _A_. - -[Illustration: FIG. 33.] - -By the practice of this process, the inventor is enabled to obtain a -purer extract than heretofore, and, at the same time, the substances -acted upon are more free from noxious odors. - -Changes may be made in the apparatus shown in Fig. 33, as, for -instance, the vessel _A_ may consist of a horizontal hollow cylinder, -and the vaporizing of the hydrocarbon may be accomplished otherwise -than by a steam-coil. - -[Illustration: FIG. 34.] - -_Adamson’s Method for Treating Substances with Liquid Hydrocarbon for -the Purpose of Extracting Oils, Fats, etc._ This invention relates -to a method of treating animal and vegetable substances with liquid -hydrocarbons, such as benzene, benzole, etc., for the purpose of -extracting from such substances oils, fats, etc. - -The object of this improvement is to prevent the fetid and other odors -imparted to the liquid hydrocarbon by the substances treated from being -recommunicated to the substances and to the extracts therefrom by the -liquid hydrocarbon when re-used. - -In Fig. 34, there is shown a sectional view of apparatus whereby this -invention may be carried into effect. - -_A_ is a vessel into which the substances to be treated are introduced -through a manhole, _x_, provided with a suitable detachable cover, -and through an opening in the upper perforated diaphragm, _B_, a -detachable perforated plate, _b_, being placed over the opening after -the substances have been passed through the same, the substances being -supported by the lower perforated diaphragm, _B´_, beneath which is a -space for receiving the extract and liquid hydrocarbon after the latter -has percolated through the mass in the vessel. The extract, which -occupies the lowest position in the vessel, may be removed therefrom -from time to time prior to being purified by distillation or otherwise. -The liquid hydrocarbon is permitted to pass from time to time through a -pipe, _d_, into a vessel, _D_, where it is met by jets of water from a -pipe, _f_, the hydrocarbon and water being thoroughly agitated in the -vessel by a revolving paddle-wheel, _E_. This washing of the liquid -hydrocarbon may be accomplished by different appliances. For instance, -the paddle-wheel may be dispensed with, and water forced upward into -the vessel from below in the form of numerous small jets. The water and -hydrocarbon after this washing operation are permitted to pass into -the subsiding-vessel, _H_, the hydrocarbon being above and the water -below, the fetid and other odors divided by the hydrocarbon from the -substances in the vessel, _A_, having, during the washing operation, -been transferred to the water, which may be drawn off from time to time. - -The washed and purified hydrocarbon may be pumped directly through -a pipe, _m_, into the vessel, _A_, to be re-used for treating the -substances therein; or it may be pumped, first, into a reservoir, and -permitted to flow from the same into the said vessel, _A_. - -More or less hydrocarbon is wasted by being drawn off with the extract, -and to make up for this loss a supply may be introduced at intervals -from a tank through the pipe, _h_. - -By the practice of the process described above, the inventor is -enabled to obtain a purer extract than by the ordinary process of -treating substances with liquid hydrocarbon. At the same time the -substances treated will be much more free from noxious odors than when -the hydrocarbon is used over and over again without washing. - -It is not essential strictly to adhere to the apparatus shown in Fig. -34, as the construction of the apparatus will, in fact, depend in a -great measure on the locality in which it is to be situated. - -_Adamson’s Process for Removing Hydrocarbons from Substances which have -been treated therewith._ This process consists of washing from animal -and vegetable substances the hydrocarbon which they retain after being -treated therewith for the extraction of oils, fats, etc., and for other -purposes. - -Different apparatus may be employed for carrying out this process, and -it may be conducted in the same vessel in which the material is treated -with hydrocarbon. - -The vessel, which is shown in Fig. 35, has been found to answer well -for this purpose. - -This vessel is furnished with a suitable detachable cover, _a_, and -with two perforated or wire-gauze diaphragms, _b_ and _d_, both -extending across the interior of the vessel, one near the top and the -other near the bottom of the same. - -A steam-coil, _B_, communicating with any adjacent steam-generator, -is contained in the vessel below the lower diaphragm, to vaporize -the hydrocarbon, the vapor passing through the substance between the -two diaphragms and out through a pipe, _D_, which passes through a -condenser, _E_, the latter restoring the hydrocarbon to a liquid form, -in which it is reconveyed to the vessel through a pipe, _D´_. - -In practicing the washing process a pipe, _m_, to introduce water -into the vessel, and one or more outlet-pipes, _n n´_, two in the -present instance, are necessary. There may also be a pipe, _p_, through -which air can be introduced into the vessel, under the circumstances -explained hereafter. - -When the treatment of the material in the vessel with hydrocarbon -vapor or liquid hydrocarbon has been completed, steam is cut off from -the coil _B_, the pipes _D_ and _D´_ are closed, and the cover _a_ may -be removed. - -[Illustration: FIG. 35.] - -Water is now admitted through the pipe _m_ to the space in the vessel -below the diaphragm _d_, and the cocks of the outlet-pipes _n n′_ are -opened. - -The water permeates the material, passes upward through the same, and -carries with it the hydrocarbon, the latter having a tendency to rise -with the water. - -As the water, and whatever hydrocarbon accompanies it, pass through -the upper diaphragm, _b_, the hydrocarbon will at once rise to the -surface, and will pass through the upper outlet-pipe, _n_, into -any suitable receptacle, the water passing off through the lower -outlet-pipe. - -If this mode of separating the hydrocarbon from the water is practiced, -the admission of water to the vessel should be such in respect to the -outflow that the liquid will remain at or near a uniform level, that -is, the surface of the liquid should bear the relation shown in the -drawing to the upper outlet. - -The water and hydrocarbon, however, may be drawn off indiscriminately -into a suitable receptacle, and then separated by decantation; but it -is advisable in all cases that the water should extend above the mass -of material in the vessel, so that the hydrocarbon can at once rise to -the surface as it escapes from the substance. - -When the material is of such a character as to be closely packed -and not easily displaced by the upwardly-flowing water (and this -is especially the case with seeds which have been treated with -hydrocarbons), it is necessary to agitate the mass, so that the water -can gain access to every part thereof. This agitation the inventor -prefers to effect by air under pressure introduced through a pipe, _p_, -although mechanical appliances may be used for the purpose. - -It will be understood that the process may be conducted in a vessel -separate from which the substances have been treated with hydrocarbon. -A vessel similar to that shown, for instance, but without the coil and -pipes, _D D´_, may be used, and may be furnished with trunnions (shown -by dotted lines) and adapted to bearings, so as to be easily tilted -when its contents have to be removed; or the vessel may have an opening -near the lower diaphragm for the withdrawal of its contents, a suitable -detachable door being adapted to the opening. - -_F. Seltsam’s apparatus._ In this process the solvent is boiled with -the bones, previously coarsely crushed and the dust sifted out, in a -strong closed vessel, so as to obtain a higher temperature, greater -penetration and avoidance of loss. The vapor ascending condenses in the -pores, extracts the fat and collects under the false bottom as a layer -of solution which is subsequently distilled. The apparatus is shown -in Fig. 36. The cylinder, _A_, is capable of withstanding a pressure -of 10 atmospheres, and serves for the generation of steam and as an -extracting vessel. It is filled with bones and hermetically closed. -The required quantity of solvent is then brought by means of the pump, -_B_, from the reservoir, _C_, through the pipe, _D_, into the cylinder, -_A_, and the latter is heated. The vapors formed force the air through -the pipe, _E_, into the condenser, _F_, where any vapor which may be -carried along is condensed and passes through the pipe, _G_, back into -the reservoir, _C_. - -[Illustration: FIG. 36.] - -When all the air has been expelled from the apparatus and the pores -of the bones, the cock on the pipe, _E_, is closed. The cylinder, -_A_, is then heated so that a pressure of a few atmospheres prevails -in it. The vapors now act energetically upon the bones, the dissolved -fat collecting upon the cylinder; the cock on the pipe, _H_, is then -opened, and the superheated fluid discharged under high pressure into -the distilling apparatus, _J_, and the solvent is distilled off from -the fat by means of steam. The vapors of the solvent pass through -the pipe, _K_, into the condenser, _F_, and from there back into the -reservoir, _C_. - -When the manometer on _A_ indicates no pressure, the cock on the pipe, -_H_, is closed and the cylinder, _A_, again heated, the pipe, _E_, -being open, so that any solvent still adhering to the bones may escape -to the condenser, _F_. - -[Illustration: FIG. 37.] - -Figs. 37 and 38 illustrate Seltsam’s apparatus as improved by Th. -Richter, whereby the operation becomes entirely free from danger, the -vaporization of the solvent being effected by steam only, and the work -is carried on continuously. - -There are two extracting vessels, _A_ and _B_, of thick boiler-plate, -and provided with false bottoms, _G_, upon which the bones are placed, -steam being admitted into the space between the true and false bottoms. -The extracting vessels are surrounded by the jackets, _C_, and are -further provided with the vacuum gauges, _E_, and the air-cocks, _F_. - -There are, in addition, two other vessels, _H_ and _J_, which contain -water, a vessel, _K_, for the solvent, and an air-pump, _L_. The -operation is carried on as follows: - -[Illustration: FIG. 38.] - -The extracting vessels, _A_ and _B_, are charged with bones, all the -cocks, with the exception of _M_ and _N_ closed, and the air-pump, -_L_, is set in motion, whereby a vacuum is formed in _A_. When this is -sufficiently large, water is admitted from _H_ through the cock _O_ -into the space _P_. The water-cock is then closed and the steam-cock, -_Q_, opened. The steam entering the space, _R_, brings the water in -_P_ to the boiling-point, and the air-pump sucks off the steam formed -after the cock, _N_, is opened. The air-pump is then stopped and all -the cocks closed, except _S_. The solvent now passes from the vessel, -_K_, into the space _P_, and after closing the cock _S_, is evaporated -by the admission of steam into _R_. The water-cock is then opened and -cold water admitted into the jacket _C_, the solvent saturated with fat -being thereby condensed in _P_. The water is then discharged from _C_ -and steam introduced into _R_{1}_, whereby the solvent is evaporated -and forced into the extracting vessel _B_ by means of the air-pump, -_L_, after closing the cocks _M_ and _V_. - -The process is then repeated in _B_, after a vacuum has been created in -the same manner as in _A_. - -In the meanwhile the vacuum in _A_ is interrupted by opening the -air-cock _F_ and the fat drawn off through _P_ by opening the cock _U_. - -The bones freed from fat are removed through the manhole _D_, and _A_ -is charged with fresh material while the operation is carried on in -_B_. Thus the operation is continuous, the solvent passing without any -loss whatever from one extracting vessel to the other. - -[Illustration: FIG. 39.] - -Alfred Leuner’s apparatus. Fig. 39, works on the Soxhlet principle, -without pressure, using solvent and steam simultaneously. The bones are -placed in _A_ above the perforated false bottom _B_. _D_ is a steampipe -by means of which the bones are steamed as a preliminary, the surplus -steam escaping through the outlet pipe _E_. After steaming, water and -benzine are run in from the reservoir _F_, into the space under the -false bottom, and heated by the steam coil _P_. The vapors evolved -are condensed in the worm _K_, and at first run back over the bones -through the cock _L_, the vapor passing upwards to the worm through -_R_, and the condensed liquid being divided into separate streams by -the spreading plate _O_. After some time the cock _G_ is opened so that -the condensed liquid runs into the reservoir _F_, instead of flowing -back into _A_. When all the solvent has volatilized nothing but water -condenses in the worm, which is known by means of a sampling cock -attached to _A_, the draw-off cock _E_ is then opened and the watery -gelatinous solution and oily matter run off into a suitable separating -receptacle. The bones in _A_ are then discharged through a manhole, and -_A_ being refilled, the whole operation is repeated. - -_Extraction with hydrochloric acid._ If the bones are to be chiefly -worked for glue, extraction with hydrochloric acid, which has been -referred to in Chapter III, under “Bones and Cartilages” may be -highly recommended, the bones being thereby freed from their mineral -constituents and the glue-yielding substance remaining behind in a -pure state. The bones are allowed to remain in contact with the acid -till they are flexible and translucent. This may be readily recognized -by laying upon the material in the vat a bone split in two. When the -latter by the treatment with acid shows the characteristic appearance -of swollen cartilage, _i. e._, has become translucent, extraction may -be considered complete. - -The solution is then drawn off through a tap immediately above -the bottom of the vat into stoneware vessels, and conveyed to the -evaporating pans. The tap is then closed and enough water to cover the -cartilage is admitted into the vat, and the whole allowed to stand for -a few hours in order to extract as much as possible the solution of -bone-salts remaining in the cartilage. The fluid is then drawn off. It -is a quite concentrated solution of bone-salts and, mixed with an equal -volume of hydrochloric acid, may be used for the extraction of fresh -quantities of bones, or be mixed with the fluid first drawn off and -evaporated. - -The further washing of the cartilage is effected by repeatedly pouring -water over it, the operation being continued until the water running -off shows no acid reaction. Washing has to be done very carefully, -since glue-solution obtained from cartilage containing but a very small -quantity of acid will not congeal. It is, therefore, advisable to add -to the last wash-water 1 per cent. of soda, this quantity being quite -sufficient for the neutralization of the last traces of acid. - -_Sulphurous acid process._ In this country sulphurous acid is largely -employed in the manufacture of glue derived from bones. When ordinary -bones are treated with a current of moist sulphurous acid gas, they -absorb from 10 to 12 per cent. of their weight of the gas in the -course of 12 hours. The amount may increase to 15 or 20 per cent. -on longer treatment, but the excess will then disappear on exposure -to air. Messrs. Grillo and Schroeder of Düsseldorf, who patented -this process in 1894, believe that this is simply due to the calcium -phosphate present in the bones, and remark that an absorption of 11 to -12 per cent. on the gross weight amounts to 16 or 17 per cent. of the -inorganic constituents, and corresponds to the equation: - - Ca_{3}(PO_{4})_{2} + SO_{2} + H_{2}O = 2CaHPO_{4} + CaSO_{3}, - -the sulphurous acid simply acting in the same way as sulphuric acid -does in the manufacture of superphosphate, but being a milder acid -than sulphuric, the alteration of the organic constituents which are -available for glue-stock can be almost entirely avoided. The acid -phosphate is soluble in water, therefore the bones after treatment are -easily disintegrated by boiling water when a large portion of the lime -remains in the sediment, while the gelatine is dissolved. - -The process as commercially conducted is very similar to the well-known -sulphite method of treating paper pulp, and is carried on in iron -cylinders or better in close wooden vats lined with lead. - -[Illustration: FIG. 40.] - -The gas is usually generated in an impure form, with a large admixture -of air and carbonic acid, by combustion of pyrites and coal, of crude -sulphur, or even of only highly pyritous fuel. - -On the other hand, since it is well established that the absorption of -a diluted gas is less ready, and is more wasteful than that of a gas in -a pure state, the employment of a definite quantity of sulphur dioxide -in a concentrated state, either prepared by the regulated burning of -sulphur, or the decomposition of sulphuric acid, yields more regular -results, and a product of better quality. Liquid sulphur dioxide, -which is now obtainable at a moderate price and in quantity, has the -advantage that it yields a continuous current of pure gas of any -required rapidity by simply opening a valve, and that the exact amount -used can be ascertained by taring the containing vessel before and -after the operation (S. Rideall). - -The washed bones are brought into the above-mentioned cylinder or vat -and treated with a saturated solution of sulphurous acid. The duration -of the action of the acid varies according to the condition of the -material and can only be determined by experience. The result of the -process is a liquor almost as clear as water, which, after evaporation -in the vacuum pan, is equal as regards clearness and lustre, to the -best quality of glue prepared from waste of hide and skin. The fat -extracted from the bleached bones is lighter in color and has not the -disagreeable odor of ordinary bone fat, and consequently brings a -better price. - -For the generation of sulphurous acid Dr. Bruno Terne, of Mass., has -constructed a very simple apparatus shown in Fig. 40. The sulphur is -burned in _S_; _A_ is the escape pipe of stone; _T_, the collecting -reservoir; _P_, the steam-pump for acid; _R_, chimney for the sulphur -burner. - - -4. CONVERSION OF CARTILAGE INTO GLUE. - -The conversion into glue of the swollen cartilage obtained by treatment -with hydrochloric or sulphurous acid may be effected by continued -boiling in open pans or in an apparatus recommended by Wm. Friedberg, -and shown in Fig. 41. - -The boiler _K_ of thick boiler-plate has a diameter equal to its -height. Underneath the perforated false bottom _S_, which serves for -the support of the bones, lies a perforated steam coil _R—D_ for the -introduction of steam. To this steam coil is fitted a branch-pipe -_d_, which reaches into the upper portion of the boiler into which -also enters the water-pipe _W_. The apparatus is further fitted -with a water-gauge, an air cock, sampling cock and manhole for the -introduction of the cartilage. - -[Illustration: FIG. 41.] - -The mode of operation with this apparatus is as follows: The boiler is -filled three-quarters full with cartilage. Enough water to fill the -boiler one-quarter full is then admitted through the pipe _W_, and -the steam-cock _D_ opened. The steam passing out through the numerous -perforations in the coil _R_, is at first condensed in the water, but -soon brings the latter to the boiling-point, and from this stage on -begins the formation of glue. The glue dissolves in the water, and -a sample of the solution is from time to time drawn off through the -sampling cock and tested as to its concentration. When the solution -possesses the required concentration, the admission of steam through -_R_ is interrupted, and the cock _d_ of the branch-pipe opened, as -well as the cock of the discharge pipe _H_, the latter being opened -gradually. The discharge pipe _H_ is connected with the perforated -plate _F_, which is covered with a closely-woven cloth and thus acts -as a filter, retaining all the solid particles suspended in the glue -solution. - -By opening the cock _d_ of the branch-pipe, the steam-pressure acts -only upon the surface of the fluid, the latter being consequently -pressed with great force through the filter-cloth. - -When the hissing noise caused by escaping steam indicates that all the -fluid has been removed from the boiler, the cock _d_ of the branch-pipe -is closed, and through a rose fitted above the boiler, water is allowed -to flow upon the latter. By this cooling the greater portion of the -steam in the boiler is condensed and water may be admitted through _W_. - -[Illustration: FIG. 42.] - -The operation of glue-boiling is then commenced anew by admitting -steam into the steam coil, and continued until the cartilaginous mass -has been reduced to about one-third of its original bulk, when the -apparatus is opened, fresh material introduced, and the whole operation -repeated. - -In order to be able to replace the filter without having to empty -the entire apparatus, it has been given the shape shown in Fig. 42. -The upper portion of the discharge-pipe _A_ is connected with the -lower portion by the box-screw _H_. In the latter is inserted a short -cylinder, _C_, with a perforated bottom upon which is placed the -filter-cloth; the latter is kept in position by the ring _R_. - -[Illustration: FIG. 43.] - -For every apparatus two of the above-described filters will be -required. If, notwithstanding a full steam pressure, the glue solution -runs off sluggishly, it is indicative of the pores of the filter being -choked up. The screw-box _H_ is then removed, the filter taken out and -replaced by another one. - -The glue solution discharged from the apparatus is in most cases -sufficiently clear to allow of its being immediately evaporated. -However, for the production of a particularly fine quality of glue, -it is advisable to clarify the solution by settling. As the liquor -has to be kept warm to allow of the solid particles to settle, W. -Friedberg recommends the use of the apparatus shown in Fig. 43. It -consists of an iron cylinder with a diameter equal to one-third of its -height. The front of the cylinder is furnished with a number of cocks -placed at equal distances from each other, and also with a pipe in -the slightly conical bottom. It is surrounded by a wooden jacket, the -intermediate space being filled with a bad conductor of heat. By this -arrangement the liquor is kept warm and in a liquid state for several -hours, giving ample time for the solid bodies held in suspension to -settle on the bottom. The condition of the liquor is from time to time -tested by allowing a small quantity of it to run into a glass from the -lowest cock in front. If the sample is perfectly clear, the liquor -may be drawn off. If, however, after several hours’ standing only the -upper portions of the liquor are clear, while the lower ones are still -turbid, further clarification by this means is impossible. The upper -portions of the liquor are then used for finer qualities of glue and -the lower ones for inferior grades. - -By treating the cartilage with high-pressure steam, a liquor is -obtained which on cooling congeals to quite a solid jelly, and it might -be immediately brought into the forming-boxes, cut into cakes, and -dried. However, as the drying of the glue is one of the most difficult -operations for the glue-maker, it is of great advantage to obtain the -liquor in as high a state of concentration as possible in order to -obtain a solid jelly, which causes the least difficulty in drying. For -this purpose the liquors leaving the clarifying vat with a strength of -about 20 per cent. dry glue are evaporated down to a strength of about -32 per cent. in winter, and 35 per cent. in summer. Evaporation may be -effected in open pans or in vacuum. - -Fig. 44 shows the arrangement of an open evaporating pan. The copper -pan _P_ has the form of a shallow cylinder with a slightly conical -bottom, in the lowest point of which is the discharge pipe for the -concentrated liquor. During the operation the discharge pipe is closed -by the ball-valve _V_, which can be raised by the lever contrivance -_M_. The pan is surrounded by an iron steam-jacket; the steam passes in -at _D_, and the condensed water runs off at _A_. _H_ is a sampling cock -for taking samples to test the concentration of the liquor. - -[Illustration: FIG. 44.] - -To prevent the workroom from being filled with steam arising from the -pan, the latter is covered with a hood of wood which terminates in the -pipe _S_ projecting above the roof, and a narrow pipe _R_ branching off -from the steam pipe _D_ passes into _S_. - -When vapors commence to arise from the liquor, the cock on the pipe _R_ -is slightly opened whereby a jet of steam is blown into the pipe _S_, -the latter then acting as an exhauster, and the vapors in the hood _C_ -are carried along by the jet of steam. By this arrangement no vapor -passes into the workroom and steam is also very rapidly evolved from -the surface of the liquor. - -Sufficient steam should be admitted to the pan for the liquor to give -out an abundance of vapor without, however, being brought to the -boiling-point, as in that case foam would be formed and the liquor in -cooling yield a product full of blisters. When the liquor has acquired -the proper degree of concentration, the admission of steam to _D_ and -_R_ is interrupted and the valve _V_ having been raised the liquor is -run into the cooling-boxes. The latter are of wood lined with zinc, or -better of stout zinc or heavily galvanized iron. They hold about ½ cwt. -and are of two shapes: one deep and nearly square, another long and -shallow, for quick cooling of clear liquors. Iron should not be used, -as it readily rusts and causes discoloration of the glue. - -Cooling is effected by cold water where it is available, but often -merely by cold air, aided by fans or blowers, in a room protected from -heat or frost. According to S. Rideal, refrigerating machines are now -also employed, which, by the evaporation of liquid gases, such as -ammonia, sulphurous or carbonic acid, reduce a tank of brine to near -freezing-point. The temperature should not be allowed below 33° or 34° -F., for if frozen the jelly is hard and difficult to cut. The brine -circulates in iron pipes placed near the ceiling of the room; they must -be kept as clear as possible of ice and dirt, and the cooling house -should be scrupulously clean and sweet. - -Spiral evaporators are recommended by Thomas Lambert as forming a ready -and economical means of evaporation. The evaporator consists of a -spiral steam coil, made of copper, and 2 inches in diameter, revolving -on a centre shaft; the lower half of the coil is covered with the -glue-liquor in the trough. The shaft rests on two plummer-blocks, one -receiving the steam, and the other discharging the spent steam and -condensed water. The shaft is hollow to the first coil, and the steam -is thus conveyed to the spiral. From the last coil to the end of the -plummer-block the shaft is also hollow, and in that portion resting on -the block two openings are made. In the inside of the plummer-block, -two openings are bored to the outside, each forming a covered channel; -as the shaft revolves, all the holes directly face each other at -intervals, and thus allow any condensed water in the coils to be blown -through. From 25 to 28 coils are generally used in each spiral. The -glue-liquors are fed into the trough at one end, and have a temperature -of 75° F.; the temperature of the evaporated liquor is 85° F. In the -rather slow passage through the trough, the liquors receiving the heat -of the revolving coils are raised in strength from 20 per cent. to 32 -per cent. dry glue, at which point they are ready for jellying. - -_Vacuum pans_ are much used in this country for evaporating -glue-liquors, though there are some complaints made of the great waste -owing to spray and froth being carried off in the steam. As is well -known the boiling-point is lowered by increasing the pressure on the -surface of a fluid. By enclosing water in a vessel connected with a -constantly working air-pump, it is brought to the boiling-point by -heating to between 95° and 104° F. The construction of vacuum pans is -based upon this principle, and such apparatus is largely used in many -manufacturing processes for evaporating to a certain degree fluids, for -instance, sugar solutions, which readily become decomposed at a higher -temperature. Vacuum pans are also very suitable for the evaporation of -glue-solution, especially in plants working on a large scale. - -Fig. 45 represents an elevation of a vacuum pan for evaporating glue -and gelatine liquors as described by Thomas Lambert. The pan is built -of steel plates, and lined outside with wood work, and rests on a -floor constructed of rolled steel plates, supported on four columns, -with a stairway leading to the working platform. One half of the -lower part is shown in section, giving a view of the coils by which -the pan is heated. The various parts are as follows: _A_, the body of -the pan; _B_, the dome; _C_, exhaust pipe leading from the dome to -the condenser; _D_, condenser; _E_, air or vacuum pump; _F_, storage -tank for glue or gelatine liquors, warmed with steam coil; _G_, supply -pipe leading from storage tank to vacuum pan; _H_, discharge valve; -_I_, barometer gauge for indicating vacuum; _J_, inlet steam pipe -for supplying the coils; _K_, exhaust end of vacuum coils; _L_, iron -staircase; _M_, steel floor. - -[Illustration: FIG. 45.] - -The accessories to the pan are placed in a convenient position above -the working floor and include a steam gauge for noting the pressure in -the coils, a gauge for indicating the height of the liquor in the pan, -vacuum gauge _I_, as shown in the drawing, air-cocks and a thermometer. -The pan is also fitted with a small apparatus, by which portions of the -boiling liquor can from time to time be drawn, without disarranging the -vacuum, so that the progress of evaporation can be ascertained. - -In working the pan, the storage tank _F_ is first filled with the weak -glue liquors to be evaporated; the valve on the supply pipe _G_ is then -closed, and the vacuum pump set in motion; a few strokes are sufficient -to reduce the internal pressure, and the valve of the supply pipe is -then opened, and the liquor allowed to fill up the pan to the desired -mark on the gauge. The valve is then closed, the steam-inlet valve _J_, -supplying the coils, opened. As the heat from the coils spreads through -the liquor, the vacuum pump is kept steadily at work reducing the -inside pressure to within 2 to 2½ inches of a perfect vacuum, as seen -on the barometrical scale. In this vacuum the liquor will boil at 120° -to 130° F., and the boiling is continued until the withdrawn samples, -as tested by the glue-meter, show the desired strength. The pump is -then stopped, the vacuum broken by opening the air-cocks, and the -concentrated liquor is run through the valve _H_ into suitably arranged -receiving tanks, for supplying the trays or glasses for jellying. - -For economical working with large quantities of weak liquors, a -combination of two, three and even four vacuum pans, forming the -double, triple and quadruple effect evaporators, have been designed -for concentration purposes. The triple effect is, however, the system -mostly in use, and consists of a grouping of three cylindrical pans, -each connected by suitably arranged piping, by which the vapors of the -first pan are conveyed to and made to heat the coils of a second pan, -the resulting vapors from the second, passing on to the third pan, for -a similar purpose. All the pans are connected with powerful pumps, -producing a nearly absolute vacuum in each. The liquor is evaporated to -a given density in the first pan, and then passed on to the second, and -ultimately to the third, at which stage 80 per cent. of its water will -have been driven off. - -To obtain in all cases a product of equal concentration, it is -advisable to have an instrument which will indicate the amount of dry -glue in the solution. (Fig. 46.) - -By immersing a glass aerometer in the glue-liquor, the percentage of -glue is indicated by a scale registering from 0 to 70 per cent. with -the jelly or glue solution at a temperature of 167° F. - -To measure the temperature quickly, a thermometer is added, and for -the execution of the entire test, a sheet-iron vessel consisting of -a large and two small tubes, _a_, which when not in use, serve for -the reception of the glass instruments contained in a special case. -For testing, the small cylinder is placed in the large tube, _a_, and -filled with jelly by means of the cap which serves as a cover. The -large tube is filled with hot water to bring the jelly to the required -temperature. The two instruments are then immersed in the tubes filled -with glue-liquors to be tested, and temperature as well as percentage -can be readily read off. - -[Illustration: FIG. 46.] - -The evaporated and cooled glue-liquor is cut into cakes and dried in -the same manner as previously described. - - -5. PROCESS FOR THE SIMULTANEOUS UTILIZATION OF BONES FOR FAT, BONE-MEAL -AND GLUE. - -Manufacturers frequently sort the bones in such a way that materials of -different quality are obtained. Thick, compact bones are utilized for -the manufacture of animal charcoal, a comparatively small percentage -of bone-meal resulting in crushing such bones. - -Incompact, porous bones, on the other hand, yield not only crummy -animal charcoal of less value, but in stamping also a larger percentage -of bone-meal than compact bones. Hence they are as a rule directly -worked for fat, glue and steamed bone-meal, no attempt being made -to convert them into such granular pieces as are suitable for the -production of charcoal. - -For this purpose, the bones are first broken by a crusher or mill into -coarse pieces, and the fat extracted by a special process or together -with the glue in one operation. The latter method would seem to be the -most suitable, time and labor being thereby saved, but it must be borne -in mind that fat extracted by itself brings a much better price than -that obtained by steaming, and besides the yield of glue is larger from -steamed bones which have been previously degreased. - -The crushed bones—whether degreased or not—are subjected to the action -of high-pressure steam. The apparatus, Fig. 47, used for this purpose -consists of a cylinder of thick boiler-plate, 10 to 13 feet high and 3 -to 4 feet in diameter. _E_ and _A_ are manholes, which can be closed -steam-tight. The pipe _D_ leads to the steam-boiler and opposite to -_D_ is a short pipe, _H_. The cylinder is further fitted with the -perforated false bottom, _S_, and the bent pipe, _L_. - -As a rule, four to six, and in larger plants even more, of such -cylinders are combined to a battery. In this case the discharge pipe, -_L_, terminates in a common collecting vessel, and the steam-pipes, -_D_, branch off from a main steampipe. The battery may be enclosed by -brickwork, but is preferably placed upon a suitable foundation and -surrounded by woodwork, the intermediate space between woodwork and -cylinders being filled with sawdust. This plan offers the best means of -keeping the heat together, and the further advantage that, in case one -of the cylinders becomes defective, it can be readily taken out and -replaced by a new one. - -[Illustration: FIG. 47.] - -In order to be able to fill the cylinders rapidly and with the least -expenditure of power, it is advisable to place the bone-crusher at such -a height that the crushed bones fall directly into carriages which are -run upon a small railway over the charging holes of the cylinders, and -emptied. In front of the manholes, _A_, for discharging the bones is -also a railway, so that the crushed bones can be directly emptied into -carriages and conveyed to the stamping mill. - -The cylinder having been filled with bones, is closed steam-tight. The -cock, _H_, is then opened and steam admitted by opening the cock _D_. -The steam passing in at first, is cooled off by coming in contact -with the bones and condensed to water. However, the temperature in the -cylinder soon becomes so high that the steam is no longer condensed -and, having first expelled the air in the cylinder through the pipe -_H_, it escapes through the latter in the form of a powerful jet. When -this is the case _H_ is closed and high-pressure steam allowed to act -upon the bones. - -The fat contained in the bones melts and trickles down. On the bottom -of the cylinder collects a fluid which contains glue, is of a milky -turbidity due to admixed drops of fat, and with a quite thick layer of -fat upon its surface. From time to time—about every hour—the cock _L_ -is slightly opened. By the pressure of the steam the glue-liquor is -expelled with great force through the pipe _L_, the latter being closed -when by the peculiar noise it is noticed that only steam escapes. - -Steaming and the occasional discharge of melted fat are continued until -on testing a sample of the liquor running off, it is noticed to be free -from fat. The liquor in the cylinder is then expelled by the pressure -of steam, the steam-cock _D_ closed, the manhole _A_ opened, and steam -again admitted through _D_. By the steam-pressure the greater portion -of the bones in the cylinder is expelled through the manhole _A_. The -bones coming from the cylinder are pliable and soft, and, after drying, -are readily converted by grinding into bone-meal. - -For the manufacture of animal charcoal it is of the utmost importance -that steaming should be interrupted at the time when the bones are -completely degreased. If, however, only fat, glue and bone-meal are to -be produced, steaming may advantageously be continued for a longer time. - -The longer the bones are subjected to the action of high-pressure -steam, the more complete the conversion of glue-yielding substance into -glue will be. To be sure, the bone-meal obtained from such bones will -contain somewhat less nitrogen than the product from bones not steamed -quite so long. However, the content of phosphates will in both cases be -the same, and on this depends, in the main, the fertilizing value of -bone-meal. - -The fluid discharged from the cylinder consists of a mixture of -glue-liquor and drops of fat. It is run into a large vat, in which it -is kept warm for a few hours, when the fat rises and collects in a -coherent mass on the surface. The fat is then drawn off through cocks -in the upper portion of the vat, while the glue-liquor is discharged -from the bottom of the vat, running first upon a very fine meshed -sieve, which retains the coarser bodies held in suspension, and then -directly into the evaporator. In the latter the liquor is evaporated -to the desired strength, when it is run into the clarifying vats, and -finally into the cooling vessels. - -With the above-described process, the simultaneous utilization of the -bones for animal charcoal is only possible if the crushed steamed bones -are passed through a sieve for the purpose of sorting out the granular -pieces of suitable size. However, in the process above described, -incompact bones are, as a rule, used which give but a small percentage -of granulated pieces, and the latter yield an inferior quality of -animal charcoal. It is therefore best to use the steamed bones from -which the fat and glue have been extracted for the production of -bone-meal. - -For the manufacture of animal charcoal, the bones have to be carefully -sorted, fresh bones rich in organic substance being best for the -purpose, and the hardest and thickest pieces should be selected. -Previous to carbonization, the bones are degreased by extraction with -benzine or carbon disulphide, and then crushed. - -Carbonization was formerly effected in iron pots having a capacity of -about 25 quarts each. However, by this process a uniform product of -good quality cannot be obtained, and, besides, the total quantity of -organic substance of the bones is lost. At present carbonization is -effected in retorts, whereby large quantities of animal charcoal are -in a comparatively short time obtained, and, besides, the products -of destructive distillation can be completely utilized. An essential -product of distillation is a large quantity of inflammable gases, which -can be used for heating the retort-furnace or for illuminating the -entire plant, it being, however, best to arrange the conduits so that -the gases can be used for either purpose. - -A detailed discussion of the methods for gaining and further working -of the products of distillation is not within the scope of this work, -and only a brief description of a plant for the manufacture of animal -charcoal will here be given. - -[Illustration: FIG. 48.] - -Figs. 48 and 49 show the arrangement of a Belgian retort-furnace, Fig. -48 representing a vertical section lengthways, and Fig. 49 a horizontal -section. The illustrations, however, are given at different heights in -order to show plainly the arrangement of the fire-place and the passage -of the fire-gases. - -The cast-iron retorts—sixteen in the apparatus shown—are placed in -rows alongside and one after another, so as to be swept as uniformly -as possible by the fire. As will be seen from Fig. 49 the firing is so -arranged that only the upper portions of the retorts are touched by the -flames. _B_ is the actual fire-place, and _A_ the ash-pit, both being -furnished with closely fitting doors so that the fire may be properly -regulated, and the retorts eventually be exclusively heated with gas. - -[Illustration: FIG. 49.] - -The retorts are cylindrical in form, with one end closed. At the open -end is fixed the frame or mouth-piece, which carries the door swung on -a hinge. The door has a slight projecting rim, some two inches wide, -which, with the surface of the frame, is ground perfectly true; on -closing, the joint is made gas-tight by a lever arrangement. - -The fire-gases escaping from _B_ are distributed as uniformly as -possible by the flues, _a_, carried underneath the pans, _E_, and -finally pass out in the direction of the arrows through a chimney. - -At the time when the extraction of fat was exclusively effected by -boiling the bones, the pans _E_ served for this purpose, and the spaces -_D_, _D__{1}, _D__{2}, etc., alongside the pans, which were also heated -by the fire-gases, were used for drying the bones. However, at present, -the extraction of fat is, as a rule, effected by means of benzine or -carbon disulphide, and it is advisable to replace the pans, _E_, by a -bonekiln, and eventually to utilize any waste heat for heating the -evaporators for glue-liquor. - -Fixed to the upper portion of each retort is a pipe, and these pipes -lead into a very wide iron-pipe, _T_. The products of destructive -distillation escaping from the retorts combine in _T_, and besides -having a very large diameter, this pipe must be considerably inclined -to avoid the accumulation of products of distillation in it. To prevent -the products of distillation from depositing in a crystalline form in -_T_, the latter is covered with a bad conductor of heat. - -The pipe _T_ is connected with a series of condensing vessels, _D_, -another series of vessels being placed alongside the first one, so that -the vapors may be conducted, as desired, into either one of them. Two -batteries of such condensing vessels are required, as one of them has -from time to time to be disengaged in order to be cleansed. - -If the products of distillation would have to overcome the entire -pressure of the column of fluid in the condensing vessels, their escape -from the retorts would be very much retarded. To avoid this, plates are -arranged horizontally a few inches below the level of the fluid, and -the pipes dip into the condensing vessels only far enough to permit the -escaping vapors to pass under these plates. By this arrangement, the -vapors sweep under the plates and are absorbed by the fluids, a strong -pressure in the apparatus being thus avoided. - -The condensing batteries may of course consist of any number of -vessels, but as a rule only a sufficient number to retain all the -ammonia is employed, five being in most cases sufficient for this -purpose. The last condenser is connected with an exhaust-pump, _p p_, -which is kept in motion by a motor, _P_. - -The pump removes all the bodies remaining in the last condenser and -forces them, according to the position of the cock back of the pump, -either into a glass-bell or through the pipe _H_ and the nozzles _a_ -into the fire-place where they are burned. - -To obtain the various products of distillation, the condensing vessels -have to be filled with acid, and should therefore be constructed of -lead or at least of sheet-iron lined with lead. The products to be -obtained depend on the fluid used for filling the vessels; if filled -with dilute sulphuric acid, ammonium sulphate is obtained, which may -be utilized in the preparation of fertilizers. If hydrochloric acid is -employed for the absorption of ammonia, solution of ammonium chloride -is obtained, which may be crystallized by evaporation. - -The products evolved in the destructive distillation of bones consist -of various hydrocarbons and appear either as badly-smelling brown -liquors—bone-tar—or as illuminating gas. The vapors contain further -considerable quantities of ammonium carbonate and cyanide of ammonium. -To