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WILLIAMS + + + +The object held constantly in view in writing this book has been to +prepare a suitable text-book in Chemistry for the average High +School,--one that shall be simple, practical, experimental, and +inductive, rather than a cyclopaedia of chemical information. + +For the accomplishment of this purpose the author has endeavored +to omit superfluous matter, and give only the most useful and +interesting experiments, facts and theories. + +In calling attention, by questions, and otherwise, to the more +important phenomena to be observed and facts to be learned, the +best features of the inductive system have been utilized. +Especially is the writing of equations, which constitute the +multum in parvo of chemical knowledge, insisted upon. As soon as +the pupil has become imbued with the spirit and meaning of +chemical equations, he need have little fear of failing to +understand the rest. To this end Chapters IX., XI., and XVI. +should be studied with great care. + +In the early stages of the work the equations may with advantage +be memorized, but this can soon be discontinued. Whenever symbols +are employed, pupils should be required to give the corresponding +chemical names, or, better, both names and symbols. + +The classification of chemical substances into acids, bases and +salts, and the distinctions and analogies between each of these +classes, have been brought into especial prominence. The general +relationship between the three classes, and the general +principles prevailing in the preparation of each, must be fully +understood before aught but the merest smattering of chemical +science can be known. + +Chapters XV.-XXI. should be mastered as a key to the subsequent +parts of the book. + +The mathematical and theoretical parts of Chemistry it has been +thought best to intersperse throughout the book, placing each +where it seemed to be especially needed; in this way, it is hoped +that the tedium which pupils find in studying consecutively many +chapters of theories will be avoided, and that the arrangement +will give an occasional change from the discussion of facts and +experiments to that of principles. In these chapters additional +questions should be given, and the pupil should be particularly +encouraged to make new problems of his own, and to solve theta. + +It is needless to say that this treatise is primarily designed to +be used in connection with a laboratory. Like all other text- +books on the subject, it can be studied without such an +accessory; but the author attaches very little value to the study +of Chemistry without experimental work. The required apparatus +and chemicals involve but little expense, and the directions for +experimentation are the result of several years' experience with +classes as large as are to be found in the laboratory of any +school or college in the country. + +During the present year the author personally supervises the work +of more than 180 different pupils in chemistry. This enables him +not only to assure himself that the experiments of the book are +practical, but that the directions for performing them are ample. +It is found advisable to perform most of the experiments, with +full explanation, in presence of the class, before requiring the +pupils either to do the work or to recite the lesson. In the +laboratory each pupil has a locker under his table, furnished +with apparatus, as specified in the Appendix. Each has also the +author's "Laboratory Manual," which contains on every left-hand +page full directions for an experiment, with observations to be +made, etc. The right-hand page is blank, and on that the pupil +makes a record of his work. These notes are examined at the time, +or subsequently, by the teacher, and the pupil is not allowed to +take the book from the laboratory; nor can he use any other book +on Chemistry while experimenting. By this means he learns to make +his own observations and inferences. + +For the benefit of the science and the added interest in the +study, it is earnestly recommended that teachers encourage pupils +to fit up laboratories of their own at home. This need not at +first entail a large outlay. A small attic room with running +water, a very few chemicals, and a little apparatus, are enough +to begin with; these can be added to from time to time, as new +material is wanted. In this way the student will find his love +for science growing apace. + +While endeavoring, by securing an able corps of critics, and in +all other ways possible, to reduce errors to a minimum, the +author disclaims any pretensions to a work entirely free from +mistakes, holding himself alone responsible for any shortcomings, +and trusting to the leniency of teachers and critics. + +The manuscript has been read by Prof. Henry Carmichael, Ph.D., of +Boston, and to his broad and accurate scholarship, as well as to +his deep personal interest in the work, the author is indebted +for much valuable and original matter. The following persons have +generously read the proof, as a whole or in part, and made +suggestions regarding it, and to them the author would return his +thanks, as well as acknowledge his obligation: Prof. E. J. +Bartlett, Dartmouth College, N.H.; Prof. F. C. Robinson, Bowdoin +College, Me.; Prof. H. S. Carhart, Michigan University; Prof. B. +D. Halsted, Iowa Agricultural College; Prof. W. T. Sedgwick, +Institute of Technology, Boston; Pres. M. E. Wadsworth, Michigan +Mining School; Prof. George Huntington, Carleton College, Minn.; +Prof. Joseph Torrey, Iowa College; Mr. C. J. Lincoln, East Boston +High.School; Mr. W. H. Sylvester, English High School, Boston; +Mr. F. W. Gilley, Chelsea, Mass., High School; the late D. S. +Lewis, Chemist of the Boston Gas Works, and others. + +R. P. W. + +BOSTON, January 3, 1888. + + + +TABLE OF CONTENTS + + + +CHAPTER I. + +THE METRIC SYSTEM. + +Length.--Volume.--Weight + +CHAPTER II. + +DIVISIBILITY OF MATTER. + +Mass.-Molecule.--Atom.--Element.--Compound.--Mixture.-- +Analysis.--Synthesis.--Metathesis.--Chemism + +CHAPTER III. + +MOLECULES AND ATOMS. + +Synthesis + +CHAPTER IV. + +ELEMENTS AND BINARIES. + +Symbols.--Names.--Coefficients.--Exponents.--Table of elements + +CHAPTER V. + +MANIPULATION. + +To prepare and cut glass, etc. + +CHAPTER VI. + +OXYGEN. + +Preparation.--Properties.--Combustion of carbon; sulphur; +phosphorus; iron. + +Chapter VII + +NITROGEN + +Separation--Properties + +CHAPTER VIII + +HYDROGEN + +Preparation--Properties--Combustion--Oxy-hydrogen blowpipe + +CHAPTER IX + +UNION BY WEIGHT + +Meaning of equations--Problems + +CHAPTER X + +CARBON + +Preparation--Allotropic forms: diamond, graphite, amorphous +carbon, coke, mineral coal.--Carbon a reducing agent, a +decolorizer, disinfectant, absorber of gases + +CHAPTER XI + +VALENCE + +Poles of attraction--Radicals + +CHAPTER XII + +ELECTRO-CHEMICAL RELATION OF ELEMENTS + +Deposition of silver; copper; lead--Table of metals and non- +metals, and discussion of their differences + +CHAPTER XIII. + +ELECTROLYSIS. + +Decomposition of water and of salts--Conclusions CHAPTER XIV. + +UNION BY VOLUME. + +Avogadro's law and its applications. + +CHAPTER XV. + +ACIDS AND BASES. + +Characteristics of acids and bases.--Anhydrides.--Naming of +acids.--Alkalies + +CHAPTER XVI. + +SALTS. + +Preparation from acids and bases.--Naming of salts.--Occurrence + +CHAPTER XVII + +CHLORHYDRIC ACID. + +Preparation and tests.--Bromhydric, iodhiydric, and fluorhydric +acids.--Etching glass + +CHAPTER XVIII. + +NITRIC ACID. + +Preparation, properties, tests, and uses.--Aqua regia: +preparation and action + +CHAPTER XIX. + +SULPHURIC ACID. + +Preparation, tests, manufacture, and importance.-Fuming sulphuric +acid + +CHAPTER XX. + +AMMONIUM HYDRATE. + +Preparation of bases.--Formation, preparation, tests, and uses of +ammonia. + +Chapter XXI. + +SODIUM HYDRATE. + +Preparation and properties.--Potassium hydrate and calcium +hydrate + +CHAPTER XXII + +OXIDES OF NITROGEN. + +Nitrogen monoxide, dioxide, trioxide, tetroaide, pentoxide. + +CHAPTER XXIII. + +LAWS OF DEFINITE AND OF MULTIPLE PROPORTION, and their +application + +CHAPTER XXIV. + +CARBON PROTOXIDE and water gas. + +CHAPTER XXV. + +CARBON DIOXIDE. + +Preparation and tests.--Oxidation in the human system.--Oxidation +in water.--Deoxidation in plants + +CHAPTER XXVI. + +OZONE. + +Description, preparation, and test + +CHAPTER XXVII + +CHEMISTRY OF THE ATMOSPHERE. + +Constituents of the air.--Air a mixture.--Water, carbon dioxide, +and other ingredients of the atmosphere + +CHAPTER XXVIII. + +THE CHEMISTRY OF WATER. + +Distillation of water.--Three states.--Pure water, sea-water, +river-water, spring-water CHAPTER XXIX. + +THE CHEMISTRY OF FLAME. + +Candle flame.--Bunsen flame.--Light and heat.--Temperature of +combustion.--Oxidizing and reducing flames.--Combustible and +supporter.--Explosive mixture of gases.--Generalizations + +CHAPTER XXX. + +CHLORINE. + +Preparation.--Chlorine water.--Bleaching properties.-- +Disinfecting power.--A supporter of combustion.--Sources and uses + +CHAPTER XXXI. + +BROMINE. + +Preparation.--Tests.--Description.--Uses + +CHAPTER XXXII. + +IODINE. + +Preparation.--Tests.--Iodo-starch paper.--Occurrence.--Uses.-- +Fluorine + +CHAPTER XXXIII. + +THE HALOGENS. + +Comparison.--Acids, oxides, and salts + +CHAPTER XXXIV. + +VAPOR DENSITY AND MOLECULAR WEIGHT. + +Gaseous weights and volumes.--Vapor density defined.--Vapor +density of oxygen + +CHAPTER XXXV. + +ATOMIC WEIGHT. + +Definition.--Atomic weight of oxygen.--Molecular symbols.-- +Molecular and atomic volumes CHAPTER XXXVI. + +DIFFUSION AND CONDENSATION OF GASES. + +Diffusion of gases.--Law of diffusion.--Cause.--Liquefaction and +solidification of gases + +CHAPTER XXXVIL + +SULPHUR. + +Separation.--Crystals from fusion.--Allotropy.--Solution.-- +Theory of Allotropy.--Occurrence and purification.--Uses.--- +Sulphur dioxide + +CHAPTER XXXVIII. + +HYDROGEN SULPHIDE. + +Preparation.--Tests.--Combustion.--Uses.--An analyzer of metals.- +-Occurrence and properties + +CHAPTER XXXIX. + +PHOSPHORUS. + +Solution and combustion.--Combustion under water.--Occurrence.-- +Sources.--Preparation of phosphates and phosphorus.--- +Properties.--Uses.--Matches.--Red phosphorus.---Phosphene + +CHAPTER XL. + +ARSENIC. + +Separation.--Tests.--Expert analysis.--Properties and +occurrence.-- Atomic volume.--Uses of arsenic trioxide + +CHAPTER XLI. + +SILICON, SILICA, AND SILICATES. + +Comparison of silicon and carbon.--Silica.--Silicates.--Formation +of silica. + +Chapter XLII + +GLASS AND POTTERY. + +Glass an artificial silicate.--Manufacture.--Importance.-- +Porcelain and pottery. + +CHAPTER XLIII. + +METALS AND THEIR ALLOYS. + +Comparison of metals and non-metals.--Alloys.--Low fusibility. -- +Amalgams + +CHAPTER XLIV. + +SODIUM AND ITS COMPOUNDS. + +Order of derivation.--Occurrence and preparation of sodium +chloride; uses.--Sodium sulphate: manufacture and uses. --Sodium +carbonate: occurrence, manufacture, and uses.-- Sodium: +preparation and uses.--Sodium hydrate: preparation and use.-- +Hydrogen sodium carbonate.--Sodium nitrate + +CHAPTER XLV. + +POTASSIUM AND AMMONIUM. + +Occurrence and preparation of potassium.--Potassium chlorate and +cyanide.--Gunpowder.--Ammonium compounds + +CHAPTER XLVI. + +CALCIUM COMPOUNDS. + +Calcium carbonate.--Lime and its uses.--Hard water.--Formation of +caves.--Calcium sulphate + +CHAPTER XLVII. + +MAGNESIUM, ALUMINIUM, AND ZINC. + +Occurrence and preparation of magnesium.--Compounds of aluminium: +reduction; properties, and uses.--Compounds, uses, and reduction +of zinc CHAPTER XLVIII. + +IRON AND ITS COMPOUNDS. + +Ores of iron.--Pig-iron.--Steel.--Wrought-iron.--Properties. -- +Salts of iron.--Change of valence and of color + +CHAPTER XLIX. + +LEAD AND TIN. + +Distribution of lead.