obtain the latter, the last condensing vessel is filled with green -vitriol solution, the cyanogen compounds remaining behind in the -solution. If the gas escaping from the last condenser is to be used for -illuminating purposes, it is freed from the greater portion of carbonic -acid contained in it by purification with lime. - -The mode of operation with Belgian retort furnaces is as follows: -The retorts having been filled with comminuted degreased bones, the -doors are closed perfectly gas-tight and firing is commenced. The pump -is set in motion until a jet of gas blows through the nozzles. When -this gas-jet burns with a luminous flame, destructive distillation of -the bones is in full blast. The pump is then run with such velocity -that the pressure in the interior of the retorts, as indicated by the -manometer, is slightly greater than the external air-pressure, and the -operation is thus continued so long as inflammable gases escape from -the pipe _H_. The pump is then stopped, and one-half of the charcoal -contained in the retorts is withdrawn to the canisters placed ready to -receive it. The lids of the canisters are then luted down with a paste -of char-dust and water, making an air-tight joint, and the charcoal is -allowed to cool. - -The retorts having been partially emptied, are at once refilled to the -brim with crushed bones and closed gas-tight. There is but little or no -loss of heat between withdrawing and charging, and distillation of the -freshly-introduced bones commences immediately after charging, and is -finished in a much shorter time than in the beginning of the operation. - -In making animal charcoal on a large scale there are obtained from 2000 -lbs. of raw material: - - Animal charcoal, 1180 to 1220 lbs. - Ammoniacal liquor, 178 to 180 lbs. - Gas, 222 to 248 cubic yards. - -However, these figures refer only to bones degreased by steaming, -whereby a considerable portion of the cartilaginous substance passes -into solution in the form of glue. In working bones degreased with -benzine, larger yields than those indicated above are as a rule -obtained. The ammoniacal liquor contains on an average 10 per cent. of -ammonia. The gas freed from carbonic acid yields 2.7 times more light -than good coal-gas. - - -6. PROCESS FOR THE SIMULTANEOUS UTILIZATION OF THE BONES FOR FAT, GLUE -AND CALCIUM PHOSPHATE. - -This process differs from the one previously described in that, in -addition to the total quantity of fat and glue-yielding substance -contained in the bones, the mineral salts are also obtained in a pure -state, and can be further utilized. - -The bones are degreased either by extraction with benzine or carbon -disulphide or steaming, the operation in the latter case being -continued so long as fat is yielded by the bones. The resulting -glue-liquor is used in place of water for boiling the cartilage. - -The bones are placed in large wooden vats furnished with well-fitting -lids, and hydrochloric acid of 12 per cent. poured over them so that -they are covered a few inches deep. With the use of acid of 1.04 -specific gravity the greater portion of the salts contained in the -bones will pass into solution in 48 to 72 hours, when the solution is -drawn off as completely as possible from the vats. - -The residue in the vats is treated with less concentrated hydrochloric -acid and left in contact with it until the bones are soft and flexible -and the thinner pieces have become translucent, this being a proof -that all the mineral salts have been extracted, and nothing but pure -cartilaginous substance remains behind. The solution is then drawn off, -and after pouring repeatedly small quantities of pure water over the -cartilage to expel the last remnants of acid liquor, it is subjected to -thorough washing until the last traces of acid have been removed. - -The resulting cartilage is white, translucent, and water-soaked. If -left in this state it would of course soon putrefy, and it is best to -work it at once, or if this cannot be done it will have to be treated -with carbolic acid in the manner previously described, or dried. - -Drying the cartilage is time-consuming work, and can properly be done -only by artificial heat in kilns. If carefully protected from moisture, -thoroughly dried cartilage may be kept without injury for any length -of time. However, before being worked to glue, such material has to -be again soaked in water previous to the actual boiling operation, -and this process requires considerable time. It is therefore best to -preserve it in carbolic acid solution, which only needs to be drawn off -when the cartilage is to be worked, and may be further utilized. - -If boiled in open vessels with water, 6 to 8 hours are required for -the complete disintegration of the cartilage. In a closed apparatus -under high pressure solution is effected in a much shorter time and the -operation progresses very smoothly. With proper attention the glue -obtained from bones degreased with benzine and freed from bone-earth by -extraction with hydrochloric acid is, as a rule, very clear, and may be -bleached with sulphurous acid. - -The extraction of the phosphates from bones may be effected in a very -suitable manner as follows: A number of vats filled with bones are -placed in terraces one above the other, and the acid is allowed to -run first into the uppermost vat. After having been for several hours -in contact with the bones it is discharged into the next vat, fresh -acid being run into the first one, and so on. By this process a highly -concentrated solution of phosphates is in a few hours obtained in the -lowest vat, solution still adhering to the bones in the other vats -being finally expelled by water. - -However, the process of extraction under decreased pressure is the -most advantageous, it requiring least time. For this purpose the bones -are brought into a vessel which can be closed air-tight and the air -is expelled. When but a slight air-pressure prevails in the vessel, -the cock of a reservoir filled with hydrochloric acid is opened, the -external air-pressure now forcing hydrochloric acid into the extracting -vessel. - -Bones, as viewed under the microscope, consist of a mass permeated -with numerous minute tubes or pores. When the air is expelled from -the vessel containing the bones, the air in the pores of the latter -is rarefied and the hollow spaces are filled with hydrochloric acid -whereby solution of the phosphates is effected. - -The yield of glue obtained from cartilage after extraction of the -mineral constituents varies according to the compactness of the bones -used. Solid and compact bones yield, on an average, 15 per cent. of -dry glue, but a comparatively large quantity of calcium phosphate. On -the other hand, porous bones rich in cartilage yield from 20 to 25 per -cent. of dry glue. The liquor obtained by treating the bones contains, -as previously mentioned, calcium phosphate, magnesium phosphate and -calcium chloride in solution, and may be utilized in the manufacture of -fertilizers or of phosphorus. - -For the first purpose which is not very remunerative, but is not -very troublesome, the liquor is treated with milk of lime until it -is slightly alkaline, whereby a finely divided precipitate of basic -calcium phosphate is obtained, whilst calcium chloride remains in -solution. The precipitate is allowed to settle, separated from the -supernatant fluid and dried. The resulting product contains, on an -average, 65 per cent. calcium phosphate, up to 20 per cent. water -and 10 to 15 per cent. calcium carbonate, quick lime and accidental -impurities. It forms an excellent fertilizer. - -If the liquor is to be utilized in the manufacture of phosphorus, it -is evaporated in shallow pans of glazed stoneware. In cooling crystals -of acid calcium phosphate are formed, which are separated from the -mother-liquor. This subject will be more fully referred to in the next -chapter. - - - - -CHAPTER VI. - -MANUFACTURE OF PHOSPHORUS. - - -In some instances the preparation of phosphorus is carried on in -conjunction with other industries, for instance, glue-boiling, the -preparation of sal ammoniac, yellow prussiate of potash, etc. Bone-ash -is the chief material used by phosphorus makers. Many manufacturers do -not burn the bones to ashes, but purchase bone-ash, large quantities -of which are brought from South America, especially from the Argentine -Republic. - -The ordinary method of preparing phosphorus includes the following -operations: - -1. Burning the bones and grinding the bone-ash to powder. - -2. Decomposition of the bone-ash by sulphuric acid, and evaporation of -the acid phosphate previously mixed with charcoal. - -3. The distillation of the phosphorus. - -4. The refining and purifying the phosphorus. - -_Burning the bones to ash._ The object of the ignition of the bones -is the complete destruction of the organic matter. The operation is -conducted in a kiln very similar to those in use for burning lime. -A layer of brush-wood having been put on the bottom of the kiln, -bones form the next stratum, and so on alternately. The wood having -been lighted, the combustion of the bones ensues. In order to carry -off the fumes, the smell of which is very offensive, a hood made of -boiler-plate is placed on the kiln, and either connected with a tall -chimney, or the smoke and gases are conducted into the fire of the -kiln and burnt. The white burnt bones are withdrawn through an opening -reserved in the wall on purpose, the kiln being kept continuously in -operation, as in the case with some lime kilns. - -This kind of kiln, however, possesses many disadvantages, and an -improved form, as proposed by Fleck, is shown in Fig. 50. - -[Illustration: FIG. 50.] - -The actual combustion chamber consists of a shaft, _A_, composed of -two inverted cones. In the lowest portion of the lower cone are four -or six apertures, _b_, which terminate in inclined channels and serve -as air-flues, as well as for withdrawing the burnt bones. Through the -aperture _a_ in the upper portion of the shaft additional bones may be -introduced. This aperture is covered with a heavy iron lid. - -As will be seen from the illustration, the shaft contracts towards the -top in the form of a retort and passes into a horizontal channel _B_ -which is provided, near its beginning, with an ordinary fire-place _d_. -The gases and fumes escaping from the burning bones must pass over the -flame of the fire-place _d_, and are thereby so completely consumed to -water, carbonic acid and free nitrogen that no odor is perceptible even -in the immediate neighborhood of the kiln. - -In order not to lose the heat yielded by the fire-place _d_ and the -burning vapors, the channel _B_ is covered with shallow pans _P_, -for the evaporation of such fluids as have to be subjected to this -treatment in the factory. - -The mode of operation with a kiln of this construction is as follows: -The shaft is filled two-thirds full with bones and dry wood split in -small pieces is placed in the channels _b_ and simultaneously ignited. -Four or six long hot flames thus strike the bones, the latter becoming -in a short time so highly heated that they commence to burn briskly and -ignite fresh portions of bones introduced through the aperture _a_. - -The white burnt bones in the lower portion of the kiln are withdrawn, -while in a glowing state, by means of iron hooks; the next layer of -bones sinks down and fresh material is introduced through _a_, the kiln -being thus kept continuously in operation. - -The quantity of substance which remains after burning the bones depends -of course on the quality of the material used. Tubular bones of old -animals contain the largest quantity of mineral substance, and give a -much more abundant yield of bone-ash than the spongy bones of younger -animals. On an average 100 parts by weight of fresh bones yield 55 -parts by weight of bone-ash. The composition of the latter is as -follows: - - Basic calcium phosphate, 80 to 84 per cent. - Basic magnesium phosphate, 2 to 3 per cent. - Calcium carbonate, } 10 to 14 per cent. - Calcium fluoride, } - -The bone-ash thus obtained is converted into a coarse powder by means -of machinery, a bone-mill being best suited for the purpose. Experience -has shown that the granules obtained by grinding should be the size of -lentils. With the use of larger pieces the acid, with which the ash is -treated later on, does not penetrate the entire thickness of the bone -mass and a portion of the latter remains undecomposed. If the granules -are too small, lumps are formed when the ash is brought together with -the acid, and the mass would have to be constantly stirred in order to, -make the action of the acid effective. - -_Decomposition of the bone-ash by sulphuric acid._ When the basic -calcium phosphate—the constituent of the bone-ash which comes here into -consideration—is brought in contact with an acid of sufficient strength -to effect its decomposition, calcium sulphate (gypsum) is formed, and -a solution of acid calcium phosphate. If the latter be mixed with -powdered charcoal, evaporated to dryness, and the mixture exposed, with -the exclusion of air, to a strong red heat, the acid calcium phosphate -is first converted into calcium metaphosphate, water being yielded. At -this high temperature the calcium metaphosphate is by the action of the -carbon decomposed to basic calcium phosphate and phosphorus; the latter -escapes in the form of vapor and may be caught in suitable condensing -vessels. - -Hence three separate processes have to be distinguished: 1. The -formation of acid calcium phosphate from the basic calcium phosphate -contained in the bone-ash. 2. The conversion of the acid calcium -phosphate into calcium metaphosphate. 3. Decomposition of the calcium -metaphosphate, phosphorus being liberated, while basic calcium -phosphate remains behind. - -Expressed in chemical symbols these processes may be embodied in the -following equations: - - I. Ca_{3}(PO_{4})_{2} + 2H_{2}SO_{4} = 2CaSO_{4} + CaH_{4}(PO_{4})_{2} - Basic calcium Sulphuric Calcium Acid Calcium - phosphate. acid. sulphate phosphate. - (gypsum). - - II. CaH_{4}(PO_{4})_{2} = 2H_{2}O + Ca(PO_{3})_{2} - Acid calcium Water. Calcium - phosphate. metaphosphate. - - III. 3Ca(PO_{3})_{2} + 10C = 10CO + Ca_{3}(PO_{4})_{2} = P_{4} - Calcium Carbon. Carbon Basic calcium - metaphosphate. monoxide. phosphate. - -If the processes mentioned under II. and III. would pass off in the -practice exactly as there stated, two-thirds, or 13.3 per cent., of -the total quantity of phosphorus contained in the basic calcium -phosphate originally present would be obtained. However, besides these -processes, others take place which cause a loss of phosphorus. By the -action of the red heat upon the acid calcium phosphate, reciprocal -action takes place between the latter, the water and carbon, so that -a portion of the water is decomposed, and in addition to carbon -monoxide, phosphoretted hydrogen is formed; the phosphorus contained -in the latter must be considered as lost. Furthermore, a portion of -the phosphorus is lost in the form of vapor, even with the use of the -best condensing contrivances. In consequence of these losses the actual -yield of phosphorus is between 8 and 11 per cent. - -The formation of acid calcium phosphate may be effected either cold or -with the assistance of heat, less time being required in the latter -case. The process without the assistance of heat is as follows: - -The bone-ash is brought into a lead-lined wooden tank, and enough -boiling water to cover it poured in. It is then thoroughly mixed with -the water by vigorous stirring with wooden rakes, and the necessary -quantity of sulphuric acid is then run in with constant stirring. When -an intimate mixture has been effected, the tank is covered with a -well-fitting lid and allowed to stand for a few hours. As heat has been -liberated by the introduction of the sulphuric acid into the mixture -prepared with hot water, the entire mass acquires a high temperature. - -Decomposition is accelerated by stirring the contents of the tank every -six hours, and the process may be supposed to be finished in 48 hours. -With the use of fresh burnt ash no special phenomena are observed, but -if the ash has been prepared for some time the caustic lime formed in -burning the bones has been completely converted into carbonate of lime, -and the carbonic acid escapes, causing a slight foaming of the mass. -In addition to carbonic acid, there also escapes a certain quantity -of hydrogen fluoride gas, which is liberated by the decomposition of -the calcium fluoride present in the ash. This gas being, even in very -small quantities, very injurious to health, the tanks should be placed -in a thoroughly ventilated room. - -When decomposition is complete, enough water is admitted for the mass -to acquire by stirring a thick milky appearance, when it is allowed to -rest until it clarifies and a perfectly clear solution of acid calcium -phosphate stands over the precipitate of gypsum. The clear solution is -drawn off, and the sediment washed with water to obtain the solution -retained by it. For this purpose the gypsum is stirred up with water, -and the thick fluid discharged into a filtering tank. Upon the bottom -of the latter is a four-inch-deep layer of coarse quartz sand; upon -this is placed a false bottom, and upon the latter is spread a linen -cloth. The liquor first running off being milky is poured back into the -tank. However, it runs off clear so soon as the pores of the filtering -cloth have become somewhat contracted by the gypsum. - -As a rule, the contents of several filtering vats are run into a common -filter, and the mass is repeatedly allowed to drain off. The dilute -solutions thus obtained are evaporated with the first liquor. A third -lixiviation of the sediment yields a fluid which is used instead of -water in a subsequent operation. - -The residue of gypsum is taken from the filtering tanks, and may be -used as a fertilizer. - -In the warm way the decomposition of the bone-ash is effected by -providing the decomposing tanks with lead pipes through which steam is -introduced, decomposition being complete in 24 hours, and the first run -of solution of acid calcium phosphate reaches the evaporating pan in a -very hot state. The lixiviation of the gypsum residue is also effected -with water heated by steam, the object of separating the acid calcium -phosphate as much as possible from the gypsum being thus obtained -more completely with a comparatively small quantity of water than is -possible by washing with cold water. - -A suitable apparatus for hot lixiviation is shown in Figs. 51 and 52 in -cross section and profile. A lead-lined tank, 13 to 16 feet in diameter -and 3½ feet deep, is fitted with a stirrer furnished with two or four -paddles, and closed by a well-fitting lid. The stirrer is kept in -motion during the entire operation. - -[Illustration: FIG. 51.] - -[Illustration: FIG. 52.] - -A lead steam pipe _D_ furnished with several narrow flat outlet -pipes placed in the direction in which the stirrer revolves, lies -about 4 inches above the bottom of the tank. _W_ is the pipe for the -admission of water, _S_ the lead pipe connected with the sulphuric -acid reservoir, and _A_ an outlet of boards for carrying off the vapor -evolved from the mass in admitting the sulphuric acid. _R_ is a wooden -hopper, which serves for the introduction of the bone-ash, and is -removed when the tank has been filled, the aperture being closed with -a well-fitting wooden lid. The bottom of the tank is furnished with a -lead discharge-cock. - -Water is run into the tank, the bone-ash being simultaneously -introduced through the hopper _R_, and the stirrer allowed to revolve -slowly to effect an intimate mixture. Sulphuric acid and steam are then -at the same time admitted. The steam heats the fluid very quickly to -the boiling-point, and assists the action of the stirrer, it passing -out from the outlet pipes in the same direction in which the stirrer -revolves. - -When the required quantity of sulphuric acid has been introduced, -the admission of steam is interrupted, the stirrer, however, being -constantly kept in motion. To keep the mass hot, steam is for a few -minutes admitted every hour. When the sulphuric acid has acted for 24 -hours, decomposition is complete, and the liquor is discharged through -the cock on the bottom of the tank. - -For the evaporation of the liquor leaden pans are used, and this -operation is continued until the fluid has attained a specific gravity -of 1.45. The pans rest upon cast-iron plates covered with a layer of -clay or sand, to prevent them from being injured by the fire gases. For -heating the pans, the fire gases escaping from the distilling furnace -or the bone kiln are utilized. - -The fluid having been evaporated to the above-mentioned specific -gravity is now mixed with charcoal powder, or rather granulated -charcoal of the size of small peas, in the proportion of 20 to 25 parts -of charcoal to 100 of liquor. The mixture is then quickly dried in -shallow cast-iron pans heated by a direct fire. Much sulphurous acid is -evolved during this operation, and provision must be made for carrying -off the vapors arising from the pans. - -When the mass has been dehydrated so far that it balls together, it -is taken from the pan by means of shovels and brought into a copper -cylinder which is furnished with a sheet-iron sieve-like bottom through -which it is forced into another pan. In this second pan the mass is -moderately heated until a sample of it still evolves slight vapors -and when pressed with the hand, after cooling somewhat, appears still -moist without, however, being sticky. The material is now ready for -distilling and 100 parts of concentrated solution of 1.45 specific -gravity and 20 to 25 parts of charcoal yield about 77 parts by weight -of so-called distilling mass. - -It is best to bring the hot mass as taken from the pan at once into -the retorts, as it is very hygroscopic and, if allowed to lie exposed -to the air, would absorb moisture and require to be again dried. If it -cannot be immediately subjected to distillation, it is advisable to -keep it in sheet-metal boxes tightly closed. - -The liquor obtained in treating bones for the manufacture of glue with -hydrochloric acid may, as mentioned in Chapter V, be advantageously -utilized in the manufacture of phosphorus. In order to obtain in -crystallized form the acid calcium phosphate contained in it, the -liquor has to be concentrated by evaporation and as during this -operation hydrochloric acid vapors constantly escape, provision must be -made for their removal from the workroom. The operation is conducted -as follows: The flue of the furnace for distilling the phosphorus, -through which the fire gases usually escape to the chimney, is made to -communicate with a long low chamber, which can be tightly closed and -connects at the other end with a high chimney. The flue is fitted with -a slide and by opening the latter, the fire gases are forced to pass -through the chamber before reaching the chimney. - -In the chamber are placed large, well-glazed, earthenware vessels which -contain the liquor to be evaporated, the vapors evolved being carried -off by the fire-gases through the chimney. Evaporation proceeds quite -rapidly, and fresh liquor is from time to time introduced through an -earthenware pipe, the operation being repeated until a sample taken -from the full vessels shows on cooling the presence of an abundance of -crystals of acid calcium phosphate. - -The admission of the fire-gases into the chamber is then interrupted, -and the contents of the vessels are brought into a wooden tank -furnished with a stirrer, which is kept in constant motion so that -when the liquor cools, only small crystals will be formed. When -crystallization is complete, the mother-liquor is drawn off and again -evaporated. By this operation more crystals of acid calcium phosphate -are obtained, which are, however, less pure than those from the first -liquor. The mother-liquor drawn off from this second yield of crystals -might, on being again evaporated, give more crystals which, however, -would be too impure to be used to advantage. - -To obtain the calcium phosphate contained in the last mother-liquor, -the latter is exactly neutralized with burnt lime, a white precipitate -of basic calcium phosphate being thereby obtained. The precipitate is -repeatedly washed in water and allowed to settle, and added in small -portions to the acid liquors obtained by extracting the bones. As these -liquors always contain a considerable quantity of hydrochloric acid in -excess, the basic calcium phosphate, being in a finely divided state, -is readily and completely dissolved. - -The crystals of acid calcium phosphate are removed from the -crystallizing tanks by means of wooden shovels and brought into baskets -covered inside with stout sack-cloth. They are left in the baskets -until no more mother-liquor drains off, when the cloths are folded -together and the crystals further freed from liquor by pressure. They -are then heated, with constant stirring, in shallow stoneware pans -until they are so dry as to crumble of their own accord. In this manner -small crystals of a mother-of-pearl lustre are obtained, which feel -like sharp quartz sand and consist of pure acid calcium phosphate. - -This mass is mixed with 25 per cent. of its weight of granulated -charcoal. The mixture is heated until it is pulverulent, and then -treated in the same manner as the distilling mass from bone-ash. - -In place of stoneware vessels, shallow lead pans may be used for -evaporating the liquor containing calcium phosphate. To prevent the -melting of the lead the pans are bricked in under a very flat arch, so -that the fire gases are forced to pass close over the liquor, the pans -being kept constantly full. When crystallization is complete the liquor -is drawn off and the pans are refilled. - -In the manufacture of phosphorus there is left after every distillation -a residue of basic calcium phosphate, and it is advisable to decompose -it with hydrochloric acid, this being effected in a vat lined with lead -or coated with paraffine. The mass is completely dissolved, and the -black sludge remaining on the bottom of the vat consists of charcoal, -which had been added to the distilling mass. - -_Distillation of the Phosphorus._—The distilling mass consists of -acid calcium phosphate, charcoal and about 4 to 6 per cent. water. By -heating in the retorts, the acid calcium phosphate is first converted -into calcium metaphosphate, water being eliminated, according to the -following equation: - -CaH_{4}(PO_{4})_{2} = Ca(PO_{3})_{2} + 2H_{2}O. - -By further heating to a white heat the calcium metaphosphate is so far -reduced as to yield two-thirds of its content of phosphorus, while -one-third remains behind as calcium phosphate, corresponding to the -following equation: - -3Ca(PO_{3})_{2} + 10C = Ca_{3}(PO_{4})_{2} + 10CO + 4P. - -The mixture of acid calcium phosphate and charcoal is distilled in -glazed fire-clay retorts, 12 to 18 of them being placed on each side of -a so-called galley-furnace. The bodies of the retorts are placed on the -side of the fire, while the necks pass through openings in the walls -of the furnace, those portions of the wall being only lightly bricked -up, as the retorts, after distillation is finished and the furnace -cooled, have to be removed in order to clear out the residue and -introduce fresh mixture. Between each pair of retorts is left a space -of 5 to 6 inches for the passage of the flames. - -[Illustration: FIG. 53.] - -Experience, however, has proved the advisability of modifying the -galley-furnace by reducing its length and increasing its height, and -placing the retorts in two or three rows, one above the other. Two -such furnaces are placed together with their narrow sides, so that the -fire-gases of both meet in a common chamber, and are conducted from -the latter under the evaporating pans. Four such furnaces may also be -arranged in the form of a cross, and their fire-gases conducted into a -common chamber. By arranging the furnace, as is most frequently done, -for three double rows of seven retorts each, it will hold 42 retorts, a -double furnace 84, and one in the form of a cross 168. The arrangement -of a double furnace is shown in Fig. 53. - -The wall _C_, which separates the two fire-places, serves for -supporting the lowest row of retorts, while the second and third rows -rest upon intermediate pieces. The fire gases pass through flues into -the space over the furnace, the top of which may be directly formed -by the evaporating pans. It is, however, more suitable to place the -evaporating pans on one side and not run the collecting chamber for -the fire gases directly into the chimney. For the introduction of the -retorts into, and their removal from, the furnace, a narrow door is -provided between each two vertical rows of retorts. After placing the -retorts in the furnace, this door is closed with stones and the joints -luted with clay. - -Every three retorts lying one above the other have a common receiver, -_p_, for the collection of the phosphorus distilled off. The necks, -_r_, of the retorts terminate in the collecting pipe, _o_. - -The galley-furnaces, previously described, require the use of a fuel -which yields a very long flame, and can, therefore, be heated only with -wood or very fat coal. - -In order to render possible the use as fuel of coal yielding a short -flame, and especially of coke, furnaces have been constructed which -hold only a small number of retorts, generally five, placed in two -rows, by twos and threes, one above the other. The retorts are -cylindrical in form, and have a capacity equal to that of several -smaller retorts. - -The _receivers_ for collecting the phosphorus distilling over from the -retorts are made of clay, and should be well glazed and smooth inside. -Each receiver consists of two parts, one of which is a cylindrical -vessel open at the top, into which the other part fits, and is fixed -by means of a rim, which is prolonged so as to form a neck, between -which and the first part is inserted a tube fitted on the neck of the -retort, while the other end of this tube dips for about 4 inches into -the receiver, the latter being filled with water. - -Under certain conditions enameled cast-iron may be used as a material -for receivers, but the enamel must be of such a nature as not to be -attacked by the phosphorus vapors, otherwise the receivers would in a -short time be destroyed. - -The retorts having been filled with the required quantity of mixture -are placed in the furnace and the brickwork is restored. The fire is -then kindled and kept up very gently for some time in order to dry -the fire clay used in joining the bricks. The receivers are filled -with water and fitted to the retorts. In each receiver a small iron -spoon is placed fastened to iron wire which serves as a stem. After -six to eight hours of firing the heat has been so much increased as to -cause the expulsion of any moisture left in the material placed in the -retorts, while quantities of hydrocarbon gases and oxide of carbon are -formed and expelled with the sulphurous acid. Subsequently other gases -are given off, and because they contain some hydrogen phosphide are -spontaneously inflammable. As soon as this phenomenon is observed the -joints of the receivers and apparatus connecting it with the retorts -are luted with clay, care being taken to leave, by the insertion of -an iron wire, a small opening for the escape of the gases, which are -as speedily as possible removed by well arranged ventilators from the -building in which the furnace is placed. The appearance of amorphous -phosphorus at the small opening indicates the commencement of the -distillation. - -The spoon is then placed in the receiver in such a direction that any -phosphorus coming over may collect in it. During the progress of the -operation, and as long as any phosphorus distils over, the evolution -of combustible gases continues, and consequently a small blue-colored -flame is observed at the opening in the lute. The water in the -receiver is kept cool during the operation. After forty-six hours, -with greatly-increased firing, a full white heat is reached, and the -quantity of phosphorus coming over has decreased so much as to make -a continuation of the ignition process wasteful. The receivers are -therefore disconnected from the retorts. - -The receivers are taken to a special room and entirely submerged -in large wooden troughs filled with water in order to drive off -inflammable gases still contained in them and to cover the phosphorus -with water. They should be opened only after this has been done, and -every manufacturer should rigidly enforce the rule of carrying on the -operation in the above-described manner. Crude phosphorus is very -inflammable, and when carelessly handled by the workmen may inflict -horrible burns and, as the phosphorus as a rule causes blood-poisoning, -such injuries generally cause death. - -The phosphorus is then removed from the receivers (always under water). -The trough in which this operation is effected should be provided, a -few inches above the actual bottom, with a perforated false bottom upon -which the receivers are placed. The larger pieces of phosphorus taken -from the receivers are collected, under water, in special vessels, -while the smaller pieces fall through the perforations of the false -bottom to the actual bottom. When all the receivers have been emptied, -the water in the trough is discharged into a large barrel in which it -remains until the particles of phosphorus have subsided. The water is -then drawn off, with the exception of a sufficient quantity to cover -the phosphorus in the barrel. - -The water from the receivers as well as from the troughs shows a quite -strong acid reaction due to phosphoric acid, which has been formed by -the combustion of phosphorus and passed into solution. In order not -to lose this phosphoric acid, the water is partly used for filling -the receivers and partly for mixing the bone-ash before adding the -sulphuric acid. - -Crude phosphorus is a mixture of crystalline (ordinary) phosphorus with -amorphous phosphorus, the reddish color of the mass being due to the -latter. It further contains phosphorus in various stages of oxidation, -free carbon, and if impure sulphuric acid has been used, arsenic in -combination with phosphorus. - -_Refining and purifying the phosphorus._ The crude phosphorus was -formerly purified by forcing it through the pores of stout wash leather -by means of a machine. The crude phosphorus contained in a tightly -tied piece of wash leather is placed on a perforated copper support -situated in a vessel filled with water at 122° to 140° F. As soon as -the phosphorus is molten, there is placed on the wash leather a wooden -plate which by the aid of a mechanical arrangement and a lever can be -forced downwards so as to cause the fluid phosphorus to pass through -the pores of the leather, the impurities being retained. The phosphorus -in the form of a slightly yellowish fluid collects on the bottom of -the vessel and is immediately moulded into the shape in which it is -brought into commerce. The residue in the wash leather consists chiefly -of charcoal dust and amorphous phosphorus. The wash leather can, as a -rule, be only used once, and only small quantities of phosphorus can be -worked at one time. - -A more suitable process of purification is as follows: Porous, unglazed -porcelain or earthenware plates are fixed in an iron cylinder connected -with a steam boiler. The cylinder having been hermetically closed is -placed in a vessel containing water at 140° F. When the phosphorus -is molten, steam of a few atmospheres’ pressure is admitted into the -cylinder, the phosphorus being thus forced through the earthenware -plates. - -The phosphorus obtained by either of these methods is free from -mechanically admixed particles of charcoal and amorphous phosphorus, -but it is by no means pure, as all the substances dissolved in it -(oxides of phosphorus) pass through the filter. The loss of phosphorus -amounts to from 5 to 6 per cent. of the weight of the crude product. -The masses taken from the filter plates are therefore collected -and subjected by themselves to distillation in order to obtain the -phosphorus contained in them. - -To obtain pure phosphorus, the crude product has to be subjected to -distillation, this operation being carried on in iron retorts of a -peculiar make, and shaped like the glass retorts used in chemical -laboratories. The necks of these retorts dip to a depth of ½ to ¾ inch -in water contained in a basin filled to the rim so that any phosphorus -which is discharged into this water causes it to overflow. The crude -phosphorus having been fused under water is next mixed with 12 to 15 -per cent. of its weight of moist sand, and this mixture placed in -the retorts, the object of the mixing with sand being to prevent the -phosphorus becoming ignited during the filling of the retorts. - -[Illustration: FIG. 54.] - -Fig. 54 shows a distilling apparatus. In consists of a cast-iron -retort, _K_, fitted with a cast-iron dome, _H_, the joint being made -tight by means of clay and screws. The dome, _A_, tapers to a cone and -terminates in a wide glass tube, _R_, bent at a right angle, and having -at the mouth a diameter of about 2⅓ inches. - -This dome, _A_, dips ¾ inch deep in water contained in the copper -gutter of the receiver filled to the brim. The copper receiver, _P_, -stands in water. It contracts below in the form of a funnel, and -terminates in a pipe closed by a cock, _G_, to which is fitted a glass -tube bent at a right angle. - -The retort having been filled with the mixture of crude phosphorus and -sand, the dome, _H_, is placed in position and the apparatus brought -into the furnace. The dome is then connected with the condensing -apparatus. - -The fire is so regulated that the retort is uniformly heated from all -sides in order to evaporate as quickly as possible the water still -adhering to the phosphorus mixture, since at a higher temperature the -water acts upon the phosphorus, and phosphoretted hydrogen is formed. -It being scarcely possible to entirely avoid the formation of the -latter, the receiver has been given the above-described form, so that -the disagreeable vapors formed by the ignition of the phosphoretted -hydrogen cannot escape into the workroom. The gas escapes through the -conical dome. _A_, and the glass pipe, _R_, into the open air, where it -burns without molesting the workmen. - -At first steam only escapes from the retort, while later on -phosphoretted hydrogen passes off. The evolution of the latter, -however, soon ceases almost entirely, and the phosphorus distils -uniformly over. Heating is continued until the retort shows a slight -red heat, all the phosphorus having by that time passed over. The -residue in the retort consists only of sand and charcoal. - -The phosphorus passing over in the various stages of distillation shows -different qualities. The portion which passes over first is perfectly -pure, and when cold presents the appearance of bleached wax; the -portions passing over later on are of a yellowish-red color, while the -last portions are colored brick-red by amorphous phosphorus, and have -to be collected by themselves. They are again brought into the retort -in the subsequent operation. - -In order to be able to separate the phosphorus passing over according -to quality, the receiver for the melted mass is fitted with a conical -bottom furnished with a glass tube which can be closed by the cock _G_. -This glass pipe leads to a tank filled with warm water, in which the -collecting vessel is immersed. The phosphorus collecting in this vessel -is from time to time allowed to run into a vessel filled with water, -another vessel being substituted when the phosphorus commences to show -a yellowish color. - -_Moulding the refined phosphorus._ It has long been the custom to -mould phosphorus into the shape of sticks formed by the aid of a glass -tube open at both ends, one of these being placed in molten phosphorus -covered by a stratum of warm water. The liquid phosphorus is sucked by -the operator into the tube until it is quite filled. The lower opening -of the tube being kept under water is closed by the finger of the -operator; the tube is instantly transferred to a vessel filled with -very cold water by which the phosphorus is solidified. It is removed -from the glass tube by pushing it out with a glass rod or iron wire -while being held under water. - -Independent of its danger, the method of moulding above described -is not suitable for the manufacture on a large scale, and various -contrivances have been introduced for this purpose; the apparatus -constructed by Seubert being much used. It consists of a copper boiler -fitted on a furnace. To the flat bottom of this boiler is fitted by -hard solder an open copper trough communicating with a water-tank. In -the boiler is fitted a copper funnel provided with a horizontal tube. -This portion of the apparatus is intended for the reception of the -phosphorus. At the end of the horizontal tube is placed a stopcock, -while the portion of the projecting mouth of the tube beyond the -cock is widened out and fitted by means of bolts and nuts, with a -flange-like copper plate, into which are inserted two glass tubes. -Into the copper trough is let a wooden partition, which serves the -purpose of supporting the glass tubes as well as of preventing the -communication of the hot water in the boiler and a portion of the -trough with the cold water of the tank and the portion of the trough -nearest to it. The phosphorus having been introduced in the boiler, the -water is gently warmed so as to cause the fusion of the phosphorus. -As the warm water reaches to the wooden partition, it is evident that -on opening and closing the cock at the end of the horizontal tube, -some phosphorus will pass through and flow out of the glass tubes, but -that remaining in these tubes will solidify, and on opening again the -cock at the end of the horizontal tube, the solid sticks of phosphorus -may be removed from the glass tubes by taking hold of the piece of -projecting phosphorus, the phosphorus being immediately immersed under -water in the tank, and kept there protected from the action of the -light. - -Notwithstanding its apparently very practical arrangement, Seubert’s -apparatus possesses many disadvantages, the principal drawback to its -use being that the phosphorus-sticks frequently stick so firmly in the -glass tubes that the operation of moulding has to be interrupted, the -tubes removed, and the phosphorus stick pushed out with a stout wire. -Furthermore, the melted phosphorus in flowing in frequently causes the -glass tubes to crack. - -Hence many factories have returned to the old method of moulding by -sucking the fused phosphorus into glass tubes. To render this operation -perfectly free from danger, the apparatus shown in Fig. 55 has been -devised, by means of which a larger quantity of phosphorus can in a -short time be moulded into sticks. - -A hollow prism, _P_, of stout sheet-iron is fitted at its lower end -with 8 to 12 short tubes. In the latter are inserted air-tight, by -means of rubber, 12 glass tubes, _G_, each about 3¼ feet long and -somewhat contracted at the lower end. Two iron rods, _E_, are fitted -to the prism and, by means of suitably-shaped pieces of cork, serve -to hold the glass tubes in their proper position. To the back of the -prism is secured a rubber tube, _L_, which communicates with a small -air-pump, and to the upper surface of the prism is fixed a handle. - -[Illustration: FIG. 55.] - -The phosphorus to be moulded is fused in a shallow vessel of such a -shape that a portion of it is covered only about 2 inches deep with -water. The glass tubes are placed in the fused phosphorus and the air -is sucked from them by means of the air-pump; the external air-pressure -forcing the fused phosphorus into the glass tube. - -The tubes are now sufficiently raised to allow of a rubber plate being -pushed under their mouths in the shallower portion of the vessel. The -rubber plate is pressed against the tubes and the entire apparatus -placed in a vessel filled with cold water. The phosphorus solidifies -very rapidly in the lower narrower portions of the tubes, and the -latter are immediately detached from the prism and replaced by others. -The phosphorus when entirely cold is pushed from the glass tubes by -means of a wire or wooden stick. - -In some factories the phosphorus is moulded in wedge-shaped sheet-metal -boxes. In packing two such wedges are laid together with their -longitudinal sides so as to form a prism. - -Phosphorus is stored either in strong sheet-iron tanks or in wooden -boxes lined with tinned sheet-iron and covered with a stratum of water -fully 1¼ inches deep. For shipping smaller quantities of phosphorus, -the sticks are packed in tinned sheet-iron boxes and the latter having -been filled up with water, the lid is soldered on. To prevent the water -from freezing in winter, it is advisable to mix it with spirits of wine. - -_Manufacture of phosphorus with the assistance of electricity._ Readman -and Parker have recently devised a process for the manufacture of -phosphorus on a large scale in a continuously working apparatus by -means of a powerful electric current, such as is yielded by a larger -dynamo. The mixture used for the operation differs from the ordinary -one of calcium phosphate and charcoal, in that it contains in addition -a slag-forming body—a flux—silicic acid (quartz