--Poisonous properties.--Some lead +compounds.-- Tin + +CHAPTER L. + +COPPER, MERCURY, AND SILVER. + +Occurrence and uses of copper.--Compounds and uses of mercury.-- +Occurrence, reduction, and salts of silver + +CHAPTER LI. + +PHOTOGRAPHY. + +Description. + +CHAPTER LII. + +PLATINUM AND GOLD. + +Methods of obtaining, and uses + +CHAPTER LIII. + +CHEMISTRY OF ROCKS. + +Classification.--Composition.--Importance of siliceous rocks.-- +Soils.--Minerals.--The earth's interior.--Percentage of elements + +CHAPTER LIV. + +ORGANIC CHEMISTRY. + +Comparison of organic and inorganic compounds.--Molecular +differences.--Synthesis of organic compounds.--Marsh-gas. +series.---Alcohols.--Ethers.--Other substitution products. -- +Olefines and other series. + +CHAPTER LV. + +ILLUMINATING GAS. + +Source, preparation, purification, and composition.--Natural gas + +CHAPTER LVI. + +ALCOHOL. + +Fermented and distilled liquors.--Effect on the system.--Affinity +for water.--Purity + +CHAPTER LVII + +OILS, FATS, AND SOAPS. + +Sources and kinds of oils and fats.--Saponification.--Manufacture +and action of soap.--Glycerin, nitro-glycerin, and dynamite. -- +Butter and oleomargarine. + +CHAPTER LVIII + +CARBO-HYDRATES. + +Sugars.--Glucose.--Starch.--Cellulose.--Gun-cotton.--Dextrin. -- +Zylonite + +CHAPTER LIX. + +CHEMISTRY OF FERMENTATION. + +Ferments.--Alcoholic, acetic, and lactic fermentation.-- +Putrefaction.--Infectious diseases + +CHAPTER LX. + +CHEMISTRY OF LIFE. + +Growth of minerals and of organic life.--Food of plants and of +man.--Conservation of energy and of matter + +CHAPTER LXI. + +THEORIES. + +The La Place theory--Theory of evolution--New theory of chemistry + +CHAPTER LXII + +GAS VOLUMES AND WEIGHTS. + +Quantitative experiments with oxygen and hydrogen--Problems + + + +AN INTRODUCTION TO CHEMICAL SCIENCE + + + +CHAPTER I. + +THE METRIC SYSTEM. + +1. The Metric System is the one here employed. A sufficient +knowledge of it for use in the study of this book may be gained +by means of the following experiments, which should be performed +at the outset by each pupil. + +2. Length. + +Experiment 1.--Note the length of 10 cm. (centimeters) on a +metric ruler, as shown in Figure 1. Estimate by the eye alone +this distance on the cover of a book, and then verify the result. +Do the same on a t.t. (test-tube). Try this several times on +different objects till you can carry in mind a tolerably accurate +idea of 10 cm. About how many inches is it? + +In the same way estimate the length of 1 cm, verifying each +result. How does this compare with the distance between two blue +lines of foolscap? Measure the diameter of the old nickel five- +cent piece. + +Next, try in the same way 5 cm. Carry each result in mind, taking +such notes as may be necessary. + +(Fig. 1) + +3. Capacity. + +Experiment 2.--Into a graduate, shown in Figure 2, holding 25 or +50 cc. (cubic centimeters) put 10 cc. of water; then pour this into +a t.t. Note, without marking, what proportion of the latter is +filled; pour out the water, and again put into the t.t. the same +quantity as nearly as can be estimated by the eye. Verify the +result by pouring the water back into the graduate. Repeat +several times until your estimate is quite accurate with a t.t. +of given size. If you wish, try it with other sizes. Now estimate +1 cc. of a liquid in a similar way. Do the same with 5 cc. + +A cubic basin 10 cm on a side holds a liter. A liter contains +1,000 cc. If filled with water, it weighs, under standard +conditions, 1,000 grams. Verify by measurement. + +4. Weight. + +Experiment 3.--Put a small piece of paper on each pan of a pair +of scales. On one place a 10 g. (gram) weight. Balance this by +placing fine salt on the other pan. Note the quantity as nearly +as possible with the eye, then remove. Now put on the paper what +you think is 10 g. of salt. Verify by weighing. Repeat, as before, +several times. Weigh 1 g., and estimate as before. Can 1 g. of +salt be piled on a one-cent coin? Experiment with 5 g. + +5. Resume--Lengths are measured in centimeters, liquids in cubic +centimeters, solids in grams. In cases where it is not convenient +to measure a liquid or weigh a solid, the estimates above will be +near enough for most experiments herein given. Different solids +of the same bulk of course differ in weight, but for one gram +what can be piled on a one-cent piece may be called a +sufficiently close estimate. The distance between two lines of +foolscap is very nearly a centimeter. A cubic centimeter is seen +in Figure 1. Temperatures are recorded in the centigrade scale. + +CHAPTER II. + +WHAT CHEMISTRY IS. + +6. Divisibility of Matter. + +Experiment 4.--Examine a few crystals of sugar, and crush them +with the fingers. Grind them as fine as convenient, and examine +with a lens. They are still capable of division. Put 3 g. of +sugar into a t.t., pour over it 5 cc. of water, shake well, boil +for a minute, holding the t.t. obliquely in the flame, using for +the purpose a pair of wooden nippers (Fig. 3). If the sugar does +not disappear, add more water. When cool, touch a drop of the +liquid to the tongue. Evidently the sugar remains, though in a +state too finely divided to be seen. This is called a solution, +the sugar is said to be soluble in water, and water to be a +solvent of sugar. + +(Fig 3.) + +Now fold a filter paper, as in Figure 4, arrange it in a funnel +(Fig. 5), and pour the solution upon it, catching what passes +through, which is called the filtrate, in another t.t. that rests +in a receiver (Fig. 5). After filtering, notice whether any +residue is left on the filter paper. Taste a drop of the +filtrate. Has sugar gone through the filter? If so, what do you +infer of substances in solution passing through a filter? Save +half the filtrate for Experiment 5, and dilute the other half +with two or three times its own volume of water. Shake well, and +taste. + +(Fig 4.) + +(Fig 5.) We might have diluted the sugar solution many times +more, and still the sweet taste would have remained. Thus the +small quantity of sugar would be distributed through the whole +mass, and be very finely divided. + +By other experiments a much finer subdivision can be made. A +solution of.00000002 g. of the red coloring matter, fuchsine, in +1 cc. of alcohol gives a distinct color. + +Such experiments would seem to indicate that there is no limit to +the divisibility of matter. But considerations which we cannot +discuss here lead to the belief that such a limit does exist; +that there are particles of sugar, and of all substances, which +are incapable of further division without entirely changing the +nature of the substance. To these smallest particles the name +molecules is given. + +A mass is any portion of a substance larger than a molecule; it +is an aggregation of molecules. + +A molecule is the smallest particle of a substance that can exist +alone. + +A substance in solution may be in a more finely divided state +than otherwise, but it is not necessarily in its ultimate state +of division. + +7. A Chemical Change.--Cannot this smallest particle of sugar, +the molecule, be separated into still smaller particles of +something else? May it not be a compound body, and will not some +force separate it into two or more substances? The next +experiment will answer the question. + +Experiment 5.--Take the sugar solution saved from Experiment 4, +and add slowly 4 cc.of strong sulphuric acid. Note any change of +color, also the heat of the t.t. Add more acid if needed. + +A substance entirely different in color and properties has been +formed. Now either the sugar, the acid, or the water has +undergone a chemical change. It is, in fact, the sugar. But the +molecule is the smallest particle of sugar possible. The acid +must have either added something to the sugar molecules, or +subtracted something from them. It was the latter. Here, then, is +a force entirely different from the one which tends to reduce +masses to molecules. The molecule has the same properties as the +mass. Only a physical force was used in dissolving the sugar, and +no heat was liberated. The acid has changed the sugar into a +black mass, in fact into charcoal or carbon, and water; and heat +has been produced. A chemical change has been brought about. + +From this we see that molecules are not the ultimate divisions of +matter. The smallest sugar particles are made up of still smaller +particles of other things which do not resemble sugar, as a word +is composed of letters which alone do not resemble the word. But +can the charcoal itself be resolved into other substances, and +these into still others, and so on? Carbon is one of the +substances from which nothing else has been obtained. There are +about seventy others which have not been resolved. These are +called elements; and out of them are built all the compounds-- +mineral, vegetable, and animal--which we know. + +8. An element is a chemically indivisible substance, or one from +which nothing else can be extracted. + +A compound is a substance which is made up of elements united in +exact proportions by a force called chemism, or chemical +affinity. + +A mixture is composed of two or more elements or compounds +blended together, but not held by any chemical attraction. + +To which of these three classes does sugar belong? Carbon? The +solution of sugar in water? + +Carbon is an element; we call its smallest particle an atom. + +An atom is the smallest particle of an element that can enter +into combination. Atoms are indivisible and usually do not exist +alone. Both elements and compounds have molecules. + +The molecule of an element usually contains two atoms; that of a +compound may have two, or it may have hundreds. For a given +compound the number is always definite. + +Chemism is the force that binds atoms together to form molecules. +The sugar molecule contains atoms, forty-five in all, of three +different elements: carbon, hydrogen, and oxygen. That of salt +has two atoms: one of sodium, one of chlorine. Should we say "an +atom of sugar"? Why? Of what is a mass of sugar made up? A +molecule? A mass of carbon? A molecule? Did the chemical affinity +of the acid break up masses or molecules? In this respect it is a +type of all chemical action. The distinction between physics and +chemistry is here well shown. The molecule is the unit of the +physicist, the atom that of the chemist. However large the masses +changed by chemical action, that action is always on the +individual molecule, the atoms of which are separated. If the +molecule were an indivisible particle, no science of chemistry +would be possible. The physicist finds the properties of masses +of matter and resolves them into molecules, the chemist breaks up +the molecule and from its atoms builds up other compounds. + +Analysis is the separation of compounds into their elements. + +Synthesis is the building up of compounds from their elements. + +Of which is the sugar experiment an example? Metathesis is an +exchange of atoms in two different compounds; it gives rise to +still other compounds. + +A chemical change may add something to a substance, or subtract +something from it, or it may both subtract and add, making a new +substance with entirely different properties. Sulphur and carbon +are two stable solids. The chemical union of the two forms a +volatile liquid. A substance may be at one time a solid, at +another a liquid, at another a gas, and yet not undergo any +chemical change, because in each case the chemical composition is +identical. + +State which of these are chemical changes: rusting of iron, +falling of rain, radiation of heat, souring of milk, evaporation +of water, decay of vegetation, burning of wood, breaking of iron, +bleaching of cloth. Give any other illustrations that occur to +you. + +Chemistry treats of matter in its simplest forms, and of the +various combinations of those simplest forms. + +CHAPTER III. + +MOLECULES AND ATOMS. + +9. Molecules are Extremely Small.