sand) being at first -used for the purpose. Numerous experiments, however, have shown kaolin -or pipe clay, _i. e._, aluminium silicate, to be more suitable. - -When a mixture of calcium phosphate, charcoal and aluminium silicate -is exposed to the action of the voltaic arc the following process -takes place: By the extraordinarily high temperature prevailing in the -proximity of the arc, the reduction to phosphorus of the phosphoric -acid contained in the calcium phosphate is very rapidly effected. The -liberated calcium combines immediately with the aluminium silicate to -a calcium-aluminium-silicate, _i. e._, to a glass fusible with the -greatest difficulty which, however, at the high temperature possessed -by the voltaic arc becomes fluid like water. - -The apparatus employed is, generally speaking, similar to the electric -furnaces now in use. The mass to be treated is contained in a carbon -crucible in which the two electrodes are placed opposite to one -another, so that the electric current must pass through the mass. -However, since the phosphorus at the moment of liberation would, on -coming in contact with oxygen, immediately burn again to phosphorus -pentoxide, the apparatus has to be so arranged that the entire process -passes off in an entirely indifferent gas, and the condensation of the -phosphorus vapors takes place under the same conditions. - -Fig. 56 shows the apparatus employed for the electrolytic manufacture -of phosphorus. - -[Illustration: FIG. 56.] - -The carbon crucible, _a_, is enclosed by a clay jacket, which serves as -an insulator of heat, and is closed by a graphite cover, _c_. Through -the bottom and the cover of the crucible pass the two electrodes, _k -k_, which conduct the current, and between which the voltaic arc is -formed. To prevent the upper electrode from becoming too highly heated -during the operation, it is constantly cooled by water admitted at _g_, -and running off at _f_. Through the pipes _h_ and _l_ an indifferent -gas—as a rule, illuminating gas—is conducted into the apparatus and -escapes together with the phosphorus vapors through the pipe _d_. - -In operating with the apparatus, the reduction soon takes place, and -the phosphorus vapors escape through _d_, while a thinly-fluid slag -remains behind in the crucible. The slag is discharged through a pipe -not shown in the illustration, and a fresh charge of the mixture -brought into the crucible _a_, the process of reduction being thus -carried on without interruption. The phosphorus vapors escaping from -_d_ are conducted through a cooled pipe and condense to a liquid in -water heated to between 122° and 140° F. contained in a receiver. - -Although the electrolytic method of manufacturing phosphorus is of -quite recent origin, a considerable portion of the phosphorus brought -into commerce is now prepared in that manner, it being cheaper than the -older processes which involve a very large consumption of fuel. - - - - -CHAPTER VII. - -METHODS OF BLEACHING GLUE. - - -Many experiments have been made to bleach glue, _i. e._, to obtain -masses as colorless as possible, or at least slightly colored, the -resulting product being more valuable than the dark-colored one. - - -a. _Bleaching in the Air._ - -The principal requisite for obtaining a beautiful bleached glue is that -the unbleached product is clear, _i. e._, transparent, even if of a -dark color, this being the best criterion of well-made glue. - -Glue may be bleached whilst being prepared, or the finished cakes may -be subjected to the bleaching process. - -For the purpose of obtaining pale-colored glue from skin or cartilage -it is advisable to expose the materials in thin layers to the direct -action of the sun. Moist oxygen when acted upon by the sun is converted -into ozone, which exerts an extraordinary bleaching effect upon organic -substances. - - -b. _Bleaching with Chlorine._ - -The powerful bleaching effect of a solution of chlorine in water upon -organic matter is well known; the water is decomposed, and bleaching is -effected by the oxygen which is liberated. Hence skin and cartilage may -also be bleached by placing them in a vessel filled with weak solution -of chlorine in water and leaving them in contact with it until the -fluid shows no longer an odor of chlorine. When bleaching is finished -the materials are suspended in a certain quantity of hydrochloric acid, -which has finally to be removed by repeated treatment with water. - - -c. _Bleaching with Animal Charcoal._ - -Animal charcoal is distinguished by its great power of absorbing -coloring as well as odoriferous matter, and may also be used for -discoloring glue-liquors. This may be done by allowing the thin liquor, -as it comes from the glue-boiler, to run through a filter filled with -animal charcoal, or with the use of charcoal dust. - -In the latter case the glue-liquor is collected in a clarifying vessel -and a quantity of charcoal dust amounting to about 3 to 4 per cent. of -the weight of the glue in the liquor stirred in. The finely divided -charcoal sinks slowly down, carrying with it the solid particles -suspended in the liquor, and collects on the bottom of the clarifying -vessel in the form of a black slime. - -In order to discolor the glue-liquor as much as possible, when working -on a large scale, it is recommended to use a number of cylinders filled -with animal charcoal. These cylinders are connected one with the other -in such a manner that the glue-liquor runs into the first cylinder from -the top, passes out from the lower end of this cylinder through a pipe -into the second cylinder, traverses this from bottom to top, passes -into the third cylinder from the top, and so on. The animal charcoal -in the first cylinder loses its discoloring power first. The cylinder -is then disengaged, freshly charged and placed last in the series of -filters, the process being the same with the second cylinder, and so -on, so that after a certain time all the cylinders have alternately -occupied the first and last places in the series of filters. - -By the use of animal charcoal it is even possible to render very dark -and badly-smelling glue, entirely colorless and free from odor. The -darker the glue is, the longer it must, of course, be subjected to the -action of the animal charcoal. - - -d. _Bleaching with Sulphurous Acid._ - -Bleaching of the glue-liquor itself by means of sulphurous acid is -best effected in the clarifying vat. For this purpose, the latter is -fitted with a lead pipe reaching to the bottom and terminating in a -perforated coil. Through this pipe gaseous sulphurous acid, generated -in a suitable sulphur-burner is forced through the liquor by means of a -force-pump. - -The sulphurous acid is dissolved in the glue-liquor, the latter being -thereby bleached. When the liquor has acquired a much paler color and -a strong odor of sulphurous acid is perceptible in the air over the -vat, the introduction of gaseous sulphurous acid is interrupted and the -liquor allowed quietly to clarify, the acid dissolved in it exerting -during this time a further bleaching effect. By this means ordinary -brown joiners’ glue of good quality may be converted into a pale-yellow -product similar to the variety known as gilder’s glue. - -[Illustration: FIG. 57.] - -For bleaching finished glue, solution of sulphurous acid in water may -be used, the apparatus shown in Figs. 57 and 58 being suitable for the -purpose. - -The apparatus for the production of the acid solution consists of the -sulphur-burner _O_, the wash-vessel for the gas _W_, and the vessel _T_ -for dissolving the gas in water. - -The sulphur-burner _O_ is a small brick vault of sufficient size to -hold a vessel _S_ having a capacity of a few quarts. In front the -sulphur-burner is provided with a well-fitting door _J_, which is -furnished with a small aperture for the introduction of an iron pipe -into the burner. The lead-pipe _R_ leads from _O_ to the bottom of the -wash-vessel _W_, and from the lid of the latter rises a pipe _R_{1}_, -and runs along the bottom of the trough filled with water. This trough -is provided with a wooden lid and the cock _H_, and by means of the -latter the fluid can be discharged into the vessel _G_. - -[Illustration: FIG. 58.] - -The trough _T_ is filled with water and _W_ is also filled -three-quarters full. In the burner _O_ is placed a dish _S_ filled with -sulphur, and the latter ignited. The door is then closed and air blown -in through _A_ by means of a bellows, the joints of the door _J_ being -at the same time luted with clay. - -In contact with air, the sulphur burns to sulphur dioxide. The latter -is freed in the wash-vessel from sulphur vapor which has been carried -along, and passes from _R_{1}_ through the numerous perforations into -the water in _T_ where it is dissolved to sulphurous acid. - -Saturation with sulphurous acid of the fluid in the trough is complete -when the suffocating odor of the acid is perceptible in the proximity -of _T_. The fluid is then discharged, replaced by water, which is again -saturated with sulphuric acid, and so on. - -The cakes of glue to be bleached are placed in a trough (Fig. 58), in -which are arranged several frames, _B_, covered with linen. The cakes -of glue are placed upon these frames and the trough is filled with -sulphurous acid so that it stands a few inches deep over the uppermost -frame. The cakes of glue swell up rapidly in the solution of sulphurous -acid, and yielding up their salts become bleached. After twelve hours -the fluid is discharged through the cock, _H_, and if glue of a -particularly fine appearance is to be produced the cakes are treated -twice more with solution of sulphurous acid. - -When bleaching is finished the trough is filled with clean water, in -which the glue is allowed to remain for a few hours, when the frames -are lifted out and the cakes dried. - -By this method glue may be bleached to such an extent as to render it -fit as a substitute for gelatine for many purposes, for instance, for -the imitation of thin plates of ivory. - -Dr. Bruno Terne’s apparatus (Fig. 40), previously described, may also -be used for the generation of sulphurous acid for bleaching purposes. - - - - -CHAPTER VIII. - -DIFFERENT VARIETIES OF GLUE AND THEIR PREPARATION. - - -Besides the broadly-distinguished forms of skin-and bone-glue, the -trade recognizes a large number of varieties, distinguished either by -their value or their fitness for special purposes. - -_Joiner’s Glue._—This variety is without doubt the oldest in use and -most in demand, and its principal requisite is its great adhesive -power. It is used for joining wood, leather, paper, etc., and varies -very much in quality and price. - -The best variety is prepared from scraps of hide and skin. A light -color not being especially demanded, there existing rather a prejudice -in favor of a dark-colored article, waste of cattle and horse skins and -tendons can be used for its manufacture. - -Joiner’s glue, which is generally preferred in thin cakes, is chiefly -manufactured in regular glue factories, though to be able to compete -with the bone-glue turned out by the large establishments, the -glue-boiler generally mixes skin and bone-glue, and is thus enabled to -turn out a tolerably good quality. The price paid for the different -varieties of joiner’s glue varies very much, being generally higher in -winter than in summer, and is frequently more regulated by the external -appearance of the article than by its actual value. Glue without gloss, -very much warped and of a very dark color, may, notwithstanding its -faulty appearance, possess excellent qualities. - -Nothing need be said about the manufacture of joiner’s glue, since what -has been said about the manufacture of glue in general suffices for the -purpose. - -_How to make and use glue._ Break the glue into small pieces, put it -into an iron kettle, cover it with water, and allow it to soak twelve -hours; after soaking boil until done. Then pour into a box which can be -covered air-tight; leave the cover off until cold, then cover up tight. -As glue is required, cut out a portion and melt in the usual way. -Expose no more of the made glue to the atmosphere for any length of -time than is necessary, as the atmosphere is very destructive to made -glue. - -All glue, as received from the factory, requires the addition of water -before it will melt properly, and every addition of water (while -the glue is fresh made) will, up to a certain point, increase its -adhesiveness and elasticity. Some glues will bear more water than -others, but all will bear more water than usually falls to their share, -and that, too, with a greater improvement in the quality of the work. -For glue to be properly effective, it requires to penetrate the pores -of the wood, and the more a body of glue penetrates the wood the more -substantial the joint will remain. Glues that take the longest to dry -are to be preferred to those that dry quickly, the slow-drying glues -being always the strongest, other things being equal. Never heat made -glue in a pot that is subjected to the direct heat of the fire or a -lamp. All such methods of heating glue cannot be condemned in terms too -strong. Do not use thick glue for joints or veneering. In all cases -work it well into the wood in a manner similar to what painters do -with paint. Glue both surfaces of your work excepting in the case of -veneering. Never glue upon hot wood, as it will absorb all the water in -the glue too suddenly, and leave only a very little residue, with no -adhesiveness in it whatever. - -_Holding power of glue._ 1. Glue exerts a far greater hold on surfaces -of wood cut across the grain than on those that have been split, or cut -with the grain. - -2. When two surfaces of split wood are laid together, the hold of the -glue is the same whether the fibres are laid parallel or crosswise to -each other. - -3. The holding power of glue on different woods estimated in -kilogrammes per square centimeter (0.155 square inch) is as follows: - - Cut across the grain. Split. - Beech, 155.55 (342.21 lbs.) 78.83 (173.42 lbs.) - Hornbeam, 126.50 (278.30 lbs.) 79.16 (174.15 lbs.) - Maple, 87.66 (192.85 lbs.) 63.00 (138.6 lbs.) - Oak, 128.34 (282.34 lbs.) 55.16 (121.35 lbs.) - Fir, 110.50 (243.10 lbs.) 24.16 (53.15 lbs.) - -_Cologne glue._ The variety of glue known under this name is prepared -from selected scraps of hide and skin, and is consequently very pure, -and possesses great adhesive power. It is of a light-brown color, -and comes into commerce in short thick cakes of great hardness. It -is an excellent quality of glue, and is preferred to all others by -bookbinders, workers in leather, etc. There are many imitations of this -variety, bone-glue being frequently sold as Cologne glue. - -The genuine article is manufactured from refuse of hide, which, after -liming, is carefully bleached in a bath of chloride of lime, the -concentration of which depends on the darker or lighter color of the -glue-stock. For 220 lbs. of glue-stock, it is generally customary to -use 1 lb. of chloride of lime mixed with sufficient water to cover the -stock. - -After thorough impregnation of the glue-stock, which generally requires -about half an hour, add sufficient hydrochloric acid to impart an acid -taste to the bath of chloride of lime. To be able to mix the mass -thoroughly, it is best to use a vat provided with a stirring apparatus. -After allowing the acid to act for a quarter of an hour, remove every -trace of it by careful washing. - -To obtain a jelly as clear as possible, the gelatinous liquor is drawn -off as soon as the thin portions of the glue-stock and the outside of -the thicker ones are dissolved, they being more thoroughly bleached -than the rest. The residue is worked into darker glue. - -_Russian glue._ This variety is of a dirty white color, and, like -Cologne glue, is brought into commerce in short, thick cakes. Its color -and opaqueness are imparted to it by an addition of 4 to 8 per cent. of -white lead, chalk, zinc white, or permanent white (sulphate of baryta). -It has been claimed that the superior adhesive power of Russian glue -is due to this addition of mineral substances, but the results of many -experiments fail to substantiate this claim. In case the glue turns -out turbid, it may be of advantage to make it opaque by an addition of -coloring matter, but the quality of the glue remains unchanged. The -best time to add the coloring matter is shortly before drawing the -glue-liquor from the clarifying vats into the cooling boxes, as the -jelly is then of sufficient consistency to prevent the substances from -settling on the bottom. Skin-glue, as well as bone-glue, is sold under -the name of Russian glue. - -Quite a considerable quantity of Russian glue brought into commerce in -the form of brownish-white sheets is prepared from bones, the latter -being degreased by boiling, steaming or extraction, and the solution of -the mineral constituents effected by means of hydrochloric acid. The -treatment with acid is, however, continued only till the bones commence -to become soft and flexible. The solution of phosphates is then drawn -off, and the softened bones are washed and in the usual manner worked -to glue. - -By this incomplete treatment with hydrochloric acid, a certain quantity -of the phosphates remains in the cartilage and is inclosed in the -glue prepared from it, the finished product acquiring thereby a dirty -whitish color, which is by many considered an evidence of its quality. -This mechanical admixture of phosphates, however, does not affect the -adhesive power of the glue, neither increasing or decreasing it. Such -white and opaque glue is manufactured to answer the demand in certain -quarters of the trade, and, as above mentioned, heavy white substances -are often intentionally incorporated with skin glue, as well as bone -glue, to give it the appearance of Russian glue. These heavy powders -add to the weight of the product, though when incorporated with it in -small quantities do not injure its adhesive power, but large quantities -render the product weaker. - -_Patent glue._ This term is applied to an indefinite number of -preparations, but particularly refers to a very pure variety of bone -glue of a deep dark-brown color not showing net marks. It is very -glossy, and swells up much in water. To satisfy the demand for thick -cakes, they must be cut from very concentrated jelly to insure their -drying. - -_Gilder’s glue_ is found in commerce in very thin, pale yellow cakes -tied up in packages weighing about 2 lbs. each. It is a variety of skin -glue bleached with chloride of lime, and dissolves with difficulty in -water. The first runnings from the boiler are used for its manufacture. - -A very superior article of gilder’s glue is obtained by cutting -rabbit skins into fine shreds and boiling in water, then turning the -mixture into a basket through which the liquid passes, leaving the -refuse behind. About 100 grammes (3.52 ozs.) of sulphate of zinc and -20 grammes (0.705 oz.) of alum are then separately dissolved in pure -boiling water and poured into the first-mentioned liquid, and the whole -well stirred together while hot. The mixture is then passed through a -sieve into a rectangular box, in which the jelly remains twenty-four -hours in winter, or forty-eight in summer. The solid mass is taken from -the box, cut into slices of proper thickness, and dried upon nets. - -_Size glue and parchment glue_ are manufactured in the same manner. -Both are skin-glues, and can be readily produced by following the -directions given for the manufacture of skin-glue. - -_Paris glue_ is used for sizing. It is brown, opaque, and almost always -soft. Being very hygroscopic, and imparting a suitable flexibility to -the felt, it is better adapted for hatter’s use than any other variety. -For its manufacture only the generative organs, or the thick tendons -of the legs of cattle and horses, are used, or other waste and fleshy -parts, and substances mixed with small bones, which, if thoroughly -cleansed, might yield a good quality of glue, but are intentionally -transformed by too long-continued boiling, whereby the gelatinous -solution is largely deprived of its adhesive power, and yields a -hygroscopic product. - -_Liquid Glues._ These are chiefly combinations of glue with some -ingredients added to destroy the gelatinizing property and yet not -impair its adhesiveness. They remain for a long time clear and syrupy, -and are used for a variety of purposes. Below are given a few receipts -for such glues. - -1. Dissolve 38 parts of glue in small pieces in 100 parts of acetic -acid. Solution is promoted by exposing the vessel to the sun or placing -it in hot water. - -2. Dissolve 50 parts of light-colored glue in 50 parts by weight of -hot water, in which 14 parts of fused magnesium chloride have been -dissolved. The solution on cooling does not gelatinize, but remains -syrupy, the density varying according to the quantity of water used. In -the preparation of printing inks it can be used as a substitute for gum. - -3. Dilute 10 parts of strong phosphoric acid with an equal weight of -water, and then gradually add 4 parts of ammonium carbonate in the dry -state. When the effervescence has subsided, add a further 5 parts of -water and warm on the water-bath or steam-chest to 158° F. Now add 20 -to 40 parts of glue, according to the consistency required, and stir -until all is dissolved. Cool. - -4. Dissolve 20 parts of glue in an equal weight of hot water, then -cautiously pour in, stirring constantly, 4 parts of strong nitric -acid, warm until the nitrous fumes have been driven off, filter, if -necessary, through fine shavings, and allow to cool. - -5. Dissolve 3 parts of glue in small pieces in 12 to 15 parts of -saccharate of lime. By heating, the glue dissolves rapidly and remains -liquid, when cold, without loss of adhesive power. Any desirable -consistency can be secured by varying the amount of saccharate of lime. -Thick glue retains its muddy color, while a thin solution becomes clear -on standing. - -The saccharate of lime is prepared by dissolving 1 part of loaf sugar -in 3 parts of water, and after adding one-fourth part of the weight of -sugar of slaked lime, heating the whole to between 149° and 185° F., -and allowing it to macerate for several days, shaking it frequently. -The solution, which has the properties of mucilage, is then decanted -from the sediment. - -The solution of the glue in saccharate of lime is readily accomplished, -even old gelatine, which has become insoluble in water, dissolving -without difficulty. This variety of liquid glue possesses great -adhesive power, and admits of many uses. - -6. Dissolve 8 parts of glue in 16 parts of hot water, then add ½ to 1 -part of hydrochloric acid, and 1½ parts of sulphate of zinc. Keep the -mixture for 8 hours at 158° F., then filter through fine shavings, and -allow to cool. - -_Steam glue._ Under this name several varieties of liquid glue are -brought into commerce. They are prepared as follows:— - -1. _Russian steam-glue._ 100 parts of a good quality of glue, 100 to -110 parts of warm water, and 5.5 to 6 parts of commercial nitric acid -of 36° B. - -2. _Pale steam-glue._ 100 parts of glue, 200 of water, and 12 of nitric -acid of 36° B. - -3. _Dark steam-glue._ 100 parts of glue, 140 of water, and 16 of nitric -acid of 36° B. - -Soak the glue in cold water, then pour the necessary quantity of warm -water over it, and heat gently on a water-bath until all the glue is -dissolved. Next add gradually the nitric acid with constant stirring, -and to the Russian steam-glue 6 parts of finely pulverized sulphate of -lead, which will impart to it the white color. - -_Chrome glue._ This preparation is very permanent and durable. To -prepare it add to a moderately concentrated solution of 5 parts of -glue 1 of dissolved acid chromate of lime, this salt being considered -better for the purpose than the bichromate of potash usually used. The -glue thus prepared becomes, after exposure to the light, insoluble -in water in consequence of a partial reduction of the chromic acid. -This preparation can be used for cementing glass articles, liable to -be exposed to boiling water, the treatment being the ordinary one of -applying the glue to both surfaces of the fractured object, and then -binding them together until dry, and exposing them for a sufficient -length of time to the light, after which boiling water will have no -effect upon them. It is suggested that this preparation is better -adapted to cementing the covers on glass slides than any now in use. -The same preparation can be applied for making fabrics water-proof, -especially sails, awnings, etc., where no great flexibility is -required. Two or three applications of the glue, either by immersion -of the object in it, or by the use of the brush, will answer the -purpose. Roofing paper is also rendered impervious, even when exposed -to long-continued rains. - -_Glue for attaching leather to metal._ A method of affixing leather to -metal, so that it will split before it can be torn off, consists in -digesting a quantity of nutgalls, reduced to powder, in eight parts of -distilled water for six hours, and filtering it through a cloth; then -dissolving one part by weight of glue in the same quantity of water, -and allowing it to remain twenty-four hours. The leather is moistened -with the decoction of nutgalls and the solution of glue applied to the -metal, previously roughened and heated. The leather is then laid upon -it, and dried under pressure. - -_Glue for leather, paper, etc._ The following process affords an -unusually adhesive paste, adapted to fastening leather, paper, etc., -without the defects of glue, and if preserved from evaporation in -closed bottles will keep for years. Cover 4 parts, by weight, of glue -with 15 parts of cold water, and allow it to soak for several hours; -then warm moderately till the solution is perfectly clear, and dilute -it with 65 parts of boiling water, intimately stirred in. Next prepare -a solution of 30 parts of starch in 200 of cold water, so as to form -a thin homogeneous liquid free from lumps, and pour the boiling glue -solution into it with thorough stirring, and at the same time keeping -the mass boiling. - -_Glue for parchment paper in making sausage skins._ The supply -of intestines soon being exhausted by the enormous quantity -of pease-sausages manufactured for the German army during the -Franco-German war, the necessity arose for a substitute. This consisted -of a tube of parchment glued together. Millions of these tubes from Dr. -Jacobsen’s factory were tested by the government, and found to answer -the purpose admirably. They were even boiled for hours without either -the glued seam or the paper itself being injured by the operation. -The secret of the composition of the glue employed for fastening -the parchment paper seems to be well kept, but the one given in the -following is equal to it in all respects, if not indeed identical: -Add to one quart of a good adhesive solution of glue ¾ to 1 oz. of -finely powdered bichromate of potash. Warm the mixture slightly on a -water-bath when about to use it, and before applying it moisten the -parchment paper. The latter, when glued with this preparation, as in -the formation of the small cylinders for sausages, must be rapidly -dried on a hurdle, and then exposed to the light until the yellow glue -becomes brownish. The cylinders are then slowly boiled in a sufficient -quantity of water to which two or three per cent. of alum has been -added, until all the chromate is dissolved out, and they are then -washed in cold water and dried, and will look very inviting, especially -if white glue has been used. A similar result may be reached by using -a concentrated solution of cellulose in ammoniacal oxide of copper. -Thus if cylinders of unsized paper are formed with this paste, and -when thoroughly dry drawn through a parchmentizing solution (a cooled -mixture of 2 volumes of fuming sulphuric acid and 1 volume of water), -they will be beautifully parchmentized, and after the neutralization -of the acid, washing, etc., it will present a striking resemblance to -natural intestines. - -_Tungstic glue._ This preparation offers an acceptable substitute for -hard India rubber. It is made by mixing a thick solution of glue with -tungstate of soda and hydrochloric acid, by means of which a compound -of tungstic acid and glue is precipitated, which, at a temperature of -86° to 104° F., is sufficiently elastic to admit of being drawn out -into very thin sheets. On cooling, this mass becomes solid and brittle, -and on being heated is again soft and plastic. It can be used for all -purposes to which hard rubber is adapted. - -_Indestructible mass for the manufacture of ornaments, toys, etc._ A -mass, which is to have the hardness of horn, consists of 50 parts of -glue, 35 of wax or rosin, 15 of glycerine and the required quantity of -a metallic oxide, or mineral color. A soft mass consists of about 50 -parts of glue, 25 of wax or rosin, and 25 of glycerine. The glue is -melted in the glycerine with the assistance of steam, and the wax or -rosin added. The latter in melting mixes with the glue and glycerine, -and finally the mineral color is added. The mass is poured in a liquid -state into moulds of plaster of Paris, wood, or metal. The degree of -hardness of the mass is increased by an addition of 30 to 35 per cent. -of zinc white, or other mineral color, according to the color the -article is to have. - -_Compound for billiard balls._ Allow 80 parts of Russian glue and 10 -parts of Cologne glue to swell up in 10 parts of water; then heat over -a water-bath, and when dissolved, add 5 parts of heavy spar, 4 parts -of chalk and 1 part of boiled linseed oil. Of a portion of the mass -form small sticks, dip them in the remainder, and allow the adherent -portion to dry, and repeat this process until a crude ball has been -formed. This is placed in a dry room for three or four months, and when -thoroughly dry, it is turned. The finished ball is placed in a bath of -sulphate of alumina for one hour, dried, and polished like an ivory -ball. - -_Coloring glue._ Common black or dark glue, while possessing all the -adhesive and other essential qualities of fine colored glue, has -heretofore, owing to its color, been confined in its use to such -purposes in the arts where color was not essential. - -The object of the following process, which is the invention of G. J. -Lesser, of Frankfort, Germany, is to color such glue so that it is both -refined and tinted, and may be used for various purposes in the arts. -It is especially applicable in the manufacture of sizing and finishing -compounds for paper hangings, compounds for the manufacture of elastic -rolls, for glue and size compounds for finishing yarns, textile -fabrics of silk, cotton, etc., for the manufacture of calcimines and -wall-coverings, for glue to be used with colored woods, and for all -other purposes where a fine, strong-colored glue is required. - -For coloring common black or dark glue take a pound and a half of -liquid extract of lead and mix it into the water in which the glue has -been soaked, as follows: Thirteen pounds of glue, sixty-three and a -quarter pounds of water. Allow the glue to soak for about twenty-four -hours, then dilute it by a slow fire, and when heated gradually pour in -one and a half pounds of the extract of lead and mix it well together. - -The extract of lead is a well-known commercial article, and it is well -suited for this purpose; but the inventor does not limit himself to -this particular preparation, as there are a larger number of neutral -and basic compounds of lead that may be so modified as to produce -results similar, if not identical, with the results obtained by the -formula above given. Gelatine may be treated instead of glue. - -_Compositions for printing rollers._ All such compositions contain -gelatine or glue. The following receipts are used: - - - | I. | II. | III.| IV.| V. | VI. | VII.| VIII. --------------+-----+-----+-----+-----+-----+-----+-----+-----+ - Glue | 8 | 10 | 4 | 2 | 32 | 2 | 1 | 3 - Molasses | 12 | — | 8 | 1 | 12 | 6 | 2 | 8 - Paris white | 1 | — | — | — | — | — | — | 1 - Sugar | — | 10 | — | — | — | — | — | — - Glycerin | — | 12 | — | — | 56 | — | — | — - Isinglass | — |1½ ozs.| — | — | — | — | — | — - India rubber| — | — | — | — | 10 | — | — | — - in naphtha - - -A patent roller composition is thus made: Gelatine 32 lbs. and glue -4 lbs. are softened in cold water and melted in a glue boiler. To -this are added 4 lbs. of glucose, 72 lbs. of glycerine, and 1 oz. of -methylated spirit. The whole is then digested for four to six hours -and cast into rollers. This composition is claimed to be unaffected by -temperature, to retain its elasticity, and not to shrink. - -In practice it is found that all these compositions from the cleansing -and remelting become gradually sticky and useless. To partially -overcome this difficulty, formaldehyde is added to the roller -composition, which renders the glue insoluble in water, and thus -prolongs the life of the roller. - -_Size._ This product is simply an undried glue and is used, not -for adhesiveness, but as a body for filling porous surfaces, such -as wood or plaster, stiffening and weighting textile fabrics, in -paper manufacture, and as a foundation for oil paints and varnishes. -According to Thomas Lambert, many firms who have a good selling -connection for size, do not go to the expense of erecting clarifying -plant and drying house for treating the glue-liquors, but prefer to -stop the process half way, as it were, and marketing the resulting -product as size. Others, again, with a complete glue plant at hand, -convert only a portion of their liquors into size, to meet trade -demands, the bulk going for the manufacture of glue. Size varies -in quality to suit the requirements of different trades. Cardboard -box-makers prefer a strong skin size, which is manufactured red or -yellow as preferred. A strong yellow size made from bone is used by -calico-printers, paper-stainers, wall-paper manufacturers, and in the -straw-hat and carpet trades. - -In the preparation of skin-glue, the first and second liquors are used -for that purpose; the residual mass is then treated with water and -steam, which practically exhausts the gelatinous matter. This, the -third liquor, is used solely for size. During the boiling, samples -are taken at intervals, cooled, and the condition of the jelly noted. -The strength is also taken by the glue meter, which registers the -percentage. At a strength of 8 to 10 per cent. the liquor is run off, -passing through a filter of fine shavings or cloth, to remove any -suspended matter, into a wooden vat fitted with a steam coil, then -heated with a moderate charge of sulphurous acid to bring up the color, -and evaporated to a strength of 36 to 38 per cent., as may be desired, -and then run into casks to jelly. If skin-glue is not made, the three -runnings are used entirely for size. - -An outline of a simple process used in an English factory devoted to -making tub-size, as given by Samuel Rideal, may be interesting. - -The material is obtained from the tanyard ready limed and freed from -hair, and consists mainly of “faces” of bullocks or cows, the noses -being cut off as food for dogs. It is soaked again in weak lime water -and re-washed, then placed in coppers made of wrought-iron wielded -in one piece, and holding about 10 to 20 gallons, enclosed in outer -jackets of the same material containing water which is kept well -boiling. There are six coppers, about five feet high by three feet in -diameter. The charge of each is about ½ cwt. The material is covered -with water and well stirred with sticks for two hours, the scum and -dross being occasionally skimmed off and thrown away as useless. At the -end the size is ladled on to sieves, from which it runs into cooling -vats, and is filled while moderately hot into clean tubs. - -The liquor is clear and of a light brown color for the best XX quality, -and darker for the common. The coolers or setting-backs are of wood or -zinc, and the liquid is not kept hot longer than it can be helped, as -it is liable to turn sour. - -Bone-size is, according to Thomas Lambert, prepared as follows: The -bones are first degreased by the naphtha process, and then passed -through the cleanser direct into the glue-boilers and steamed, as in -the manufacture of glue. The resulting liquors are forced up to the -clarifying vats and partially bleached with a current of sulphurous -acid, passing through bag-filters to the evaporating troughs, and -concentrated from 30 to 38 per cent., as required, and then jellied in -casks. - -The manufacturer with no benzine or glue plant at his disposal washes -the bones in a revolving drum, and, after crushing, they are fed into -a boiler and subjected to an alternate current of steam and water, the -latter coming from a spray pipe fixed at the top of the boiler. The -liquors are generally drawn in two portions, having a strength of 14 to -16 per cent. of glue. After separating the fat, which is refined and -sold to the soap-maker, the liquors are run into a large wooden vat -about 8 × 6 × 4 feet, fitted with a steam coil, partly bleached with -liquid sulphurous acid, and then boiled down to the required strength. - -For a common size the bones are crushed but unwashed, and are fed -direct into the boiler and treated as above. The liquors are not -bleached, and boiled to a strength of about 25 per cent. glue. The -composition of the different grades may be given as follows: - - Common size. 25 per cent. glue, 75 per cent. water, etc. - Medium size. 30 per cent. glue, 70 per cent. water. - Best size. 38 per cent. glue, 62 per cent. water. - -A concentrated size is now prepared by many manufacturers. It is a -bone-size, and is sold at a Baumé strength at 122° C. - - No. 1. 15° Bé. at 122° C., 40.5 per cent. glue. - No. 2. 20° Bé. at 122° C., 44.5 per cent. glue. - No. 3. 25° Bé. at 122° C., 49 per cent. glue. - -Under the name of concentrated size also are sold a series of powdered -glues of different qualities. They are the off-color and twisted cakes, -sorted out in the warehouse, and ground to a fine condition by passing -through a mill, and their value is based on the quality of the cake -ground. - -Size rapidly ferments and becomes sour and mouldy unless some -preservative is added. Sulphate of zinc is mainly used for this purpose. - -_Bookbinders’ Size._—I. Water, 2 quarts; powdered alum, 1 oz.; Russian -isinglass, 2 ozs.; curd soap, 40 grains. Simmer one hour, strain -through linen or a fine sieve, and use while warm. - -II. Water, 2 gallons; best glue, 1 lb.; alum, 4 ozs. Prepare and use as -above. - -III. Water, 2 quarts; isinglass, 5 ozs.; alum, 240 grains. - -_Water-proof Glue._—Solution of glue by itself or mixed with pigments -is used in painting walls in distemper. A water-proof coat is obtained -as follows: Boil 1 part of powdered gall-nuts and 12 parts of water -until the mass is reduced to two-thirds of its bulk. Then strain -through a cloth and apply the solution to the dry coat of distemper -paint, the latter becoming thereby as solid and insoluble as oil-paint. -The tannin of the gall-nuts acting only upon soft glue, the solution -has to be applied so the lower layer of glue becomes thoroughly soaked -through. - -To render _wrapping paper_ water-proof the following glue-solution may -be used: Dissolve 24 parts of alum and 4 parts of white soap in 32 -parts of water in one pot, and in another 2 parts of gum arabic and 6 -parts of glue in 32 parts of water, and mix the two solutions. Heat -the mixture, immerse the wrapping paper in it, and pass it through hot -rolls, or dry upon twine stretched in frames. - -_Fabrics may be rendered water-proof_ with glue and tannin. The process -is based on the fact that by the action of tannin or bichromates, -compounds insoluble in water are formed. It is, however, of first -importance that both solutions—tannin and glue—should fully penetrate -the fabric. If the latter is dipped directly into strong solution of -glue and then of tannin, the glue will only become insoluble on the -outside, and that which has penetrated deeper into the fibre will be -unchanged, having been protected by the superficial insoluble layer. -Hence, the treatment is commenced with a very weak solution of glue, -prepared by leaving glue broken small in hundred times its weight of -water for twenty-four hours. By that time the glue will have swelled -up, and the whole is boiled, whilst being constantly stirred, so as -to get a perfectly clear solution in which the fabric is boiled for -10 to 15 minutes. This time is no more than necessary for complete -penetration. The fabric is then well wrung between two rollers placed -over the glue-bath so that excess of solution runs back into it. The -fabric is then hung up, and when nearly dry is passed through a tannin -solution. The latter may be made from tannin itself, or from a tannin -extract, or by boiling galls or oak bark in water. The tannin solution -can be used fairly strong, as only so much of it is taken up as -corresponds to the glue present, and it can be used over again as long -as it can supply the tannin required, and can then be reinforced with -more tannin as required. - -It is not necessary for the fabric to stay long in the tannin, as it -reacts quickly with the glue. The tanned material is again hung up -to dry, and when quite dry is washed in plain water to remove any -excess of tannin. The whole process from the beginning is then twice -repeated. After this second repetition there is so thick a layer of -tannate of gelatine on the fabric that the dry cloth has acquired -considerable solidity and a smoothness which recalls that of leather. -The fabric is now passed through a stronger glue solution, using three -or even four parts of glue per hundred of water, but never exceeding -the latter limit. After the glue-bath the fabric goes through the -tannin bath, whereby it becomes quite thickly coated with tannate of -gelatine. By repeatedly treating with glue and tannin alternately, -this coating can be made as thick as desired, and finally masses are -obtained in which the texture of the fabric is entirely hidden, and -especially after the fabric has been calendered under heavy pressure -after water-proofing. The color acquired by goods thus water-proofed is -a more or less dark leather-brown. - -Muratori and Landry treat the fabric with a solution made in three -separate operations: - -1. Potash alum 100 lbs. dissolved in 10 gallons of boiling water. - -2. In another vessel 100 lbs. of glue are soaked in cold water till the -glue has trebled in weight. The remaining water is poured off, and the -glue liquefied by the application of heat. When the glue is boiling, 5 -lbs. of tannin and 2 lbs. of soda water glass are put in it. - -3. The two solutions are boiled together, being stirred constantly. - -When the mixture is complete, it is allowed to cool to a jelly. To -water-proof the goods some of the jelly is boiled with water (1 gallon -to 1 lb., or a little over) for three hours, adding water to compensate -for evaporation, so as to keep the volume of the solution constant, -as shown by tests of its specific gravity with a hydrometer. The bath -is then allowed to cool to 176° F., and the fabric is soaked in it -for half an hour and then stretched out horizontally for six hours -to drain. The fabric must be kept horizontal, so that the solution -remains uniformly distributed through it. The drainings are collected -to be used over again. The fabric is then dried in the open air or in a -drying room, still in the horizontal position. If a drying room is used -the temperature of it should not exceed 122° F. - -Muzmann and Krakowitzer dissolve 10 lbs. of gelatine and 10 lbs. of -tallow soap in 30 gallons of boiling water, and mix the solution in -4 gallons of water in which 15 lbs. of alum have been dissolved. The -whole is boiled for half an hour, and then allowed to cool to 104° -F. At that temperature the fabric is thoroughly soaked in it, dried, -rinsed, again dried, and finally calendered. In this process the alum -partially decomposes the soap, forming either free fatty acid or an -acid alumina soap. The gelatine forms an insoluble compound with the -alum. The free fatty acid or acid soap is mostly carried down on the -fibre by the precipitate formed by the alum and the gelatine. - -_Glue for Joints in Leather Driving Belts._—Soak equal parts of good -hide glue and isinglass in water for 10 hours, and then boil with pure -tannin till the product becomes sticky. The surfaces to be cemented -together should be roughened and the glue applied hot. - -According to another method 2 lbs. of best glue are dissolved at a -moderate heat in 3 lbs. of water and about 3 drachms of carbolic acid -stirred into the hot solution. The mixture is poured into shallow iron -pans to congeal, when it is cut in pieces and dried in the air. For use -the glue is liquefied by adding a small quantity of vinegar and applied -with a brush to the leather. The joint is finally pressed between iron -plates at a temperature of about 77° F. - -_Hectograph Mass._—Soak a good quality of glue for 24 hours in -sufficient cold water to cover it. Then take the swelled glue from -the water and melt it in an enameled pot over a moderate fire. When -perfectly liquid add the required quantity of glycerine (see formulas -below) and intimately mix both by continued stirring. - -The vessel containing the mixture should for some time be kept hot, so -that the mass remains thinly fluid. The purpose of this is to allow -the air-bubbles formed by stirring to rise to the