--It has been estimated that a +liter of any gas at 0 degrees and 760 mm. pressure contains 10^24 +molecules, i.e. one with twenty-four ciphers. + +Thomson estimates that if a drop of water were magnified to the +size of the earth, and its molecules increased in the same +proportion, they would be larger than fine shot, but not so large +as cricket balls. + +A German has recently obtained a deposit of silver two-millionths +of a millimeter thick, and visible to the naked eye. The computed +diameter of the molecule is only one and a half millionths of a +millimeter. + +By a law of chemistry there is the same number of molecules in a +given volume of every gas, if the temperature and pressure are +the same. Hence, all gaseous molecules are of the same size, +including, of course, the surrounding space. They are in rapid +motion, and the lighter the gas the more rapid the motion. This +gives rise to diffusion. See page 114. + +10. We Know Nothing Definite of the Form of Molecules.--In this +book they will always be represented as of the same size, that of +two squares. A molecule is itself composed of atoms,--from two to +several hundred. The size of the atom of most elements we +represent by one square.11. Atoms.--If the gaseous molecules be +of the same size, it is clear that either the atoms themselves +must be condensed, or the spaces between them must be smaller +than before. We suppose the latter to be the case, and that they +do not touch one another, the same thing being true of molecules. +Atoms composing sugar must be crowded nearer together than those +of salt. These atoms are probably in constant motion in the +molecule, as the latter is in the mass. If we regard this square +as a mass of matter, the dots may represent molecules; if we call +it a molecule, the dots may be called atoms, though many +molecules have no more than two or three atoms. + +The following experiments illustrate the union of atoms to form +molecules, and of elements to form compounds. + +12. Union of Atoms. + +Experiment 6.--Mix, on a paper, 5 g. of iron turnings, and the +same bulk of powdered sulphur, and transfer them to an ignition +tube, a tube of hard glass for withstanding high temperatures. +Hold the tube in the flame of a burner till the contents have +become red-hot. After a minute break it by holding it under a jet +of water. Put the contents into an evaporating-dish, and look for +any uncombined iron or sulphur. Both iron and sulphur are +elements. Is this an example of synthesis or of analysis? Why? Is +the chemical union between masses of iron and sulphur, or between +molecules, or between atoms? Is the product a compound, an +element, or a mixture? + +Experiment 7.--Try the same experiment, using copper instead of +iron. The full explanation of these experiments is given on page +13. + +CHAPTER IV. + +ELEMENTS AND BINARIES. + +13. About Seventy Different Elements are now recognized, half of +which have been discovered within little more than a century. +These differ from one another in (1) atomic weight, (2) physical +and chemical properties, (3) mode of occurrence, etc. Page 12 +contains the most important elements. + +The symbol of an element is usually the initial letter or letters +of its Latin name, and stands for one atom of the element. C is +the symbol for carbon, and represents one atom of it. O means one +atom of oxygen.[The symbols of elements will also be used in this +book to stand for an indefinite quantity of them; e.g. O will be +used for oxygen in general as well as for one atom. The text will +readily decide when symbols have a definite meaning, and when +they are used in place of words.] Write, explain, and memorize +the symbols of the elements in heavy type. + +14. The Atomic Weight of an element is the weight of its atom +compared with that of hydrogen. H is taken as the standard +because it has the least atomic weight. The atomic weight of O is +16, which means that its atom weighs 16 times as much as the H +atom. Every symbol, then, stands for a definite weight of the +element, i.e. its atomic weight, as well as for its atom. + +How much bromine by weight does Br stand for? What do these +symbols mean--As, Na, N, P? If O represents one atom, how much +does O2 or 2 O stand for? How much by weight? Most elements have +two atoms in the molecule. How many molecules in 6 H? 10 N? S8? +I20? + +The symbol of a compound is formed by writing in succession the +symbols of the elements of which it is composed. How many atoms +in the following molecules, and how many of each element: C2H60? +HNO3? PbSO4? MgCl2? (Hg2(NO3)2?) + +15. The Simplest Compounds are Binaries.--A binary is a substance +composed of two elements; e.g. common salt, which is a compound +of sodium and chlorine. Its symbol is NaCl, its chemical name +sodium chloride. The ending ide is applied to the last name of +binaries. How many parts by weight of Na and of Cl in NaCl? What +is the molecular weight, i.e. the weight of its molecule? Name +KCl. How many atoms in its molecule? Parts by weight of each +element? Molecular weight? Does the symbol stand for more than +one molecule? How many molecules in 4 NaCl? How many atoms of Na +and of Cl? Name these: HCl, NaBr, NaI, KBr, AgCl, AgI, HBr, HI, +HF, HgO, ZnO, ZnS, MgO, CaO. Compute the proportion by weight of +each element in the last three. + +A coefficient before the symbol of a compound includes all the +elements of the symbol, and shows the number of molecules. How +many in these: 6 KBr? 3 Sn0? 12 NaCl? How many atoms of each +element in the above? + +An exponent, always written below, applies only to the element +after which it is written, and shows the number of atoms. Explain +these: AuCl3, ZnCl2, Hg2Cl2. + +Write symbols for four molecules of sodium bromide, one of silver +iodide (always omit coefficient one), eight of potassium bromide, +ten of hydrogen chloride; also for one molecule of each of these: +hydrogen fluoride, potassium iodide, silver chloride. + +In all the above cases the elements have united atom for atom. +Some elements will not so unite. In CaCl2 how many atoms of each +element? Parts by weight of each? Give molecular weight. Is the +size of the molecule thereby changed? Name these, give the number +of atoms of each element in the molecule, and the proportion by +weight, also their molecular weights: AuCl3, ZnCl2, MnCl2, Na2O, +K2S, H3P, H4C. + +Principal Elements. +Name. Sym. At. Wt. Valence. Vap.D. At.Vol. Mol.Vol. State. +Aluminium Al 27. II, IV ... ... ... Solid +Antimony Sb 120. III, V. ... ... ... " +Arsenic As 75. III, V 150. " +Barium Ba 137. II ... ... ... " +Bismuth Bi 210. III, V ... ... ... " +Boron B 11. III ... ... ... " +Bromine Br 80. I, (V) 80. Liquid +Cadmium Cd 112. II 56. Solid +Calcium Ca 40. II ... ... ... " +Carbon C 12. (II), IV ... ... ... " +Chlorine Cl 35.5 I, (V) 35.5 Gas +Chromium Cr 52. (II),IV,VI ... ... ... Solid +Cobalt Co 59. II, IV ... ... ... Gas +Copper Cu 63. I, II ... ... ... " +Fluorine F 19. I, (V) ... ... ... Gas +Gold Au 196. (I), III ... ... ... Solid +Hydrogen H 1. I 1. Gas +Iodine I 127. I, (V) 127. ... ... Solid +Iron Fe 56. II,IV,(VI) ... ... ... " +Lead Pb 206. II, IV ... ... ... " +Lithium Li 7. I ... ... ... " +Magnesium Mg 24. II ... ... ... " +Manganese Mn 55. II, IV, VI ... ... ... " +Mercury Hg 200. I, II 100. Liquid +Nickel Ni 59. II, IV ... ... ... Solid +Nitrogen N 14. (I),III,V 14. Gas +Oxygen O 16. II 16. " +Phosphorus P 31. (I),III, V 62. Solid +Platinum Pt 197. (II), IV ... ... ... " +Potassium K 39. I ... ... ... " +Silicon Si 28. IV ... ... ... " +Silver Ag 108. I ... ... ... " +Sodium Na 23. I ... ... ... " +Strontium Sr 87. II ... ... ... " +Sulphur S 32. II,IV,(VI) 32(96) " +Tin Sn 118. II, IV ... ... ... " +Zinc Zn 65. II 32.5 " + +If more than one atom of an element enters into the composition +of a binary, a prefix is often used to denote the number. SO2 is +called sulphur dioxide, to distinguish it from SO3, sulphur +trioxide. Name these: CO2, SiO2, MnO2. The prefixes are: mono or +proto, one; di or bi, two; tri or ter, three; tetra, four; pente, +five; hex, six; etc. Diarsenic pentoxide is written, As2O5. +Symbolize these: carbon protoxide, diphosphorus pentoxide, +diphosphorus trioxide, iron disulphide, iron protosulphide. Often +only the prefix of the last name is used. + +16. An Oxide is a Compound of Oxygen and Some Other Element, as +HgO. What is a chloride? Define sulphide, phosphide, arsenide, +carbide, bromide, iodide, fluoride. + +In Experiment 6, where S and Fe united, the symbol of the product +was FeS. Name it. How many parts by weight of each element? What +is its molecular weight? To produce FeS a chemical union took +place between each atom of the Fe and of the S. We may express +this reaction, i.e. chemical action, by an equation:-- + + + Iron + Sulphur = Iron Sulphide +Or, using symbols Fe + S = FeS +Using atomic weights, 56 32 = 88. + + +These equations are explained by saying that 56 parts by weight +of iron unite chemically with 32 parts by weight of sulphur to +produce 88 parts by weight of iron sulphide. This, then, +indicates the proportion of each element which combines, and +which should be taken for the experiment. If 56 g. of Fe be used, +32 g. of S should be taken. If we use more than 56 parts of Fe +with 32 of S, will it all combine? If more than 32 of S with 56 +of Fe? There is found to be a definite quantity of each element +in every chemical compound. Symbols would have no meaning if this +were not so. + +Write and explain the equation for the experiment with copper and +sulphur, using names, symbols, and weights, as above. + +CHAPTER V. + +MANIPULATION. + +17. To Break Glass Tubing. + +Experiment 8.--Lay the tubing on a flat surface, and draw a sharp +three-cornered file two or three times at right angles across it +where it is to be broken, till a scratch is made. Take the tube +in the hands, having the two thumbs nearly opposite the scratch, +and the fingers on the other side. Press outward quickly with the +thumbs, and at the same time pull the hands strongly apart, and +the tubing should break squarely at the scratch. + +To break large tubing, or cut off bottles, lamp chimneys, etc., +first make a scratch as before; then heat the handle of a file, +or a blunt iron--in a blast-lamp flame by preference--till it is +red-hot, and at once press it against the scratch till the glass +begins to crack. The fracture can be led in any direction by +keeping the iron just in front of it. Re-heat the iron as often +as necessary. + +18. To Make Ignition-Tubes. + +Experiment 9.--Hold the glass tubing between the thumb and +forefinger of each hand, resting it against the second finger. +Heat it in the upper flame, slowly at first, then strongly, but +heat only a very small portion in length, and keep it in constant +rotation with the right hand. Hold it steadily, and avoid +twisting it as the glass softens. The yielding is detected by the +yellow flame above the glass and by an uneven pressure on the +hands. Pull it a little as it yields, then heat a part just at +one side of the most softened portion. Rotate constantly without +twisting, and soon it can be separated into two closed tubes. No +thread should be attached; but if there be one, it can be broken +off and the end welded. The bottom can be made more symmetrical +by heating it red-hot, then blowing, gradually, into the open +end, this being inserted in the mouth. The parts should be +annealed by holding above the flame for a short time, to cool +slowly. + +For hard glass--Bohemian--or large tubes, the blast-lamp or +blowpipe is needed. In the blast-lamp air is forced out with +illuminating gas. This gives a high degree of heat. Bulbs can be +made in the same way as ignition-tubes, and thistle-tubes are +made by blowing out the end of a heated bulb, and rounding it +with charcoal. + +19. To Bend Glass Tubing. + +Experiment 10.