surface. If any scum -is formed on the surface, remove it carefully with a shallow spoon. -The composition is then ready to be poured into the vessel intended -for its reception, which may be made especially for the purpose, or a -shallow baking pan of tin may be used. When the pan is filled with the -composition place it perfectly level in a cool place free from dust and -allow to remain at least for several hours. - -_Formulas for Hectograph Masses._—I. Gilder’s glue, 100 parts; -glycerine of 28° Bé., 500. - -The glue is allowed to swell in water, as described above, then melted, -mixed with the glycerine, and evaporated to the required consistency. - -II. Gilder’s glue, 100 parts; glycerine of 28° Bé., 400; water, 200. - - - - -CHAPTER IX. - -MANUFACTURE OF GELATINE, AND PRODUCTS PREPARED FROM IT. - - -Gelatine, like glue, is produced from hides and skins, and bones. It is -distinguished by its purity, has a slight yellowish tint, and is very -hard and elastic. In cold water it softens, swells up, becomes opaque, -but does not dissolve. In hot water it dissolves completely, and on -cooling for several hours, an almost colorless, transparent and very -firm jelly results. This property of becoming jellied is in part lost -if the solution is for some time exposed to a temperature higher than -212° F. - -The chemical constitution of gelatine is entirely changed by -concentrated sulphuric or nitric acid. Concentrated acetic acid, on the -other hand, renders softened gelatine transparent, and then dissolves -it; the solution does not become viscid, but preserves its adhesive -property. Dilute acids have no appreciable effect either on the -coagulating or the adhesive power. - -Tannin is a valuable and delicate test of the presence of gelatine. -When added to a solution containing only 1/5000th part of gelatine, -nebulosity is immediately apparent. When more concentrated gelatinous -liquors are treated with tincture or infusion of nut gall, a dense, -white, caseous subsidence occurs which, on desiccation, becomes -brownish-yellow, agglutinates, and forms a hard, brittle mass easily -reduced to powder. - -Gelatine is much used for culinary and medicinal purposes, and for -fining beer, wine and other liquids. Considered medicinally, it is -emollient and demulcent, and for this end is dissolved in water or -milk, and rendered palatable by the addition of acid and sugar. In -pharmacy, it is used for the formation of capsules intended to conceal -the nauseous odor and taste of medicinal preparations inclosed in them. -It is likewise employed for coating pills. - - -SKIN GELATINE. - -But few changes have been made in the process of manufacturing skin -gelatine since the method introduced and patented, in 1839, by George -Nelson. This patent relates to the preparation of a transparent -gelatine from waste of calf skins, and of an inferior variety from -other skins freed from hair, wool, and fleshy and fatty matters. The -mode of procedure is the same in both cases, and is as follows: The -cuttings being washed are macerated in solution of caustic soda or -caustic potash at a temperature of 60° F., until they are partially -softened. Ten days is the average period required to effect this. -They are then placed in closed vessels and permitted to remain until -a thorough softening is effected. They are now washed in a revolving -cylinder, through which a current of water passes to free them from -adhering alkali; exposed in a well-closed chamber to the action of -sulphurous acid, and finally submitted to pressure to remove the -adhering water. The softened mass bleached by sulphurous acid is then -placed in a suitable vessel and subjected to the action of steam until -it is, as far as possible, dissolved. The liquor is then strained -and set aside at a temperature of 100° to 120° F. for the impurities -which may have remained to subside. The clarified solution is poured -upon slabs of slate or marble to the depth of about half an inch and -allowed to remain there till sufficiently solidified, when it is cut, -and washed to remove all traces of acid. It is subsequently redissolved -by means of a steam bath at a temperature of 95° F., finally again -solidified, and dried by exposure to dry air upon nets. - -Messrs. J. and G. Cox, of Edinburgh, patented in 1844, a process by -which a perfectly pure substance, superior to that prepared from -isinglass is obtained. Shoulders and cheeks of ox-hides are preferred -by the patentees. They are thoroughly cleansed in water, after which -they are cut into pieces by a machine similar to that used for cutting -straw, and then subjected to the action of a paper-maker’s pulp-mill. -By this process the gelatinous fibre is well washed and cleansed, as -a stream of water flows through the mill during the whole operation, -carrying off all the impurities. The comminuted material is next -pressed between rolls, mixed with fresh water, sufficient to effect its -solution, and heated to a temperature varying from 150° to 212° F. The -resulting gelatine-solution is then allowed to cool to 150° F., and -mixed with fresh bullock’s blood—1 part of the latter to 700 parts of -solution. At a somewhat increased temperature the albumen of the blood -coagulates and rises in the form of foam to the surface, or subsides -in the shape of flakes, carrying with it the impurities, and thus -clarifying the liquor. The latter is allowed to stand for some time, -when it is poured upon stone slabs and allowed to solidify. - -G. P. Swinborne’s improved patented process for the preparation of -gelatine from hides, skins and glue pieces, relates mainly to the -cleansing of the raw material. The latter is reduced by means of -suitable instruments to shavings or slices, and soaked in cold water, -which is drained off and replaced by fresh water three times a day, -until no odor or taste is perceptible. The shavings are then heated -with water, not above boiling, strained through filter cloths, and the -liquor is then run on to slate or other material to dry. - -The modern process of preparing skin gelatine is, according to Thomas -Lambert, carried out as follows: The first treatment the cleansed skins -undergo is the “steeping” process with caustic soda or milk of lime. -In some factories a mixture of caustic (slaked) lime and soda ash is -used, in the proportion of 6 lbs. soda ash and 6 lbs. slaked lime to -every hundred-weight of skins treated, the chemical change being that -the whole of the carbonate of soda (soda ash) is converted into caustic -soda by its equivalent of caustic lime, the excess of the latter -remaining as such. The equation representing this is— - - Na_{2}CO_{3} + CaH_{2}O_{2} = 2NaHO + CaCO_{3} - Soda ash. Caustic lime. Caustic soda. Carbonate of lime. - -This steeping is conducted in large wooden vats, each having a length -of 12 feet, width 8 feet, and depth 3 feet, and fixed with a slight -gradient to the overflow, which is placed at the most convenient corner -of the vat and protected by perforated boards. The skins in the vat -are nearly covered with water, and then the solution of caustic soda, -or the slaked lime mixed in water to a cream, is sprayed equally over -the mass, the whole being intimately mixed with long stirring poles. -The water is renewed twice during a period of 12 days, the time allowed -for the skins to soak. They are now removed to a chamber, in which a -moderate increase of heat facilitates the saponification of the fat and -the dissolving of the fleshy matter. The chamber is a brick building, -with a cemented floor, on which the skins are spread to a uniform depth -of about six inches and is heated by steam pipes running round the -building. At a temperature of about 70° F. the skins are exposed two -or three days, with frequent turning. They are now transferred to the -washing machine and washed until the effluent is practically free of -soda or lime. The skins then undergo a bleaching process to whiten, and -thus destroy any injurious coloring matter. For this purpose the washed -skins are removed to a number of vats fitted with folding covers, and -treated to a solution of sulphurous acid of ½° Twaddell strength for 24 -hours, each vat being well stirred at intervals to allow the “bleach” -to permeate equally the mass. - -In some factories this process is carried out with dry sulphurous -acid, the gas being generated in a sulphur burner and, after washing, -passed into a chamber containing the skins. The vats are now drained, -then filled up with water, well stirred, and the water run off. This -is repeated until the effluent is practically free of any sulphurous -smell, and the work of dissolving the gelatine is proceeded with. -The digesting of the skins is carried on in stoutly built, circular -wooden vats, each having a size, generally of 4 feet 6 inches diameter -and 6 feet deep, and fitted with 2¼ inch copper steam coil. The vats -are provided with a double wooden bottom to divide the heat. They -are arranged on the first floor of the building, the liquors running -through a shallow filter of fine copper gauze to the clarifying vats -beneath. The skins are raised by an elevator and fed direct into the -vats by suitably-arranged troughs, then covered with water, and steam -is sent through the coils. The temperature is frequently taken by the -thermometer and should never exceed 177° F. During the digestion, -any unsaponified fat and dirt comes to the surface as a scum, and is -carefully skimmed off from time to time. Samples are also drawn of the -liquors, cooled, and the appearance and strength of the jelly noted. -After five to six hours’ heating, the first liquors are run off to the -clarifying vats, at a strength of about 17 per cent. gelatine. - -The vats are refilled with water, and a second digestion made, the -liquor running to the clarifying vats at a strength of 12 per cent. -In the third digestion the temperature is raised a few degrees to -practically exhaust the gelatinous matter, and can either be clarified -to form an inferior gelatine, or concentrated for size. The exhausted -matter is taken to the manure-shed for mixing purposes. The clarifying -of the first and second liquors—and if used for gelatine the third -liquor—is done separately in the clarifying vats. The clearing agent -used is alum, to the extent of ½ per cent., or a little blood diluted -with water; both are mixed with a small portion of the hot liquors in -a bucket, and then well stirred in the vats. The liquors are raised -to 177° F. to coagulate the impurities, and then lowered to 149° F. -and allowed to stand for two hours. During this time the coagulated -matter rises to the surface, and is skimmed off. On leaving the vats, -the liquors are filtered through fine copper gauze into a receiver from -which is fed the vacuum pan. - -Gelatinous liquors being peculiarly sensitive, especially as regards -color, to high temperatures, it is found advisable to evaporate them in -vacuo; and this method is adopted by all continental makers. The three -grades of the liquors, concentrated to the required strength, are run -on to squares of glass, 4´ × 4´, fixed in a wood framing, to a depth -of ½ inch for cake and ¼ inch for leaf gelatine, then placed perfectly -level on racks for jellying. In 24 hours the jelly is firm, and can -be easily cut to the desired size of cake or leaf wanted. A very fine -gelatine is produced by cutting the jelly into small pieces, washing -well with cold water, and remelting at a temperature of 176° F., and -poured again on the glasses for jellying. - -The drying is carried on by exposing the cut cakes, on nets fixed to -a framework of wood, to a rapid current of dry air in the tunnels, as -described in the drying of glue. - - -BONE GELATINE. - -The materials used for this purpose should be of the best description, -the most suitable bones being calves’ feet, waste of turners and button -makers, the bony cores of the horns of the ox and cow. Such bones do -not require comminution, but if large bones of oxen, horses, etc., are -to be used, it is recommended to break them as small as possible by -means of a wooden mallet, and to avoid the use of iron stampers, as the -bones become heated by the heavy blows and friction to which they are -subjected during the process, and acquire an empyreumatic odor which is -retained by the gelatine. - -The next step in the process is the solution of the glue cartilage. -This was formerly effected by the use of steam and water. The crushed -bones were placed in a wire basket or cage and this inserted in a small -cast-iron cylinder and steam introduced. The apparatus is connected -with a steam boiler, and provided with an air-tight lid, and a pipe -and a rose connected with a water reservoir for pouring water over -the bones in order to promote the solution of the glue cartilage. But -this process is very slow, 20 hours being required without completely -exhausting the bones. - -The resulting gelatinous liquor is drawn off every hour, the first run, -which contains the dirt and grease, being, of course, kept separate -from the rest. - -[Illustration: FIG. 59.] - -As will be readily understood this process consumes much fuel, and -leaves a residue which, though not completely exhausted, cannot be -further utilized for the preparation of gelatine. In fact the entire -process is obsolete, but as it is still in use in some localities, -a description is here given, for the sake of completeness, of the -apparatus and improved manner of manufacture employed in the factory of -D. J. Briers, which is well known for the beautiful product turned out. - -Fig. 59 shows a longitudinal section of the entire apparatus. - -Fig. 60 is the horizontal section of the boiler. - -_a_, is the cylindrical boiler 6 meters (19.68 feet) long, and 2 -meters (6.56 feet) in diameter. It is made of strong boiler plate -doubly riveted, and capable of resisting a pressure of six or seven -atmospheres. - -_b_, is the manhole. It is closed by an oval lid secured by two iron -rods and two bolts, so that after placing the lid in position, the -boiler is hermetically closed by tightening the nuts upon the bolts. - -_c_, is a cast-iron fork with two safety valves with levers graduated -from 1 to 100 atmospheric degrees. - -[Illustration: FIG. 60.] - -_d_, is a float upon the surface of the water, and provided with a -wheel graduated from Nos. 1 to 6. Its object is to indicate during the -operation how much water is lost and how much remains in the boiler. -Care must be had not to allow the indicator of the wheel to get below -No. 1. This figure indicates that the water has reached the highest -point in the boiler exposed to the fire, which is consequently the -lowest point which the water can be allowed to reach. On the other hand -the indicator must not move above No. 6, as the water when standing -too high in the boiler and too close to the pipes conducting the steam -into the various apparatuses might mix with the steam and spoil the -operation carried on in the drum, _e_, Fig. 60. - -_f_, Fig 60, is a manometer, which indicates the degrees of pressure -exerted by the steam in the interior of the boiler. It consists of -a wrought-iron pipe bent double, and is filled with mercury 1.22 -meter (4.002 feet) high counted from its base. One end of the pipe -communicates with the boiler, while the other end is provided with a -small brass wheel. Upon the latter is a thread of twisted silk, to -the end of which is suspended an iron cylinder of somewhat smaller -circumference than the bore of the pipe, so that it can move up and -down in it without friction. This cylinder rests always upon the -mercury. To the other end of the thread is fastened an indicator of -somewhat less weight than the cylinder, which, by sliding in a groove -in a graduated board placed alongside the pipe, indicates the degrees -of steam pressure. - -_g_ is a cast-iron pipe for heating the drying room, and - -_h_ another cast-iron pipe for heating the store-room for the bones. - -_i_ is the forcing pump for feeding the boiler with water. - -_k_ is a sheet-iron reservoir placed close to the end of the boiler. -It is filled with water, which is heated by the heat lost in the -fire-place in consequence of the draught, and by allowing the smoke -to circulate under the reservoir before passing into the chimney. The -reservoir communicates with the forcing-pump by means of a pipe and -stopcock, so as to avoid feeding the boiler with cold water. - -_l_ is the fire-place, consisting of the grate, door and cast-iron -frame. - -The drum, _e_, is a spherical vessel of strong sheet-iron doubly -riveted. It is 3 meters (9.84 feet) in diameter, and capable of -resisting a pressure of six to seven atmospheres. It serves for -softening the bones with the assistance of steam passed into it from -the boiler, _a_. It is provided with a manhole similar to that of the -boiler. - -_n_ is a wrought-iron shaft passing horizontally through the drum and -revolving in the brasses, _o_. - -_g_, Fig. 61, is a gearing with a crank, by means of which the drum _e_ -is revolved. The power of the gearing must be so calculated that one -man can turn the wheels when the drum is filled with water. - -[Illustration: FIG. 61.] - -_r_ is a false bottom perforated in its entire length with holes 12 -millimeters (0.47 inch) in diameter, and is placed about 15 centimeters -(5.9 inches) above the true bottom of the drum. It consists of two -pieces, and is secured by two nuts, so that it can be easily removed -and replaced. Its object is to prevent the bones from clogging up the -pipe _s_, and the cocks _t_, _u_. - -_a_, _a_, Fig. 61, are angular iron points inside of the drum _e_. -Their object is to facilitate the shifting of the bones when the drum -is revolving. - -_x_, Fig. 59, is a cock near the manhole. It is opened about 2 -millimeters (0.079 inch) during the operation in the drum. It serves -also for the escape of the steam from the drum when the operation is -finished. - -The cocks _t_, _u_, placed in the lower part of the drum, serve for the -escape of steam condensed during the operation. - -The steam pipe _p_, Fig. 59, conducts the steam from the vessel _a_ -into the drum _e_. - -_y_, Fig. 59, is a cock graduated into eight equal parts and placed -on the steam pipe _p_, to conduct the steam from the box _z_, into the -stuffing box _a´_, and from there into the pipe _s_, then under the -false bottom _r_, into the drum _e_. - -The lid of the cast-iron box _z_, is provided with a safety valve -loaded with a weight corresponding to the pressure of one atmosphere. - -The wooden vessel or box _d_, the ground-plan of which is shown in Fig. -62, serves for boiling the comminuted bones in order to extract the -jelly. This box consists of the following parts:— - -[Illustration: FIG. 62.] - -_n_, are cast-iron steam pipes occupying the entire surface of the box, -being placed at equal distances from each other, and connected on their -ends by semicircular pieces. The steam, which is allowed to circulate -in the pipes in order to boil the liquid, enters through one of the -ends which rises up vertically and is connected with the cock _h´_, -Fig. 59. The other end is secured to the inner side of the box, which -is perforated for the admittance of the cock _o´_. Upon the steam pipes -lies a wooden framework with linen nailed upon it, the object of which -is to prevent the comminuted bone substance from falling under the -pipes. The frame must, of course, fit closely into the box. - -The cock _h´_ graduated in eight equal parts serves to admit steam into -the pipes _n´_, and is opened either entirely or half, or one-quarter, -or one-eighth, according to the stronger or gentler ebullition to be -produced. - -To prevent the steam from becoming stagnant in the steam pipes _n´_, -a small jet is allowed constantly to escape through the cock _o´_. The -latter serves also to run off the condensed steam when it no longer -possesses the heat required to keep up ebullition. - -_p´_, Fig. 62, is a cock in the bottom of the box _d´_ for drawing off -the gelatinous solution from the residue. The box _e´_, Fig. 62, a -ground-plan of which is shown in Fig. 63, serves for evaporating the -gelatinous solution, which is effected by circulating steam through -several tubular pieces of cast-iron which form the bottom of the box -and are connected in a similar manner as the pipes in the box _d´_. - -The cock _i_ is graduated and similar to _h´_. - -[Illustration: FIG. 63.] - -The cock _r´_, Fig. 63, is similar to _o´_, Figs. 59 and 62. - -_s´_, Fig. 63, is a cock for drawing off the evaporated gelatinous -solution. - -The wooden box _f´_, Fig. 59, a ground-plan of which is shown in Fig. -64, serves for the reception and settling of the evaporated gelatinous -solution. Its bottom is constructed in a manner similar to that of the -box _e´_. - -[Illustration: FIG. 64.] - -The cock _n´_, which is placed 14 millimeters (0.55 inch) above the -bottom of the box, serves for running the gelatinous solution into the -wooden cooling-boxes. - -The bones as received in the factory are sorted by throwing out the -spongy material, etc. They are then steeped in lime-water for a few -days to free them from adhering particles of flesh, after which they -are dried and stored away for future use. - -The boiler _a_, is filled two-thirds with water, and heated until the -manometer indicates a pressure of 30°. In the meanwhile the drum _e_, -is filled seven-eighths with perfectly dry bones, and steam is then -admitted from the boiler _a_, through the graduated cock _y_. The fact -that the bones in the drum are exposed to the proper temperature of -250° F. is recognized by the thermometer _b´_, placed between the cock -and the drum. - -To prevent the stagnation of the steam in the drum, _a_ small jet of -it is allowed constantly during the operation to escape through the -cock _x_. The cock must not be opened wider than is necessary to keep -the temperature at 250° F. By opening it wider, this degree would be -exceeded, and the gelatine-yielding substance would, in consequence, -undergo alteration. A quarter of an hour after admitting the steam into -the drum, the cock _t_, is opened, and again closed after allowing a -small portion of the condensed steam to escape to the cock _u_, and, -through this, into a box. This operation is repeated every quarter of -an hour. - -To change the position of the bones, the drum is revolved twice every -half hour, by means of the gearing _q_, of course closing the cock _x_ -during the operation. - -By carefully following the above rules, the bones will be thoroughly -reduced in four hours. If, for instance, steam has been introduced into -the drum at 5 o’clock a. m. the operation will be finished at 9 a. m. -The cock _y_, is then closed, and the steam allowed to escape through -the cock _x_. After the escape of the steam, the drum is emptied, by -removing the lid and turning it upside down. It is then refilled with -entirely dry bones, and the operation continued in a like manner, day -and night, if necessary. - -After the bones have been taken from the drum, they are spread out -under a shed, and, when dry, ground in a suitable mill. The resulting -flour, which contains the jelly-yielding substance, is brought into -the vessel _d´_, which, in the meanwhile, has been furnished with -sufficient water to cover the flour 65 centimeters (25.59 inches) deep. -The mixture is boiled for three-quarters of an hour, being constantly -stirred to prevent the flour from forming a heavy and dense mass -which would hinder the quick extraction of the jelly. Ebullition is -then interrupted by closing the cock _h_, and the fat floating on the -surface skimmed off. After allowing the gelatinous solution to settle, -it is drawn off by means of a faucet placed above the level of the -flour. Thirty bucketfuls of the gelatinous solution are then at once -poured into a vat and mixed with the condensed steam drawn off by means -of the cocks _t u_, during the reduction of the bones in the drum. -After allowing the mixture to cool to 160° to 155° F., 20 kilogr. (44 -lbs.) of pulverized alum are added at once and as quickly as possible. -When the gelatinous solution has become transparent, it is drawn off -into the box _e´_, and a few bucketfuls of hot water are poured upon -the sediment in the vat in order to extract the remaining jelly, which -is effected by thorough stirring and allowing to settle until the water -is entirely clear. - -After disposing of the 30 bucketfuls in the manner mentioned, -the remainder of the gelatinous solution is evaporated. This is -accomplished in the box _e´_, which is filled 8 centimeters (3.15 -inches) deep with gelatinous solution, and steam is then admitted -into the tubular bottom pieces. To promote evaporation and keep the -fluid constantly in motion, the cock _i´_ is only opened far enough -to keep up gentle ebullition. During evaporation the solution should -be frequently stirred with an implement resembling a rake. The nearer -the required degree of concentration is approached, the greater care -must be exercised to prevent the solution from boiling too strongly. -The proper degree of consistency is obtained when half a saucer full -of the solution placed in a shady place in the air acquires in a short -time such a consistency that when touched with the finger no impression -remains. The cock _i´_ is then closed, and the jelly is drawn off into -the box _d´_, which contains the 30 bucketfuls of clarified jelly, -care being had to mix the two solutions as quickly as possible. After -evaporating all the gelatinous solution and mixing it in the box _d´_, -the whole is heated to 158° F., by admitting steam through the cock -_k´_, care being had not to forget closing it as soon as the above -temperature has been reached. The solution is then thoroughly stirred -and permitted to settle for three hours to allow of the precipitation -of the lime salts decomposed by the alum. The fluid, which is now -perfectly transparent and of a beautiful dark-yellow color, is then -drawn off into wooden cooling boxes 2 to 2.5 meters (6.56 to 8.2 feet) -long, 20 centimeters (7.87 inches) wide, and 16 centimeters (6.30 -inches) deep. The following day the gelatine is cut into leaves 25 -centimeters (9.84 inches) long and 12 centimeters (4.72 inches) wide, -which are dried upon nets. When quite dry, the drying process is -finished by bringing the leaves into the drying-room which is heated by -the pipe _g_. (Fig. 59.) - -The bone flour remaining in the box _d´_ still contains much jelly, -which is extracted by pressure. This is accomplished immediately after -running off the gelatinous solution into the evaporating vessel. The -liquid which has drained through the cloth frame previously mentioned, -is drawn off by opening the cock _p´_, Fig. 62, while the residue -in the box _d´_ is placed in coarse bags and the jelly extracted by -subjecting the bags to strong pressure under an iron screw-press. -Before mixing the extracted fluid with the solution in the evaporating -vessel, it is recommended to allow it to settle, as it is always more -or less turbid. The residue remaining in the bags is an excellent -manure. - -The modern process of preparing bone gelatine, which is now almost in -general use is as follows: Clean bones are selected for the purpose, -and the operation commences with the extraction of the fat by means -of benzine, though some manufacturers prefer carbon disulphide as a -solvent, because it is claimed that by reason of its low boiling-point -it does not injure the gelatine in the same manner as benzine, and -besides it leaves no smell in the degreased bones. It is advisable -to bleach the degreased bones, spread out in thin layers and kept -constantly moist, by exposure to the action of air and light. The -bleached bones are conveyed to large vats for the purpose of extracting -their mineral constituents by digestion with hydrochloric acid. If -the gelatine is to be used as an article of food, or for medicinal -purposes, only the purest hydrochloric acid obtainable should be used, -while the ordinary article suffices for that for technical purposes. - -The vats are filled three parts full with bones and the latter covered -with a solution of hydrochloric acid of 10 per cent. strength. -Digestion is carried on until the bones become soft, flexible and -semi-transparent. The acid water is now drained off, and a supply of -fresh water added, and then discharged. This is repeated until the last -water is entirely free of acid, which is known by adding a few drops of -silver nitrate, the absence of any white precipitate indicating that -the water is entirely free of acid. - -The bones are now bleached in the manner as described under -skin-gelatine, preferably with solution of sulphurous acid, the -process with gaseous sulphurous acid being difficult to carry out and -considerable time is required for the gas to completely permeate the -cartilaginous mass. The bleached bones are then conveyed to the boiling -vats and the resulting liquors treated in the same manner as described -under skin-gelatine. - -As bone-gelatine solidifies with a larger content of water than the -product from skins, evaporation of the liquors may be early interrupted -and the resulting jelly cut into thin leaves which are finally dried. - - -COLORED GELATINE. - -Cakes or leaves not entirely colorless may be utilized for colored -gelatine which is employed for various purposes. Coloring is effected -by simply dissolving and distributing uniformly a suitable quantity -of coloring matter in the clarified gelatine liquor previous to -solidifying; of course only water-soluble coloring matter should be -used. - -Colored gelatines are frequently used by confectioners and in the -household in the preparation of jellies, and the use of poisonous -colors should under all conditions be avoided. Sufficient attention is -not paid to this, because many of the aniline colors which are now so -much used for the purpose are at least open to suspicion, while others, -especially picric acid, which yields a beautiful yellow color, are -decidedly poisonous. - -The following coloring matters are perfectly harmless and yield good -results in coloring gelatine: - -_Yellow_: Caramel or sugar color. A still more beautiful yellow is -obtained by the use of an aqueous extract of saffron. - -_Red_: Extract of cochineal. - -_Blue_: Indigo-carmine solution. - -_Green_: Mixture of indigo-carmine and caramel. - -_Violet_: Mixture of extract of cochineal and indigo-carmine. - -While gelatine colored with the above-mentioned coloring matter does -not present such a beautiful appearance as the product colored with -aniline colors, it is entirely harmless and suitable for culinary -purposes. - -Leaves of gelatine colored with aniline colors exhibit beautiful colors -and are used for many technical purposes. The following colors may be -employed: - -_Yellow_: Picric acid soluble in hot water. - -_Red_: Fuchsine or eosine. - -_Blue_: Water-soluble blue. - -_Green_: Iodine green. - -_Violet_: Methyl violet. - - -_Gelatine for Fining Purposes._ - -For fining beer, wine, etc., gelatine in leaves or in powder is brought -into commerce. For the preparation of leaves, gelatine particularly -well dried is carefully melted over a water-bath and then ladled into -sheet-metal moulds, and allowed slowly to solidify. - -The product brought into commerce under the name of _Gelatine Lainée_ -which commands a high price is in many cases nothing but thoroughly -purified bone-glue of a dark honey-yellow to brown color. - -Fining powder for wine and beer is made by grinding off-color gelatine -cakes and freeing the resulting powder from coarser pieces by sifting. -The powder is white. - -_Liquid fining gelatine._ This preparation consists of -gelatine-solution suitably prepared, and represents a colorless, or at -the utmost slightly opalescent, product just sufficiently concentrated -to remain liquid. - -Skin-liquors can only be used for the preparation of liquid gelatine, -as bone-liquors already gelatinize when they contain scarcely more than -1 per cent. of glue. The skin liquors are concentrated so far as to -remain liquid at a temperature of from 60° to 68° F. - -A product answering all demands is obtained as follows: A good quality -of gelatine of a pale color is dissolved in a sufficient quantity of -water, the solution, in case it shows a slight odor, filtered through -animal charcoal, and then brought into bottles. To prevent putrefaction -the liquid gelatine is sterilized as follows: - -The filled bottles being placed in a boiler filled to a proper depth -with water, the latter is slowly brought to boiling which is kept up -for 15 to 20 minutes. The bottles are then closed with corks previously -boiled in the water. - - -_Preparation of Gelatine from Ordinary Glue._ - -For this purpose ordinary pale-colored glue is allowed to swell up -for two days in cold strong vinegar. The vinegar is then drained off -and the glue which is now almost colorless, is placed upon a sieve and -allowed to float in a vessel filled with water for 10 to 12 hours. It -is then placed upon a linen cloth, stretched in a room heated to at -the utmost 68° F., allowed to drain and dry to such an extent that -on heating it to between 158° and 167° F., a thick clear liquid is -obtained. This liquid is carefully poured upon plates of glass or -marble, so as to avoid the formation of air bubbles and when solidified -the leaves are removed and completely dried in the air. The product -thus obtained being entirely tasteless and almost colorless may be used -in the preparation of jellies, as well as for foils for pictures, etc. - - -_Preparation of Gelatine for Photographic Printing and for Photographic -Purposes in General._ - -Gelatine suitable for this purpose should be colorless and free from -all salts, since the latter would exert a disturbing effect upon the -chemical processes which take place during the photographic operation. -For the removal of the salts the gelatine is treated as follows: -Colorless gelatine of the best quality is broken into small pieces and -covered with 10 to 12 times the quantity of water, the latter being -changed every 15 to 20 minutes until the last water shows no trace -of lime, which is known by adding to the water solution of oxalate; -the absence of turbidity indicates that the water is free from lime. -The white of an egg is now mixed with five drops of ammonia and twice -the volume of distilled water and shaken to froth in a bottle. This -quantity suffices for 6 to 8 ozs. of gelatine. The washed gelatine is -next melted in a dish and mixed with the white of egg. One part of -glacial acetic acid mixed with 250 parts of water is then added drop -by drop, stirring constantly until sensitive litmus paper shows an -acid reaction. The liquid is now rapidly brought to the boiling-point, -whilst stirring constantly, and then filtered in a warm place to avoid -gelatinization. The gelatine now contains only the salts of the white -of egg, some ammonium acetate and free acetic acid. For their removal -the solidified gelatine is cut into pieces, which are placed in water. - - -_Gelatine Capsules for Medicinal Purposes._ - -Considerable use is made of gelatine in medicine. To disguise the -disagreeable taste of some medicines they are either mixed with -gelatine solution or inclosed in gelatine capsules. To prepare the -latter, dissolve 8 parts of gelatine, 2 of sugar, and 1 of gum-arabic -in 8 of water in a water-bath, and dip the pear-shaped ends of iron -rods into the lukewarm solution. To facilitate the detaching of the -gelatine film from the rods, grease the pear-shaped ends with oil. The -capsules are dried by placing them in holes of a corresponding size -in boards. When dry they are filled with the respective medicine, and -closed with a drop of the same solution. - - -_Court Plaster._ - -Gelatine or isinglass 155 grains, alcohol 13½ fluid drachms, glycerine -15½ grains. Water, tincture of benzoin, each a sufficient quantity. -Dissolve the gelatine in a sufficient quantity of hot water to make the -solution weigh 4½ ozs. Spread one-half of this in successive layers by -means of a brush upon taffeta stretched upon a frame so as to present -a level surface, waiting after each application until the layer is -dry. For the first two applications the gelatine solution should be -warmed merely to above its congealing point, so that when spread out -it may rapidly solidify and at the same time adhere to, but not pass -through the fabric. Mix the second half of the gelatine solution with -the alcohol and glycerine, and apply it in the same manner. Then -reverse the taffeta, coat it on the back with the tincture of benzoin -and allow it to become perfectly dry. The tincture of benzoin applied -to the reverse side leaves a thin layer of resin which in a measure -renders the plaster water-proof; it is, however, advisable to repeat -this application once or twice. The addition of glycerine to the last -portion of the gelatine solution prevents the plaster from breaking, -and preserves its flexibility for a long time. When the plaster is dry -it is cut in pieces of suitable length and preserved in well-closed -vessels. - - -_Gelatine Foils._ - -Large quantities of gelatine foils, which are leaves of gelatine about -as thick as a sheet of paper, are produced in England and France where -their manufacture forms a special branch of industry. They are either -simply colored or printed with neat designs in gold or silver. - -The fabrication is quite simple. Cover pure gelatine with water, and -after swelling up, pour off the water and dissolve the jelly over a -water-bath. After allowing the solution to cool somewhat, add the -coloring matter previously dissolved in water. - -In place of pure gelatine, a solution of ordinary bone-glue may be -used. In order to clarify it add O.14 oz. of oxalic acid dissolved in -water to every 5.5 lbs. of glue. To make the foils more flexible add -also one-half pint of spirit of wine and O.28 oz. of rock candy or a -small quantity of glycerine. - -Aniline colors soluble in water are best adapted for coloring the -foils; for _red_, fuchsine, eosine or ponceau, for _blue_, _blue de -Parme_, for _green_, aldehyde green, for _yellow_, picric acid, and for -the various shades, mixtures of the above colors. - -A durable blue is also produced by indigo solution, yellow, by -decoction of saffron, green, by mixing blue and yellow, red, by a -solution of carmine in spirit of sal ammoniac, and violet, by mixing -blue and carmine. - -The gelatine solutions are poured upon ground-glass plates, previously -polished with elutriated rouge, and rubbed with Spanish chalk. The -foils are so smooth upon the glass side that when dry they can be -detached without much difficulty. If both sides are required to be -smooth, the foils are dried between two glass plates. In many respects -their manufacture resembles that of “Gelatine Veneers.” - -Gelatine foils are used for printing sacred images, visiting cards, -labels, in the manufacture of fancy articles, artificial flowers, etc. - -For the manufacture of artificial flowers very soft and flexible sheets -are made by adding ½ part of glycerine to 1 part of gelatine and mixing -intimately in dissolving the gelatine. - -Such gelatine sheets brushed over in addition with Peruvian balsam can -also be advantageously used for tying up wounds instead of gutta-percha -cloth which tears easily and rots soon. They form an air-tight bandage -which clings closely to the parts of the body, and beside the glycerine -contained in them exerts a beneficial cooling effect and acts as an -antiseptic. - - -_Gelatine Veneers._ - -Franchi, as far back as 1814, prepared artificial ivory by mixing -gelatine solution with earthy substances. This idea has been again -taken up in modern times for the manufacture of veneers imitating -not only ivory, but also avanturin, lapis lazuli, malachite, -mother-of-pearl, and tortoise shell. These imitations are much liked by -manufacturers of fancy articles, workers in leather, cabinet-makers, -etc. They are prepared as follows:— - -The process may be divided into five principal operations: 1. -Preparation of the glass and marble plates; 2. Preparation of the -glue solutions; 3. Pouring the colored solutions upon the plates; 4. -Transferring the layer of glue to the layer of gelatine; and 5. Drying -the veneers and detaching them from the plates. - -1. _Preparation of the plates._ Both marble and glass plates are used -for imitations of marble, but glass plates only for imitations of -mother-of-pearl. The glass plates must be ground, but need not exceed -O.11 to O.15 in. in thickness, and only require careful washing and -drying for imitations of mother-of-pearl. For imitations of marble -they should be rubbed with an oiled linen rag. Other glass plates, -after being washed and polished with elutriated rouge and water, are -wiped with a soft rag to remove any particle of the polishing powder. -The polished surface is then gently rubbed with a rag dipped in pure -Spanish chalk, and the excess of chalk carefully dusted off. - -2. _Preparation of the glue solutions._ For one dozen plates, each 10¾ -square feet, soak 2 lbs. of good, colorless glue in water for 24 hours, -pour off the water and melt the glue in a water-bath and stir in 3½ -ozs. of glycerine. For imitating marbles of two colors, compound 20 to -24 fluidounces of this glue solution with the quantities of thoroughly -ground mineral colors given below; the rest of the glue solution is -mixed with 6.34 ozs. of zinc white ground very fine. For imitating -marble of three colors mix 14 fluidounces of the glue solution with -one of the coloring matters and 14 fluidounces with the other coloring -matter, and the remainder with zinc white. For imitating marble with -four colors, take 10 fluidounces of the glue solution to each of the -three coloring matters, and mix the rest with 4½ ozs. of zinc white. - -The proportions by weight of the mixtures for 10 different varieties of -imitations of marble and enamel are as follows:— - -_a._ Mix 20 fluidounces of the glue solution with 1¾ ozs. of rouge and -2½ ozs. of zinc white, and the rest of the glue solution with 6⅓ ozs. -of zinc white. - -_b._ Mix 20 fluidounces of the glue solution with 1¾ ozs. of rouge, and -the rest of the glue solution with 5¼ ozs. of zinc white. - -_c._ Mix 14 fluidounces of the glue solution with 1¼ ozs. of zinc white -and 1 oz. of rouge, 14 fluidounces of the glue solution with 1 oz. of -yellow ochre, and the rest with 5¼ ozs. of zinc white. - -_d._ Mix 14 fluidounces of the glue solution with 1 oz. of rouge, 14 -fluidounces of the glue solution with ¾ oz. of sepia, and the rest with -5¼ ozs. of zinc white. - -_e._ Compound 20⅓ fluidounces of the glue solution with 1 oz. of quite -concentrated and filtered solution of aniline black, and the rest with -6⅓ ozs. of zinc white. - -_f._ Mix 10 ozs. of the glue solution with 0.8 oz. of rouge, 10 -fluidounces of the glue solution with 0.8 oz. of yellow ochre, 10 -fluidounces of the glue solution with 0.8 oz. of sepia, and the rest -with 4¼ ozs. of zinc white. - -_g._ Mix 20.3 fluidounces of the glue solution with 1.41 ozs. of -lampblack. For gray add sufficient zinc white to produce the desired -shade. The rest of the glue solution is mixed with 6⅓ ozs. of zinc -white. - -_h._ Mix 10 fluidounces of the glue solution with 0.8 oz. of umber, 10 -fluidounces of the glue solution with 0.8 oz. of bole, 10 fluidounces -of the glue solution with 0.8 oz. of ochre, and the rest with 4½ ozs. -of zinc white. - -_i._ _For enamels_ mix 20.3 fluidounces of the glue solution with 1 oz. -of ultramarine, and the rest with 6⅓ ozs. of zinc white. - -_k._ Mix 20.3 fluidounces of the glue solution with 1.41 ozs. of chrome -green, and the rest with 6⅓ ozs. of zinc white. - -For imitating mother-of-pearl veneers, 0.42 oz. of silver bronze, which -need not be genuine, is ground with a little glue solution or water and -intimately mixed with the above solution of glue. The bronze powder -must not be in a dry state when stirred into the glue, as lumps would -be formed and the veneers become spotted. In place of bronze, essence -of fish scales, which is of course far more costly, can be used.[2] The -glue solution thus prepared is then compounded with different aniline -colors according to the tint desired. - -[2] This preparation is also known by the name _Essence d’Orient_. The -material for its production is furnished by a small white fish very -common in the rivers of continental Europe. It accompanies the scales -of this fish, and is detached when the scales are triturated for a -considerable time and thrown into a vessel of water. To collect the -essence the water is poured off upon a fine hair sieve, which retains -the scales and allows the water and the product sought to pass through. -The latter sinks to the bottom, and is obtained pure by decanting the -water. A little ammonia is added to prevent decomposition. - -_a._ For yellowish veneers no coloring matter is required, or the -desired shade is obtained by an addition of some solution of picric -acid. - -_b._ For colorless veneers or those of slightly reddish tints a smaller -or greater number of drops of a concentrated solution of fuchsine are -added in order to counteract the yellowish color of the glue solution. -For these imitations of mother-of-pearl veneers, concentrated solution -of gelatine compound with 15 per cent. of glycerine can be employed, -especially when essence of fish scales is used. - -_c._ For _blue_, the glue solution is compounded with _bleu de Lyons_, -care being had not to use too much, as otherwise the imitation becomes -indistinct. The proper degree of coloring is tested by allowing a few -drops of the colored glue solution to fall upon a glass plate. - -_d._ For _red_, solution of fuchsine or carmine is used, the latter -being obtained by dissolving commercial carmine powder in alcohol. - -_e._ _Orange colors_ are produced by an addition of solution of -_chrysaniline_ generally sold under the name of Victoria orange, and -_violet_ by adding aniline violet. For these, as well as for the -solution colored with fuchsine, the plates must _not_ be rubbed with -oil, as even the smallest trace of the latter discolors these colors in -drying, or at least the veneers will show spots without color. - -3. _Pouring the colored solutions of glue upon the plates._ For -imitations of marble and enamel, the glass plates, after rubbing with -oil, are placed, rubbed surface up, in a perfectly level position. -The proper portion of the white ground-mass, after becoming somewhat -thickish, is then poured upon the plates, and the gaps left free in -pouring filled in and smoothed with a knife-shaped tool of horn or -bone. Upon this white ground the respective colored glue solutions -are then poured in a zigzag form, and in conformity with the desired -design, drawn through the ground-mass with a glass rod. If several -differently colored glue solutions are to be applied, as given, for -instance, under 2_f_, they should be poured in quick succession, so -that the succeeding color runs into the preceding, and a white strip -or spot remains between each color. The whole is then intermingled -by the glass rod, according to the design. If the latter is to have -sharply defined lines and spots, the respective colored solution of -glue is used somewhat thicker, but if, on the other hand, the design is -to be somewhat blended, the glue solutions are used somewhat warmer, -and consequently more thinly fluid. After solidification of the glue -solutions the plates are placed in a cool room for two or three hours. - -Imitations of malachite are prepared in a similar manner. Four glue -solutions of different shades of green from the darkest to the lightest -tint are prepared and poured upon a slightly greenish ground, so as -to imitate the characteristic curves and veins of malachite, which -are then further traced with a comb with teeth standing at unequal -distances from each other. - -The glass plates set aside to be used for imitation of mother-of-pearl -are now taken in hand. The solutions of glue are kept warm over a water -bath and thoroughly stirred every time before pouring them upon the -plates. The formation of a film on the surface of the glue solution -must be strictly avoided. - -For pouring out the solutions it is best to use a porcelain vessel -provided with a spout and handle, and having a capacity of about 6¾ -fluidounces. The portion of glue solution required for each plate -(1¾ flu. oz.) is then measured into one of the porcelain vessels, -and, after standing a short time, poured upon the plate and uniformly -distributed. The production of a mother-of-pearl design requires some -skill and practice. A comb with teeth set ½ inch apart is used. It is -held in a somewhat oblique position, the teeth are gently pressed upon -the glass plate, and, with frequent turnings of the comb at a right -angle, cycloidal motions executed. The operation is carried on from the -front to the back edge of the glass plate, and when the glue begins to -thicken on the edges, continued at the softer places until the desired -design is produced, care being had not to touch places which have -already acquired a certain degree of solidity, as this would mar the -pattern. After treating all the plates in this manner, they are set -aside in a cool room for two or three hours. - -4. _Transferring the layer of glue to a layer of gelatine._ For each -dozen of veneers soak 2½ ozs. of gelatine, and then melt them in a -water-bath, and after adding glycerine equal to 10 per cent. of the dry -gelatine, let the mixture settle. - -The glass plates treated with rouge and Spanish chalk are now placed in -a perfectly level position, and after pouring 5½ fl. ozs. of gelatine -solution upon each of them, the gaps left in pouring are filled in -and smoothed with the glass rod. The front edge of a plate covered -with a colored layer of glue is now, glue side down, placed upon the -front edge of a gelatine plate, while the back edge of the former is -gradually lowered until the glue plate lies firmly upon the gelatine -plate. - -It may here be remarked that the gelatine solution must only be allowed -to cool off sufficiently to prevent the melting of the glue plate on -touching it. If it is cooler the veneers will have blisters. It must -further be looked to that, before placing the first plate upon the -gelatine plate, no gelatine escapes, and that any excess only runs off -after the back edge of the glue plate touches that of the gelatine -plate. - -The plates are now allowed to rest quietly until the gelatine is -congealed, when they are removed to a cool place where they remain five -or six hours. - -Imitations of mother-of-pearl are treated in the same manner with the -exception that the gelatine solution is colored with the same coloring -matter as the glue solution. For colorless or yellowish veneers the -gelatine solution is not colored. - -After six hours the first glass plate is detached from the layer of -glue by loosening the latter around the edges with a knife blade, and -the plate gradually lifted off commencing at one corner. With some care -and skill, this operation is readily accomplished without detaching the -gelatine mass. - -5. _Drying and detaching the veneers._ The veneers with the gelatine -layer still adhering to the glass plate are now dried. This is done -in a heated room in which the veneers are arranged upon frames so -that they stand almost perpendicular. The hot air for heating the -room enters near the ceiling while the moist air is drawn away near -the floor. The temperature of the lower zone where the fresh plates -are placed should not exceed 68° F. The plates are moved up higher -every day until, on the third or fourth day, they have become entirely -dry. Before removing the veneers from the drying-room they should be -tested in regard to their dryness. They are sufficiently dry, when, on -pressing the finger nail upon the glue, no impression is made. - -After removal from the drying-room the plates are allowed to cool off -for at least two hours before detaching the veneers. The operation -begins by detaching the gelatine layer on the edges with a very thin -knife blade. The operator then takes hold of one corner of the veneer -and draws it gradually and carefully from the glass plate. After -trimming the edges the veneers are ready for use. - -If the veneers are required to resist the action of water, mix with the -solution of gelatine compounded with glycerine ⅓ fl. oz. of a solution -of 5 parts of chrome-alum in 100 of water to every plate, and immerse -the veneers for a short time after they have been detached from the -first plate, in a similar solution of chrome-alum. - -Veneers prepared by these methods can be used for various purposes in -architecture and in the manufacture of furniture. Tennessee and other -marbles have been so closely imitated, that when used for table plates, -etc., the fact of their being imitations could only be detected by the -closest scrutiny. The veneers are also much used for fancy and inlaid -work, for coating columns, etc. To prevent their blistering and coming -off, it is recommended to add one-quarter of its weight of glycerine to -the glue with which they are to be attached to the articles. - - -_Formo-Gelatine._ - -This product is used as a dressing in surgery, and, according to -Samuel Rideal, is obtained as follows: Gelatine in aqueous solution is -precipitated by formaldehyde H.COH, or CH_{2}O, as a substance which on -drying is a white powder, neutral, inodorous, and insoluble in water -and dilute chemical agents. In commerce formaldehyde is met with in -aqueous solution as “formalin” containing 40 per cent. of formaldehyde. -If 1 Cc. of formalin be added to 200 Cc. of a 5 per cent. gelatine -solution, the latter is changed into a gelatinous mass, not melted by -heat nor reduced by water. If a smaller quantity of the formalin is -added (1 in 1000; the jelly is said to be meltable, but with a higher -tenacity) when dried it becomes insoluble in warm water. Formalin in -less proportion, though it does not prevent the dried gelatine from -dissolving in warm water, is said to improve the “body” of the jelly -and its keeping qualities, and also the tenacity of the glue. The -results of investigation show that with up to 1 per cent. of formalin -the solidity of the jelly increases; above that it declines. Up to -0.02 per cent. (1 in 5,000) it redissolves in water after drying. -Even with this small proportion the firmness of the jelly is sensibly -increased. The English patent, 4,696, 1894, claims the addition of -formalin during the manufacture of size and glue in such proportion -that the product shall liquefy in warm water. - -In examining commercial sheet gelatines for printers’ and photographic -use, they were often found to contain small quantities of formalin. -It seems to improve the quality, a very small percentage increasing -the tenacity, flexibility and keeping qualities, while not affecting -the transparency or rendering the material acid. When applied to -articles that may be used as food, a strength of 1 in 50,000 in the -final prepared product is not injurious to health, but should not be -exceeded. (Rideal and Foulerton, _Public Health_, May, 1899, p. 568.) - -Zimmermann applies dilute formaldehyde mixed with glycerine, vaseline, -oil or yolks of eggs, with or without flour, to the surface of -photographic films which are claimed to be thereby rendered more -pliable and not so hard as when the formalin is applied by itself. - -It will be seen that formaldehyde in more than traces renders gelatine -insoluble; the product, moreover, is almost unaffected by water, is -more or less hard and elastic and, owing to the antiseptic properties -of the formaldehyde is nearly imperishable. - - -_Use of Gelatine in Bacteriology._ - -Gelatine fit for this purpose must be clear and bright, fairly neutral -and of high gelatinizing power. For bacteriological purposes a 10 to 20 -per cent. solution of gelatine in sheets or strips is made with meat -broth, and this nutrient jelly, which is obtained by clarification with -albumen perfectly clear and bright, forms a most useful medium for the -cultivation of micro-organisms. - - -_Artificial Silk from Gelatine._ - -For the production of textile threads, Millar utilizes the property of -gelatine solution mixed with potassium dichromate, becoming insoluble -on exposure to light. For this purpose a clear solution of gelatine is -mixed with solution of potassium dichromate in the proportion of 100 -parts of gelatine to 2 or 2½ parts of potassium dichromate. The fluid -should be of such a consistency as to allow of its being drawn out into -fine threads which on exposure to light become insoluble. Silk woven -from such threads is equal in appearance to the genuine article but of -course is not so strong. It is affected by moisture, becoming limp, but -regains its normal strength when dry.[3] - -[3] For further information on this interesting subject, the reader is -referred to “Cellulose and Cellulose Products.” By Dr. Joseph Bersch. -Henry Carey Baird & Co., Philadelphia, 1904. - - - - -CHAPTER X. - -ISINGLASS AND ITS SUBSTITUTES. - - -Isinglass is obtained from the air-bladder or sound, as it is sometimes -termed, of different kinds of fishes, especially of the sturgeon, -species _Acipenser_. It is used for culinary purposes, fining beer and -other liquids, for making court-plaster and stiffening silk, though a -good quality of gelatine is practically equal to it for these purposes. -A good quality of isinglass should be pure white, semi-transparent, -dry and horny in texture, and free from odor. It should dissolve in -water of 95° to 122° F., without leaving any residue, and, on cooling, -should yield an almost colorless jelly. From gelatine imitations it -is distinguished by soaking it in warm water and examining under -the microscope, when true isinglass will show a net-work of long, -curling fibres, while gelatine will be simply hyaline. Isinglass is -often imitated with the intestinal membranes of the calf and of the -sheep. This spurious article may be readily recognized because it does -not exhibit, like isinglass, a sort of shining appearance when held -before the eye and daylight, and because, although inodorous, it has -a saltish flavor. If it be torn asunder it will be observed that it -may be rent in all directions, while true isinglass cannot be divided -otherwise than in the direction of its fibres. If a piece of artificial -isinglass be macerated in water it swells, but instead of retaining -its shape as is the case with the genuine article, it becomes divided -into several pieces, forming a sort of curdy precipitate; and if -treated with boiling water, about one-third of its weight is left in an -insoluble state, and the liquor does not form a good jelly. Isinglass -is frequently adulterated with gelatine, which is inserted between the -leaves and rolled up with it. The best indication of this adulteration -is the amount of ash; isinglass yields only 0.9 per cent., while -gelatine yields 4 per cent., and adulterated isinglass 1.5 per cent. or -more. - -1. _Russian isinglass._ Russia produces the best and most isinglass. -It is chiefly obtained from several varieties of sturgeon, species -_Acipenser_, which inhabit the Caspian and Black Seas, and their -tributary rivers. The _Acipenser Gueldenstaedtii_, Br. yields the -finest, best and whitest isinglass. It is known by the name of -_Patriarch_, and consists of small horseshoe-shaped pieces rolled -tightly together. It is quite scarce and expensive. When the bladder is -merely dried in sheets, it constitutes _leaf isinglass_. When several -bladders are put together and folded before they are completely dry, -they form _book isinglass_. Each bladder may also be rolled up and -folded around a few pegs in the form of a horseshoe, heart, or lyre, in -which shape it is dried. The latter is the _staple isinglass_, which, -according to its dimensions, is again divided into _long and short -staple_. - -Long staple isinglass of fine quality is produced in the Oural. It is -imported in loose leaves, and at times it is twisted like ropes, this -kind being preferred, as it is inferior in quality only to Patriarch. - -_Siberian_ purse isinglass is of moderately good quality and is in -general demand. A small kind of strings in a necklace form is sometimes -imported. - -A very good sort of Russian isinglass comes into commerce in leaves -and books, and is known by the name of _Samovey_ leaf. It is obtained, -according to the statements of Russian merchants, from the common -sheath-fish (_Siluris Glanis_). The pieces are as large as a hand, -of the thickness of pasteboard, very solid, not very flexible and -of a white-yellowish color. It is inferior in quality to Astrakhan -isinglass, which is one of the best kinds. - -In _Russia_ the isinglass is generally prepared by boys under the -supervision of elder experts. The swimming bladder is first placed in -water and left there for some days with frequent changes of the water -and removal of all fatty and bloody particles. The warmer the water -the more rapidly the operation is completed. The bladders are finally -removed and cut longitudinally into sheets which are exposed to the -sun and air, being laid out to dry, with the outer face turned down, -upon boards of linden or bass wood. The inner face is pure isinglass, -which, when well dried, can with care be removed from the external -lamellæ. The finer sheets thus obtained are placed between cloths to -protect them from the flies, and are then subjected to a heavy pressure -so as to flatten them out and render them uniform. After this they -are assorted and tied up in packages. The packages composed of the -isinglass of the large sturgeon usually contain from ten to fifteen -sheets and weigh a pound and a quarter; those of the other contain -twenty-five sheets weighing a pound. Eighty of these packages are -usually sewed up in a cloth bag, or sometimes inclosed in sheet lead. - -The outer lamellæ of the air-bladder, after the isinglass has been -removed, also contain a considerable quantity of glue which, when -softened in water, is scraped off with a knife and moulded into little -tablets of about the size of a silver dollar, and then dried. - -2. _North American or New York Isinglass._ It is in thin strips -several feet long but ½ to 1½ inch wide. It is less soluble than -Russian isinglass, and yields frequently a dark-colored solution. It -is prepared, according to Dr. J. V. C. Smith’s statements, from the -air-bladder of the common hake (_Gadus merluccius_), which is macerated -in water for a short time, cut open and subjected to pressure between -iron rollers, by which it is elongated to the extent of half a yard -or more. It is then carefully dried, packed and sent to market. The -air-bladder of the common cod (_Gadus morrhua_) is prepared in a -similar manner, but yields a poorer kind of isinglass. - -3. _East India Isinglass._ It would seem that for a long time this -has been exported from _Calcutta_ to _China_, but has only lately -attracted the attention of European dealers. It is prepared from the -air-bladder of the _Polynemus plebejus_, and comes into commerce either -in the form of leaves or purses which seem to consist of the unopened -air-bladder. East Indian isinglass has a disagreeable fish odor, due -very likely to careless preparation, which makes its use impossible for -many purposes, and, of course, depreciates its commercial value. The -oval-oblong purses are about nine inches long, three and a half inches -wide, weigh about 7 ozs. and have a dark-yellow color. East India leaf -isinglass, _i. e._, the opened and dried air-bladder, consists of -yellowish-colored leaves eight to nine inches long, six to seven inches -wide, and about three-tenths of an inch thick. The leaves are sometimes -rolled out into long ribbons about one-tenth of an inch thick, the -surface of which is covered in places with a thin film of lime. - -What is known as picked East India isinglass is brought into commerce -in small shreds about two to three inches long, and tapering at the -extremities. - -A variety of isinglass very white and pure and scarcely inferior to -Samovey leaf is brought from Manila. The fish which yields it is caught -on the coast of the Philippine Islands, especially at Luzon. - -4. _Hudson Bay Isinglass._ It is brought into commerce in the purse -form. Some specimens measure twelve inches in length and three and -a half inches in diameter, and weigh one and a half ounces. It is -of light-yellow color, nearly transparent, without odor or taste. -The inner lining of the sac, which can be readily stripped off, is -insoluble in water, while the remaining portion dissolves to a slightly -colored jelly. We have been unable to ascertain from what species of -fish this isinglass is procured. - -5. _Brazilian Isinglass._ This is imported from _Para_ and _Maranham_, -and is also called _Cayenne_ isinglass. For a long time there existed -a doubt from what species of fish this isinglass was procured, but it -is now settled that it is prepared from the air-bladder of _Silurus -Parkerii_, a fish which is frequently found in the muddy waters of the -rivers in the province of Grao Para, where these waters mingle with the -sea. - -_Brazilian_ isinglass comes in the form of pipe, lump and honeycomb. -On account of its dark color it is not in much demand for ordinary -use, but is frequently employed in England for clarifying glue. When -digested in water it leaves much insoluble substance behind, being in -this respect also inferior to Russian isinglass. - -6. _German Isinglass._ Under this name we may mention the mucous -membrane of the sturgeon (_Acipenser sturio_), prepared in Hamburg. -When boiled with water it leaves 16 per cent. of insoluble substance. - -It is said that an excellent isinglass can be made from the scales of -shad and herring, which are first freed from their silvery coating. -This may furnish a useful hint to persons who are near some of the -great fishery establishments of the country, at _Gloucester, N. J._, -and _Alexandria, Va._, for instance, where thousands of shad are scaled -and salted every year. - -To give inferior qualities of isinglass a better appearance and make -them more salable, they are frequently bleached with sulphurous acid. - -_Ichthyocolle Française._ Under this name, Rohan has introduced a -substitute for isinglass. The material used for its manufacture is -blood fibrin, which, after washing in running water, is thoroughly -kneaded and, after draining, digested at 59° F. with dilute sulphuric -acid of 8° to 10° Bé. for eight days, after which the mass is freed -from acid by washing in running water. - -The fibrin freed from acid becomes transparent and gelatinous by -treating with weak soda lye of 3° to 4° Bé. at 59° F., whereby it -swells up and increases hourly in volume. After twenty-four hours -it is taken from the soda lye, and after removing the free soda by -washing, heated to 212° F, in a water-bath. The fibrin dissolves and -becomes so thinly fluid that it can be filtered. 75 to 80 per cent. of -the water is then evaporated, and the fibrin thus prepared can be used -as a substitute for isinglass for fining purposes. Ichthyocolla swells -more quickly in cold water than isinglass; 15 to 20 per cent. divided -in water forms a thickly fluid substance, which on heating dissolves to -a perfectly clear fluid. For fining beer with ichthyocolla add 2 to 10 -per cent. of pure tannin, which does not injure its power of dissolving. - -_Isinglassine._ Under this name is known an isinglass substitute -prepared from the gelatinous material from calves’ feet and other -sources. The material is reduced by machinery to a pliable homogeneous -mass, rolled out into sheets, dried, pressed and shredded. - -_Chinese isinglass_ is identical with the _Japanese Agar-Agar_, and is -obtained by cleansing and boiling certain species of algae found in -Chinese and Japanese waters. This isinglass, or gelatine, possesses the -following properties: - -Placed in cold water it softens without dissolving like gelatine, and -forms a structureless tubular mass which is not sticky. By boiling, -it dissolves more readily than isinglass, but with greater difficulty -than gelatine. A 1 to 2 per cent. solution is easily filtered through -paper or linen, and when cold forms a solid jelly clear as water and -without taste or odor. Jelly prepared with one-half per cent. of -Chinese gelatine is more solid than one prepared with 4 per cent. of -French white gelatine, retains its consistency longer, and will stand a -temperature of 86° to 122° F. before becoming liquid. Used for jellies, -or mixed with other foods, it does not impart to them a glue taste -never wanting in bone gelatine. When decomposed by long standing, it -does not acquire a disagreeable odor, while decomposed isinglass or -gelatine exhales a putrid smell. - -Agar-Agar contains, according to analyses: Cellulose, starch, gum, -dextrine, vegetable mucus, vegetable wax, resin, chlorophyll, albumen, -a peculiar acid, and several mineral substances. - -_Irish moss_ (_Chondrus crispus_) which grows on rocks of the American -and European shores of the Atlantic Ocean, yields a jelly which has -been employed as a substitute for isinglass, as a size, for thickening -colors in calico printing, and in stiffening silk. In a fresh or -softened state the plant is cartilaginous, of a brownish or purple, or -frequently yellow or green color. After washing in water and drying in -the sun it turns whitish or yellowish, and becomes somewhat translucent -and of a horny appearance. It has a slight seaweed-like odor and a -mucilaginous, somewhat saline taste. One part of it boiled with 20 -parts of water gelatinizes on cooling. - - -_Fish Glue._ - -This product, which is prepared in many localities from fishes, must -not be confounded with isinglass, though the purer varieties may serve -as substitutes for the latter or for gelatine. - -Jennings gives the following process for the preparation of fish glue. -The fishes are treated with dilute sulphuric acid until the skin can -be detached. The acid water is then drained off and replaced by milk -of lime to neutralize adhering sulphuric acid as well as to saponify -the fat. The milk of lime is several times drained off and renewed, the -mass thoroughly washed, cut up in a hollander and treated cold with -solution of sodium hyposulphite, common salt and alum. After a few days -the liquor is drawn off and replaced by a mixture of alum solution, -dilute sulphuric acid and nitric acid in which the mass is allowed -to remain for a few days. Fishes with dark skins are treated with a -mixture of hydrochloric and sulphuric acids. After washing, the skin -is removed and the fibres which have become detached from the bones -are separated by digestion in dilute solution of mercuric chloride and -alum. Adhering fatty parts are removed with warm milk of lime, the lime -is neutralized with hydrochloric acid, and the mass boiled with water -for the formation of glue. The resulting glue-liquor is clarified with -sulphurous acid and alum, and when all the impurities have subsided, -compounded with acid sodium carbonate till all the acid is neutralized. -The finished solution is concentrated so that it gelatinizes on cooling -and can be cut in cakes which are dried in the usual manner. - -Fish scales, especially those of carps, are treated in a similar -manner. The bone-earth is extracted with hydrochloric acid, the -extracted material thoroughly washed, and then boiled in soft water -till it can be readily stirred. The liquor is drawn off from the horny -sediment, clarified with alum, evaporated, and after all the impurities -have subsided, poured into moulds and treated like ordinary glue. - -Considerable quantities of fish glue are produced on the Norwegian -coast from waste obtained in the preparation of codfish. The fish when -caught are cut open and the air-bladders removed, which are dried and -brought into commerce as isinglass. The head is then cut off and the -bones detached in one piece. The flesh is dried in the air, and forms -the codfish of commerce. The heads and bones are first treated with -hydrochloric acid or directly boiled under slight pressure in water, -and the resulting liquor concentrated so that it will gelatinize. - -A substitute for isinglass, also for gelatine and glue, is prepared by -C. A. Sahlströhm, of Stockholm, according to his patent, from fish and -fish waste by treatment with bleaching powder, potassium permanganate, -and nitrous and sulphurous gases. - -For this purpose the fishes, or portions of fishes, are first well -washed in fresh water and then left for from three to four hours in a -solution of bleaching powder (in the proportion of 2 lbs. of bleaching -powder to 300 quarts of water). After washing they are treated for -about 30 minutes with a solution of potassium permanganate (in the -proportion of 1¾ ozs. of potassium permanganate to 250 or 300 quarts of -water), and then exposed to the action of the nitrous gas, produced by -heating 10 to 15 ozs. of nitric acid for every 88 lbs. of raw material. -This gas may be first absorbed by water, as in the manufacture of -sugar, or sulphur dioxide may be used instead of nitrous gas. The -former would be obtained by burning about 7 ozs. of sulphur for every -88 lbs. of raw material. - -The material, after this treatment, is washed. Those portions intended -for the production of isinglass substitute are freed from their outer -skins and dried and pressed at a gentle heat. The portions destined to -produce gelatine or glue are, on the contrary, exposed to a temperature -of from 104° to 122° F. for from ten to twelve hours, by which the -material is mainly dissolved. The mass is then forced through a -strainer or sieve, and the liquor allowed to gelatinize by standing for -some hours. The jelly is finally dried, as is usual in the manufacture -of glue or gelatine. - -_Whale glue_ is, according to Culmann, obtained in the Russian island -Jeretike from the liquor remaining in the boilers after the extraction -of the oil by means of superheated steam. By reason of the raw and -moist atmosphere which prevails in that locality, even in summer, -drying the glue is not practicable, and for this reason it is brought -into commerce in the form of a compact jelly mixed with a preservative -and packed in tin boxes. The commercial article contains 41.65 per -cent. water. It is liquefied by placing the can in boiling water, and -melts at 176° F. As shown by mechanical tests, it possesses great -tenacity, and two pieces of wood glued together lengthwise cannot be -separated at the joint but break alongside of it. - - - - -CHAPTER XI. - -TESTING GLUE AND GELATINE. - - -It is of importance that the manufacturer as well as the dealer should -know how to test the quality of a glue. This may be done by chemical -means and in a mechanical way. - -_Determination of moisture._ For this purpose a weighed quantity -of the sample, finely powdered, is for fourteen hours exposed to a -temperature of 217° to 230° F. It is then cooled under the dessicator -and reweighed. The content of moisture is then calculated from the loss -in weight. - -_Determination of ash._ The origin of a sample of glue may be traced -by examining the ash for phosphates of lime and magnesia, bone-glue -containing both, while skin-glue is free from phosphates. Reduce -a portion of the sample to a fine powder, and weigh it in a tared -constant crucible. Heat slowly over a Bunsen flame until carbonized, -then remove the crucible to the muffle, and heat to bright redness for -10 hours. Cool under the dessicator and weigh. The increase in weight -of the crucible is the ash of the sample. This will vary from 1 to 2 -per cent. in a gelatine, 2 to 3 per cent. in a good glue, 6 to 8 per -cent. in a common quality. - -_Determination of Acidity._ Kissling elsewhere determines the acidity -by suspending 30 grammes of the sample in 80 Cc. of cold water for 10 -to 12 hours in a flask connected with a condenser. The volatile acids -are then driven over by a current of steam into a graduated cylinder. -When the distillate amounts to 200 Cc., distillation is interrupted, -and the distillate treated with standard decinormal alkali. When the -distillate contains sulphurous acid, a known quantity of the standard -alkali is previously added to the cylinder. - -An undue quantity of acid may be detected by the taste. Glues may be -alkaline from the addition of excess of lime in the manufacture to -correct the sourness of the jelly. For uses where colors are concerned -the glue must be neutral to litmus; for adhesive uses this does not -matter unless the alkalinity or acidity is due to defective preparation -(Samuel Rideal). - -_Determination of Glutin._ The percentage of glutin in a glue solution -is determined by precipitating it with tannin. The dense white -precipitate formed is thrown on to a tared filter, washed with hot -water, dried and weighed. The calculation is made on the basis that the -tannate of glutin has a percentage composition of 42.74 per cent. of -glutin and 57.26 per cent. of tannin. - -Bisler-Beumat while employing the same principle prepares two -solutions: _a._ 10 grammes of pure tannin to the liter. _b._ 10 grammes -of pure isinglass and 20 grammes of alum to the liter. The ratio in -which the tannin is precipitated by the isinglass solution, which -Risler considers as pure glutin, is then determined by titration. The -tannin solution is then diluted so that exactly an equal volume of glue -solution is precipitated by it. - -In order to test a sample of glue, dissolve 10 grammes of it together -with 20 grammes of alum in a liter of water, heat being applied if -necessary. Next 10 cubic centimeters of the tannin solution are taken -to which an equal bulk of glue solution is at once added, as one may be -sure that this quantity is not sufficient for the precipitation of the -measured quantity of tannin, because no glue found in commerce is as -pure as isinglass. The vessel containing the mixed liquids being well -shaken and the precipitate having subsided, another cubic centimeter of -glue solution is added to the tannin solution which is next filtered -through a moist cotton filter. If _one_ drop of the glue solution still -produces a precipitate in the clear filtrate, another cubic centimeter -is added to the tannin solution, and then again filtered, these -operations being repeated until the filtrate is no longer rendered -turbid by the glue solution. - -With the known relation of the tannin solution to pure glue -(isinglass), a conclusion may be formed from the number of cubic -centimeters of glue solution used as to the content of glutin in the -sample examined. - -The percentage of glutin varies, of course, according to the quality -and origin of the glue. Bone glue of good quality contains from 50 to -52 per cent. and skin glue from 65 to 75 per cent. - -S. Dana Hayes analyzed two samples of American glue of best quality and -obtained the following results: - - a. b. - Water (escaping at 212° F.) 16.70 16.28 - Glue substance 79.85 80.42 - Calcium carbonate 1.42 1.33 - Calcium sulphate 0.41 0.34 - Magnesium phosphate 0.35 0.31 - Alkaline salts 0.17 0.12 - Silica, ferric oxide, etc. 0.09 0.08 - Zinc oxide 1.01 1.12 - -The chemical modes of testing glue give only the quantity of glutin -contained in it, but do not prove that the substance combined with -tannin corresponds to the actual adhesive power of the glue, for it is -possible that a glue containing a large quantity of glutin may possess -but little adhesive power, and a jelly from which the glue is formed -may contain an equal amount of glutin with the latter, but not possess -an equal power of adhesion. - -It is certain that the determination of the glutin alone is not a -criterion of the quality of glue. In the absence of a reliable method -of direct analysis, attempts have been made to deduce the quality of -glue from indirect properties. - -One of these methods consists in immersing the sample of glue in a -large quantity of water at 59° F. for a considerable time. The glue -swells up, absorbing 5 to 16 times its own weight of water. The -more consistent and elastic the glue in this state is found to be, -the greater its adhesive power, and the larger the quantity of water -absorbed the more economical the glue will be in use. This method does -not give thoroughly reliable results, and should only be employed with -bone-glue, as skin-glue does not behave in a similar manner. - -[Illustration: FIG. 65.] - -A more reliable method is to test the strength of a glue by the method -first proposed by Lipowitz, which is based on the weight-sustaining -power of a jelly of known strength and temperature. The test is -executed as follows: Soak 5 parts of the sample in water, then dissolve -it in sufficient hot water to make the weight of the solution equal -to 50 parts, and allow to stand for 12 hours at 64.4° F. in a glass -cylinder of uniform width to gelatinize. Cover the glass cylinder with -a tin cap perforated in the centre, Fig. 65. Through the perforation -is passed freely a stout iron wire, at the lower end of which is -soldered a piece of tin shaped like a saucer, the convex side of it -resting on the surface of the jelly. To the upper end of the wire, -which together with the tin saucer should weigh 5 grammes, is soldered -a funnel weighing 5 grammes, and capable of holding up to 50 grammes -of fine shot. The apparatus is gradually loaded with shot until the -saucer-shaped piece of tin is forced into the jelly. The greater the -strength of the jelly, the heavier will be the weight required. From -the determined weight of the shot used, the relative value of the glue -as to its adhesive power is determined. - -The following results have been obtained by comparative experiments -with this apparatus: - - Variety of Glue. Weight required to force - the saucer down. - - Breslau 1704 grammes = 3.74 lbs. - Russian 1446 grammes = 3.18 lbs. - Cologne 1215 grammes = 2.67 lbs. - Muhlhausen I. 727 grammes = 1.599 lbs. - Nördlingen 724 grammes = 1.592 lbs. - Muhlhausen II. 387.5 grammes = 0.85 lbs. - -The results of these experiments agree to a remarkable degree with the -market prices of the varieties of glue, which is not the case with -glues tested by the methods previously mentioned. The results of these -tests are given in the table below: - -Table Key: - -Variety of Glue. - - 1. Best White isinglass in three qualities - 2. Translucent yellowish bone glue in tablets and easily soluble - 3. Pale yellow glue similar to No. 2 - 4. Brown-reddish, brittle in fracture and soluble - 5. Clear translucent glue of medium brown color - 6. Brown-yelow glue in thick tablets and possessing but little - translucency - 7. Pale brown-yellow glue, readily soluble and elastic before breaking - 8. Pale amber-colored glue with but little translucency - 9. Brown glue, solution turbid - 10. Amber-colored glue, opalizing and readily soluble - 11. Thich tablets or dark-brown glue, solution very turbid - 12. Dark horn-like glue with little translucency - 13. Very translucent glue of a light brown color and very clean - solution - 14. Translucent dark-brown glue, giving a very clear solution - - ----+----------------+--------------+------+-------------+------------- - |Loss of water | 100 parts |Glutin| Water |A 100 per cent. - |in drying for | of glue are | per | absorbed in |solution of - |several hours at| precipitated |cent. |24 hours by 5|glue will bear - |239° to 248° F. |by tannic acid| |parts of glue|a weight of - ----+----------------+--------------+------+-------------+------------- - 1. | 20 to 21 | 74.62 | 55.69| — | - | | | | | - 2. | 13.2 | 76.2 | 56.8 | 40 |64 grammes - | | | | | (2.25 ozs.) - 3. | 13.0 | 70.0 | 52.2 | 35 |60 grammes - | | | | | (2.11 ozs.) - 4. | 10.0 | 71.0 | 52.9 | 12 |Does not - | | | | | gelatinize. - 5. | 11.0 | 71.5 | 53.3 | 20 |20 grammes - | | | | | (0.705 oz.) - 6. | 12.5 | 68.0 | 50.7 | 27 |15 grammes - | | | | | (0.52 oz.) - 7. | 13.0 | 66.6 | 49.7 | 30 |36 grammes - | | | | | (1.26 oz.) - 8. | 9.5 | 68.5 | 51.1 | 33 |60 grammes - | | | | | (2.11 oz.) - 9. | 10.0 | 82.0 | 53.7 | 30 |50 grammes - | | | | | (1.76 oz.) - 10.| 9.5 | 73.0 | 54.4 | 35 |56 grammes - | | | | | (1.97 oz.) - 11.| 13.5 | 64.0 | 47.7 | 18 |23 grammes - | | | | | (0.81 oz.) - 12.| 9.0 | 72.6 | 54.2 | 29 |12 grammes - | | | | | (0.42 oz.) - 13.| 13.5 | 70.0 | 52.2 | 30 |40 grammes - | | | | | (1.41 oz.) - 14.| 15.0 | 66.0 | 49.4 | 25 |42 grammes - | | | | | (1.48 oz.) - ----+----------------+--------------+------+-------------+------------- - -This table shows the following facts: - -1. The percentage of water in the 14 dry varieties of glue examined -varies between 9.0 and 21. The loss of water from isinglass is -surprisingly large, especially as it cannot be explained by an -artificial admixture of water, since the six varieties examined -reabsorbed the same percentage of water from the air. The percentage of -water in the other varieties of glue differs but little. - -2. The various varieties of glue required different quantities of -tannic acid for their precipitation, the amount for 100 parts of glue -varying between 66 parts and 76.2, or calculated to per cent., between -49.4 and 56.8. - -3. Placed in cold water, glue swells up and absorbs from 12 to 40 parts -of water. The behavior of the various varieties differs very much in -this respect, and in most of the experiments, with the exception of -variety No. 4, the percentage of glutin is in exact proportion to the -quantity of water absorbed. - -4. The strength of the gelatinized glue varies between 12 grammes -(185.18 grains) and 64 grammes (987.67 grains) for a 10 per cent. -solution. This property corresponds neither with the absorption of -water nor the percentage of glutin. - -Variety No. 4, in the table, contains 52 per cent. of glutin, but does -not gelatinize, its strength being therefore equal to 0, while variety -No. 14, with 49.4 per cent. of glutin, therefore less than No. 4, -shows a strength of 42. As no close connection between the properties -mentioned in the table can be recognized, it is best not to be guided -by these properties alone, but to test also the behavior of the glue in -practical use. Such test consists in estimating the adhesive power of -the glue from the weight required to tear asunder two pieces of wood -glued together and dried. But as the results obtained by this purely -practical test must necessarily vary on account of the impossibility of -having two surfaces of wood always exactly alike, and the uncertainty -of applying every time the same quantity of glue, Weidenbusch’s method -may here be given. It is based upon the principle that sticks of -plaster of Paris cast of exactly the same material and of uniform size -break under the same weight when placed upon two supports and loaded in -the centre. If now such plaster sticks be saturated with glue solutions -prepared according to the same method, but from different qualities -of glue, a greater force will be required for breaking them, and this -force will be the greater the better the quality of glue is. - -The plaster sticks are prepared as follows: Reduce pure crystallized -gypsum to a fine powder, pass the latter through a sieve having 324 -meshes per square centimeter and heat it to between 284° and 302° F. -For casting the sticks moulds of soap-stone are used. The moulds are -made by boring in a piece of soap-stone, at a distance of about 1 -centimeter from each other, holes with a diameter of 6 millimeters on -top and 7½ millimeters on the bottom. - -The gypsum is weighed off in portions of 1 gramme each, mixed with 1 -gramme water and cast in the moulds. The solidified sticks are first -dried at a moderate heat and then over calcium chloride, and kept for -use in an air-tight vessel. - -[Illustration: FIG. 66.] - -The glue solution is prepared as follows: The glue dried at 212° F. is -weighed, soaked over night in water, then melted in a small glass in -the water-bath, and finally enough water is added so that the solution -contains 10 per cent. of dry glue. - -The plaster sticks are for one or two minutes immersed in the glue -solution heated to 212° F., and then placed vertically upon a glass -plate until superficially dry, when they are completely dried at 212° -F. It is recommended to color the glue solution with indigo, the -uniform saturation of the sticks being thereby more easily recognized. - -The apparatus for testing the strength of the sticks consists of a -brass ring _a_, Fig. 66, having two notches to receive the stick, and -its diameter is divided into two equal parts by an indicator. The ring -is supported by a pin, by means of which it is secured in a stand. The -apparatus is completed by an iron or glass cup which is suspended by -three cords, _i_, and the hook _f_ to the plaster stick _b_. The hook -_f_ is placed in the position indicated by the indicator. Mercury is -now poured into the cup until the plaster stick commences to break. The -weight required is recorded and compared with a standard glue. During -the experiment the cup is suspended by the three cords _h_ to the ring -_a_, and is thus caught when the plaster stick breaks. On the lower end -of the cup is a clip for emptying the mercury into a vessel so that -none of it is lost. - -The “Artillery Werkstätte” at Spandau has adopted the severing strain -of two blocks of wood glued together. The test is executed as follows: -Three parts of glue (but not less than 250 grammes) are mixed with -6 parts of water and boiled in a steam bath until the weight of the -boiled glue amounts to only 5/9 of the original mixture. The reason for -this continued boiling is to ascertain whether the glue to be tested -retains the required adhesive power even after six hours continued -heating in a steam bath as frequently happens in the workshop. With the -glue thus prepared the following breaking test is made: - -Blocks of hard or soft wood 420 millimeters long and 40 × 40 -millimeters cross section are cut in two, so that each piece thus -obtained is 210 millimeters in length. These two pieces are then again -glued together across the grain with the glue to be tested. The -block is then placed in a dry room at a temperature of 62° to 68° F. -for 72 hours, when the joint is tested as to its resisting power. At -a distance of 180 millimeters from the joint a hole is bored in the -block. Through this hole is pushed a bolt furnished on the lower end -with a hook to which a scale is suspended. The block of wood is clamped -to a table so that the joint projects 1 centimeter beyond the edge. The -scale is at the start loaded with 25 kilograms, the load being every -five minutes increased 5 kilograms till fracture takes place. - -Two such blocks, one of hard and one of soft wood, are subjected to the -test, and a serviceable glue must stand at least an average load of 70 -kilograms. - -_Determination of adulterations._ White lead, sulphate of lead, zinc -white, or chalk in quantities varying from 4 to 8 per cent. are -frequently mixed with the melted glue to improve the appearance of the -finished product. Thus, according to analyses by A. Faisst, Russian -glues contained in 100 parts foreign admixtures as follows: - - I. II. III. IV. - Zinc white 1.66 - Chalk 2.40 2.95 3.79 2.10 - Sulphate of lead — 4.16 2.35 