--Hold the tube in the upper flame. Rotate it so as +to heat all parts equally, and let the flame spread over 3 or 4 +cm. in length. When the glass begins to yield, without removing +from the flame slowly bend it as desired. Avoid twisting, and be +sure to have all parts in the same plane; also avoid bending too +quickly, if you would have a well-rounded joint. Anneal each bend +as made. Heated glass of any kind should never be brought in +contact with a cool body. For making O, H, etc., a glass tube -- +delivery-tube--50 cm. long should have three bends, as in Figure +6. The pupil should first experiment with short pieces of glass, +10 or 15 cm. long. An ordinary gas flame is the best for bending +glass. + +20. To Cut Glass. + +Experiment 11.--Lay the glass plate on a flat surface, and draw a +steel glass-cutter--revolving wheel--over it, holding this +against a ruler for a guide, and pressing down hard enough to +scratch the glass. Then break it by holding between the thumb and +fingers, having the thumbs on the side opposite to the scratch, +and pressing them outward while bending the ends of the glass +inward. The break will follow the scratch. + +Holes can be bored through glass and bottles with a broken end of +a round file kept wet with a solution of camphor in oil of +turpentine. + +21. To Perforate Corks. + +Experiment 12.--First make a small hole in the cork with the +pointed handle of a round--rat-tail--file. Have the hole +perpendicular to the surface of the cork. This can be done by +holding the cork in the left hand and pressing against the larger +surface, or upper part, of the cork, with the file in the right +hand. Only a mere opening is made in this way, which must be +enlarged by the other end of the file. A second or third file of +larger size may be employed, according to the size of the hole to +be made, which must be a little smaller than the tube it is to +receive, and perfectly round. + +CHAPTER VI. + +OXYGEN. + +22. To Obtain Oxygen. + +Experiment 13.--Take 5 g. of crystals of potassium chlorate +(KClO3) and, without pulverizing, mix with the same weight of +pure powdered manganese dioxide (MnO2). Put the mixture into a +t.t., and insert a d.t.--delivery-tube--having the cork fit +tightly. Hang it on a r.s.--ring-stand,-- as in Figure 7, having +the other end of the d.t. + +(Fig 7.) + +under the shelf, in a pneumatic trough, filled with water just +above the shelf. Fill three or more receivers--wide-mouthed +bottles--with water, cover the mouth of each with a glass plate, +invert it with its mouth under water, and put it on the shelf of +the trough, removing the plate. No air should be in the bottles. +Have the end of the d.t. so that the gas will rise through the +orifice. Hold a lighted lamp in the hand, and bring the flame +against the mixture in the t.t. Keep + +the lamp slightly in motion, with the hand, so as not to break +the t.t. by over-heating in one place. Heat the mixture strongly, +if necessary. The upper part of the t.t. is filled with air: +allow this to escape for a few seconds; then move a receiver over +the orifice, and fill it with gas. As soon as the lamp is taken +away, remove the d.t. from the water. The gas contracts, on +cooling, and if not removed, water will be drawn over, and the +t.t. will be broken. Let the t.t. hang on the r.s. till cool. + +With glass plates take out the receivers, leaving them covered, +mouth upward (Fig. 8), with little or no water inside. When cool, +the t.t. may be cleaned with water, by covering its mouth with +the thumb or hand, and shaking it vigorously. + +What elements, and how many, in KClO3? In Mn02? It is evident +that each of these compounds contains O. Why, then, could we not +have taken either separately, instead of mixing the two? This +could have been done at a sufficiently high temperature. Mu02 +requires a much higher temperature for dissociation, i.e. +separation into its elements, than KClO3, while a mixture of the +two causes O to come off from KClO3 at a lower temperature than +if alone. It is not known that Mn02 suffers any change. + +Each molecule of potassium chlorate undergoes the following +change:-- + + +Potassium Chlorate = Potassium Chloride + Oxygen +KClO3 = KCl + 3 O. + + +Is this analysis or synthesis? Complete the equation, by using +weights, and explain it. Notice whether the right- hand member of +the equation has the same number of atoms as the left. Has +anything been lost or gained? What element has heat separated? +Does the experiment show whether O is very soluble in water? How +many grams of O are obtainable from 122.58 g. KCIO3? PROPERTIES. + +23. Combustion of Carbon. + +OXYGEN Experiment 14.--Examine the gas in one of the receivers. +Put a lighted splinter into the receiver, sliding along the glass +cover. Remove it, blow it out, and put in again while glowing. Is +it re-kindled? Repeat till it will no longer burn. Is the gas a +supporter of combustion? How did the combustion compare with that +in air? Is it probable that air is pure O? Why did the flame at +last go out? Has the O been destroyed, or chemically united with +something else? + +Wood is in part C. CO2 is formed by the combustion; name it. The +equation is C + 2O = CO2. Affix the names and weights. Is CO2 a +supporter of combustion? Note that when C is burned with plenty +of O, CO2 is always formed, and that no matter how great the +conflagration, the union is atom by atom. Combustion, as here +shown, is only a rapid union of O with some other substance, as C +or H. + +24. Combustion of Sulphur. + +Experiment 15.--Hollow out one end of a piece of electric-light +pencil, or of crayon, 3 cm. long, and attach it to a Cu wire +(Fig. 9). Put into this a piece of S as large as a pea, ignite it +by holding in the flame, and then hold it in a receiver of O. +Note the color and brightness of the flame, and compare with the +same in the air. Also note the color and odor of the product. The +new gas is SO2. Name it, and write the equation for its +production from S and O. How do you almost daily perform a +similar experiment? Is the product a supporter of combustion? + +25. Combustion of Phosphorus. + +Experiment 16.--With forceps, which should always be used in +handling this element, put a bit of P, half as large as the S +above,into the crayon, called a deflagrating-spoon. Heat another +wire, touch it to the P, and at once lower the latter into a +receiver of O. Notice the combustion, the color of the flame and +of the product. After removing, be sure to burn every bit of P by +holding it in a flame, as it is liable to take fire if left. The +product of the combustion is a union of what two elements? Is it +an oxide? Its symbol is P2O5. Write the equation, using symbols, +names, and weights. Towards the close of the experiment, when the +O is nearly all combined, P2O3 is formed, as it is also when P +oxidizes at a low temperature. Name it and write the equation. + +26. Combustion of Iron. + +Experiment 17.--Take in the forceps a piece of iron picture-cord +wire 6 or 8cm long, hold one end in the flame for an instant, +then dip it into some S. Enough S will adhere to be set on fire +by holding it in the flame again. Then at once dip it into a +receiver of O with a little water in the bottom. The iron will +burn with scintillations. Is this analysis or synthesis? What +elements combine? A watch-spring, heated to take out the temper, +may be used, but picture-wire is better. + +The product is Fe3O4. Write the equation. How much Fe by weight +in the formula? How much O? What per cent by weight of Fe in the +compound? Multiply the fractional part by 100. What per cent of +0? Whatper cent of C0 .is C? O2? Find the percentage composition +of SO2. P2O5. + +From the last five experiments what do you infer of the tendency +of O to unite with other elements? + +27. Oxygen is a Gas without Color, Odor, or Taste. + +It is chemically a very active element; that is, it unites with +almost everything. Fluorine is the only element with which it +will not combine. When oxygen combines with a single element, +what is the compound called? We have found that O makes up a +certain portion of the air; later, we shall see how large the +proportion is. Its tendency to combine with almost everything is +a reason for the decay, rust, and oxidation of so many +substances, and for conflagrations, great and small. New +compounds are thusformed, of which O constitutes one factor. +Water, H2O, is only a chemical union of O and H. Iron rust, Fe2O3 +and H2O, is composed of O, Fe, and water. The burning of wood or +of coal gives rise to carbon dioxide, CO2, and water. Decay of +animal and vegetable matter is hastened by this all-pervading +element. O forms a portion of all animal and vegetable matter, of +almost all rocks and minerals, and of water. It is the most +abundant of all elements, and makes up from one-half to two- +thirds of the earth's surface. Compute the proportion of it, by +weight, in water, H2O. It is the union of O in the air with C and +H in our blood that keeps up the heat of the body and supports +life. See page 81. + +There are many ways of preparing this element besides the one +given above. It may be obtained from water (Experiment 38) and +from many other compounds, e.g. by heating mercury oxide, +HgO. + +CHAPTER VII. + +NITROGEN. + +28. Separation. + +Experiment 18.--Fasten a piece of electric-light pencil, or of +crayon, to a wire, as in Experiment 15, and bend the wire so it +will reach half-way to the bottom of a receiver. Using forceps, +put into the crayon a small piece of phosphorus. Pass the wire up +through the orifice in the shelf of a p.t. (pneumatic trough), +having water at least l cm. above the shelf. Heat another wire, +touch it to the P, and quickly invert an empty receiver over the +P, having the mouth under water, so as to admit no air (Fig. 10). +Let the P burn as long as it will, then remove the wire and the +crayon, letting in no air. Note the color of the product, and +leave till it is tolerably clear, then remove the receiver with a +glass plate, leaving the water in the bottom. + +Do the fumes resemble those of Experiment 16? Does it seem likely +(Fig 10.) that part of the air is O? Why a part only? Find what +proportion of the receiver is filled with water by measuring the +water with a graduate; then fill it with water and measure that; +compute the percentage which the former is of the latter. What +proportion of the air, then, is O? What was the only means of +escape for the P2O6, and P2O2 formed? These products are solids. +Are they soluble in water? Compute the percentage composition, +always by weight, of P2O2 and P2O5. + +The gas left in the receiver is evidently not O. Experiment 19 +will prove this conclusively, and show the properties of the new +gas. + +29. Properties. + +Experiment 19.--When the white cloud has disappeared, slide the +plate along, and insert a burning stick; try one that still +glows. + +See whether the P and S on the end of a match will burn. Is the +gas a supporter of combustion? Since it does not unite with C, +S, or P, is it an active or a passive element? Compare it with +O. Air is about 14 1/2 times as heavy as H. Which is heavier, air +or N? See page 12. Air or O? + +Write out the chief properties, physical and chemical, of N, as +found in this experiment. + +30. Inactivity of N.--N will scarcely unite chemically except on +being set free from compounds. It has, however, an intense +affinity for boron, and will even go through a carbon crucible to +unite with it. It is not combined with O in the air; but the two +form a mixture (page 86), of which N makes up four-fifths, its +use being to dilute the O. What would be the effect, in case of a +fire, if air were pure O? What effect on the human system? + +Growing plants need a great deal of N, but they are incapable of +making use of that in the air, on account of the chemical +inactivity of the element. Their supply comes from compounds in +earth, water, and air. By reason of its inertness N is very +easily set free from its compounds. For this reason it is a +constituent of most explosives, as gunpowder, nitro-glycerine, +dynamite, etc. These solids, by heat or concussion, are suddenly +changed to gases, which thereby occupy much more space, causing +an explosion. + +Nitrogen exists in many compounds, such as the nitrates; but the +great source of it all is the atmosphere. See page 85. + +CHAPTER VIII. + +HYDROGEN. + +31. Preparation. + +Experiment 20.--Prepare apparatus as for making O. Be sure that +the cork perfectly fits both d.t. and t.t., or the H will escape. +Cover 5 g. granulated Zn, in the t.t., with 10 cc. H2O, and add 5 +cc. chlorhydric acid, HCl. Adjust as for O (Fig. 7), except that +no heat is to be applied. If the action is not brisk enough, add +more HCl. Collect several receivers of the gas over water, adding +small quantities of HCl when necessary. Observe the black +floating residuum; it is carbon, lead, etc. With a glass plate +remove the receivers, keeping them inverted (Fig. 11), or the H +will escape. + +32. The Chemical Change is as follows:-- + +Zinc + hydrogen chloride = zinc chloride + hydrogen. + +Zn + 2 HCl = ZnCl2 + 2H. + +Complete by adding the weights, and explain. Notice that the +water does not take part in the change; it is added to dissolve +the ZnCl2 formed, and thus keep it from coating the Zn and +preventing further action of the acid. Note also that Zn has +simply changed places with H, one atom of the former having +driven off two atoms of the latter. The H, having nothing to +unite with, is set free as a gas, and collected over water. Of +course Zn must have a stronger chemical affinity for Cl than H +has, or the change could not have taken place. Why one Zn atom +replaces two H atoms will be explained later, asfar as an +explanation is possible. This equation, should be studied +carefully, as a type of all equations. The left-hand member shows +what were taken, i.e. the factors; the right-hand shows what were +obtained, i.e. the products. H2SO4 might have been used instead +of HCl. In that case the reaction, or equation, would have been: +-- + +Zinc + hydrogen sulphate = zinc sulphate + hydrogen. + +Zn + H2SO4 = ZnSO4 + 2H. + +Iron might have been used instead of zinc, in which case the +reactions would have been:-- + +Iron + hydrogen chloride = iron chloride + hydrogen. + +Fe + 2 HCl = FeCl2 + 2 H. + +Iron + hydrogen sulphate = iron sulphate + hydrogen. + +Fe + H2SO4 = FeSO4 + 2 H. + +Write the weights and explain the equations. The latter should be +memorized. + +33. Properties. + +Experiment 21.--Lift with the left hand a receiver of H, still +inverted, and insert a burning splinter with the right (Fig. 12). +Does the splinter continue to burn? Does the gas burn? If so, +where? Is the light brilliant? Note the color of the flame. Is +there any explosion? Try this experiment with several receivers. +Is the gas a supporter of combustion? i.e. will carbon burn in +it? Is it combustible? i.e. does it burn? If so, it unites with +some part of the air. With what part?34. Collecting H by Upward +Displacement. + +Experiment 22.--Pass a d.t. from a H generator to the top of a +receiver or t.t. (Fig. 13). The escaping H being so much lighter +than air will force the latter down. To obtain the gas unmixed +with air, the d.t. should tightly fit a cardboard placed under +the mouth of the receiver. When filled, the receiver can be +removed, inverted as usual, and the gas tested. In this and other +experiments for generating H, a thistle-tube, the end of which +dips under the liquid, can be used for pouring in acid, as in +Figure 13. + +35. Philosopher's Lamp and Musical Flame. + +Experiment 23.--Fit to a cork a piece of glass tubing 10 or 15 +cm. long, having the outer end drawn out to a point with a small +opening, and insert it in the H generator. Before igniting the +gas at the end of the tube take the, precaution to collect a t.t. +of it by upward displacement, and bring this in contact with a +flame. If a sharp explosion ensues, air is not wholly expelled +from the generator, and it would be dangerous to light the gas. +When no sound, or very little, follows, light the escaping gas. +The generation of H must not be too rapid, neither should the +t.t. be held under the face, as the cork is liable to be forced +out by the pressure of H. A safety-tube, similar to the thistle- +tube above, will prevent this. This apparatus is called the +"philosopher's lamp." Thrust the flame into a long glass tube 1- +1/2 to 3 cm. in diameter, as shown in Figure 14, and listen for a +musical note. + +36. Product of Burning H in Air. + +Experiment 24.--Fill a tube 2 or 3 cm. in diameter with calcium +chloride, CaCl2, and connect one end with a generator of H (Fig. +15). At the other end have a philosopher's lamp-tube.Observing +the usual precautions, light the gas and hold over it a receiver, +till quite a quantity of moisture collects. All water was taken +from the gas by the dryer, CaCl2. What is, therefore, the product +of burning H in air? Complete this equation and explain it: 2H + +O = ? Figure 16 shows a drying apparatus arranged to hold CaCl2. + +[Fig. 15][Fig. 16] + +37. Explosiveness of H. + +Experiment 25. -- Fill a soda-water bottle of thick glass with +water, invert it in a pneumatic trough, and collect not over 1/4 +full of H. Now remove the bottle, still inverted, letting air in +to fill the other 3/4. Mix the air and H by covering the mouth of +the bottle with the hand, and shaking well; then hold the mouth +of the bottle, slightly inclined, in a flame. Explain the +explosion which follows. If 3/4 was air, what part was O? What +use did the N serve? Note any danger in exploding H mixed with +pure O. What proportions of O and H by volume would be most +dangerously explosive? What proportion by weight? + +By the rapid union of the two elements, the high temperature +suddenly expanded the gaseous product, which immediately +contracted; both expansion and contraction produced the noise of +explosion. + +38. Pure H Is a Gas without Color, Odor, or Taste. + +--It is the lightest of the elements, 14 1/2 times as light +asair. It occurs uncombined in coal-mines, and some other places, +but the readiness with which it unites with other elements, +particularly O, prevents its accumulation in large quantities. It +constitutes two-thirds of the volume of the gases resulting from +the decomposition of water, and one-ninth of the weight. Compute +the latter from its symbol. It is a constituent of plants and +animals, and some rocks. Considering the volume of the ocean, the +total amount of H is large. It can be separated from H2O by +electrolysis, or by C, as in the manufacture of water gas. + +When burned with O it forms H2O. Pure O and H when burning give +great heat, but little light. The oxy-hydrogen blow-pipe (Fig. +17) is a device for producing the highest temperatures of +combustion. It has O in the inner tube and H in the outer. Why +would it not be better the other way? These unite at the end, and +are burned, giving great heat. A piece of lime put into the flame +gives the brilliant Drummond or calcium light. + +Chapter IX. UNION BY WEIGHT. + +39. In the Equation -- + +Zn + 2 HCl = ZnCl2 + 2 H +65 + 73 = 136 + 2 + +65 parts by weight of Zn are required to liberate 2 parts by weight of +H; or, by using 65 g Zn with 73 g HCl, we obtain 2 g H. If twice as +much Zn (130 g) were used, 4 g H could be obtained, with, of course, +twice as much HCl. With 260 g. Zn, how much H could be liberated? +A proportion may be made as follows:-- + +Zn given : Zn required :: H given : H required. +65 : 260 :: 2 : x. + +[footnote: Given, as here used, means the weight called for by the +equation; required means that called for by the question.] + +Solving, we have 8 g H. + +How much H is obtainable by using 5 g Zn, as in the experiment? + +To avoid error in solving similar problems, the best plan is as +follows:-- + +Zn + 2HCl = ZnCl2 + 2 H | 65:5::2:x +65 2 | 65 x = 10 +5 x | x = 10/65 = 2/13 Ans. 2/13 g. + +The equation should first be written; next, the atomic or molecular +weights which you wish to use, and only those, to avoid confusion; +then, on the third line, the quantity of the substance to be used, with +underneath the substance wanted. The example above will best +how this. This plan will prevent the possibility of error. The proportion +will then be:-- + +a given : a required :: b given : b required. + +How much Zn is required to produce 30 g. H? + +Zn + 2HCl = ZnCl2 + 2H | 2:30::65:x +65 2 | 2x = 1950 + x 30 | x = 975 Ans. 975 g. Zn. + +Solve:-- + +(1) How much Zn is necessary for 14 g. H? + +(2) How many pounds of Zn are necessary for 3 pounds of H? + +(3) How many grams of H from 17 g. of Zn? + +(4) How many tons of H from 1/2 ton of Zn? + +Suppose we wish to find how much chlorhydric acid--pure gas-- +will give 12 g. H. The question involves only HCl and H. Arrange +as follows:-- + +Zn + 2HCl = ZnCl2 + 2 H | H giv. : H req. :: HCl giv. : HCl req. + 73 2 | 2 : 12 :: 73 x + x 12 | 2x=876 x=438 + Ans. 438 g. HCl. + +Solve:-- + +(1) How much HCl is needed to produce 100 g. H? + +(2) How much H in 10 g. HCl? + +(3) How much ZnCl2 is formed by using 50 g. HCl? The question +is now between HCl and ZnCl2. + +Zn + 2HC1 = ZnCl2 + 2H + 73 136 | Arrange the proportion, and solve. + 50 x + +Suppose we have generated H by using H2S04: the equation is +Zn + H2S04 = ZnSO4 + 2 H. There is the same relation as before +between the quantities of Zn and of H, but the H2S04 and ZnS04 are +different. + +How much H2SO4 is needed to generate 12 g. H? + +Zn + H2SO4 = ZnS04 + 2 H + 98 2 | Make the proportion, and solve + x 12 + +Solve:-- + +(1) How much H in 200 g. H2S04? + +(2) How much ZnS04 is produced from 200 g. H2S04? +(3) How much H2S04 is needed for 7 1/2 g H? +(4) How much Zn will 40 g. H2SO4 combine with? +(5) How much Fe will 40 g. H2SO4 combine with? +(6) How much H can be obtained by using 75 g Fe? + +These principles apply to all reactions. Suppose, for example, we +wish to get l0 g. of O: how much KClO3 will it be necessary to use? +The reaction is:-- + +KClO3 = KCl + O3 | 48 : 10 :: 122.5 : x +122.5 48 | +x 10 | Ans. 25.5+ g. KClO3. + +The pupil should be required to make up problems of his own, +using various reactions, and to solve them. + +CHAPTER X. + +CARBON. + +Examine graphite, anthracite coal, bituminous coal, cannel coal, +wood, gas carbon, coke. + +40. Preparation of C. + +Experiment 26.--Hold a porcelain dish or a plate in the flame of +a candle, or of a Bunsen burner with the openings at the bottom +closed. After a minute examine the deposit. It is carbon, i.e. +lamp- black or soot, which is a constituent of gas, or of the +candle. Open the valve at the base of the Bunsen burner, and hold +the deposit in the flame. Does the C gradually disappear? If so, +it has been burned to CO2. C + 2 O = CO2. Is C a combustible +element? + +Experiment 27.--Ignite a splinter, and observe the combustion and +the smoke, if any. Try to collect some C in the same way as +before. + +With plenty of O and high enough temperature, all the C is burned +to CO2, whether in gas, candle, or wood. CO2 is an invisible gas. +The porcelain, when held in the flame, cools the C below the +point at which it burns, called the kindling-point, and hence it +is deposited. The greater part of smoke is unburned carbon. + +Experiment 28.