3.18 - —— —— —— —— - 4.06 7.08 6.14 5.28 - -The so-called patent glue which is opaque and of a white color is -produced by adding considerable quantities of white lead to ordinary -glue. - -According to Barreswil, glue is frequently mixed with lead acetate -solution to protect it from putrefaction. Such an addition, as well -as the presence of white lead or sulphate of lead, is detected by the -introduction of sulphuretted hydrogen into very dilute glue solution. -In the presence of lead acetate a black precipitate of lead sulphide -appears in the clear solution; if white lead or lead sulphate is -present, the white powder settling on the bottom is blackened by the -formation of lead sulphide. - -For the detection of other earthy additions, prepare a very dilute -solution of the glue in question and allow it to stand quietly for -a few hours. The heavy additions subside, and after decanting the -supernatant fluid is collected upon a small filter and examined by the -customary analytical methods. - -It is difficult to say what quantities of earthy constituents actually -constitute an adulteration, since it is claimed by many practical men -that a considerable content of earthy parts is of advantage as regards -the cementing power of glue. Generally speaking it may, however, be -said that a glue containing more than 6 to 8 per cent. of earthy -constituents must be considered adulterated. - -For many purposes, especially if the glue comes in contact with colored -materials as, for instance, in book-binding, a content of free acid -would exert an injurious effect upon the colors, destroying or changing -them. It is therefore advisable to test the glue with blue litmus paper -which, in the presence of free acid, is reddened. - -In testing a large number of samples of glue, Kissling obtained the -following results: - - Number Smallest Largest Average - SKIN GLUE. of samples. percentage. percentage. percentage. - - Water 15 13.4 18.1 15.7 - Ash 16 1.0 4.13 2.15 - Fat 21 0.01 0.090 0.037 - Volatile acids, free } 8 {0.084 0.238 0.178 - Volatile acids, fixed } {0.084 0.334 0.191 - - BONE GLUE. - - Water 25 11.5 17.7 13.4 - Ash 26 1.16 5.07 2.46 - Fat 5 0.047 0.217 0.113 - Volatile acids, free } 7 {0.088 1.451 0.655 - Volatile acids, fixed } {0.097 0.721 0.460 - -However, those who from their practical knowledge are most competent to -judge the commercial value of a glue, scarcely require such complicated -tests, as by taking the sample in their hand and looking at it, -they can in most cases tell its quality. Great hardness, a clear, -rattling sound when struck, and resistance to breaking are signs of -good quality, and if the cake is cut thick, it shows that the jelly -possessed great consistency. Many kinds of glues are intentionally -cut thin so that they will dry before spoiling. The derivation of -a glue from a sound jelly is recognized by the fine cutting lines. -When the jelly possesses but little gelatinizing power and is in the -first stages of decomposition or putrefaction, or formation of sugar -has already set in, it cannot be poured into moulding boxes, as it -would putrefy before it has a chance to gelatinize. Such sick jelly is -poured in thin layers upon glass or metal plates so that it may acquire -sufficient solidity to allow of its being cut up into leaves and dried -upon nets. If the edges of the glue are deeply indented and raised, the -jelly, before drying, possessed but little concentration (25 to 30 per -cent.), and if notwithstanding this, it acquired sufficient consistency -to allow of its being cut, it must have been very sound. Glues cut -thick and showing no indentations and raised edges, are derived from -excessively concentrated jellies (30-35-40 per cent.). Such jellies -lose in quality in evaporating. - -A high degree of transparency is a favorable sign as regards the purity -of a glue, substances inducing putrefaction having been eliminated. -Hence this property should be worthy of recommendation, but the -consumer having been disappointed in the use of thin glass-clear glues, -distrusts also the thick-cut transparent product, preferring a turbid, -translucent or opaque article. For this reason the manufacturer is -forced to render glass-clear glue turbid with coloring matter. - -The color of the glue is also a means of judging it. To be sure, -chemically pure glutin is a colorless substance, but glue is always -colored more or less dark brown. Although this coloration does not in -the least impair the adhesive power, the manufacturer endeavors to -produce a product of as light a color as possible, and this is best -effected by bleaching with sulphurous acid. By this means the glue not -only acquires a lighter color, but also becomes more stable, substances -inducing putrefaction being destroyed by the acid. - - - - -PART II. - -CEMENTS, PASTES, MUCILAGES. - - - - -CHAPTER XII. - -CLASSIFICATION OF CEMENTS. - - -The great variety of substances entering into the manufacture of -cements and pastes makes a division of them extremely difficult. -Stohmann divides them into the following groups: - - 1. _Oil cements._ - 2. _Resinous cements._ - 3. _Cements containing rubber or gutta percha._ - 4. _Cements containing glue, or starch paste._ - 5. _Lime cements._ - -Generally speaking, this division is correct; the only change we -would suggest is to apply the term _agglutinant_ or _paste_ to bodies -containing glue and starch paste. - -When we attempt a division of the cements according to the bodies to be -cemented, we find that the result will be a larger number of groups; -as we must take into consideration whether the articles to be cemented -have to be heated or not, whether they are to come in contact with -water or other liquids, and other circumstances which would necessitate -modifications in the composition of the cements themselves. - -According to this, we might group the cements as follows: - - 1. _Cements for glass and porcelain, for repairing broken articles, - for fastening glass letters upon show-windows, etc._ - - 2. _Cements for metals not exposed to an increase of temperature, for - instance, for tightening the joints of gas and water pipes._ - - 3. _Cements for stoves and other articles, which have to stand an - increased temperature._ - - 4. _Cements for chemical apparatus, i. e., such as will have to resist - the action of chemical agents._ - - 5. _Cements to protect vessels of glass, porcelain, or metal against - the action of fire._ - - 6. _Cements for filling hollow teeth, for microscopical preparations, - and other delicate articles._ - - 7. _Cements for special purposes, for instance, for cementing - meerschaum, tortoise shell, etc._ - -_Chemical nature of cements._ The different varieties of cement -frequently contain substances which act chemically upon each other, -or upon the bodies to be united with them. To determine the practical -availability of a variety of cement for a determined purpose, it is of -importance to know the reciprocal behavior of these substances towards -each other, as from this we are able to judge at once whether a cement -is suitable for a certain purpose or not. - -_Oil cements._ The fluid fats, commonly called oils—though there are -oils which remain solid at the ordinary temperature, as, for instance, -palm oil and cocoanut oil—may, as regards their behavior on exposure to -the air, be divided into two large groups, namely, drying and nondrying -oils. As samples of these groups may be mentioned olive oil and linseed -oil. - -If a thin layer of olive oil protected from dust is exposed to the -air, it will remain fluid for years and retain its characteristic oily -consistency. The only change it undergoes is that it becomes somewhat -more viscid and rancid, and acquires a darker color, but it never dries -up. - -Linseed oil treated in the same manner solidifies in the course of a -few weeks to a hard, tough and elastic mass, resembling, as regards its -physical qualities, resin or rubber. - -By compounding a drying oil with a small quantity of litharge, -pyrolusite, manganous borate, etc., and heating the admixture to the -boiling-point, it acquires the property of drying in a few hours when -exposed to the air in a thin layer. Oil so treated has been changed to -a varnish. - -By bringing a drying oil in contact with a body possessing strong basic -properties a peculiar process takes place; the sebacic acids contained -in the oil combine with the basic bodies to solid combinations which -are insoluble in water, and, on exposure to the air, change gradually -into masses as hard as stone. Such combinations, as regards their -chemical composition, resemble ordinary soap, and for this reason are -called insoluble soaps to distinguish them from ordinary soap which is -soluble in water. - -Burned lime, calcined magnesia, whiting, ferric oxide, litharge, and -minium possess the capacity for forming insoluble soaps on coming -in contact with drying oils and, still more quickly, with varnishes -prepared from them. - -The hardness of these soaps in time increases considerably by the oil -not saponified drying in. The oil cements are principally used for -tightening water and gas pipes, as they resist the action of water, -steam and gas. - -The only drawback connected with these cements is that they must reach -a certain age before becoming entirely hard, and that, on account of -the high price of drying oil or varnish which is absolutely required -for their preparation, they are rather expensive. The ordinary -glazier’s putty and the red lead and linseed-oil cement used in -constructing water and gas conduits belong to this group. - -_Resinous cements._ By resins are understood a number of constituents -of plants which exude in thick viscous masses through incisions made -in the trees, and on exposure to air are gradually converted into -less transparent, brittle masses. When heated they melt more or less -readily, forming a thick, ropy liquid, and brought in contact with an -ignited body they burn with a bright flame and much sooty smoke. - -By making incisions in the bark of any of the whole genus of _Pinus_ -belonging to the _Coniferæ_ family, a viscous mass of a strong odor, -called turpentine, is obtained. It consists of a solution of common -rosin in the essential oil of turpentine, and when distilled yields -from 75 to 90 per cent. of colophony or rosin, which remains in the -retort, and from 25 to 10 per cent. of the essential oil, commonly -called spirits of turpentine. Pure rosin is a brittle, tasteless, and -almost inodorous mass of a light yellow color and a smooth, shining -fracture. - -The various resins found in commerce, such as shellac, mastic, elemi, -copal, etc., are formed in a similar manner. - -The principal points of importance for our purpose are the different -degrees of hardness and brittleness and the melting-points of the -various resins. While some possess but slight hardness, for instance -elemi, others, such as copal and amber, excel in this respect and their -brittleness and high melting-point. - -To decrease the brittleness of resins, essential oils are sometimes -added, or resinous cements are mixed with oil cements or a fat drying -oil, or compounded with rubber cement. - -Resinous cements are either softened by heating or entirely melted, -or solutions of resins in volatile solvents are used, which, in -evaporating, leave the resin behind. - -The resinous cements possess great power of resistance, and are -therefore well adapted for tightening water and gas pipes, but they -have the disadvantage of not standing a high temperature and possessing -a certain degree of brittleness which renders them unfit for the -cementing of articles exposed to frequent shocks. - -Many of these cements, especially those prepared with pitch or -asphaltum, can be produced at a very low cost, and do excellent service -for water-proofing vessels, water-reservoirs, brickwork, etc. - -_Rubber and gutta-percha cements._ Caoutchouc, commonly called India -rubber, or briefly rubber, is derived from the milky juices of -certain tropical plants. It is distinguished by great elasticity and -indifference to chemical agents. - -Both these properties make it a valuable material for cement, and it -is much used for this purpose either in the form of solution or as -a constituent of other compositions. For cements which are to have -a certain degree of elasticity combined with indifference toward -chemical agents, it is absolutely indispensable, as no other known body -possesses these properties in such a high degree. - -The derivation of gutta percha is similar to that of rubber. At an -ordinary temperature it forms solid and very tenacious masses, of a -leather-like consistency, but at a somewhat higher temperature (below -the boiling-point of water) it is converted into a very plastic, soft -mass, which can be drawn into very fine threads, and rolled to very -thin plates. - -By itself or mixed with other substances it furnishes an excellent -cement, possessing the valuable properties of tenacity and pliancy -when exposed to shocks. As regards resistance to the action of water -and chemical agents it is almost equal to rubber, and, for certain -purposes, is frequently preferred to the latter. - -_Glue and starch cements._ By itself, _i. e._, converted by boiling -with water into a viscous mass which solidifies on cooling, glue cannot -be classed with the cements; the same applies to paste, _i. e._, starch -or flour swelled and boiled in water. - -But compounded with other substances both yield excellent cements, -in which a part of the properties distinguishing glue solution and -paste is preserved. They both possess the property of decreasing the -brittleness of many cements, but unfortunately the latter thereby lose -their power of resisting the action of water; for starch as well as -glue swells in water, and the latter, when moist, passes quickly into -putrefaction and destroys the cement. - -In a wider sense isinglass, compounds of glue and vinegar, of lime and -glue, etc., must be classed with the glue cements, and ordinary flour -and shoemakers’ paste with starch cements. - -_Lime Cements._ Lime possesses the property of forming insoluble -combinations with egg albumen or caseine, this being the reason why -lime cements, of which there are a great number, are generally composed -of burned lime and one or the other of the above substances. Lime -compounded with a solution of water-glass forms also very solid and -durable cements. - -Although the cements and agglutinants mentioned in the foregoing -are most frequently used, a compound of different cements is often -employed, in consequence of which the composition of many cements is -very complicated. - -In the following we give a description of the preparation of the -different kinds of cement, according to the manner of their employment. - - - - -CHAPTER XIII. - -PREPARATION OF CEMENTS, PASTES, AND MUCILAGES. - - -OIL CEMENTS. - -Oil cements, as already explained, must be considered as a variety -of soaps insoluble in water, formed by the action of drying oils or -varnish upon various basic combinations. - -The most important of this class is the cement used for securing -window-panes. Good glaziers’ putty is a product of extraordinary -durability, and, besides for puttying glass and wood, can also be used -for joining many other bodies. - -_Putty._ This is prepared by mixing fine whiting with linseed oil or -linseed-oil varnish. The whiting should be passed through a sieve of 42 -meshes to the inch. It should be perfectly dry before sifting, and be -thoroughly incorporated with the oil. - -As the work of kneading large masses with the hands or feet must be -continued for a long time in order to obtain an entirely uniform -product, and is consequently very laborious, it is recommended to use -the following contrivance: - -Two wooden rollers rest in a suitable frame, and can be brought -together or removed from each other by means of two screws. When the -mixture of whiting and linseed oil is of sufficient consistency to -allow kneading, it is fashioned into a cylinder and rolled out between -the above rollers to a long, thin band, which is caught in a vessel. -The band is balled together, the ball reformed into a cylinder, and the -latter again passed through the rollers, the operation of balling and -rolling being continued until a uniform mass is obtained. - -The finished product should be kept in oiled paper or under water. -White lead is sometimes mixed with the putty, and other pigments to -give color as desired. Hard putty may be softened by rolling between -the hands. - -_French putty._ Boil 7 lbs. of linseed oil with 4 lbs. of burnt umber -for 2 hours. Then add 10 lbs. of white lead and 5½ lbs. of chalk. - -_Soft putty._ Whiting 20 lbs., white lead 2 lbs., linseed oil and olive -oil 1 gill each. - -Mix the whiting and the white lead with the necessary quantity of -linseed oil, to render the putty of the proper consistence, the olive -oil being added to the linseed oil before kneading. The object of using -olive oil is to prevent the white lead from hardening, and it preserves -the putty in a state sufficiently soft to adhere at all times, and not, -by getting hard and cracking off, suffering the wet to enter, as is -often the case with ordinary hard putty. - -_Litharge cement._ By mixing litharge reduced to a fine powder with -linseed oil, a yellow cement is obtained which gradually solidifies to -a mass as hard as stone. - -_Red lead cement_ is made by mixing red lead with linseed oil to a -paste. It is used for cementing the joints of metal pipes. - -Lead preparations furnish excellent cements, but have the disadvantage -of great weight and a high price. For many purposes a part of the lead -combination can be suitably replaced by a substance of less weight, -such as whiting, or, still better, burned lime slacked with sufficient -water to convert it into a powder. - -The quantity of the substitute added varies very much, there being, -for instance, many varieties of so-called red lead oil cement, which -contain only about 10 per cent. of red lead. - -_Cement for wash basins._ Finely powdered glass (sifted) 2 parts, -litharge 2 parts, linseed-oil varnish 1 part. - -Wet the powders slightly with the oil, heat and gradually add the -rest. Do not use the basin for several days. Finely powdered glass or -glass meal may be made by heating glass, throwing it in cold water, -grinding the fractured pieces, and washing by stirring up in water, and -allowing the finer particles to float off into a second vessel. Collect -this fine powder when sufficient has settled in the vessel and sift it -through a very fine sieve. - -_Zinc-white cement_ is prepared similar to putty or red-lead cement. -It may, however, be made as follows: Mastic 2 parts, dammar 4 parts, -sandarac 6 parts, Venetian turpentine 8 parts, turpentine 10 parts, -benzole 12 parts, zinc white 14 parts. - -The resins are powdered, while the Venetian turpentine, ordinary -turpentine, and benzole, are put in a bottle, and then the powdered -resins put in. The whole is shaken and allowed to stand for the resins -to dissolve. The solution is filtered through cotton-wool and rubbed -up with sufficient zinc-white to form a cement. Dilute with benzine if -necessary. - -_Mastic cement, mastic or pierres de mastic._ Under this name masses -are brought into commerce which are well adapted for moulding -ornaments, such as figures, columns, etc., to be exposed to the -weather. They are comparatively cheap, and it is rather remarkable that -they are not more generally known and used for technical purposes. - -To prepare large quantities of this cement suitable mills and mixing -vessels are required, as the conversion of the materials into a -dust-like flour is an indispensable condition of the success of the -work. The materials most generally used are fine quartz sand, finely -ground calcareous sand, and varying quantities of litharge or zinc -oxides, besides as small a quantity of linseed oil as possible. - -The linseed oil combines with the litharge or zinc oxide to an -insoluble soap, which incloses the other material and forms a mass -acquiring the hardness of sandstone in thirty to fifty hours. - -After converting the materials into a fine powder, the mixing is -accomplished in barrels filled about three-quarters full and revolved -by water-power. When a thorough mixture has been effected the -pulverulent mass is placed in sheet-iron vessels and saturated with -linseed oil, and then moulded at once, as it solidifies in one or two -days. - -_French mastic._ Quartz sand 300 parts, pulverized limestone 100, -litharge 50, linseed oil 35. - -_Paget’s mastic._ Sand 315 parts, whiting 105, white lead 25, calcined -red lead 10, lead acetate solution 45, linseed oil 35. - -The mastic may be colored by adding pigments. - -_Water-proof cement._ _A._ Rubber 7 parts, oil of turpentine 140, -linseed oil 40. _B._ Turpentine 100 parts, sulphuric acid 3, zinc-white -10. - -To prepare solution _A_, place the rubber in the oil of turpentine in a -bottle. It swells very much without actually dissolving. After adding -the linseed oil, reduce the entire mass by boiling to one-half the -volume originally occupied by it. - -Solution _B_ is prepared by stirring the sulphuric acid into the -turpentine and allowing it to stand for twelve hours. To remove the -sulphuric acid, the thick mass which has been formed is then kneaded in -water in which the zinc oxide has been distributed. After drying, the -resulting mass is dissolved in the warm fluid _A_. - -_Another formula_ is as follows: Linseed oil 8 parts, litharge 12, -burnt lime 88. - -Boil the linseed oil and litharge half an hour, then stir the lime into -the hot mass, and use the mixture hot. This cement is excellent for -filling in joints between stones, for flat roofs, water reservoirs, -etc. For a better adhesion of the cement, apply a coat of linseed -oil varnish to the surfaces to be cemented. Porous stones are made -water-proof by heating the cement in a boiler and adding sufficient -linseed oil to form a mass which can be readily worked with a smoothing -board. Apply as hot as possible. - -_Serbat’s mastic._ Pyrolusite 60 parts, sulphate of lead 60, linseed -oil 10. - -After thoroughly drying the materials, mix the sulphate of lead with -the linseed oil, then add 20 parts of the pyrolusite and, after mixing -and working it thoroughly, add gradually the rest of the pyrolusite in -small portions and kneading constantly. - -_Stephenson’s oil cement._ Litharge 20 parts, unslaked lime 10 parts, -sand 10 parts, hot linseed oil 3 parts. - -_Alum cement._ Dissolve good hard soap, by heating in rain water, -dilute the thickly fluid mass and add saturated alum solution as -long as a precipitate is formed. Collect the gelatinous precipitate -of alumina soap thus formed upon a cloth, and, after draining, pour -rain water over it ten to twelve times to remove the salts as much as -possible. After washing, dry the alumina soap, and rub it to a fine -powder. - -To prepare cement rub a portion of the powder with sufficient -linseed-oil varnish to form a plastic dough, which is used for filling -in the joints. - -This cement is water-proof, resists high temperatures without being -absolutely fire-proof, and, on account of its light color, is well -adapted for joining marble plates, etc. - -_Oil cement for glass._ Litharge 30 parts, burnt lime 20, pipe-clay 10, -linseed-oil varnish 6. - -_Oil cement free from lead for steam pipes._ Graphite 12 parts, heavy -spar 16, slaked lime 6, boiled linseed oil 6. - -_Oil cements for steam pipes._ I. Litharge 25 parts, air-slaked lime -10, quartz sand 10. - -Mix the ingredients quickly with the linseed oil and work the mass -thoroughly in a hot mortar. Coat the defective places in the pipes with -linseed-oil varnish, apply the cement hot and when partially solid, -make it still tighter by heating. - -II. Boil 60 parts of graphite, 50 of air-slaked lime, 60 of elutriated -heavy spar in 35 of linseed oil, stirring constantly. Apply the mixture -hot. - -_Oil cement for marble._ Elutriated litharge 10 parts, brick dust 100, -linseed oil 20. - -Prepare in the same manner as glaziers’ putty. For various colors add -zinc white for white, red lead for red, pyrolusite for brown, etc. -Previous to applying the cement saturate the surfaces of the stones to -be cemented with linseed-oil varnish. - -_Oil cement for porcelain._ Stir 20 parts of white lead and 12 of white -pipe-clay into 10 of boiling linseed oil previously boiled and knead -the mass thoroughly. After cementing let the articles stand quietly for -several weeks. - -_Diamond cement._ Litharge 30 parts, air-slaked lime 10, whiting 20, -graphite 100, linseed oil 40. Apply hot. This is an excellent cement -for metal. - -_Hager’s diamond cement._ Whiting 16 parts, elutriated graphite 50, -litharge 16. - -Mix the pulverized ingredients with sufficient old, thick linseed oil -to form a plastic dough. - - -RESINOUS CEMENTS. - -_Resinous cement for amber_ is obtained by melting mastic in linseed -oil. Volatile copal lacquer can also be advantageously used for the -purpose. - -_Cement for turners._ Melt 1 lb. of rosin in a tin can over the fire, -and when melted add 4 ozs. of pitch; while these are boiling add brick -dust until, by dropping a little on a cold stone, you think it is hard -enough. In winter it may be found necessary to add a little tallow. - -By means of this cement a piece of wood may be fastened to the chuck, -which will hold when cool, and when the work is finished, it may be -removed by a smart blow with the tool. All traces of the cement may be -removed from the work by repeated applications of benzine. To use this -cement, chip off as much as will cover the chuck to the 1/16th of an -inch, spread it over the surface in small pieces, mixing it with ⅛ of -its bulk of gutta-percha, then heat an iron to a dull red heat, and -hold it over the chuck till the mixture and gutta-percha are melted and -liquid. Stir the cement until it is homogeneous, chuck the work, lay -on a weight to enforce contact, leave it at rest 20 minutes. - -The following cement is much employed and serviceable for the use of -turners and artisans in general. - -Reduce 1 lb. of whiting to a fine powder, and heat to redness so as to -expel all the water. When cold this is mixed with 1 lb. of black rosin -and 1 oz. of beeswax previously melted together, and the whole stirred -till of uniform consistence. - -_Cement for ivory and bone._ Melt at a moderate heat equal parts of -white wax, rosin, and oil of turpentine to form a thickly-fluid mass. -For coloring the cement add elutriated red lead, ultramarine, etc. - -_Cement for white enameled clock-faces._ Dammar resin 100 parts, copal -100, Venice turpentine 110, zinc white 60, ultramarine 3. - -Apply hot and polish when cold and hard. - -_Cements for glass._ 1. Melt carefully 60 parts of bleached shellac and -10 of turpentine. If too thick, dilute with turpentine. - -2. Shellac 20 parts, elemi 5, turpentine 10. Prepare as above. - -_Cement for glass upon glass._ Shellac 10 parts, turpentine 2, -pulverized pumice stone 10. - -_Cement for glass upon metal._ Melt together 40 parts of rosin, 20 of -rouge, 10 of wax, and 10 of turpentine. Apply hot to the surfaces to be -cemented. - -_Cement for metal letters upon glass._ Rosin 42 parts, turpentine 4, -plaster of Paris 5. - -_Cement for wood._ 100 parts of shellac and 45 of strong spirit of wine. - -This cement serves for joining wood, which, on account of exposure to -water, cannot be glued. Apply the cement to the surface of one of the -pieces, and after placing upon it a piece of tissue paper press upon it -the other piece of wood previously coated with the cement. - -_Cement for knife handles._ Melt together 20 parts of rosin, 5 of -sulphur, and 8 of iron filings. - -Pour some of the hot mixture into the handle, and then push in the -knife previously heated. - -_Cement for petroleum lamps._ Boil 12 parts of rosin in 16 of strong -lye until it is entirely dissolved and on cooling forms a tenacious -solid mass. Dilute this with 20 parts of water, and carefully work into -it 20 parts of plaster of Paris. This cement is insoluble in petroleum, -and is especially adapted for cementing the glass parts of lamps to the -metal. It is also a good material for stoppers for petroleum bottles. - -_Cement for porcelain._ Rosin, 14 parts; elemi, 7; shellac, 7; mastic, -7; sulphur, 42; brick dust, 20. - -_Cement for porcelain which is to be heated._ Heat carefully 10 parts -of amber in a large spoon, stirring constantly, until it evolves heavy -vapors of a strong odor. Rub the melted mass as finely as possible, -and after placing the powder in a bottle pour over it a mixture of -bisulphide of carbon and benzine. Close the bottle air-tight to -prevent the evaporation of the very volatile solvent. When the powder -is dissolved remove the cork and replace it by one provided with a -small brush. The application of the cement and pressing together of -the parts to be cemented must be effected as quickly as possible. -In articles properly cemented the joint can only be detected by the -closest examination. This cement holds so well that cups and saucers, -soup-tureens, etc., mended with it can be used for years. - -_Cement to withstand the action of petroleum._ Dissolve 5 parts of -shellac, 1 of turpentine in 15 of petroleum. This cement is quite -elastic. - -_Cement for mica._ A colored cement for joining sheets of mica is -prepared as follows: Soak clean gelatine in water, and when swelled -squeeze out the excess of water by pressure between a cloth, then melt -the gelatine by the heat of a water-bath, and stir in just enough proof -spirit to make it fluid. To each part of this solution add, while -stirring, ¼ oz. of gum ammoniac and 1½ ozs. of gum mastic dissolved in -4 ozs. of rectified alcohol. Put the mixture into bottles, and when -required for use stand the bottle in hot water. This cement resists -cold water. - -_Cement for horn, whalebone and tortoise shell._ Dissolve gum mastic 10 -parts and turpentine 4, in 12 of linseed oil. Apply hot. - -_Cement for terra-cotta articles._ Melt together 70 parts of rosin, -70 of wax and 16 of sulphur, and stir into the mass 8 parts of hammer -slag and 8 of quartz sand. Coat the fractured surfaces with oil of -turpentine, apply the cement as quickly as possible, and press the -surfaces together. It is advisable to heat the terra cotta previously -to 158° or 176° F. After cementing the article, smooth the joint with a -heated knife and dust very fine terra-cotta powder through a linen bag -upon the soft cement in order to give it exactly the same color as the -article itself. - -_Mastic cement for glass._ Gum mastic 15 parts, bleached shellac 10, -turpentine 5. - -This mass sufficiently diluted with hot oil of turpentine furnishes -an excellent cement for fractured glass and gems. Being colorless, -the joint can scarcely be detected, provided the cementing has been -skilfully done. - -To attach gems to glass of the same color, the cement is colored with -aniline colors dissolved in spirit of wine, care being had to give it -the same shade as the gem and the glass. - -_Stick mastic cement._ Melt together, at as low a temperature as -possible, 10 parts of mastic and one of turpentine, and pour the mass -into suitable moulds. - -For use, heat the fractured surfaces of the article strongly, so that -the cement on being rubbed over them melts, then press the surfaces -together and continue the pressure until the cement solidifies. - -_Sulphur cement for porcelain._ White pitch 18 parts, sulphur 28, -bleached shellac 4, gum mastic 8, elemi 8, glass meal 28. Melt all -together, except the glass meal and stir the latter into the melted -mass. - -_Insoluble cement for wooden vessels._ Melt together 60 parts of rosin, -20 of asphalt, and 40 of brick dust. Pour the hot mixture into the -joints. This cement resists the action of lye, quick lime, sulphuric -and hydrochloric acids. - - -RUBBER CEMENTS. - -These cements are very useful, but owing to the inflammable nature of -the components, great care should be taken to guard against fire while -preparing them. They should never be made near a naked fire, as the -benzine, carbon disulphide or chloroform used to dissolve the rubber is -very volatile, and the vapor given off permeates the air until, coming -near a source of light, the whole air becomes one vivid sheet of flame. -Vessels which are used should be closed, and if possible put out of -doors. If heat is required to assist the solvent action, use a sand or -hot-water bath, but on no account bring near a fire. - -_Cements for glass._ I. Rubber 1 part, gum mastic 12, dammar 4, -chloroform 50, benzine 10. - -II. Rubber 12 parts, chloroform 500, gum mastic 120. - -This cement adheres immediately, and possesses a high degree of -elasticity. It may be used to advantage for joining together the glass -panes of hot-houses. - -III. Dissolve, without application of heat, rubber 2 parts and gum -mastic 6, in 100 of chloroform. This cement is perfectly transparent. -It should be applied as quickly as possible, as it sets in a very short -time. - -_Soft rubber cement._ Melt 10 parts of tallow in a brass pan and -gradually add 150 parts of rubber in small pieces, and stir constantly -until all the rubber is dissolved. Keep in readiness a well-fitting -lid to be able to extinguish the flame immediately in case the rubber -catches fire. When all is melted stir in 10 parts of slaked lime. - -This cement is especially adapted for sealing bottles containing -caustic substances, such as nitric acid, etc. It remains always -tenacious, being therefore suitable for cementing bodies exposed to -repeated shocks. - -_Hard rubber cement._ Rubber, 150 parts; tallow, 10; red lead, 10. - -This cement is prepared in the same manner as the above. The addition -of red lead gives it a red color, and solidifies it in a short time to -a mass as hard as stone. - -_Elastic cement._ Carbon disulphide, 8 ozs.; fine rubber, 1 oz.; -isinglass, 4 drachms; gutta-percha, 1 oz. Dissolve the solids in the -fluid. - -This cement is used for cementing leather and rubber. For use the -leather is roughened and a thin coat of the cement applied and allowed -to dry completely; then the two surfaces to be joined are warmed and -placed together and allowed to dry. - -_Marine glue._ This cement, which is only a glue in name, is -water-proof, and can be used to cement metal, wood, glass, stone, -pasteboard, etc., and is especially adapted for caulking vessels. - -Suspend 10 parts of rubber inclosed in a bag in a vessel containing 120 -parts of refined petroleum, so that only half of the bag is immersed, -and allow it to remain ten to fourteen days in a warm place. Then melt -20 parts of asphalt in an iron boiler and add the rubber solution in a -thin jet, and heat the mixture, while constantly stirring, until it is -perfectly homogeneous. Pour it into greased metallic moulds, where it -forms into dark-brown or black plates difficult to break. In using it, -it should be melted in a kettle placed in boiling water to prevent its -burning, which it is very apt to do, as it is a bad conductor of heat. -After it has been liquefied remove the kettle from the water and place -it over a fire, where it can be heated, if necessary, to make it more -fluid, to 302° F., carefully stirring it to prevent burning. - -If possible, the surfaces to be glued together should be heated to -212° F., as the glue can then be slowly applied. The thinner the layer -of glue in cementing together smooth surfaces, the better will it -adhere. But a somewhat thicker layer is required for rough surfaces, -for instance, boards not planed, the excess of glue being forced out by -strong pressure. Generally speaking, it is best to subject all articles -cemented together with marine glue to as strong a pressure as possible -until the glue is congealed. - -Repeated experiments have shown that with the aid of this cement square -vats perfectly water-tight can be constructed of boards. Wooden pegs -dipped in the compound should be used for putting the vats together. - -_Jeffrey’s marine glue._ Dissolve 1 part of rubber in benzine, and mix -the solution with 2 parts of shellac by the assistance of heat. - -_Another formula_ is as follows: Coal naphtha 1 quart, rubber cut in -shreds 2 ozs. Macerate for 10 or 12 days and then rub smooth with a -spatula on a slab; add 2 parts by weight of shellac to 1 part of this -solution. To use the compound melt it at about 240° F. - -_Marine glue for damp walls._ Rubber 10 parts, whiting 10, oil of -turpentine 20, carbon disulphide 10, rosin 5 and asphalt 5. Dissolve -the ingredients in a suitable vessel and stand in a warm place, shaking -it frequently. - -Scrape the wall smooth and clean, and apply the glue with a broad brush -on the damp place and about 8 inches higher than the line of dampness. -Before the glue is dry lay on plain paper which will adhere tightly. On -this plain paper the wall paper can be pasted in the usual manner. If -carefully done, the wall paper will always remain dry. - - -GUTTA-PERCHA CEMENTS. - -_Cement for leather._ Gutta-percha 100 parts, pitch or asphalt 100, oil -of turpentine 15. - -This cement should be used hot. It is suitable for cementing all kinds -of substances, but adheres particularly well to leather. - -_Cement for hard rubber combs._ _A._ Prepare a very thick solution of -bleached gutta-percha in bisulphide of carbon. - -_B._ Dissolve sulphur in bisulphide of carbon. - -The cementing is effected by applying solution _A_ to the fractured -surfaces and pressing them together. When dry brush solution _B_ over -the cemented place. - -_Elastic gutta-percha cement._ Dissolve 10 parts of gutta-percha in 100 -of benzine, then pour the clear solution into a bottle containing 100 -parts of linseed-oil varnish and unite both by shaking. This cement -excels in elasticity, and is especially suitable for attaching the -soles of shoes, as it is so elastic that it will not break, no matter -how much it is bent. To make it adhere tightly roughen the leather on -the side to be cemented. - -_Cement for horses’ hoofs._ For filling cracks and fissures in horses’ -hoofs a cement is required which possesses great resistance to the -action of water combined with elasticity and solidity. A mass answering -all demands consists of 10 parts by weight of gum ammoniac and 20 to -25 of purified gutta-percha. Heat the gutta-percha to between 194° -and 212° F., and then work it with the finely powdered gum ammoniac -to a homogeneous mass. In using it, soften the cement by heating, and -after carefully cleansing the crack in the hoof, apply it with a heated -knife. The cement solidifies immediately after cooling to the ordinary -temperature, and becomes soon so hard as to allow of nails being driven -into it. - -_Cement for crockery._ Gutta-percha 1 part, shellac 1. - -Place the two ingredients in an earthenware jar, and melt the two -together by standing this jar on a vessel of boiling water, or else one -filled with hot sand, the vessel holding the water or sand being heated -over a fire or gas furnace. Stir the melted ingredients well together. -The resulting cement is one possessing great hardness and toughness, -which suits it admirably for mending crockery. Warm the edges to be -joined together, smear the cement on, join together, and hold the -article thus joined until cool. - -_Cement for leather._ Mix 10 parts of carbon disulphide with 1 part -of turpentine, and then add sufficient gutta percha to make a tough, -thickly-fluid mass. Before using this cement, free the surface to be -joined from grease. To effect this, sprinkle a little bicarbonate of -soda, carbonate of ammonia or borax on the surfaces to be joined, lay -a cloth over them, and then place a hot iron on top, and keep it there -a short time so as to cause the alkali to cut the grease, then put the -cement on both surfaces to be joined, put them together and subject to -pressure until they are cemented. - -Gutta percha dissolved in carbon disulphide to the consistency of syrup -is also a good cement for joining leather. The parts to be joined -should be well covered with cement so as to fill the pores of the -leather, then the cement is heated and the parts hammered until the -cement is cold. - - -CASEINE CEMENTS. - -_Preparation of pure caseine._ Although the caseine contained in old -cheese can be used, the other constituents, such as fat, salt, and free -acid, exert an injurious influence upon the solidity of the cement -prepared with it. It is, therefore, best to prepare pure caseine, which -is easily accomplished in the following manner: - -Put milk in a cool place, and after taking off the cream as long as any -is formed, remove the skimmed milk to a warm place to coagulate. After -heating the curd, place it upon a filter and wash the caseine remaining -upon the filter with rainwater until the water running off shows no -trace of acid. - -To remove the last traces of fat tie the washed caseine in a cloth and -after boiling it in water, spread it upon blotting paper in a warm -place to dry. It will shrivel up to a horny mass. - -When thoroughly dried pure caseine will keep for a long time without -suffering alteration. To obtain the caseine in a form suitable -for preparing cements it is only necessary to pour water over a -corresponding quantity and allow it to stand for some time. Caseine -combines with lime to a hard insoluble mass. - -Ordinary technical caseine may be readily and cheaply prepared as -follows: Skim milk is heated in a copper boiler, if necessary by the -introduction of steam, to 122° F. Then add for every 1000 quarts of -milk, 3 quarts of crude hydrochloric acid diluted with 5 to 6 times -the quantity of water. After coagulation, the whey is drained off, the -curd spread out upon an inclined table and allowed to cool. The curd is -then washed by pouring cold water over it through a rose, or stirring -it up with water in a barrel, allowing to settle, and pouring off the -supernatant water. The residue is subjected to moderate pressure. The -caseine while still moist is comminuted in a curd-mill and packed in -bags. In this state it must be worked at once, as otherwise it spoils -readily and is attacked by worms. If it is to be kept for a longer -time, it has to be dried. This is effected by spreading it out upon -linen cloths and placing it in a drying chamber. - -In this manner 8.5 per cent. of moist, or 3.5 per cent. of dry, caseine -is obtained which is brought into commerce as technical caseine or -lactarine. It being insoluble in water, 10 per cent. of an alkali—soda, -borax, or ammonia—has to be added to effect solution. Water-soluble -caseine is seldom found in commerce, the consumer preparing it, as a -rule, himself. - -A purer technical caseine is obtained according to John A. Just’s -method as follows: Dissolve, stirring constantly, in 115 quarts of -water heated to between 104° and 131° F., 17 to 26 ozs. of bicarbonate -of soda and 176 lbs. of moist, or 118 lbs. of dry, caseine, and dry the -solution upon a heated revolving metal cylinder. After each revolution -of the cylinder, the dry material is scraped off with brushes and by -being forced through a fine-meshed sieve yields soluble caseine powder. - -_Caseine cement which can be kept for a long time._ Convert into -powder, each by itself, 200 parts of caseine, 40 of burned lime, and -1 of camphor. Mix the powders intimately and keep the mixture in an -air-tight bottle. For use, mix some of the powder with the requisite -quantity of water and use the cement at once. - -_Cement for glass._ Old dry cheese 100 parts, water 50, slaked lime 20. - -Free the cheese from rind, and rub it with the water until a -homogeneous mass drawing threads is formed. Then stir in quickly the -lime powder, and use the cement at once. It unites not only glass to -glass, but can also be used for cementing metal to glass. - -_Cement for metals._ Elutriated quartz sand, 10 parts; caseine, 8; -slaked lime, 10, and sufficient water to form a cream-like mass. - -_Cement for porcelain._ Caseine dissolves readily in solution of -water-glass, and forms then one of the best cements for porcelain -known. To prepare it, fill a bottle one-quarter full with fresh -caseine, and after filling the bottle with solution of water-glass, -effect the solution of the caseine by frequent shaking. - -_Cement for meerschaum._ Dissolve caseine in water-glass, and after -stirring quickly finely-pulverized calcined magnesia into the mass, use -it at once, as it solidifies very soon. By adding, besides magnesia, -genuine meerschaum finely pulverized, a mass closely resembling -meerschaum is obtained, which can be used for manufacturing imitation -meerschaum. - -_Cement for wood, etc._ Rub 10 parts of caseine and 5 of borax -to a thick, milky mass, and use it like glue. This cement can be -advantageously used for pasting labels upon wine bottles, as it neither -moulds nor becomes detached in the cellar. - -_Another formula_ is as follows: Dissolve borax by boiling in water, -and pour the solution over fresh caseine. The result will be a clear, -thick mass of extraordinary power of adhesion, which can be kept for -any length of time without suffering decomposition. - -Applied to leather, paper, linen or cotton goods, it forms a coat of -beautiful lustre, and for this reason is much used in the manufacture -of fancy articles of paper and leather. - -_Cement for porcelain._ Dissolve 10 parts of caseine in 60 of -water-glass solution. Apply the cement quickly and dry the cemented -articles in the air. - - -WATER-GLASS AND WATER-GLASS CEMENTS. - -_Water-glass._ Water-glass (silicate of soda or soluble glass) is -found in commerce as a thickly-fluid, tenacious mass. It is generally -prepared by fusing 15 parts of quartz sand with 8 of carbonate of -soda and 1 of charcoal. The silicic acid combining with the soda -disengages the carbonic acid, the expulsion of which is facilitated by -the presence of charcoal, which converts it into carbonic oxide. It -dissolves readily in water. The solution has a strongly alkaline taste, -and possesses the property of being gradually converted, on exposure to -the air, to a gelatinous mass which finally solidifies. For this reason -water-glass should be kept in bottles hermetically closed with corks. -Glass stoppers are of no use, as they are so firmly cemented to the -bottle that on attempting to open the latter the neck breaks off. - -By combining water-glass with cement or burned lime the resulting mass -solidifies quite rapidly to a mass as hard as stone, and generally -capable of resisting chemical action. - -Water-glass by itself is only fit for cementing glass to glass, but -combined with other substances it furnishes very durable and solid -cements. - -_Cement for cracked bottles._ Select a cork which will fit the bottle -air-tight and place it loosely upon the bottle, and heat the latter -gradually to at least 212° F. Then press the cork down and apply a -thick solution of water-glass to the cracks. In cooling, the air in the -bottle contracts strongly, and the pressure of the exterior air drives -the water-glass with great force into the cracks closing them entirely -so that they cannot be detected. - -_Cement for glass and porcelain._ Stir quickly together 10 parts of -elutriated glass meal, 20 of powdered fluor spar, and 60 of water-glass -solution, and apply the homogeneous paste at once. In a few days the -cement will be so hard that the cemented vessels can be heated without -danger. - -_Cement for hydraulic works._ Finely powdered cement, and solution of -water-glass. Mix the two bodies quickly together. - -As this cement hardens very quickly, it should be used fresh. It -hardens under water, and is therefore excellent for hydraulic works. -The stones should be coated with a solution of water-glass before -applying the cement. - -_Cement for uniting metals._ A strong cement, which hardens rapidly, is -made by stirring the finest whiting in a solution of soda-glass of 33° -B., made so as to form a plastic mass. This can be readily colored to -any desired shade. The addition of sifted sulphide of antimony gives -a black cement, which by polishing acquires a metallic lustre; iron -filings render it grayish-black; zinc dust turns it green, but after -polishing, it appears like metallic zinc, and may be employed for the -permanent repair of zinc ornaments, etc. Carbonate of copper imparts a -light green shade. Other additions may be made, as oxide of chrome for -dark green, cobalt blue for blue, red lead for orange, vermilion for -scarlet, carmine for violet, etc. - -_Cement for tightening joints of pipes exposed to a red heat._ Mix 80 -parts of pyrolusite, 100 of zinc white, and 20 of water-glass. - -This cement fuses at a temperature not too high, and then forms a -glass-like mass which adheres very firmly and closely. - -_Cement for marble and alabaster._ The point of fracture of articles -cemented with the following mixture is difficult to find, and the -cemented place is much stronger than the material itself. Mix 12 -parts of Portland cement, 6 of slaked lime, 6 of fine sand, and 1 of -infusorial earth with sufficient water-glass to form a thick paste. The -article to be cemented need not be heated. It hardens in twenty-four -hours. - - -GLYCERINE AND GLYCERINE CEMENTS. - -Commercial glycerine is a yellowish or nearly colorless and more or -less viscid liquid having an intensely sweet taste. In combination with -lead oxide and intimately worked into it, by heating and stamping, -it furnishes very strong and durable cements deserving general -introduction, though thus far they have been but little used. - -For the manufacture of cements the use of pure odorless glycerine -is not required, the yellow crude article, which is much cheaper, -answering all purposes. The principal point is to use very highly -concentrated glycerine, as otherwise the cements prepared with it -solidify very slowly and besides do not possess a proper degree of -hardness and solidity. - -It is of especial importance to have the lead oxide free from water. To -accomplish this, heat it thoroughly and mix it with the glycerine while -still hot. Cement thus prepared solidifies very quickly, and can be -used for many purposes. It is an excellent material for quickly joining -the stones of submarine works. - -_Glycerine and litharge cement._ Moisten elutriated litharge with -glycerine so that a thin homogeneous paste is formed. This cement is -adapted for uniting the joints of steam pipes, cementing wood, glass, -porcelain, and also glass upon metal, etc. It solidifies to a very hard -mass in a quarter to three-quarters of an hour. Before applying the -cement coat the surfaces to be joined with pure glycerine. - - -LIME CEMENTS. - -Quick lime, slaked lime and chalk are used for this purpose. Quick -lime, which is obtained by burning limestone, combines gradually with -the fats to insoluble lime soaps. Slaked lime, which consists of a -combination of lime with water, acts in the same manner. - -For the preparation of cements the lime is slaked by placing it in a -dish and pouring as much water over it as it will absorb. Good lime, -technically called _fat lime_, should eagerly combine with water, -evolving much heat, swelling greatly, and crumbling to a light white -powder. - -Quick lime exposed to the air until, by the absorption of moisture and -carbonic acid, it is converted into a powder is called _air-slaked_. - -Cements prepared with quick lime will, as a rule, solidify more quickly -than those prepared with air-slaked lime. - -Chalk is a carbonate of lime consisting of the shells of microscopic -animals, and can be readily pulverized and elutriated. In the latter -state it is known as _whiting_. For the preparation of entirely white -cements the use of pure white lime or chalk is absolutely necessary. -Yellow or reddish lime contains oxide of iron, and furnishes cements of -the same tinge. - -_Cement for glass._ Litharge 30 parts, quick lime 20, linseed-oil -varnish 5. - -_Cement for joiners._ A cement for filling up cracks and holes is -obtained by mixing slaked lime 50 parts, flour 100, linseed-oil varnish -15. - -_Cement for cracked clay crucibles and porcelain._ By applying to the -cracks a mixture of 10 parts of slaked lime, 10 of borax, and 5 of -litharge in sufficient water to form a stiff paste, and drying after -heating the crucible, the cracked places will be united so firmly that -the crucible, when thrown to the ground, will generally break in any -other place than the cemented one. - -This cement can also be used for porcelain capable of standing a strong -heat. - -_Lime and glue cement._ Stir air-slaked lime into hot glue. This cement -is especially suitable for attaching metal to glass. It forms a very -hard yellowish-brown mass. - - -GYPSUM CEMENTS. - -Sulphate of lime in combination with water is met with in nature, both -in the form of transparent prisms of _selenite_, and in opaque and -semi-opaque masses, known as _alabaster_ and _gypsum_. By pulverizing -the latter and heating to about 302° F. it loses its water, and is -converted into anhydrous gypsum or _plaster of Paris_, which on mixing -with water recombines with it to form a mass of hydrated sulphate of -lime, the hardness of which nearly equals that of the original gypsum. -When the powder is mixed with water to a cream and poured into a mould, -the minute particles of anhydrous sulphate of lime combine with the -water to reproduce the original gypsum, and this act of combination -is attended with a slight expansion which forces the plaster into the -finest lines of the mould. - -By using a solution of alum instead of ordinary water, a plaster is -obtained which, although it takes much longer to set than the ordinary -kind, is much harder, and therefore takes a good polish. - -For preparing cements only perfectly white plaster of Paris should be -used, as the gray article possesses but little adhesive power. - -_Cement for plaster of Paris statues._ To repair plaster of Paris -statues so that the point of fracture cannot be detected, proceed in -the following manner: - -Moisten the fractured surfaces with water by means of a brush until -they absorb no more and remain moist. Mix plaster of Paris with -water to a thin cream and stir until the heat appearing at first has -ceased, which will prevent the conversion of the plaster into a solid -coherent mass. Apply quickly a thin layer of the plaster to one of the -fractured surfaces, press the other against it until the plaster has -set, and, when dry, carefully remove the excess by scraping. - -_Cement for glass and porcelain._ Mix quickly 50 parts of plaster of -Paris, 10 of quick lime, and 20 of white of egg. Use at once, as the -cement solidifies very rapidly. - -_Cement for iron and stone._ A very useful cement for securing iron -railing in stone is obtained by mixing 30 parts of plaster of Paris, 10 -of iron filings and 20 of vinegar. - -_Cements for porcelain._ I. Mix plaster of Paris with saturated -solution of alum to a cream. After moistening the fractured surfaces -apply a thin layer of the cement, press the surfaces together, wrap a -wire or cord tightly around them, and let the article stand quietly for -a few weeks. The cement is converted into a mass as hard as stone. - -II. Mix plaster of Paris with a thick, clear solution of gum arabic and -cement the articles as soon as possible. Although this cement adheres -very tightly, porcelain vessels cemented with it cannot be used for -liquids. - -_Universal plaster of Paris cement._ Mix 21 parts of plaster of Paris, -3 of iron filings, 10 of water, and 4 of white of egg. This cement is -suitable for attaching metal to glass, metal to stone, etc. - - -IRON CEMENTS. - -_Heat-resisting cement._ Clay 10 parts, iron filings 5, vinegar 2, -water 3. - -_Water and steam-proof cement._ Iron filings 100 parts, sal-ammoniac 2, -water 10. - -This cement rusts very much in a few days, and is converted into an -extremely solid mass which is perfectly steam- and water-proof. - -_Cement for iron._ Mix 65 parts of wrought-iron filings, 2.5 of sal -ammoniac, and 1.5 of flowers of sulphur, and then add 1 part of -sulphuric acid diluted with sufficient water to form a stiff paste. -This cement solidifies in two to three days, and rusts, with the parts -of iron to be cemented, to an extraordinarily durable mass. - -_Fire-proof cement for iron pipes._ Wrought-iron filings 45 parts, clay -20, fire-clay 15, common salt solution 8. - -_Cements resisting high temperatures._ 1. Iron filings 20 parts, clay -powder 45, borax 5, common salt 5, pyrolusite 10. - -Dissolve the borax and common salt in the water, add and mix quickly -the clay powder, pyrolusite, and iron filings. Apply the cement at -once. Exposed to a white heat, it hardens to a tightly adhering, glassy -mass. - -2. Mix 52 parts of pyrolusite, 25 of zinc white, and 5 of borax with -solution of water-glass to a paste, and use at once. This cement -requires to be gradually dried. It will stand the highest temperatures. - -_Cement for filling in defects in castings._ Stir 100 parts of iron -filings free from rust with sufficient water to form a thick paste, and -press the mixture into the fissures, cracks, etc. The cement becomes -solid only after the iron filings become strongly rusted. To free the -ingredients from adhering fat, wash them, before mixing, in liquid -ammonia. - -_Cement for cracked stove plates, etc._ Knead 20 parts of iron filings, -12 of iron scale, 30 of plaster of Paris, and 10 of common salt with -blood to a stiff paste, and use at once. Instead of blood, water-glass -can be used, it having the advantage of being odorless on strong -heating, while blood cement evolves a disagreeable odor. - -_Cement for iron water tanks._ Knead iron filings with vinegar to -paste. Allow the mixture to stand until it turns brown, and then force -it into the joints by means of a chisel. - -_Cement for cracked iron pots._ Knead 10 parts of iron filings and -60 of clay with linseed oil to a thick paste. Before applying it add -a little linseed oil, and allow it to dry slowly. In a few weeks the -cement will be so hard that the vessels can be used without danger. - -_Black cement for stoves._ Iron filings 10 parts, sand 12, bone black -10, slaked lime 12, glue water 5. - -_Cements for iron stoves._ 1. Pulverize as finely as possible and mix -intimately 4 to 5 parts of clay, 2 of iron filings free from rust, 1 of -pyrolusite, ½ of common salt, and ½ of borax with water to a paste, and -apply the cement quickly to the places to be cemented and allow it to -dry slowly. This cement will stand a white heat, and resist the action -of boiling water. - -2. Mix intimately and as quickly as possible 1 part of pulverized -pyrolusite, and 1 of zinc white with solution of water-glass to a -plastic mass, which solidifies quickly. The power of resistance of this -cement, it is claimed, is not inferior to No. 1, though experiments -have proved No. 1 to be preferable. - - -CEMENTS FOR CHEMICAL APPARATUS. - -Cements to be used for the above purpose must possess various -properties difficult to combine in one preparation. They must be -gas-proof, and capable of resisting the action of different vapors and -acid fluids. As regards resistance to the action of chemical agents, -there is nothing better than caoutchouc, but unfortunately it can -only be used for tightening chemical apparatus not exposed to a high -temperature. - -In chemical laboratories bran of almonds, either by itself or kneaded -with water to a thick paste, is frequently used, or rye or wheat -bran mixed with a little flour and water. These cements, though very -suitable for cementing glass distilling apparatus, are strongly acted -upon by chlorine and the vapors of nitric acid. - -For small apparatus to be used for the development of fluoric acid, -plaster of Paris mixed with a little water can be used as a cement. -To make the joint entirely gas-tight, paste a strip of paper over it. -Although this cement does not resist the action of fluoric acid for -any length of time, it suffices generally for the protection of the -Workmen during the time the development of the acid is in progress, as, -for instance, in chemical analyses, etc. - -To cement chemical apparatus exposed to a temperature not exceeding 86° -to 104° F. paraffine does excellent service; as it possesses the power -of resisting the action of the strongest acids and alkalies. - -Below will be found a few receipts for cements which have proved -reliable. - -_Linseed oil and clay cement._ Knead 10 parts of dry clay with 1 of -linseed oil to a homogeneous mass. This cement will stand heating to -the boiling-point of mercury. - -_Linseed oil, zinc and manganese cement._ Knead 10 parts of pyrolusite, -20 of zinc white, and 40 of clay with sufficient boiled linseed oil -(not exceeding 7 parts) to a plastic mass. This cement will stand a -somewhat higher temperature than the preceding one. - -_Cements resisting very high temperatures._ I. Clay 100 parts, powdered -glass 2. - -The glass melts on exposure to great heat and slags the clay to a hard -mass. The same effect is produced by adding small quantities of soda -and borax to the clay. An admixture of chalk and boric acid, as in the -following receipt, also gives excellent results. - -II. Clay 100 parts, chalk 2, boric acid 3. - -_Cement resisting acids._ Melt rubber with double the quantity of -linseed oil, and then knead in sufficient bole to form a paste. This -cement resists the action of nitric and hydrochloric acids, and can -be advantageously used for closing bottles containing them. As it -solidifies very slowly, it can readily be detached from the bottles, -and used again. - -For cement which is to solidify quickly on exposure to the air, add a -few per cent. by weight of red lead or litharge. - -_Rubber cement for chemical apparatus._ Cut 8 parts of rubber in small -pieces and throw them gradually into a mixture of 2 parts of tallow -and 16 of linseed oil previously strongly heated. After effecting an -intimate mixture of the constituents by vigorous and constant stirring, -add 3 parts of white bole. - -Although this cement does not stand a high temperature, it possesses an -extraordinary power of resisting the action of acid vapors. - -_Scheibler’s cement for chemical apparatus._ Melt together 1 part of -wax and 3 of shellac, and work into the mixture 2 parts of gutta-percha -cut up in very small pieces. This cement will bear considerable heat -without actually melting. - - -CEMENTS FOR SPECIAL PURPOSES. - -_Cement for attaching metal letters to glass, marble, wood, etc._ -Dissolve over a water-bath 5 parts of glue in a mixture of 15 parts -of copal varnish, 5 parts of boiled linseed oil, 3 parts of crude oil -of turpentine, and 2 parts of rectified oil of turpentine, and add 10 -parts of slaked lime to the mixture. - -_Cement for joints of iron pipes._ Mix 5 lbs. of coarsely powdered iron -borings, 2 ozs. of powdered sal ammoniac, and 1 oz. of sulphur with -sufficient water to form a paste. This composition hardens rapidly, but -if time can be allowed it sets more firmly without the sulphur. It must -be used as soon as mixed, and rammed tightly into the joint. - -Another receipt is as follows: - -Mix 2 ozs. of sal ammoniac, 1 oz. of sublimated sulphur and 1 lb. of -cast-iron filings or fine turnings in a mortar, and keep the powder -dry. When it is to be used, mix it with 20 times its weight of clean -iron turnings or filings and grind the whole in a mortar; then wet it -with water until it becomes of convenient consistency, when it is to be -applied to the joint. After a time it becomes as hard and strong as the -metal. - -_Steam boiler cement._ Mix 10 parts of finely-powdered litharge with -1 part of fine sand and 1 part of air-slaked lime. The mixture may be -kept for any length of time without deterioration. For use a portion -of it is made into a paste with linseed oil or, better, boiled linseed -oil. In this state it must be applied quickly, as it soon becomes hard. - -_Cement for rubber._ Powdered shellac is softened in 10 times its -weight of strong water of ammonia, whereby a transparent mass is -obtained, which becomes fluid after keeping some little time without -the use of hot water. In three to four weeks the mixture is perfectly -liquid, and when applied it will be found to soften the rubber. As soon -as the ammonia evaporates it hardens again, and thus becomes impervious -both to gases and to liquids. For cementing sheet rubber, or rubber -material in any shape, to metal, glass, and other smooth surfaces, this -cement is highly recommended. - -_Cement for tires._ 1. Isinglass 1 oz., gutta-percha 1 oz., rubber 2 -ozs., carbon disulphide 8 fluid ozs. Mix and dissolve. - -2. Shellac 4 ozs., gutta-percha 4 ozs., red lead and sulphur, each ½ -oz. Melt the shellac and gutta-percha, and add with constant stirring -the red lead and sulphur, melted. Use while hot. - -3. Crude rubber 1 oz., carbon disulphide 8 ozs. Macerate 24 hours, and -then add a solution of: - -Rosin 2 ozs., beeswax ½ oz., carbon disulphide 8 ozs. - -4. Rubber 20 parts, rosin 10, Venetian red 10, tallow 5. Melt the -rubber over a fire, then add the rosin and the tallow and finally the -Venetian red. - -_Cement for steam pipes, etc._ A cement of specially valuable -properties for steam pipes, in filling up small leaks, such as a -blow-hole in a casting, without the necessity of removing the injured -piece, is composed of 5 lbs. Paris white and 5 lbs. yellow ochre, 10 -lbs. litharge, 5 lbs. red lead and 4 lbs. black oxide of manganese. -Mix the materials thoroughly and make into a paste with a small -quantity of asbestos and boiled linseed oil. The composition, as thus -prepared, will harden in from 2 to 5 hours, and has the advantage of -not being subject to expansion and contraction to such an extent as to -cause a leakage afterwards, and its efficiency in places difficult of -access is of special importance. - -_Cement for marble._ Stir to a thick batter with silicate of soda 12 -parts of Portland cement, 6 of slaked lime, 6 of fine white lead and 1 -of infusorial earth. This is excellent for marble and alabaster. The -cemented objects need to be heated. After 24 hours the fracture is -firm, and the place can scarcely be found. - -_Cement for attaching wood, glass, etc., to metal._ Acetate of lead 23 -parts by weight, alum 23, gum arabic 38, wheat flour 250. - -Dissolve the acetate of lead and the alum in a little water and -separately dissolve the gum arabic in a fair quantity of boiling -water. Thus if the 250 parts of wheat flour represent half a pound, -the quantity of water needed will be about a pint. The gum having -dissolved, add the flour, put the whole on the fire, stir well with a -wooden stick, then add the solution of lead acetate and alum. Continue -the stirring in order to avoid the formation of lumps, then take it off -the fire without allowing it to boil. This cement is used cold, and -will not scale. It is very useful in making wood, glass, cardboard, -etc., adhere to metal, and is extremely strong. - -_Brushmakers’ cement._ Rosin 5 lbs., rosin oil or spirit 1 quart. - -Reduce the rosin to small pieces, run down in a pot, add the other -ingredient, and stir until mixed and syrupy, then run out into tins. -It is used for cementing the bristles in the stocks, also for string -binding on sash tools, etc. - -_Cement for electrical apparatus._ Mix together 1 lb. of beeswax -added to 5 lbs. of rosin, 1 lb. of red ochre, and 2 tablespoonfuls of -plaster of Paris. It will make an excellent composition for electrical -apparatus. - -A cheaper composition for cementing voltaic plates into wooden troughs -is made with 6 lbs. of plaster of Paris and ¼ pint of linseed oil. The -ochre and the plaster of Paris should be well dried and added to the -other ingredients when these are in a melted state. - -_Jewelers’ cement._ Dissolve over the water-bath 25 parts of fish glue -in a small quantity of strong spirits of wine, add 2 parts of gum -ammoniac; separately dissolve 1 part of mastic in 5 of spirits of wine. -Mix the two solutions and keep them in well-stoppered bottles. - -_American cement for jewelers._ Soak 4 ozs. of isinglass in 2 lbs. of -water for 24 hours, then evaporate in the water-bath; to 1 lb. add 1 -lb. of rectified spirits of wine, and strain. Then mix in a solution -of 2 ozs. of mastic and 1 oz. of gum ammoniac in 16 ozs. of rectified -spirit. - -_Cement for celluloid._ Shellac 2 ozs., spirits of camphor 2, 90 per -cent. alcohol 6 to 8. - -_Stratena._ This well-known household cement is said to be prepared -as follows: Dissolve 12 parts of white glue in 16 of acetic acid, and -then add this solution to one of 2 parts gelatine in 16 of water. After -mixing add 2 parts shellac varnish. - -_Cement for cloth._ Gutta-percha 16 parts, rubber 4, pitch 2, shellac -1, linseed oil 2 pints. Dissolve the whole by heat, stirring constantly. - - -HOW TO USE CEMENTS. - -It is unquestionably true that quite as much depends upon the manner in -which a cement is applied, as upon the cement itself. The best cement -that was ever compounded would prove entirely worthless improperly -applied. In the foregoing a number of cements have been given which -answer every reasonable demand when properly prepared and properly -used. Good common glue will unite two pieces of wood so firmly that -the fibres will part from each other rather than from the cementing -material; two pieces of glass can be so joined that they will part -anywhere rather than on the line of union; glass can be united to -metal, metal to metal, stone to stone, and all so strongly that the -joint will certainly not be the weakest part of the resulting mass. -What are the rules to be observed in effecting these results? - -The first point that demands attention is to bring the cement itself -into intimate contact with the surface to be united. If glue is -employed, the surface should be made so warm that the melted glue -will not be chilled before it has time to effect a thorough adhesion. -The same is more eminently true in regard to cements that are used -in a fused state, such as mixtures of resins, shellac, and similar -materials. These matters will not adhere to any substance unless the -latter has been heated to nearly or quite the fusing point of the -cement used. This fact was quite familiar to those who used sealing-wax -in the olden days of seals. When the seal was used, in succession, -rapidly so as to become heated, the sealing-wax stuck to it with -a firmness that was annoying, so much so that the impression was -generally destroyed, from the simple fact that the sealing-wax would -rather part in its own substance than at the point of adhesion to the -seal. Sealing-wax or ordinary so-called electric cement is a very good -agent for uniting metal to glass or stone, provided the masses to be -united are made so hot as to fuse the cement; but if the cement is -applied to them while they are cold, it will not stick at all. This -fact is well known to those itinerant venders of cement for uniting -earthenware. By heating two pieces of delf so that they will fuse -shellac, they are able to smear them with a little of this gum and -join them so that they will rather break at any other part than along -the line of union. But although people see the operation constantly -performed and buy liberally of the cement, it will be found that in -nine cases out of ten, the cement proves worthless in the hands of the -purchasers, simply because they do not know how to use it. They are -afraid to heat a delicate glass or porcelain vessel to a sufficient -degree, and they are apt to use too much of the material, and the -result is a failure. - -The great obstacles to the junction of any two surfaces are air and -dirt. The former is universally present, while the latter is due to -accident or carelessness. All surfaces are covered with a thin adhering -layer of air, which it is difficult to remove, and which, although -it may at first sight seem improbable, bears a relation to the outer -surface of most bodies different from that maintained by the air a few -lines away. The reality of the existence of this adhering layer of air -is well known to all who are familiar with electrotype manipulation. -It is also seen in the case of highly polished metals which may be -immersed in water without becoming wet. Unless this adhering layer -of air is displaced, the cement cannot adhere to the surface to -which it is applied because it cannot come in contact with it. The -most efficient agent in displacing this air is heat. Metals warmed -to a point a little above 203° F. become instantly and completely -wet when immersed in water. Hence, for cements that are used in a -fused condition, heat is the most efficient means of bringing them in -contact with the surfaces to which they are to be applied. Another -very important point is to use as little cement as possible. When the -surfaces are separated by a large mass of cement we have to depend -upon the strength of the cement itself and not upon its adhesion to -the surfaces which it is used to join; and, in general, cements are -comparatively brittle. - -The cement forced out of the joint by pressing the surfaces together -should be removed while the cement is in a fused state or liquid. -This can generally be effected by wiping the surplus off, while after -solidification a certain amount of force has to be used which may -frequently break the joint. - -Oil cements, which generally solidify slowly, have the advantage of -being water-proof. In cementing with oil cements, coat the surfaces to -be joined with linseed oil, or, still better, boiled linseed oil, but -in working with resinous cements apply oil of turpentine, spirit of -wine, or a fluid which will readily dissolve the cementing constituent -of the cement. - -For cleansing the surfaces from grease and dirt place the articles in -strong lye and rinse off in clean water without touching the surfaces -with the hands. For painted porcelain articles which cannot be placed -in lye, it is recommended to brush the surfaces several times with -carbon disulphide. - - -PASTES AND MUCILAGES. - -_Preparation of paste._ Ordinary paste is prepared either from flour or -starch, and according to the raw material used in its preparation, may, -therefore, be divided into starch and flour paste. - -Starch is an indispensable constituent of certain parts of plants, and -plays an important part in the nutrition of the plant. It is chiefly -manufactured from potatoes, Indian corn and grain. Examined under the -microscope, it is seen to be composed of small granules consisting of -layers placed one above the other. - -_Starch paste._ In stirring starch with water to a thin paste and -gradually heating it, it will be observed that at a temperature between -140° and 158° F. a peculiar change takes place; the thin milk-white -liquid becomes transparent, opalizes, and at the same time becomes -thickly fluid, in short, the starch is converted into paste. During -this process the separate layers of the starch granules become detached -somewhat in the same manner as an opening bud, whereby they absorb -water, and the peculiar mass, called paste, is formed. That paste is -not a solution is easily proved by the fact that on attempting to -filter starch-paste only water drains off, while the starch remains -upon the filter and gradually dries to a horny mass. - -Paste left to itself soon decomposes, especially during the hot season -of the year; it becomes sour through the formation of lactic acid, -butyric acid, acetic acid, and other substances, and loses its adhesive -power. - -In preparing paste, the following rules must be especially observed: -Divide the starch in water by constant stirring so as to form a -homogeneous, rather thinly liquid fluid, and then add boiling water -in small portions, stirring constantly. The conversion of the starch -into paste is recognized by the thickening of the entire mass and -the appearance of opalescence, when it is only necessary to add the -required quantity of water to give the paste the desired consistency. - -If white lumps are observed, it is an indication that the starch has -not been thoroughly mixed with the water, and that certain portions of -it have remained dry. Paste containing such lumps cannot be applied -with any degree of uniformity, and besides it possesses less adhesive -power. Nothing can be done to remedy the evil except diluting the -paste with a considerable quantity of water and boiling, with constant -stirring, until the mass is perfectly homogenous. - -Starch paste prepared in a proper manner possesses great adhesive -power, and, when applied in a thin layer, dries to an almost colorless -coating. Pure starch paste is used for many purposes. It serves not -only for pasting paper, wall paper, etc., but also for sizing tissues, -such as paper-muslin, linen, etc., in order to give them lustre, body, -and, under certain circumstances, greater weight. To increase the -weight of linen, white lead or heavy spar is frequently mixed with the -starch. - -_Flour paste._ The principal constituent of flour, besides starch, is -gluten. It is obtained in a pure state by tying flour in a linen bag -and kneading it under water so long as the latter is rendered turbid by -particles of starch. The gluten remaining in the bag is a light-brown, -very tenacious mass, drawing threads between the fingers, and, as -regards its chemical properties, is closely allied to albumen and -caseine. Gluten, like the last-mentioned substances, shows a tendency -to form combinations with lime which gradually solidify, and it can -therefore be used for preparing cements. Like albumen and caseine, -it speedily putrefies if exposed to the air in a moist state, and in -decomposing forms products which have a very unpleasant odor. - -Flour paste is prepared in precisely the same manner as starch paste, -but while the latter is white, flour paste, even if prepared from the -best wheat flour, has always a yellow-brown color. As regards adhesive -power it is superior to starch paste, but is less durable. - -There are many means to prevent the spoiling of paste. With paste -once dry and kept so, there is no danger of spoiling, but if it -is alternately exposed to dampness and dryness, as for instance -with wall-paper hung on walls not entirely dry, decomposition will -unavoidably take place, and the wall paper will become spotted and fall -off the wall. - -Provided either starch or flour paste is protected against drying in, -it can be kept unchanged for a long time by the addition of a small -quantity of carbolic acid. - -For hanging wall-paper an addition of alum is, generally speaking, more -suitable than carbolic acid. - -In hanging wall-paper the wall is generally first sized with -glue water. By the alum coming in contact with glue an insoluble -leather-like combination is formed, which not only resists -decomposition, but by far surpasses ordinary paste as regards adhesive -power, so that when the paper is to be removed from the wall it has -to be scraped and torn off in small pieces, while that hung without -previous sizing of the wall is readily removed in large pieces. - -But alum cannot be used for preserving a glue solution, as it would -cause it to coagulate to a flaky mass. Carbolic acid is, on the -other hand, an excellent means for the purpose, but to prevent its -characteristic empyreumatic odor from making itself too sensibly -felt, no more than about one two-thousandth of the weight of the glue -solution should be added. - -_Shoemakers’ paste._ In addition to being cheap, no other paste adheres -as well to leather as the so-called shoemakers’ paste. With it leather -can be secured not only to leather, but also to woven materials, paper, -etc. Though its preparation is very simple, it is connected with some -disagreeable features consisting chiefly in the development of a truly -terrible stench. - -The paste is prepared by stirring crushed barley with hot water to -a thick paste and adding small portions of hot water, so that the -temperature of the mass is kept at between 86° to 104° F. In a few -days the mass commences to develop gas, which shows at first no odor, -but soon the development of gas becomes stronger and an acid odor is -perceptible, which in a short time is replaced by a terrific stench -which, as before mentioned, affects the olfactory organs in a most -unpleasant manner. - -In consequence of the acid and putrid fermentation the pasty mass -gradually loses its granular condition, and is finally converted into a -homogeneous, thickly fluid mass of a brown color, which draws threads -between the fingers, and possesses great adhesive power. When this is -the case, decomposition, which otherwise would go on until nothing -remained but a watery and acid fluid, is interrupted by lowering the -temperature of the paste by ladling it from the vat or by adding a -small quantity of carbolic acid. - -To render the stench developed during the fermentation of the paste -innoxious, the vat in which it is prepared should be provided with -a well-fitting cover, in which is fitted a stovepipe passing into a -chimney connected with a kitchen range or furnace, in which a fire is -frequently burnt. - -By kneading shoemaker’s paste together with indifferent substances it -can be used as a cement for various purposes. The substances best -adapted for the purpose are burnt lime slaked to a powder, whiting, -zinc white, pipe clay, ochre, etc. - -_Gum arabic._ This gum is an exudation from certain tropical species of -acacia, and consists essentially of arabine, which has the composition -C_{12}H_{11}O_{11}. The best gum arabic is that in the form of very -pale-yellow, brittle pieces; golden-yellow to brownish pieces are not -valued as highly, though they give a solution of considerable adhesive -power. - -Gum arabic dissolves in water, but not in alcohol, and therefore can -not be employed for cements in the preparation of which solutions of -resins in spirit of wine are to be used. - -There are other products of vegetable life, which are also in commerce, -called gums, but dissolve partly in spirit of wine. To this class -belongs the gum ammoniac mentioned in some receipts for cements. As it -is rather expensive, it is seldom used by itself as a cement. - -_Dextrine_ is extensively used in place of gum arabic in printing -wall-papers, for stiffening and glazing cards and paper, for thickening -the colors of calico printers, in making mucilages, etc. It is prepared -by heating starch previously moistened with nitric acid in an oven, -and can also be produced by heating paste with malt extract or very -dilute sulphuric acid. There is a current anecdote which attributes the -discovery of dextrine to a conflagration at a starch factory where one -of the workmen who assisted in quenching the fire observed the gummy -properties of the water which had been thrown over the torrefied starch. - -Commercial dextrine forms pale-yellow to dark-brown masses. These -masses dissolve readily in water, and form solutions which, as regards -adhesive power, compare favorably with those prepared from gum arabic. -The mucilage is prepared by simply stirring the pulverized dextrine -with water to a thickly-fluid liquid. - -To preserve mucilage unchanged for any length of time, and to -prevent the disagreeable formation of mould upon its surface, it is -recommended to dissolve some salicylic acid in the water to be used for -preparing the mucilage. - -Dextrine is usually prepared on a large scale by moistening 10 parts of -starch with 3 parts of water acidulated with 1/100 part of nitric acid. -The mixture is allowed to dry, and is then spread upon trays in layers -about three-quarters of an inch deep in an oven, where it is heated for -about one hour to 239° F. Sometimes large drums revolving over a fire -are used, or, in order to keep up a uniform temperature, the starch is -placed in a copper cylinder suspended in a vessel with oil which is -heated to 356° F. The object of the addition of nitric acid is to allow -the starch to be converted into dextrine at a temperature which would -be inadequate to effect the transformation of starch alone. - -Dextrine is also frequently prepared by allowing germinated barley or -malt to act upon starch. Heat 350 to 400 parts of water to about 77° -F., and after adding 5 to 10 parts of dry malt, raise the temperature -to 140° F. Then add 100 parts of starch, and after mixing the whole -thoroughly together, raise the temperature to about 158° F. for twenty -minutes. The mass, which appears at first milky and sticky, will -gradually become as liquid as water by the conversion of the starch -into gum through the action of the malt. To prevent the conversion -of the gum into sugar by the diastase of the malt, the fluid must be -quickly brought to the boiling-point, and, after cooling, filtered -and evaporated to the consistency of syrup. In cooling, the mass -gelatinizes to a jelly, which after drying is hard and brittle. - -According to Blumenthal’s method, a drum which can be hermetically -closed, is filled two-thirds full with dry starch flour by means of a -funnel. A stirring apparatus is then set in motion, and the acid which -is contained in a graduated cylinder is sprayed into the drum by means -of a special contrivance. - -In a drum 5 feet long and 3¼ feet in diameter, 220 lbs. of potato -starch can be uniformly mixed in 5 minutes with about 9 ozs. of nitric -acid of 40° B., and the drum emptied by opening the slide. Starch thus -treated may be brought into the oven without previous drying. - -Heuzé gives the following method: Four and a half pounds of nitric -acid of 1.4 specific gravity together with 300 quarts of water are -mixed with 2,200 lbs. of starch, and boiled to form a mass which, -when exposed to the air becomes dry. It is sometimes effected at 177° -F., but it becomes a paste at 212° to 230° F. The starch changes into -dextrine in an hour or an hour and a half at the most; it is white and -soluble in water. - -_Tragacanth, or gum tragacanth_, exudes from _Astragalus verus_, a -tree indigenous to Asia. The term gum is a misnomer, as tragacanth -does not actually dissolve in water nor in spirit of wine, but merely -swells up in water to a soft gelatinous mass. Tragacanth consists of -irregular pieces of a pure white to yellowish color. It is chiefly used -for confectioner’s purposes, though sometimes as a paste for fancy -articles. This variety of gum is found, together with arabine, in the -gum which exudes from cherry, plum, almond, and apricot trees, and -gives the mucilaginous character to the watery decoctions prepared from -certain seeds, such as linseed and quince-seed, and from the root of -marshmallow. - - -PASTES AND MUCILAGES FOR SPECIAL PURPOSES. - -_Starch paste._ Corn starch 8 ozs., cold water ½ pint, boiling water 1 -gallon. - -Beat up the starch in the cold water until reduced to a creamy -consistence, then pour the mixture into the boiling water and stir -briskly until the white, semi-opaque mass, becomes transparent. Should -it fail to do so, place it over the fire, and boil until the desired -result is obtained, stirring constantly. - -_Flour paste._ Wheat flour 4 lbs., cold water 2 quarts, alum 2 ozs., -hot water ½ pint, boiling water 2 gallons. - -Work the wheat flour into a batter free from lumps with the cold -water. Dissolve the alum in the hot water. Then stir the batter into -the boiling water, and if necessary, continue boiling until the paste -thickens into a semi-transparent mucilage, after which stir in the alum -solution. This makes a very fine paste for wall-paper. - -_Strong adhesive paste._ Rye flour 2 lbs., cold water 1 quart, boiling -water 3 quarts, pulverized rosin 1 oz. - -Make the flour into a batter with the cold water, free from lumps, and -pour into the boiling water. Boil, if necessary, and while hot stir in -the pulverized rosin, a little at a time. This paste is very strong, -and will fasten heavy wall-paper or thin leather. If too thick, thin -with hot water. Never thin paste with cold water. - -_Paste that will not sour._ Allow 4 parts by weight of glue to soften -in 15 parts of cold water for some hours, and then heat moderately -till the solution becomes quite clear; then add, while stirring, 65 -parts of boiling water. In another vessel stir up 30 parts of starch -paste with 20 parts of cold water, so that a thin, milky fluid without -lumps is obtained. Into this pour the boiling glue solution, stirring -constantly, and keep the whole at the boiling temperature. After -cooling, add 5 to 10 drops of carbolic acid to the paste. Preserve the -paste in closed bottles to prevent evaporation of the water. It will -thus keep good for years. - -_Venetian paste._ White or fish glue 4 ozs., cold water ½ pint, Venice -turpentine 2 fluid ozs., rye flour 1 lb., cold water 1 pint, boiling -water 2 quarts. - -Soak the 4 ozs. of glue in the cold water for 4 hours. Dissolve over -a water-bath, and while hot stir in the Venice turpentine. Make up -the rye flour into a batter free from lumps with the pint of water, -and pour the latter into the boiling water. Stir briskly, and finally -add the glue solution. This makes a very strong paste, and it will -adhere to a painted surface, owing to the Venice turpentine in its -composition. - -_Label paste._ A good paste for attaching labels to bottles may be made -by soaking glue in strong vinegar, then heat to boiling and add flour. -This is very adhesive, and will not decompose when kept in wide-mouthed -bottles. - -_Elastic or pliable paste._ Starch 4 ozs., white dextrine 2 ozs., cold -water 10 fluid ozs., borax 1 oz., glycerine 3 fluid ozs., boiling water -2 quarts. - -Beat the starch and dextrine into paste with the cold water. Dissolve -the borax in the boiling water, then add the glycerine, and pour -the starch and dextrine mixture into the borax solution. Stir until -it becomes translucent. This paste will not crack, and, being very -pliable, is suitable for paper, cloth, leather and other material where -flexibility is required. - -_Mucilage for labels._ Macerate 5 parts of good glue in 20 parts of -water for 24 hours, and to the liquid add 9 parts of rock candy, and -3 parts of gum arabic. The mixture may be brushed upon paper while -lukewarm. It keeps well, does not stick together and adheres firmly to -bottles. - -_Mucilage._ A strong aqueous solution of dextrine forms a most adhesive -and cheap mucilage. Dilute alcohol is usually employed as the solvent -where the mucilage is to be used for gumming envelopes, postage stamps, -etc., and in order to facilitate the drying, acetic acid is added to -increase the mobility of the fluid. The strong aqueous solution is -more adhesive than that prepared with alcohol, for the reason that it -contains a greater proportion of dextrine. - -To prepare this add an excess of dextrine to boiling water, stir for -a minute or two, allow to cool and settle, and strain the liquid -through a cloth. The addition of a little powdered sugar increases the -glossiness of the dried gum. The sugar should be dissolved in the water -before the dextrine is added. - -_According to another formula_, dextrine is mixed with hot water until -a syrupy liquid is obtained. Then add a few drops of oil of cloves, and -cool for use. - -_Another formula is as follows_: Dextrine 120 parts, powdered alum 6, -sugar 30, carbolic acid 1, water 300. Mix gradually the