--Hold an inverted dry t.t. or receiver over the +flame of a burning candle, and look for any moisture (H2O). What +two elements are shown by these experiments to exist in the +candle? The same two are found in wood and in gas. Experiment +29.--Put into a small Hessian crucible (Fig. 18) some pieces of +wood 2 or 3 cm long, cover with sand, and heat the crucible +strongly. When smoking stops, cool the crucible, remove the +contents, and examine the charcoal. The gases have been driven +off from the wood, and the greater part of what is left is C. + +Experiment 30.--Put 1 g. of sugar into a porcelain crucible, and +heat till the sugar is black. C is left. See Experiment 5. Remove +the C with a strong solution of sodium hydrate (page 208). + +41. Allotropic Forms.--Carbon is peculiar in that it occurs in at +least three allotropic, i.e. different, forms, all having +different properties. These are diamond, graphite, and amorphous +--not crystalline--carbon. The latter includes charcoal, lamp- +black, bone-black, gas carbon, coke, and mineral coal. All these +forms of C have one property in common; they burn in O at a high +temperature, forming CO2. This proves that each is the element C, +though it is often mixed with some impurities. + +Allotropy, or allotropism, is the quality which an element often +has of appearing under various forms, with different properties. +The forms of C are a good illustration. + +42. Diamond is the purest C; but even this in burning leaves a +little ash, showing that it is not quite pure. It is a rare +mineral, found in India, South Africa, and Brazil, and is the +hardest and most highly refractive to light of all minerals. +Boron is harder. [Footnote: B, not occurring free, is not a +mineral.] When heated in the electric arc, at very high +temperatures, diamond swells and turns black. 43. Graphite, or +Plumbago, is One of the Softest Minerals.--It is black and +infusible, and oxidizes only at very high temperatures, higher +than the diamond. It contains from 95 to 98 per cent C. Graphite +is found in the oldest rock formations, in the United States and +Siberia. It is artificially formed in the iron furnace. Graphite +is employed for crucibles where great heat is required, for a +lubricant, for making metal castings, and, mixed with clay, for +lead-pencils. It is often called black-lead. + +44. Amorphous Carbon comprises the following varieties. + +Charcoal is made by heating wood, for a long time, out of contact +with the air. The volatile gases are thus driven off from the +wood; what is left is C, and a small quantity of mineral matter +which remains as ash when the coal is burned. + +45. Lamp-black is prepared as in Experiment 26, or by igniting +turpentine (C1OH16), naphtha, and various oils, and collecting +the C of the smoke. It is used for making printers' ink, India +ink, etc. A very pure variety is obtained from natural gas. + +Bone-black, or animal charcoal, is obtained by distilling bones, +i.e. by heating them in retorts into which no air is admitted. +The C is the charred residue. + +Gas Carbon is formed in the retorts of the gas-house. See page +182. It is used to some extent in electrical work. + +46. Coke is the residue left after distilling soft coal. It is +tolerably pure carbon, with some ash and a little volatile +matter. It burns without flame. 47. Mineral Coal is fossilized +wood or other vegetable matter. Millions of years ago trees and +other vegetation covered the earth as they do to-day. In certain +places they slowly sank, together with the land, into the +interior of the earth, were covered with sand, rock, and water, +and heated from the earth's interior. A slow distillation took +place, which drove off some of the gases, and converted vegetable +matter into coal. All the coal dug from the earth represents +vegetable life of a former period. Millions of years were +required for the transformation; but the same change is in +progress now, where peat beds are forming from turf. + +Coal is found in all countries, the largest beds being in the +United States. From the nature of its formation, coal varies much +in purity. + +Anthracite, or hard coal, is purest in carbon, some varieties +having from 90 to 95 per cent. This represents most complete +distillation in the earth; i.e. the gases have mostly been driven +off. It is much used in New England. + +48. Bituminous, or soft coal, crocks the hands, and burns rapidly +with much flame and smoke. The greater part of the coal in the +earth is bituminous. It represents incomplete distillation. +Hence, by artificially distilling it, illuminating gas is made. +See page 180. It is far less pure C than anthracite. + +49. Cannel Coal is a variety of bituminous coal which can be +ignited like a candle. This is because so many of the gases are +still left, and it shows cannel to be less pure C than bituminous +coal. + +50. Lignite, Peat, Turf, etc., are still less pure varieties of +C. Construct a table of the naturally occurring forms of this +element, in the order of their purity. Carbon forms the basis of +all vegetable and animal life; it is found in many rocks, mineral +oils, asphaltum, natural gas, and in the air as CO2. + +51. C a Reducing Agent. + +Experiment 31.--Put into a small ignition-tube a mixture of 4 or +5 g. of powdered copper oxide (CuO), with half its bulk of +powdered charcoal. Heat strongly for ten or fifteen minutes. +Examine the contents for metallic copper. With which element of +CuO has C united? The reaction may be written: Cu0 + C = CO + Cu. +Complete and explain. + +A Reducing, or Deoxidizing, Agent is a substance which takes away +oxygen from a compound. C is the most common and important +reducing agent, being used for this purpose in smelting iron and +other ores, making water-gas, etc. + +An Oxidizing Agent is a substance that gives up its O to a +reducing agent. What oxidizing agent in the above experiment? + +52. C a Decolorizer. + +Experiment 32.--Put 3 or 4 g. of bone-black into a receiver, and +add 10 or 15 cc.of cochineal solution. Shake this thoroughly, +covering the bottle with the hand. Then pour the whole on a +filter paper, and examine the filtrate. If all the color is not +removed, filter again. What property of C is shown by this +experiment? Any other coloring solution may be tried. + +The decolorizing power of charcoal is an important +characteristic. Animal charcoal is used in large quantities for +decolorizing sugar. The coloring matter is taken out mechanically +by the C, there being no chemical action. 53. C a Disinfectant. + +Experiment 33.--Repeat the previous experiment, adding a solution +of H2S3 i.e. hydrogen sulphide, in water, instead of cochineal +solution. See page 120. Note whether the bad odor is removed. If +not, repeat. + +Charcoal has the property of absorbing large quantities of many +gases. Ill-smelling and noxious gases are condensed in the pores +of the C; O is taken in at the same time from the air, and these +gases are there oxidized and rendered odorless and harmless. For +this reason charcoal is much used in hospitals and sick-rooms, as +a disinfectant. This property of condensing O, as well as other +gases, is shown in the experiment below. + +54. C an Absorber of Gases and a Retainer of Heat. + +Experiment 34.--Put a piece of phosphorus of the size of a pea, +and well dried, on a thick paper. Cover it well with bone-black, +and look for combustion after a while. O has been condensed from +the air, absorbed by the C, and thus communicated to the P. Burn +all the P at last. + +VALENCE. + +55. The Symbols NaCl and MgCl2 differ in two ways.--What are +they? Let us see why the atom of Mg unites with two Cl atoms, +while that of Na takes but one. If the atoms of two elements +attract each other, there must be either a general attraction all +over their surfaces, or else some one or more points of +attraction. Suppose the latter to be true, each atom must have +one or more poles or bonds of attraction, like the poles of a +magnet. Different elements differ in their number of bonds. Na +has one, which may be written graphically Na-; Cl has one, -Cl. +When Na unites with Cl, the bonds of each element balance, as +follows: Na-Cl. The element Mg, however, has two such bonds, as +Mg= or -Mg-. When Mg unites with Cl, in order to balance, or +saturate, the bonds, it is evident that two atoms of Cl must be +used, as Cl-Mg-Cl, or MgCl2. + +A compound or an element, in order to exist, must have no free +bonds. In organic chemistry the exceptions to this rule are very +numerous, and, in fact, we do not know that atoms have bonds at +all; but we can best explain the phenomena by supposing them, and +for a general statement we may say that there must be no free +bonds. In binaries the bonds of each element must balance. + +56. The Valence, Quantivalence, of an Element is its Combining +Power Measured by Bonds.--H, having the least number of bonds, +one, is taken as the unit. Valence has always to be taken into +account in writing the symbol of a compound. It is often written +above and after the elements [i.e. written like an exponent], as +K^I, Mg^II. + +An element having a valence of one is a monad; of two, a dyad; +three, a triad; four, tetrad; five, pentad; six, hexad, etc. It +is also said to be monovalent, di- or bivalent, etc. This theory +of bonds shows why an atom cannot exist alone. It would have free +or unused bonds, and hence must combine with its fellow to form a +molecule, in case of an element as well as in that of a compound. +This is illustrated by these graphic symbols in which there are +no free bonds: H-H, O=O, N[3-bond symbol]N, C[4-bond symbol]C. A +graphic symbol shows apparent molecular structure. + +After all, how do we know that there are twice as many Cl atoms +in the chloride of magnesium as in that of sodium? The compounds +have been analyzed over and over again, and have been found to +correspond to the symbols MgCl2 and NaCl. This will be better +understood after studying the chapter on atomic weights. In +writing the symbol for the union of H with O, if we take an atom +of each, the bonds do not balance, H-=O, the former having one; +the latter, two. Evidently two atoms of H are needed, as H-O-H, +or + +H + = O , or H2O. In the union of Zn and O, each has two bonds; +H + +hence they unite atom with atom, Zn = O, or ZnO. + +Write the grapbic and the common symbols for the union of H^I and +Cl^I; of K^I and Br^I; Ag^I and O^II; Na^I and S^II; H^I and +P^III. Study valences. It will be seen that some elements have a +variable quantivalence. Sn has either 2 or 4; P has 3 or 5. It +usually varies by two for a given element, as though a pair of +bonds sometimes saturated each other;. e.g. =Sn=, a quantivalence +of 4, and |Sn=, a quantivalence of 2. There are, therefore, two +oxides of tin, SnO and SnO2, or Sn=O and O=Sn=O. Write symbols +for the two chlorides of tin; two oxides of P; two oxides of +arsenic. + +The chlorides of iron are FeCl2 and Fe2Cl6. In the latter, it +might be supposed that the quantivalence of Fe is 3, but the +graphic symbol shows it to be 4. It is called a pseudo-triad, or +false triad. Cr and Al are also pseudo-triads. + +Cl Cl | | Cl--Fe--Fe--Cl | | Cl Cl + +Write formulae for two oxides of iron; the oxide of Al. + +57. A Radical is a Group of Elements which has no separate +existence, but enters into combination like a single atom; e.g. +(NO3) in the compounds HNO3 or KNO3; (SO4) in H2SO4. In HNO3 the +radical has a valence of 1, to balance that of H, H-NO3). In +H2SO4, what is the valence of (SO4)? Give it in each of these +radicals, noting first that of the first element: K(NO3), +Na2(SO4), Na2(CO3), K(ClO3), H3(PO4), Ca3(PO4)2, Na4(SiO4). + +Suppose we wish to know the symbol for calcium phosphate. Ca and +PO4 are the two parts. In H3(PO4) the radical is a triad, to +balance H3. Ca is a dyad, Ca==(P04). The least common multiple of +the bonds (2 and 3) is 6, which, divided by 2 (no. Ca bonds), +gives 3 (no. Ca atoms to be taken). 6 / 3 (no. (PO4) bonds) gives +2 (no. PO4 radicals to be taken). Hence the symbol Ca3(P04)2. +Verify this by writing graphically. + +Write symbols for the union of Mg and (SO4), Na and (PO4), Zn and +(NO3), K and (NO3), K and (SO4), Mg and (PO4), Fe and (SO4) (both +valences of Fe), Fe and (NO3), taking the valences of the +radicals from HNO3, H2SO4, H3PO4. + +Chapter XII. + +ELECTRO-CHEMICAL RELATION OF ELEMENTS. + +58. Examine untarnished pieces of iron, silver, nickel, lead, +etc.; also quartz, resin, silk, wood, paper. Notice that from the +first four light is reflected in a different way from that of the +others. This property of reflecting light is known as luster. +Metals have a metallic luster which is peculiar to themselves; +and this, for the present, may be regarded as their chief +characteristic. Are they at the positive or negative end of the +list? See page 43. How is it with the non-metals? This +arrangement has a significance in chemistry which we must now +examine. The three appended experiments show how one metal can be +withdrawn from solution by a second, this second by a third, the +third by a fourth, and so on. For expedition, three pupils can +work together for the three following experiments, each doing +one, and examining the results of the others. + +59. Deposition of Silver. + +Experiment 35.--Put a ten-cent Ag coin into an evaporating-dish, +and pour over it a mixture of 5 cc. HNO3 and 10 cc. H2O. Warm +till all, or nearly all, the Ag dissolves. Remove the lamp. 3 Ag ++ 4 HNO3 = 3 AgNO3 + 2 H2O + NO. Then add 10 cc. H2O, and at once +put in a short piece of Cu wire, or a cent. Leave till quite a +deposit appears, then pour off the liquid, wash the deposit +thoroughly, and remove it from the coin. See whether the metal +resembles Ag. 2 AgNO3 + Cu =?60. Deposition of Copper. + +Experiment 36.--Dissolve a cent or some Cu turnings in dilute +HNO3, as in Experiment 35, and dilute the solution. 3 Cu + 8 HN09 +- 3 Cu (NOA+4 H2O+2 NO.) + +Then put in a clean strip of Pb, and set aside as before, +examining the deposit finally. Cu(NO3), + Pb - ? + +61. Deposition of Lead. + +Experiment 37.--Perform this experiment in the same manner as the +two previous ones, dissolving a small piece of Pb, and using a +strip of Zn to precipitate the Pb. 3 Pb + 8 HNO3 - 3 Pb (NO4)2 + +4 Ha0 + 2 NO. Pb (NO3) 2 + Zn = ? h. + +62. Explanation. -These experiments show that Cu will replace Ag +in a solution of AgNO3, that Pb will replace and deposit Cu from +a similar compound, and that Zn will deposit Pb in the same way. +They show that the affinity of Zn for (NO3) is stronger than +either Ag, Cu, or Pb. We. express this affinity by saying that Zn +is the most positive of the four metals, while Ag is the most +nega- tive. Cu is positive to Ag, but negative to Pb and Zn. +Which of the four elements are positive to Pb, and which +negative? Mg would withdraw Zn from a similar solution, and be in +its turn withdrawn by Na. The table on page 43 is founded on this +relation. A given element is positive to every element above it +in the list, and negative to all below it. + +Metals are usually classed as positive, non-metals as negative. +Each in union with O and 1=I gives rise to a very important class +of compounds,=--the negative to acids, the positive to bases. + +In the following, note whether the positive or the negative +element is written first:--HCl, Na20,-As2S3, -MgBr2, Ag2S. Na2SO4 +is made up of two parts, Na2 being positive, the radical SO4 +negative. Like elements, radicals are either positive or +negative. In the following, separate the positive element from +the negative radical by a vertical line: Na2CO3, NaNO3, ZnSO4, +KClO3. + +The most common positive radical is NH4, ammonium, as in NH4Cl. +It always deports itself as a metal. The commonest radical is the +negative OH, called hydroxyl, from hydrogen- oxygen. Take away H +from the symbol of water, H-O-H, and hydroxyl --(OH) with one +free bond is left. If an element takes the place of H, i.e. +unites with OH, the compound is called a hydrate. KOH is +potassium hydrate. Name NaOH, Ca(OH)2, NH4OH, Zn(OH)2, Al2(OH)6. +Is the first part of each symbol above positive or negative? + +H has an intermediate place in the list. It is a constituent of +both acids and bases, and of the neutral substance, water. + +ORDER. + +-- + + +Negative or Non-Metallic Elements. +Acid-forming with H(usually OH). + +Oxygen +Sulphur +Nitrogen +Fluorine +Chlorine +Bromine +Iodine +Phosphorus +Arsenic +Carbon +Silicon +Hydrogen + +Positive or Metallic Elements. +Base-forming with OH. + +Gold +Platinum +Mercury +Silver +Copper +Tin +Lead +Iron +Zinc +Aluminium +Magnesium +Calcium +Sodium +Potassium + +CHAPTER XIII. + +ELECTROLYSIS. + +The following experiment is to be performed only by the teacher, +but pupils should make drawings and explain. + +63. Decomposition of Water. + +Experiment 38.--Arrange "in series" two or more cells of a Bunsen +battery (Physics, page 164), [References are made in this book to +Gage's Introduction to Physical Science.] and attach the terminal +wires to an electrolytic apparatus (Fig. 19) filled with water +made slightly acid with H2SO4. Construct a diagram of the +apparatus, marking the Zn in the liquid +, since it is positive, +and the C, or other element, -. Mark the electrode attached to +the Zn -, and that attached to the C +; positive electricity at +one end of a body commonly implies negative at the other. +Opposites attract, while like electricities repel each other. +These analogies will aid the memory. At the + electrode is the - +element of H2O, and at the - electrode the + element. Note, page +43, whether H or O is positive with reference to the other, and +write the symbol for each at the proper electrode. Compare the +diagram with the apparatus, to verify your conclusion. Why does +gas collect twice as fast at one electrode as at the other? What +does this prove of the composition of water? When filled, test +the gases in each tube, for O and H, with a burning stick. +Electrical analysis is called electrolysis. + +If a solution of NaCl be electrolyzed, which element will go to +the + pole? Which, if the salt were K2SO4? Explain these +reactions in the electrolysis of that salt. K2SO4 = K2 + S03 + O. +SO4 is unstable, and breaks up into SO3 and O. Both K and SO3 +have great affinity for water. K2 + 2 H2O = 2 KOH + H2. S03 + H2O += H2SO4. + +The base KOH would be found at the - electrode, and the acid +H2SO4 at the + electrode. + +The positive portion, K, uniting with H2O forms a base; the +negative part, S03, with H2O forms an acid. Of what does this +show a salt to be composed? + +64. Conclusions.--These experiments show (1) that at the + +electrode there always appears the negative element, or radical, +of the compound, and at the - electrode the positive element; (2) +that these elements unite with those of water, to make, in the +former case, acids, in the latter, bases; (3) that acids and +bases differ as negative and positive elements differ, each being +united with O and H, and yet producing compounds of a directly +opposite character; (4) that salts are really compounded of acids +and bases. This explains why salts are usually inactive and +neutral in character, while acids and bases are active agents. +Thus we see why the most positive or the most negative elements +in general have the strongest affinities, while those +intermediate in the list are inactive, and have weak affinities; +why alloys of the metals are weak compounds; why a neutral +substance, like water, has such a weak affinity for the salts +which it holds in solution; and why an aqueous solution is +regarded as a mechanical mixture rather than a chemical compound. +In this view, the division line between chemistry and physics is +not a distinct one. These will be better understood after +studying the chapters on acids, bases and salts. + +Chapter XIV. + +UNION BY VOLUME. + +66. Avogadro's Law of Gases.--Equal volumes of all gases, the +temperature and pressure being the same, have the same number of +molecules. This law is the foundation of modern chemistry. A +cubic centimeter of O has as many molecules as a cubic centimeter +of H, a liter of N the same number as a liter of steam, under +similar conditions. Compare the number of molecules in 5 l. of +N2O with that in 10 l. Cl. 7 cc. vapor of I to 6 cc. vapor of S. +The half-molecules of two gases have, of course, the same +relation to each other, and in elements the half-molecule is +usually the atom. + +The molecular volumes--molecules and the surrounding space--of +all gases must therefore be equal, as must the half-volumes. +Notice that this law applies only to gases, not to liquids or +solids. Let us apply it to the experiment for the electrolysis of +water. In this we found twice as much H by volume as O. +Evidently, then, steam has twice as many molecules of H as of O, +and twice as many half-molecules, or atoms. If the molecule has +one atom of O, it must have two of H, and the formula will be +H2O. + +Suppose we reverse the process and synthesize steam, which can be +done by passing an electric spark through a mixture of H and O in +a eudiometer over mercury; we should need to take twice as much H +as O. Now when 2 cc. of H combine thus with 1 cc. of O, only 2 +cc.of steam are produced. Three volumes are condensed into two +volumes, and of course three molecular volumes into two, three +atomic volumes into two. This may be written as follows:-- + +H + H + O = H2O. + +This is a condensation of one-third. + +If 2 l. of chlorhydric acid gas be analyzed, there will result 1 +l. of H and 1 l. of Cl. The same relation exists between the +molecules and the atoms, and the reaction is:-- + +HCl = H + Cl. + +Reverse the process, and 1 l. of H unites with 1 l. of Cl to +produce 2 l. of the acid gas; there is no condensation, and the +symbol is HCl. In seven volumes HCl how many of each constituent? + +The combination of two volumes of H with one volume of S is found +to produce two volumes of hydrogen sulphide. Therefore two atoms +of H combine with one of S to form a molecule whose symbol is +H2S. + +H + H + S = H2S. + +What is the condensation in this case? + +PROBLEMS. + +(1) How many liters of S will it take to unite with 4 l. of H? +How much H2S will be formed? + +(2) How many liters of H will it take to combine with 5 l. of S? +How much H2S results? + +(3) In 6 l. H2S how many liters H, and how much S? Prove. + +(4) In four volumes H2S how many volumes of each constituent? + +(5) If three volumes of H be mixed with two volumes of S, so as +to make H2S, how much will be formed? How much of either element +will be left? An analysis of 2 cc. of ammonia gives 1 cc. N and 3 +cc. H. The symbol must then be NH3, the reaction,-- + +NH3 = N + H + H + H. + +What condensation in the synthesis of NH3? + +In 12 cc. NH3 how many cubic centimeters of each element? In 2 +1/2 cc? How much H by volume is required to combine with nine +volumes of N? How many volumes of NH3 are produced? + +In elements that have not been weighed in the gaseous state, as +C, the evidence of atomic volume is not direct, but we will +assume it. Thus two volumes of marsh gas would separate into one +of C and four of H. What is its symbol and supposed condensation? +Two volumes of alcohol vapor resolve into two of C, six of H, and +one of O. What is its symbol? its condensation? + +The symbol itself of a compound will usually show what its +condensation is; e.g. HCl, HBr, HF, etc., have two atoms; hence +there will be no shrinkage. In H2O, SO2, CO2, the molecule has +three atoms condensed into the space of two, or one-third +shrinkage. In NH3 four volumes are crowded into the space of two, +a condensation of one-half. + +P, As, Hg, Zn, have exceptional atomic volumes. + +Chapter XV. + +ACIDS AND BASES. + +66. What Acids Are. + +Experiment 39.