dextrine, alum -and sugar with the water, boil to effect solution, and when cold, add -the carbolic acid. - -The solubility of dextrine may be enhanced by the addition of a calcium -salt readily soluble in water, the resulting mixture dissolving with -ease in cold water. Calcium nitrate has proved especially suitable for -the purpose. By pouring 1 quart of water over a mixture of 18 ozs. of -dextrine and 7 ozs. of calcium nitrate, a mass of great adhesive power -is immediately obtained. - -_Mucilage for postage stamps._ Dextrine 2 parts, acetic acid 1, water -5, alcohol 1. Mix all together. - -_Caseine mucilage._ Take the curd of skim milk, wash it thoroughly, and -dissolve it to saturation in a cold concentrated solution of borax. - -_Tragacanth mucilage._ Powdered tragacanth 2 drachms, glycerine 12 -drachms, water enough to make 20 ozs. - -Put the tragacanth in a mortar with the glycerine, and then add the -water. This will produce at once a mucilage of excellent quality. - -_Adhesive paste._ Steep 4 ozs. of ordinary gelatine in 16 ozs. of water -until it becomes soft, then dissolve it by the heat of a water bath, -and while still hot pour into a mixture of 2 lbs. of good flour paste -and 1 part of water. Heat the whole to boiling and when thickened -remove from the fire. While cooling add 6 drachms of silicate of soda -and stir the mixture with a wooden spatula. This preparation will keep -good for an indefinite period, and is very adhesive. The addition of 2 -drachms of oil of cloves is an improvement. - -_Fluid pastes._ I. Gum arabic 10 lbs., sugar 2 lbs., nitric acid 1¾ -ozs., water as required. - -Dissolve the gum and sugar in the water, then add the acid and heat to -the boiling-point. The resulting paste is liquid, does not mould, and -dries to a transparent layer upon paper. It is especially suitable for -flaps of envelopes, fine bookbinders’ work, etc. - -II. Potato starch 10 lbs., water 5 quarts, nitric acid 8 ozs. - -Mix the acid and water and pour it on the starch in an earthenware -basin, put the latter in a warm place, and allow it to remain 24 hours, -with occasional stirring. Then boil it until it becomes thickly-fluid -and very transparent. If necessary it should be diluted with water and -filtered through a cloth. - -_Sugar and lime paste._ Dissolve 12 parts of white sugar in 36 of -water. Heat the solution to the boiling-point and add 3 parts of slaked -lime. Allow the liquid to stand in a covered vessel for several days, -stirring frequently and, when settled, pour off the supernatant thick -fluid from the excess of lime. - -The paste thus obtained has all the properties of gum arabic solution -and dries to a lustrous mass. - -_Liquid sugar and lime paste._ Allow 3 parts of glue to swell in 10 to -15 parts of the foregoing paste. Heat the mixture to the boiling-point. -The paste thus obtained does not congeal on cooling and possesses -considerable adhesive power. - -By reason of its caustic properties, due to the content of lime, this -paste should not be used for pasting colored materials. - -_Pastes for paper and fine fancy articles._ I. Dissolve, with the -assistance of heat, 100 parts of gilder’s glue in 200 of water, and add -a solution of 2 parts of bleached shellac in 10 of alcohol. - -II. Dissolve, with the assistance of heat, 50 parts of dextrine in 50 -of water, stir solutions 1 and 2 together, strain through a cloth into -a flat prismatic mould, and allow it to congeal. For use, melt a piece -of corresponding size, and dilute the liquid, if necessary, with water. - -_Albumen paste._ This is a misnomer, as it contains no albumen. It is -partly decayed gluten from flour, washed with water and then heated to -60° or 68° F., when it ferments and becomes partly fluid. It is then -dried at 77° to 86° F., and is claimed to keep any length of time in a -dry place. Dissolved in twice its weight of water it can be used as a -paste for all purposes. - -_Glycerine paste._ Dissolve 2 ozs. of gum arabic and 4 drachms of -glycerine in 6 ozs. of boiling water. This is a good paste for office -use. - -_Paste for fixing labels on machines._ Make a paste of rye flour and -glue and add to every pound thereof ½ oz. each of boiled linseed oil -and turpentine. This paste resists damp and thus prevents printed -labels from falling off metallic surfaces. - -_Paste for mounting maps._ Stiff rye flour paste is best for this -purpose. - -_Paste for fastening paper on tin-foil._ Make a paste by dissolving rye -flour in solution of caustic soda; dilute with water, stirring all the -time. Add to this paste a few drops of Venice turpentine for each ½ lb. -of flour. - -_Paste for paper bags._ Add to 3 parts of starch 24 to 30 parts of cold -water. Stir together to a homogeneous mass of about the thickness of -syrup. Pour over this, stirring constantly, boiling water until the -paste is of the required consistency. Stir until nearly cold. Take a -portion of the paste and add to it 6 to 15 per cent. liquefied Venice -turpentine; rub together until a kind of emulsion is formed, then mix -the whole together and work thoroughly. - -_Caseine mucilage for photographer’s use._ Separate the caseine from -milk by means of a little tartaric acid, and treat the caseine while -still warm with a solution of 6 parts of borax to 100 parts water, -and warm gently while stirring which will cause the caseine to be -dissolved. Of the borax solution enough should be used to leave only a -little undissolved caseine behind. - -_Paste for scrap-books._ Rice starch 1 oz., gelatine 3 drachms, water ½ -pint. - -Heat, stirring constantly, until the milky fluid becomes thick and -gluey. When the paste is nearly thick put in a bottle closely corked. -It is well to add a few drops of oil of cloves to each bottle. - -_Paste for skins._ Pour enough boiling water over 1 lb. of rye flour in -a basin to make a stiff paste, almost as stiff as ordinary dough for -puddings. Stir and beat up well with a stick for three or four minutes, -then cover up and let it stand for two days before using, when it will -be much softer and stick better. Spread thinly and evenly on the back -of the skin with a stiff brush or pad. It will stick firmly and not -crack. - -_Strong mucilage_ capable of fastening wood or china and glass together -is made of 3½ ozs. of strong gum arabic solution, to which a solution -of 30 grains of sulphate of aluminium dissolved in ⅔ oz. of water is -added. - -_Dextrine mucilage._ I. Dissolve with the assistance of heat 60 parts -of borax in 420 parts of water, add 480 parts of pale yellow dextrine -and 50 parts of glucose, and heat carefully, stirring constantly until -solution is complete, replacing the water lost by evaporation. Strain -through flannel. - -The resulting mucilage is quite clear, has great adhesive power, and -dries very quickly. In heating the mixture, great care should be -exercised not to exceed a temperature of 194° F. and not to heat too -long, otherwise the product readily becomes brown and brittle. - -II. Dextrine 120 parts, powdered alum 6, sugar 30, carbolic acid 1, -distilled water 300. Gradually mix the dextrine, alum and sugar with -the water, effect solution by boiling and when the solution is cold, -add the carbolic acid. - -_Paste for joining leather to pasteboard._ Dissolve 50 parts of strong -glue with a little water at a gentle heat, then add a small quantity of -Venice turpentine, and next a thick paste made with 100 parts of starch -in water. Apply quickly when cold. - -_Another formula_ for a similar paste is as follows: Rye whisky 2 -pints, water 1 pint, powdered starch 4¼ ozs., good glue 1¼ ozs., Venice -turpentine 1¼ ozs. Mix the whisky and water together, then stir in the -starch and make a thick paste. Separately dissolve the glue in an equal -weight of water, and mix the Venice turpentine therein, mix thoroughly, -and then compound this mixture with the thick paste by constantly -stirring until all is well incorporated. - -_Paste for attaching labels to polished nickel._ Dissolve 400 parts by -weight of dextrine in 600 parts of water, and add 20 parts of glycerine -and 10 parts of glucose. Heat the mixture to 194° F. - -_Another formula_ is as follows: Mix 400 parts by weight of dextrine -with water, and add 200 parts of water together with 20 parts of -glucose and 10 parts of aluminium sulphate. - -_Mucilage for attaching labels to tin._ I. Shellac 8 parts, borax 4 -parts, water 60 parts. Boil until the shellac is dissolved. - -II. To 2 parts of dammar varnish add 8 parts of tragacanth mucilage. - -III. An excellent mucilage for the purpose consists of starch paste to -which a small quantity of Venice turpentine has been added. - -IV. Make a paste of corrosive sublimate 2½ parts, wheat flour 200, -absinthe 100, tansy 50, water 3000. This mucilage is useful for vessels -kept in a damp place. - -_Mucilage for office use._ Gum arabic 100 parts, aluminium sulphate -6 parts, glycerine 10, dilute acetic acid 20, distilled water 140. -Dissolve, in a wide-mouthed glass bottle, the gum arabic in cold -distilled water, stirring frequently. Let the solution stand 2 or 3 -days, then add the glycerine, later on the dilute acetic acid and -finally the aluminium sulphate. Strain through a hair sieve, allow to -clarify, and decant from the sediment. - -_Glycerine paste for office use._ Dissolve 4 ozs. of gum arabic and 8 -drachms of glycerine in 12 ozs. of boiling water. - -_Clean and durable paste._ Dissolve 5 ozs. of gum arabic in 4 quarts -of warm water, and thicken to a paste with wheat flour. Then add a -solution of alum and sugar of lead, 3 ozs. of each in water. Heat the -mixture and stir it until it is about to boil, and then cool it. If too -thick, add gum solution. - -_Banknote or mouth glue._ Dissolve by the aid of heat a fine quality -of glue or gelatine with about a quarter or one-third of its weight of -brown sugar, in as small a quantity of water as possible. Then when -perfectly liquid cast the mixture into thin cakes on a flat surface -very slightly oiled, and when cold cut up into pieces of convenient -size. When required for use moisten one end. A piece of this glue kept -in the desk will be found very convenient for many purposes. - -_Paste for cardboard._ Dissolve 3½ ozs. of best French glue in 6½ ozs. -of water by soaking and heating. Then add a solution of ½ drachm of -shellac in 3½ drachms of alcohol and stir as long as the solution is -warm. Next dissolve 2 drachms of dextrine in 1¾ ozs. of alcohol and -14 drachms of water, stir, and place the vessel in warm water until -solution is complete. Mix this solution with that of the glue, and pour -the whole into a suitable vessel, in which it may solidify. When wanted -for use cut off a small piece and liquefy it by warming. - -_Paste for attaching cloth or leather to table tops._ Wheat flour 1 -lb., powdered rosin 2 tablespoonfuls, powdered alum 1 tablespoonful. -Heat and stir to a stiff consistency. - -_Caseine mucilage._ Separate the caseine from milk with a little -tartaric acid, and treat the caseine while still warm with a solution -of 6 parts borax to 100 parts water and warm gently while stirring, -which will cause the caseine to be dissolved. Of the borax solution -enough should be used to leave only a little undissolved caseine behind. - -_Very adhesive paste which may be used for wood and parchment._ Gum -arabic 60 parts, fine wheat starch 45, sugar 15. Dissolve the gum in -as much water as is required for boiling the quantity of paste to be -made. Then add the starch and sugar and boil it in a vessel suspended -in boiling water until the mixture is clear and has the consistency of -liquid tar. Keep in a well-closed vessel protected from mould by the -addition of a few drops of oil of cloves. - -_Paste for pads._ Glue 4 parts by weight, glycerine 2, linseed oil ½, -sugar 4, aniline dye sufficient to color. Soften the glue by soaking in -cold water, then dissolve together with the sugar in the glycerine by -the aid of heat over the water-bath, then add the dye and stir in the -oil. Use the paste hot. - -_Paste for fastening paper on tin-foil._ Make a paste by dissolving -rye flour in a solution of caustic soda; dilute with water, stirring -constantly. Add to this paste a few drops of Venice turpentine for each -½ lb. flour used. This paste adheres to all kinds of metal, tin-foil, -glass, etc. - -_Paste for attaching labels to glass, porcelain, and metal._ Gum -arabic 15 parts, pulverized tragacanth 7½, glycerin 45, thymol 0.3, -alcohol 3¾, water 120. Dissolve the gum arabic in 15 parts of water and -triturate the tragacanth with 30 parts of water. Mix the two fluids and -strain. Then add the glycerine and finally the thymol dissolved in the -alcohol. - -_Preparation of arabol-gum._ Mix intimately 44 lbs. of wheat starch -with 176 lbs. of water. Bring the mass into a water-bath, mix it with -a solution of 4.4 lbs. of oxalic acid in 44 lbs. of water and heat -for four hours at 194° F., stirring frequently. The conversion of the -starch is as a rule effected during this time, but should such not be -the case, continue heating, constantly replacing the evaporated water, -until the mass is clear and liquid. While still hot, neutralize the -mass with marble dust, allow to settle, filter, and evaporate the clear -solution in a water-bath to a solid gum containing about 15 per cent. -of water. - -_Preparation of an adhesive substance from desaccharized beet-root -slices_ (German patent 96316 f. G. Eichelbaum). The insoluble -metarabin contained in the slices is converted into soluble arabin by -treating the slices under pressure with hot aqueous sulphurous acid or -with aqueous solutions of the bisulphites of the alkalies or alkaline -earths. - -According to a later patent (German patent 121422 f. Fabrik -Bettenhausen Marquart and Schulz), the insoluble metarabin is converted -into soluble arabin by heating the desaccharized beet-root slices with -phosphoric acid and water. According to a supplement to this patent -(122048), conversion is effected by heating the slices with aqueous -solutions of organic acids and phenols, or the acid salts of oxalic, -tartaric or phosphoric acids. - - - - -INDEX. - - - Acid calcium phosphate, 120 - - —— —— —— crystallization of, 125, 126 - - —— —— —— formation of, 121-124 - - —— sodium sulphate, use of, in drying glue, 72, 73 - - Acidity, determination of, in glue, 205, 206 - - Acids, dilute, effect of, on glue solution, 7 - - Adamson, Wm., method of, for removing hydrocarbons from substances - which have been treated therewith, 84-86 - - —— —— method of, for treating substances with hydro carbon vapor for - the purpose of extracting oils, fats, etc., 79-82 - - —— —— method of, for treating substances with liquid hydrocarbons for - the purpose of extracting oils, fats, etc., 82-84 - - —— —— and Simonis, Chas. F. A., apparatus of, for extracting bones - with benzine, 76-79 - - Adhesive paste, 264 - - Adulterations of glue, determination of, 214, 215 - - Agar-Agar, 12, 201, 202 - - Air-bladders, 16, 41 - - —— bleaching glue in the, 141 - - —— drying the cakes of glue in the, 64 - - Alabaster, 244 - - —— cement for, 242 - - Albumen paste, 265, 266 - - —— —— use of, for clarifying glue liquor, 54 - - Alum cement, 228 - - —— —— effect of, on glue solution, 7 - - —— —— use of, for clarifying glue liquor, 54 - - —— —— —— —— preserving paste, 257 - - Amber, resinous cement for, 229 - - American cement for jewelers, 252 - - American glue, analysis of, 207 - - Ammonium sulphate, use of, in drying glue, 72, 73 - - Animal charcoal, bleaching glue with, 142 - - —— —— bones for the manufacture of, 107 - - —— —— carbonization of bones for, 108-112 - - —— —— decolorizing glue liquor with, 55 - - —— —— manufacture of, 112, 113 - - —— —— yield of, 113 - - —— skin, constitution of, 17, 18 - - Antiseptics for the preservation of glue-stock, 30 - - Arabin, conversion of metarabin into, 271 - - Arabol-gum, preparation of, 270 - - Ash, burning bones to, 117-119 - - - Bacteriology, use of gelatine in, 194 - - Banknote glue, 269 - - Barium chloride, effect of, on glue solution, 7 - - Basic calcium phosphate, 120 - - Beet-root slices, desaccharized, preparation of an adhesive - substance from, 270, 271 - - Belgian retort-furnace for the carbonization of bones, 109-112 - - Benzine, extracting fat from bones with, 76-92 - - Billiard balls, compound for, 155, 156 - - Bleaching glue, methods of, 141-145 - - —— —— stock, 55, 56 - - Blood, fresh, use of, for clarifying glue liquor, 54 - - Blumenthal’s method of preparing dextrine, 260, 261 - - Boiler for glue boiling, 44 - - Boiling bones, 74, 75 - - —— —— duration of, 45 - - —— —— or cooking glue, 44-52 - - Bone ash, composition of, 119 - - —— —— conversion of, into a coarse powder, 119 - - —— —— decomposition of, by sulphuric acid, 119-125 - - —— —— kiln for, 117-119 - - —— —— preparation of, 117-119 - - —— —— yield of, 119 - - —— cartilage, composition of, 32 - - —— cement for, 230 - - —— crusher, 36 - - —— gelatine, 170-180 - - —— —— modern process of preparing, 179, 180 - - —— -glue, manufacture of, 74-116 - - —— meal, glue and fat, simultaneous utilization of bones for, 104-113 - - —— -mill, Crosskill, 36 - - —— raw materials, 16 - - —— size, 159, 160 - - Bones, absorption of sulphurous acid by, 92 - - —— Adamson and Simonis’ apparatus for extracting, 76-79 - - —— and cartilages, 31-39 - - —— apparatus for extracting the fat from, with benzine, 76-94 - - —— Belgian retort-furnace for the carbonization of, 109-112 - - —— boiling of, 74, 75 - - —— burning of, to ash, 117-119 - - —— buying of, 32 - - —— carbonization of, 108-112 - - —— constitution of, 32 - - —— crushed, sorting of, 36, 37 - - —— crushing or grinding of, 33-36 - - —— extraction of, 76-94 - - —— —— —— phosphates from, 115 - - —— fatty matters in, 32 - - —— for the manufacture of animal charcoal, 107 - - —— honey-combed, 39 - - —— Leuner’s apparatus for extracting, 90-92 - - —— lime bath for, 37 - - —— products obtained in the distillation of, 112 - - —— Seltsam’s apparatus for extracting, 84-86 - - —— —— apparatus for extracting, improved by Th. Richter, 88-90 - - —— simultaneous utilization of, for fat, bone-meal and glue, 104-113 - - —— —— utilization of, for fat, glue and calcium phosphate, 113-116 - - —— sorting of, 32, 33, 104, 105 - - —— sulphurous acid for extracting, 92-94 - - —— treatment of, with high pressure steam, 105-107 - - —— utilization of the liquor obtained in the treatment of, with - hydrochloric acid, 125-127 - - —— value of, 32 - - —— waste of, from the preparation of tinned provisions, 19 - - Bookbinder’s glue, 12 - - —— size, 160 - - Book isinglass, 197 - - Boric acid, preservation of glue-stock with, 30 - - Bottles, cracked, cement for, 240, 241 - - Bouillon tablets, 12 - - Brazilian isinglass, 199, 200 - - Briers, D. J., process for the preparation of bone gelatine - employed by, 171-179 - - Brochette, 43 - - Brushmaker’s cement, 251 - - Bullock’s feet, 18 - - —— hide, waste of, 18 - - —— leather, 30 - - Burning bones to ash, 117-119 - - - Cakes, cutting glue into, 57-64 - - —— drying the, 64-73 - - —— machines for cutting the jelly into, 60-64 - - —— shape of, 57, 58 - - —— tools for cutting the jelly into, 59 - - Calcium chloride, 116 - - —— metaphosphate, 120, 127 - - —— phosphate, 115 - - —— —— fat and glue, simultaneous utilization of bones for, 113-116 - - Calf leather, 30 - - —— skin waste, 18 - - Calves’ feet, 30 - - —— heads, 18, 30 - - Carbolic acid, preservation of glue-stock with, 29 - - —— —— use of, for preserving paste, 257, 258 - - Carbon disulphide, use of, for extracting bones, 76 - - Cardboard, paste for, 269 - - Cartilage, 1 - - —— conversion of, into glue, 94-104 - - —— drying of, 114 - - —— preservation of, 114 - - —— treatment of, with high-pressure steam, 98 - - —— yield of glue from, 115 - - Cartilages and bones, 31-39 - - Caseine cement which can be kept for a long time, 239 - - —— cements, 237-240 - - —— mucilage, 264 - - —— —— for photographer’s use, 266 - - —— ordinary technical, preparation of, 238, 239 - - —— pure, preparation of, 237, 238 - - Castings, cement for filling in defects in, 246 - - Cattle, pieces of hide from the lower parts of the limbs of, 30 - - Cayenne isinglass, 199, 200 - - Cellular tissue, 1 - - Celluloid, cement for, 252 - - Cement resisting acids, 248 - - —— —— —— very high temperatures, 248 - - Cements, caseine, 237-240 - - —— chemical nature of, 219 - - —— classification of, 218-223 - - —— for chemical apparatus, 247-249 - - —— —— —— —— special purposes, 249-252 - - —— glue and starch, 222, 223 - - —— glycerine, 242 - - —— gypsum, 244, 245 - - —— how to use, 252-255 - - —— iron, 245-247 - - —— lime, 223, 243, 244 - - —— oil, 219, 220, 224-229 - - —— pastes and mucilages, preparation of, 224-271 - - —— resinous, 220, 221, 229-233 - - —— resisting high temperatures, 246 - - —— rubber and gutta-percha, 222, 233-237 - - —— water glass, 240-242 - - Chalk, 243 - - Charcoal, animal, bleaching glue with, 142 - - —— —— bones for the manufacture of, 107 - - —— —— carbonization of bones for, 108-112 - - —— —— manufacture of, 112, 113 - - —— —— yield of, 113 - - —— mixing calcium phosphate with, 124 - - Chemical apparatus, cements for, 247-249 - - Chinese isinglass, 201, 202 - - Chlorbarium, soaking hides in, 20 - - Chloride of lime, bleaching glue-stock with, 55 - - Chlorine, bleaching glue with, 141 - - Chondrin, chemical composition of, 5, 6 - - —— conversion of, into glutin, 6 - - —— formation of, 3 - - —— properties of, 5 - - —— pure, preparation of, 5 - - Chrome glue, 153 - - Clarifying glue liquor, 52-56 - - —— —— —— apparatus for, 98 - - —— —— —— vats, 53 - - Clay crucibles, cracked, cement for, 243 - - Clearness of glue, definition of, 53 - - Clock faces, white enameled, cement for, 230 - - Cloth, cement for, 252 - - —— paste for attaching, to table tops, 269 - - Colle franche, 43 - - Cologne glue, 148 - - Color mixtures, glue for, 11 - - —— of glue, definition of, 53 - - Colored gelatine, 181, 182 - - Coloring glue, 156 - - —— matters for gelatine, 181, 182 - - —— substances, removal of, from glue liquor, 54-56 - - Combs, hard rubber, cement for, 236 - - Common salt, effect of, on glue solution, 7 - - Constitution of glue, 3-6 - - Conversion of cartilage into glue, 94-104 - - Cooking, duration of, 44 - - —— or boiling glue, 44-52 - - Cooling boxes, 100 - - —— glue liquor, 100 - - Corium, 1, 17 - - Court-plaster, 12, 184, 185 - - Cox, J. and G., process for the manufacture of gelatine patented - by, 166, 167 - - Crockery, cement for, 236, 237 - - Crosskill bone mill, 36 - - Crucibles, cement for, 243 - - Crude glue, definition of, 3 - - —— —— preparation of, 43 - - Culinary purposes, glue for, 12-14 - - - Dark steam glue, 152 - - Devoulx, cutting apparatus invented by, 62-64 - - Dextrine mucilage, 267 - - —— —— preparation of, 259-261 - - Diamond cement, 229 - - Distillation of crude phosphorus, 133-135 - - —— —— phosphorus, 127-132 - - Drying, acceleration of, 72, 73 - - —— cakes of glue, 64-73 - - —— galleries, 68-71 - - —— house, modern, 71, 72 - - Drying room, 65 - - —— —— regulating the temperature of the, 67, 68 - - - East India isinglass, 199 - - Elastic cement, 234 - - —— gutta-percha cement, 236 - - —— masses, glue for, 14 - - —— paste, 263 - - Electric furnace for the manufacture of phosphorus, 138-140 - - Electrical apparatus, cement for, 251, 252 - - Emery paper, use of glue in the manufacture of, 12 - - Epidermis, 17 - - Epsom salt, behavior of glue solution towards, 7 - - —— —— use of, in drying glue, 72, 73 - - Evaporating pan, open, 98-100 - - —— pans, 124 - - Evaporators, spiral, 100, 101 - - Extraction of bones, 76-94 - - - Fabrics, water-proofing of, 161-163 - - Fancy articles, fine, paste for, 265 - - Fans, gelatine veneers for, 15 - - Fat, bone meal and glue, simultaneous utilization of bones - for, 104-113 - - —— extraction of, with benzine, 76-92 - - —— —— —— hydrocarbon vapors, 79-82 - - —— —— —— liquid hydrocarbons, 82-84 - - —— glue and calcium phosphate, simultaneous utilization of - bones for, 113-116 - - Fertilizers, utilization of liquors for, 116 - - Fining, gelatine for, 182 - - Fish bladders, 1 - - —— —— glue, 202-204 - - —— —— —— points to be observed in the manufacture of, 41, 42 - - —— —— —— raw materials for, 41, 42 - - —— scales, 16, 42 - - —— —— preparation of glue from, 203 - - Fleck’s kiln for burning bones, 118, 119 - - —— process of accelerating the drying of glue, 72, 73 - - Flour paste, 256-258, 261, 262 - - Fluid pastes, 264, 265 - - Foils, gelatine, 15, 185, 186 - - Formaldehyde, preservation of glue-stock with, 29, 30 - - Forming or moulding the glue, 56-64 - - Formo-gelatine, 193, 194 - - French mastic, 227 - - —— putty, 225 - - Friedberg’s apparatus for clarifying glue liquor, 98 - - —- —— —— conversion of cartilage into glue, 94-97 - - Furnace, electric, for the manufacture of phosphorus, 138-140 - - - Galley furnace, 128, 129 - - Galvanized iron-wire netting, 66 - - Gelatin, pure, preparation of, 4 - - Gelatine and glycerine, compound of, 12 - - —— and products prepared from it, manufacture of, 165-195 - - —— artificial silk from, 195 - - —— capsules, 14, 184 - - —— colored, 181, 182 - - —— constitution of, 165 - - —— Cox’s process for the manufacture of, 166, 167 - - —— foils, 15, 185, 186 - - —— for fining purposes, 182 - - —— for photographic printing and photographic purposes in - general, 183, 184 - - —— Jullion and Pirie’s process for the preparation of, 38 - - —— Nelson’s process for the manufacture of, 166 - - —— preparation of, from ordinary glue, 182, 183 - - —— substitute for, 203, 204 - - —— Swinborne’s improved patented process for the preparation of, 167 - - —— testing of, 205-217 - - —— veneers, 15, 186-193 - - —— yielding tissues, 1 - - German isinglass, 200 - - Gilder’s glue, 150 - - Glass, cement for, 230, 233, 239, 241, 243, 245 - - —— —— for attaching metal letters to, 249 - - —— —— —— —— —— to metal, 251 - - —— mastic cement for, 232 - - —— oil cement for, 228 - - —— paper, use of glue in the manufacture of, 12 - - —— paste for attaching labels to, 270 - - —— plates, gelatinizing liquors upon, 58, 59 - - —— upon glass, cement for, 230 - - —— —— metal, cement for, 230 - - Glauber’s salt, use of, in drying glue, 72, 73 - - Gloves, waste from the manufacture of, 43 - - Glue, acceleration of the drying of, 72, 73 - - —— addition of mineral substances to, 149 - - —— American, analysis of, 207 - - —— and starch cements, 222, 223 - - —— as a binding agent, 11 - - —— —— —— joining medium, 10, 11 - - —— banknote or mouth, 269 - - —— boiler, Terne’s, 51, 52 - - —— boiling, boiler for, 44 - - —— —— convenient apparatus for, 46, 47 - - —— —— in open jacketed pans, 49, 50 - - —— —— or cooking, 44-52 - - —— —— with steam, boiler for, 47-49 - - —— chemical composition of, 8 - - —— chrome, 153 - - —— clearness of, 53 - - —— Cologne, 148 - - —— color of, 53 - - —— coloring of, 156 - - —— constitution of, 3-6 - - —— conversion of cartilage into, 94-104 - - —— cooking, process of, 51 - - —— crude, definition of, 3 - - —— —— preparation of, 43 - - —— cutting the, into cakes, 57-64 - - —— deduction of the quality of, from indirect properties, 207, 208 - - —— determination of acidity in, 205, 206 - - —— —— of adulterations of, 214, 215 - - —— —— of glutin in, 206, 207 - - —— —— of moisture in, 205 - - —— different varieties of, and their preparation, 146-164 - - —— drying cakes of, 64-73 - - —— —— room for, 65 - - —— factory, location of a, 21 - - —— —— manner of carrying on the work in a, 26-30 - - —— fat and bone-meal, simultaneous utilization of bones for, 104-113 - - —— for attaching leather to metal, 153 - - —— —— culinary and medicinal purposes, 12-14 - - —— —— elastic masses and as a partial substitute for rubber, 14 - - —— —— fancy articles, 14, 15 - - Glue joints in leather driving belts, 163 - - —— —— —— leather, paper, etc., 153, 154 - - —— —— —— parchment paper in making sausage skins, 154, 155 - - —— formation of, 6 - - —— from various materials, external characteristics of, 6, 7 - - —— gilder’s, 150 - - —— holding power of, 147, 148 - - —— how to make and use, 147 - - —— in animal organism, 2 - - —— —— sizing, 12 - - —— inferior qualities of, 12 - - —— joiner’s, 146 - - —— Kissling’s results in testing, 215 - - —— liquid, 151, 152 - - —— liquor, apparatus for clarifying, 98 - - —— —— clarifying the, 52-56 - - —— —— concentration of, 50 - - —— —— cooling of, 100 - - —— —— decolorizing of, with animal charcoal, 55 - - —— —— instrument for measuring the percentage of glue in, 103 - - —— measuring the percentage of, in glue liquor, 103, 104 - - —— methods of bleaching, 141-145 - - —— moulding or forming of, 56-64 - - —— nature of, 1-9 - - —— nets for drying, 66, 67 - - —— ordinary, preparation of gelatine from, 182, 183 - - —— parchment, 150 - - —— Paris, 150, 151 - - —— patent, 150 - - —— practical testing of, 215-217 - - —— principal substances employed as raw material for, 16 - - —— properties of, and its behavior towards other substances, 6-9 - - —— raw materials and their preparation for the manufacture of, 16-38 - - —— results obtained by comparative experiments in testing, 209, 210 - - —— Russian, 149, 150 - - —— size, 150 - - —— solution, behavior of, towards salts, 7, 8 - - —— steam, 152 - - —— stock, bleaching of, 55, 56 - - —— —— dry-limed, 19 - - —— —— dry, uncured, or salted, 19 - - —— —— green-limed, 19 - - —— —— green-salted, 19 - - —— —— influence of the age of animals on the product from, 20 - - —— —— limed, washing of, 21-26 - - —— —— notes in reference to judging, 19, 20 - - —— —— preparation of, 21-38 - - —— —— preservation of, 29 - - —— —— sheds for, 26 - - —— —— transformation in boiling the, 2 - - —— —— washer, 22-26 - - —— substitute for, 203, 204 - - —— transition stages of, 2 - - —— uses of, 10-15 - - —— testing of, 205-217 - - —— tungstic, 155 - - —— water-proof, 160 - - —— yield of, from cartilage, 115 - - —— —— —— from tannery waste, 18 - - —— -yielding substance, production of, 2 - - —— —— tissues, 1 - - Glutin, conversion of chondrin into, 6 - - —— determination of, in glue, 206, 207 - - —— formation of, 3 - - —— properties of, 4, 5 - - —— pure, preparation of, 4 - - Glycerine and glycerine cements, 242 - - —— —— litharge cement, 242 - - —— paste, 266 - - —— —— for office use, 268 - - —— properties of, 242 - - Glycocoll, 6 - - Goat leather, 31 - - Gray lime, 28 - - Green waste, liming of, 26, 27 - - Gum tragacanth, 261 - - Gutta-percha and rubber cements, 222, 233-237 - - Gypsum, 244 - - Gypsum cements, 244, 245 - - - Hager’s diamond cement, 229 - - Hard rubber cement, 234 - - —— combs, cement for, 236 - - Hare skins, 18, 31 - - Hartshorn, 1 - - Hayes, S. Dana, analysis of American glue by, 207 - - Heat-resisting cement, 245 - - Hectograph mass, 14, 163, 164 - - Heuzé’s method of preparing dextrine, 261 - - Hide, transformation in drying the, 2 - - Hides for glue-stock, classification of, 30, 31 - - —— soaking of, in chlorbarium, 20 - - Hoeveller, W. A., apparatus for drying glue invented by, 68-71 - - —— glue-stock washer of, 22-26 - - Hog skins, 18 - - Hollander, 39 - - Horn, cement for, 232 - - —— piths, 19 - - Horses’ hoofs, cement for, 236 - - Hudson Bay isinglass, 199 - - Hydraulic works, cement for, 241 - - Hydrocarbon vapors, extraction of fats, oils, etc., with, 79-82 - - Hydrocarbons, liquid, extraction of fats, oils, etc., with, 82-84 - - —— removal of, from substances, 84-86 - - Hydrochloric acid, treatment of bones with, 37 - - —— —— utilization of the liquor obtained in treating bones - with, 125-127 - - - Ichthyocolle Française, 200, 201 - - Irish moss, 202 - - Iron and stone, cement for, 245 - - —— cement for, 245, 246 - - —— cements, 245-247 - - —— pipes, fire-proof cement for, 246 - - —— pots, cracked, cement for, 246 - - —— water tanks, cement for, 246 - - Isinglass, adulteration of, 196, 197 - - —— and its substitutes, 196-204 - - —— chemical composition of, 8 - - —— preparation of, in Russia, 197, 198 - - —— sources of, 196 - - —— spurious, 196 - - —— substitute for, 203, 204 - - Isinglassine, 201 - - Ivory, cement for, 230 - - - Jeffrey’s marine glue, 235 - - Jelly, definition of, 3 - - —— effect of tannin on, 8 - - —— machines for cutting the, into cakes, 60-64 - - —— properties of, 7 - - —— tools for cutting the, into cakes, 59 - - —— transformation in boiling the, 2 - - Jennings’ method for the preparation of fish glue, 202, 203 - - Jewelers, American cement for, 252 - - —— cement, 252 - - Joiners, cement for, 243 - - —— glue, 146 - - Jullion and Pirie’s process for the preparation of gelatine, 38 - - Kid leather, waste from paring, 31 - - Kiln for burning bones, 117-119 - - Kissling’s results in testing glue, 215 - - Knapsack leather, 31 - - Knife handles, cement for, 231 - - - Label paste, 263 - - Labels, mucilage for, 263 - - —— paste for attaching, to glass, porcelain and metal, 270 - - —— —— for attaching, to polished nickel, 268 - - —— —— for attaching, to tin, 268 - - Lamb leather, 31 - - Leaf isinglass, 197 - - Leather, cement for, 235, 237 - - —— driving belts, glue for joints in, 163 - - —— for glue-stock, classification of, 30, 31 - - —— glue for, 153, 154 - - —— —— —— attaching, to metal, 153 - - —— paste for attaching, to table tops, 269 - - —— —— —— joining, to pasteboard, 267, 268 - - —— skins, actual, 17 - - —— waste, 39-42 - - —— —— comminution of, 39, 40 - - Leucine, 6 - - Leuner’s apparatus for extracting bones, 90-92 - - Lime and glue cement, 244 - - —— —— sugar paste, 265 - - —— bath for bones, 37 - - —— cements, 223, 243, 244 - - —— milk of, preparation of, 26, 27 - - —— precipitation of, by oxalic acid, 54 - - —— slaked, effect of, on glue solution, 7 - - —— testing of, 27, 28 - - Limed glue-stock, washing of, 21-26 - - Liming green waste, 26, 27 - - —— waste, 20 - - Linseed oil and clay cement, 248 - - —— —— —— manganese cement, 248 - - Lipowitz’s method of testing glue, 208, 209 - - Liquid fining gelatine, 182 - - —— glue, 151, 152 - - —— sugar and lime paste, 265 - - Litharge cement, 225 - - - Magnesium sulphate, 116 - - Manufacture of bone-glue, 74-116 - - —— —— gelatine, and products prepared from it, 165-195 - - —— —— phosphorus, 117-140 - - —— —— skin glue, 43-73 - - Maps, paste for mounting, 266 - - Marble, cement for, 242, 251 - - —— —— for attaching metal letters to, 249 - - —— oil cement for, 228, 229 - - Marine glue, 234, 235 - - Matches, use of glue in the manufacture of, 11 - - Mastic, 226, 227 - - —— cement, 226, 227 - - Medicinal purposes, glue for, 12-14 - - Meerschaum, cement for, 239 - - Meta-gelatin, 7 - - Metal, cement for attaching wood, glass, etc., to, 251 - - —— glue for attaching leather to, 153 - - —— letters upon glass, cement for, 230, 249 - - —— paste for attaching labels to, 270 - - Metals, cement for, 239 - - —— —— for uniting, 241 - - Metarabin, conversion of, into arabin, 271 - - Mica, cement for, 231, 232 - - Milk of lime, preparation of, 26, 27 - - Moisture, determination of, in glue, 205 - - Mother-of-pearl, glue imitations of, 15 - - Moulding boxes, 56 - - —— or forming the glue, 56-64 - - —— refined phosphorus, 135-137 - - Mouth glue, 269 - - Mucilage, 263, 264 - - —— caseine, 264 - - —— —— for photographers’ use, 266 - - —— dextrine, 267 - - —— for attaching labels to tin, 268 - - —— —— labels, 263 - - —— —— office use, 268 - - —— —— postage stamps, 264 - - —— preservation of, 259, 260 - - —— strong, 267 - - —— tragacanth, 264 - - Mucilages and pastes, 255-271 - - —— —— —— for special purposes, 261-271 - - —— —— pastes and cements, preparation of, 224-271 - - Muratori and Landry’s method of water-proofing fabrics, 162, 163 - - Muzmann and Krakowitzer’s method of water-proofing fabrics, 162, 163 - - - Nature of glue, 1-9 - - Nelson, G., process of, for the manufacture of gelatine, 166 - - Nets for drying glue, 66, 67 - - Netting, metallic, 66 - - —— twine, 66, 67 - - Neutral potassium tartrate, behavior of glue solution towards, 7 - - New York isinglass, 198 - - Nickel, polished, paste for attaching labels to, 268 - - North American isinglass, 198 - - - Office use, glycerine paste for, 268 - - —— —— mucilage for, 268 - - Oil cements, 219, 220, 224-229 - - Oils, extraction of, with hydrocarbon vapors, 79-82 - - —— —— —— with liquid hydrocarbons, 82-84 - - Ornaments, indestructible mass for, 155 - - Osseine, 1 - - Oxalic acid, effect of, on glue solution, 7 - - —— —— precipitation of lime by, 54 - - - Pads, paste for, 270 - - Paget’s mastic, 227 - - Pale steam glue, 152 - - Pan, open evaporating, 98-100 - - Pans, evaporating, 124 - - —— open jacketed, 49, 50 - - —— vacuum, 101-103 - - Paper bags, paste for, 266 - - —— colored, use of glue in the manufacture of, 11 - - —— glue for, 153, 154 - - —— hangings, glue in the manufacture of, 11 - - —— paste for, 265 - - —— —— —— fastening, on tin-foil, 266, 270 - - Parchment glue, 150 - - —— paper, glue for, in making sausage skins, 154, 155 - - —— scraps, 18 - - Paris glue, 150, 151 - - Paste, adhesive, 264 - - —— albumen, 265, 266 - - —— clean and durable, 268, 269 - - —— elastic or pliable, 263 - - —— fluid, 264, 265 - - —— for attaching cloth or leather to table tops, 269 - - —— —— —— labels to glass, porcelain and metal, 270 - - —— —— —— —— to polished nickel, 268 - - —— —— cardboard, 269 - - —— —— fastening paper on tin foil, 266, 270 - - —— —— joining leather to pasteboard, 267, 268 - - —— —— mounting maps, 266 - - —— —— pads, 270 - - —— —— paper and fine fancy articles, 265 - - —— —— —— bags, 266 - - —- —— scrap-books, 266, 267 - - —— —— skins, 267 - - —— glycerine, 266 - - —— —— for office use, 268 - - —— label, 263 - - —— preparation of, 255 - - —— preservatives for, 257 - - —— rules to be observed in the preparation of, 256 - - —— strong adhesive, 262 - - —— sugar and lime, 265 - - —— that will not sour, 262 - - —— Venetian, 262 - - Paste-board, paste for joining leather to, 267, 268 - - Pastes and mucilages, 255-271 - - —— —— —— for special purposes, 261-271 - - —— mucilages and cements, preparation of, 224-271 - - Patent glue, 150 - - Patriarch isinglass, 197 - - Permanent white, addition of, to glue, 149 - - Petroleum, cement to withstand the action of, 231 - - —— lamps, cement for, 231 - - Phosphates, extraction of, from bones, 115 - - Phosphorus, crude, composition of, 131, 132 - - —— —— distillation of, 133-135 - - —— —— purification of, 132 - - —— distillation of, 127-132 - - —— galley furnace for distilling, 128, 129 - - —— loss of, 132 - - —— manufacture of, 117-140 - - —— —— of, with the assistance of electricity, 138-140 - - —— operations in the preparation of, 117 - - —— refined, moulding of, 135-137 - - —— refining and purifying of, 132-135 - - —— receivers for, 129 - - —— removal of, from the receivers, 131 - - —— residue in the manufacture of, 127 - - —— sticks, mode of forming, 135-137 - - —— storing of, 138 - - Photographers, caseine mucilage for 266 - - Photographic printing, gelatine for 183, 184 - - Photo-lithography, use of glue in, 14 - - Pierres de mastic, 226, 227 - - Pipes exposed to a red heat, cement for tightening joints of, 241 - - Plaster of Paris, 244 - - —— —— —— cement, universal, 245 - - —— —— —— statues, cement for, 244, 245 - - Pliable paste, 263 - - Porcelain, cement for, 231, 239, 240, 241, 243, 245 - - —— oil cement for, 229 - - —— paste for attaching labels to, 270 - - —— sulphur cement for, 232, 233 - - Postage stamps, mucilage for, 264 - - Potassium carbonate, behavior of glue solution towards, 7 - - Printing rollers, compositions for, 157 - - Putty, 224, 225 - - - Quick lime, 243 - - - Rabbit skins, 18, 31 - - Rag-engine, 39 - - Raw materials and their preparation for the manufacture of glue, 16-38 - - —— —— collection and buying of, 16 - - —— —— division of, 16 - - Receivers for collecting phosphorus, 129 - - —— —— removal of phosphorus from the, 131 - - Red lead cement, 225 - - Resinous cements, 220, 221, 229-233 - - Retort-furnace, Belgian, for the carbonization of bones, 109-112 - - Retorts, 127, 128 - - Rochelle salts, behavior of glue solution towards, 7 - - Rubber and gutta-percha cements, 222, 233-237 - - —— cement for, 250 - - —— —— —— chemical apparatus, 248, 249 - - —— glue as a partial substitute for, 14 - - Russia, preparation of isinglass in, 197, 198 - - Russian glue, 149, 150 - - —— isinglass, 197, 198 - - —— steam glue, 152 - - - Sahlstrom’s process for preparing a substitute for isinglass, gelatine - and glue, 203, 204 - - Sal ammoniac, effect of, on glue solution, 7 - - Saltpetre, effect of, on glue solution, 7 - - Salts, behavior of glue solution towards, 7, 8 - - Samovey leaf isinglass, 197 - - Sandpaper, use of glue in the manufacture of, 12 - - Sausage skins, glue for parchment paper in making, 154, 155 - - Scheibler’s cement for chemical apparatus, 249 - - Schneible, J., machine for cutting the jelly into cakes invented - by, 60-62 - - Scrap-books, paste for, 266, 267 - - Selenite, 244 - - Seltsam’s apparatus for extracting bones, 84-86 - - —— —— for extracting bones improved by Th. Richter, 88-90 - - Serbat’s mastic, 227, 228 - - Seubert’s apparatus for moulding phosphorus, 135, 136 - - Sheds for glue-stock, 26 - - Sheep leather, 31 - - —— skin waste, 18 - - Shell lime, 28 - - Shoemakers’ paste, 258, 259 - - Siberian purse isinglass, 197 - - Sieve for sorting crushed bones, 36, 37 - - Silicate of soda, 240 - - Silk, artificial, from gelatine, 195 - - Sinews, 1 - - Size, 157-160 - - —— glue, 150 - - Sizing, glue in, 12 - - Skin gelatine, 166-170 - - —— —— modern process of preparing, 167-170 - - —— glue, classification of operations in the manufacture of, 43 - - —— —— manufacture of, 43-73 - - —— -like raw materials, 16 - - Skins, paste for, 267 - - —— steeping of, 18 - - —— used for packing, use of, for glue, 19 - - Sodium carbonate, behavior of glue solution towards, 7 - - Soft putty, 225 - - —— rubber cement, 233, 234 - - Sounds, 41 - - Spiral evaporators, 100, 101 - - Stamping mill for crushing bones, 34, 35 - - Staple isinglass, 197 - - Starch and glue cements, 222, 223 - - —— paste, 255, 256, 261 - - Steam, apparatus for boiling glue with, 47-49 - - Steam boiler cement, 250 - - —— glue, 152 - - —— high-pressure, treatment of bones with, 105-107 - - —— pipes, cement for, 250, 251 - - —— —— oil cement free from lead for, 228 - - —— —— —— cements for, 228 - - Steaming bones, 75, 76 - - Stephenson’s oil cement, 228 - - Stick mastic cement, 232 - - Stone lime, 28 - - Stove plates, cracked, cement for, 246 - - Stoves, black cement for, 246 - - Stratena, 252 - - Straw, use of, as a filter, 44 - - Sugar and lime paste, 265 - - Sulphate of alumina, use of, for clarifying glue liquor, 54 - - —— —— baryta, addition of, to glue, 149 - - Sulphuric acid, decomposition of bone ash by, 119-125 - - Sulphurous acid, absorption of, by bones, 92 - - —— —— bleaching glue with, 143-145 - - —— —— glue-stock with, 55, 56 - - —— —— dilute, treatment of bones with, 38 - - —— —— generation of, 93, 94 - - —— —— process for extracting bones, 92-94 - - —— —— solution, apparatus for the production of, 143, 144 - - Surrons, 31 - - Swinborne’s improved patented process for the preparation of - gelatine, 167 - - - Table tops, paste for attaching cloth or leather to, 269 - - Tannery waste, yield of glue from, 18 - - Tannin as a test for the presence of gelatine, 165 - - —— effect of, on glue solution, 8 - - —— removal of, from leather waste, 39-41 - - Tendons, 1 - - Terne’s apparatus for the generation of sulphurous acid, 94 - - —— glue boiler, 51, 52 - - Terra-cotta articles, cement for, 232 - - Testing glue and gelatine, 205-217 - - Tin foil, paste for fastening paper on, 266, 270 - - Tin paste for attaching labels to, 268 - - Tires, cement for, 250 - - Tools for cutting the jelly into cakes, 59 - - Tortoise shell, cement for, 232 - - —— —— glue imitations of, 15 - - Toys indestructible mass for, 155 - - Tragacanth, 261 - - —— mucilage, 264 - - Transition stages of glue, 2, 3 - - Tub-size, manufacture of, 158, 159 - - Tungstic glue, 155 - - Turners, cement for, 229, 230 - - Twine netting, objections to, 66, 67 - - - Under skin, 17 - - Uses of glue, 10-15 - - - Vacuum pans, 101-103 - - Vasa lymphatica, 1 - - Vats, clarifying, 53 - - Veneers, gelatine, 15, 186-193 - - Venetian paste, 262 - - - Walls, damp, marine glue for, 235 - - Wash basins, cement for, 225, 226 - - Washing drum, 22 - - Waste, green, liming of, 26, 27 - - —— liming of, 20 - - —— putrefaction of, 20, 21 - - Water-glass and water-glass cements, 240-242 - - —— —— constitution of, 240 - - Water-proof cement, 227 - - —— —— glue, 160 - - —— proofing fabrics, 161-163 - - —— —— wrapping paper, 160, 161 - - —— tanks, iron, cement for, 246 - - Weavers’ looms, worn-out hinges from, 30 - - Weidenbusch’s method of testing glue, 211-213 - - Whalebone, cement for, 232 - - Whale glue, 204 - - Whip leather, 30 - - White-lead, addition of, to glue, 149 - - Wood, cement for, 230, 239, 240 - - —— —— —— attaching metal letters to, 249 - - —— —— —— —— to metal, 251 - - Wooden vessels, insoluble cement for, 233 - - Wrapping paper, water-proof, 160, 161 - - - Zinc plates, gelatinizing liquors upon, 58, 59 - - —— white cement, 226 - - —— addition of, to glue, 149 - - * * * * * - -Transcriber's Notes - -Obvious typographical errors have been silently corrected. Variations -in hyphenation have been standardised but all other spelling and -punctuation remains unchanged. - -Italics are represented thus _italic_. - -Within the chemical formulae subscripted numerals are shown thus _{2}_. - -The following corrections have been made: - - Line 4516 From - III. 3Ca(PO_{3})_{2} + 10C = 10CO + Ca_{3}(PO_{4})_{2} = P_{2} - to - III. 3Ca(PO_{3})_{2} + 10C = 10CO + Ca_{3}(PO_{4})_{2} + P_{4} - - Line 4742 From - 3Ca(PO_{3})_{2} + 5Ca_{2}_ = Ca_{3}(PO_{4})_{2} + 10CO + 4P. - to - 3Ca(PO_{3})_{2} + 10C = Ca_{3}(PO_{4})_{2} + 10CO + 4P. - - - - - - -End of the Project Gutenberg EBook of Glue, Gelatine, Animal Charcoal, -Phosphorous, Cements, Pastes and, by F. 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