--Pour a few drops of chlorhydric acid, HCl, into a +clean evaporating-dish. Add 5 cc. H2O, and stir. Touch a drop to +the tongue, noting the taste. Dip into it the end of a piece of +blue litmus paper, and record the result. Thoroughly wash the +dish, then pour in a few drops of nitric acid, HNO3, and 5 cc. +H2O, and stir. Taste, and test with blue litmus. Test in the same +way sulphuric acid, H2SO4. Name two characteristics of an acid. +In a vertical line write the formulae of the acids above. What +element is common to them all? Is the rest of the formula +positive or negative? + +67. An Acid is a substance composed of H and a negative element +or radical. It has usually a sour taste, and turns blue litmus +red. Litmus is a vegetable extract obtained from lichens in +Southern Europe. Acids have the same action on many other +vegetable pigments. Are the following acid formulae, and why? +H2SO3, HBr, HNO2, H3PO3, H4SiO4. Most acids have O as well as H. +Complete the symbols for acids in the following list, and name +them, from the type given:-- + + + +HCl, chlorhydric acid. HN03, nitric acid. +?Br, ? ?Cl? ? +?I, ? ?Br? ? +?F, ? ?I? ? +H3PO4, phosphoric acid. H3PO3, phosphorous acid. +?As? ? ?As? ? + +Complete these equations:-- + +H2SO3 - H2O = ? | 2 HN03 - H2O = ? +H2SO4 - H2O = ? | 2 HNO2 - H2O = ? +H2CO3 - H2O = ? | 2 H3AsO4 - 3 H2O = ? + + +Are the products in each case metallic or non-metallic oxides? +They are called anhydrides. Notice that each is formed by the +withdrawal of water from an acid. Reverse the equations; as, SO3 ++ H2O = ? + +68. An Anhydride is what remains after water has been removed +from an acid; or, it is the oxide of a non- metallic element, +which, united with water, forms an acid. SO2 is sulphurous +anhydride, SO2 sulphuric anhydride, the ending ic meaning more O, +or negative element, than ous. Name the others above. + +Anhydrides were formerly called acids,--anhydrous acids, in +distinction from hydrated ones, as CO2 even now is often called +carbonic acid. + +Experiment 40.--Hold a piece of wet blue litmus paper in the +fumes of SO2, and note the acid test. Try the same with dry +litmus paper. + +Experiment 41.--Burn a little S in a receiver of air containing +10 cc. H2O, and loosely covered, as in the O experiment. Then +shake to dissolve the SO2. H2O + SO2 = H2SO3. Apply test paper. + +69. Naming Acids.--Compare formulae H2SO3 and H2SO4. Of two acids +having the same elements, the name of the one with least O, or +negative element, ends in ous, the other in ic. H2SO3 is +sulphurous acid, H2SO4, sulphuric acid. Name H3PO4 and H3PO3; +H3AsO3 and H3ASO4; HNO2 and HNO3. + +If there are more than two acids in a series, the prefixes hypo, +less, and per, more, are used. The following is such a series: +HClO, HClO2, HClO3, HClO4. + +HClO3 is chloric acid; HClO2, chlorous; HClO, hypochlorous; HClO4 +perchloric. Hypo means less of the negative element than ous; per +means more of the negative element than ic. Name: H3PO4 (ic), +H3PO3, H3PO2. Also HBrO (HBrO2 does not exist), HBrO3 (ic), +HBrO4. + +What are the three most negative elements? Note their occurrence +in the three strongest and most common acids. Hereafter note the +names and symbols of all the acids you see. + +70. What Bases Are. + +Experiment 42.--Put a few drops of NH4OH into an evaporating- +dish. Add 5 cc. H2O, and stir. Taste a drop. Dip into it a piece +of red litmus paper, noting the effect. Cleanse the dish, and +treat in the same way a few drops NaOH solution, recording the +result. Do the same with KOH. Acid stains on the clothing, with +the exception of those made by HNO3, maybe removed by NH4OH. +H2SO4, however, rapidly destroys the fiber of the cloth. + +Name two characteristics of a base. In the formulae of those +bases, what two common elements? Name the radical. Compare those +symbols with the symbol for water, HOH. Is (OH) positive or +negative? Is the other part of each formula positive or negative? +What are two constituents, then, of a base? Bases are called +hydrates. Write in a vertical line five positive elements. Note +the valence of each, and complete the formula for its base. Affix +the names. Can you see any reason why the three bases above given +are the strongest? + +Taking the valences of Cr and Fe, write symbols for two sets of +hydrates, and name them. Try to recognize and name every base +hereafter met with. + +A Base is a substance which is composed of a metal, or positive +radical, and OH. It generally turns red litmus blue, and often +has an acrid taste. + +An Alkali is a base which is readily soluble in water. The three +principal alkalies are NH4OH, KOH, and NaOH. + +Alkali Metals are those which form alkalies. Name three. + +An Alkaline Reaction is the turning of red litmus blue. + +An Acid Reaction is the turning of blue litmus red. + +Experiment 43.--Pour 5 cc. of a solution of litmus in water, into +a clean t.t. or small beaker. Pour 2 or 3 cc. of HCl into an +evaporating-dish, and the same quantity of NH4OH into another +dish. Take a drop of the HCl on a stirring-rod and stir the +litmus solution with it. Note the acid reaction. Clean the rod, +and with it take a drop (or more if necessary) of NH4OH, and add +this to the red litmus solution, noting the alkaline reaction. +Experiment in the same way with the two other principal acids and +the two other alkalies. + +Litmus paper is commonly used to test these reactions, and +hereafter whenever the term LITMUS is employed in that sense, the +test-paper should be understood. This paper can be prepared by +dipping unglazed paper into a strong aqueous solution of +litmus. + +CHAPTER XVI. + +SALTS. + +71. Acids and Bases are usually Opposite in Character.--When two +forces act in opposition they tend to neutralize each other. We +may see an analogy to this in the union of the two opposite +classes of compounds, acids and bases, to form salts. + +72. Neutralization. + +Experiment 44.--Put into an evaporating-dish 5 cc. of NaOH +solution. Add HCl to this from a t.t., a few drops at a time, +stirring the mixture with a glass rod (Fig. 20), and testing it +with litmus paper, until the liquid is neutral, i.e. will not +turn the test paper from blue to red, or red to blue. Test with +both colors. If it turns blue to red, too much acid has been +added; if red to blue, too much base. When it is very nearly +neutral, add the reagent, HCl or NaOH, a drop at a time with the +stirring-rod. It must be absolutely neutral to both colors. +Evaporate the water by heating the dish over asbestus paper, wire +gauze, or sand, in an iron plate (Fig. 21) till the residue +becomes dry and white. Cool the residue, taste, and name it. The +equation is: HCl + NaOH = NaCl + HOH or H2O. Note which elements, +positive or negative, change places. Why was the liquid boiled? +The residue is a type of a large class of compounds, called +salts. + +(Fig. 20) (Fig. 21) + +Experiment 45. -- Experiment in the same way with KOH solution +and H2SO4, applying the same tests. H2SO4 + 2 KOH = K2SO4 + 2 +HOH. What is the solid product? + +Experiment 46.--Neutralize NH4OH with HNO3, evaporate, apply the +tests, and write the equation. Write equations for the +combination of NaOH and H2SO4; NaOH and HNO3; KOH and HCl; KOH +and HNO3; NH4OH and HCl; NH4OH and H2SO4. Describe the experiment +represented by each equation, and be sure you can perform it if +asked to do so. What is the usual action of a salt on litmus? How +is a salt made? What else is formed at the same time? Have all +salts a saline taste? Does every salt contain a positive element +or radical? A negative? + +73. A Salt is the product of the union of a positive and a +negative element or radical; it may be made by mixing a base and +an acid. + +The salt KI represents what acid? What base, or hydrate? Write +the equation for making KI from its acid and base. Describe the +experiment in full. Classify, as to acids, bases, or salts: KBr, +Fe(OH)2, HI, NaBr, HNO2, Al2(OH)6, KClO3, HClO3, H2S, K2S, H2S03, +K2SO4, Ca(OH)2, CaCO3, NaBr03, CaSO4, H2CO3, K2CO3, Cu(OH)2, +Cu(NO3)2, PbSO4, H3P04, Na2P04. In the SALTS above, draw a light +vertical line, separating the positive from the negative part of +the symbol. Now state what acid each represents. What base. Write +the reaction in the preparation of each salt above from its acid +and base; then state the experiment for producing it. + +74. Naming Salts.--(NO3) is the nitrate radical; KNO3 is +potassium nitrate. From what acid? (NO2) is the nitrite radical; +KN02 is potassium nitrite. From what acid? Note that the endings +of the acids are OUS and IC; also that the names of their salts +end in ITE and ATE. From which acid--IC or OUS--is the salt +ending in ATE derived? That ending in ITE? + +Name these salts, the acids from which they are derived, and the +endings of both acids and salts: NaNO3, NaNO2, K2SO4, K2SO3, +CaSO4, CaSO3, KClO3, KClO2, KClO, KClO4 (use prefixes HYPO and +PER, as with acids), Ca3(PO4)2, Ca3(P03)2, CuSO4, CuSO3, AgNO3, +Cu(NO3)2. FeS, FeS2, are respectively FERROUS SULPHIDE and FERRIC +SULPHIDE. Name: HgCl, HgCl2, FeCl2, Fe2Cl6, FeSO4, Fe2(SO4)3.75. +Acid Salts.--Write symbols for nitric, sulphuric, phosphoric +acids. How many H atoms in each? Replace all the H in the symbol +of each with Na, and name the products. Again, in sulphuric acid +replace one atom of H with Na; then in phosphoric replace first +one, then two, and finally three H atoms with Na. HNaSO4 is +hydrogen sodium sulphate; HNa2P04 is hydrogen di-sodium +phosphate. Name the other salts symbolized. Name HNaNH4P04. +Though these products are all salts, some contain replaceable H, +and are called acid salts. Those which have all the H replaced by +a metal are normal salts. Name and classify, as to normal or acid +salts: Na2CO3, HNaCO3, K2SO4, HKSO4, (NH4)2SO4, HNH4SO4, Na3P04, +HNa2P04, H2NaP04. + +The BASICITY of an acid is determined by the number of +replaceable H atoms in its molecule. It is called MONOBASIC if it +has one; DIBASIC if two; TRI- if three, etc. Note the basicity of +each acid named above. How many possible salts of H2SO4 with Na? +Of H3P04 with Na? Which are normal and which acid? What is the +basicity of H4Si04? + +Some normal, as well as acid, salts change litmus. Na2CO3, +representing a strong base and a weak acid, turns it blue. There +are other modes of obtaining salts, but this is the only one +which we sball consider. + +76. Salts Occur Abundantly in Nature, such as NaCl, MgSO4, CaCO3. +Acids and bases are found in small quantities only. Why is this? +Why are there not springs of H2SO4 and NH4OH? We have seen that +acids and bases are extremely active, have opposite characters, +and combine to form relatively inactive salts. If they existed in +the free state, they would soon combine by reason of their strong +affinities. This is what in all ages of the world has taken +place, and this is why salts are common, acids and bases rare. +Active agents rarely exist in the free state in large quantities. +Oxygen seems to be an exception, but this is because there is a +superabundance of it. While vast quantities are locked up in +compounds in rocks, water, and salts of the earth, much remains +with which there is nothing to combine. + +CHAPTER XVII. + +CHLORHYDRIC ACID. + +77. We have seen that salts are made by the union of acids and +bases. Can these last be obtained from salts? + +78. Preparation of HCl. + +Experiment 47.--Into a flask put 10 g. coarse NaCl, and add 20 +cc. H2SO4. Connect with Woulff bottles [Woulff bottles may be +made by fitting to wide-mouthed bottles corks with three holes, +through which pass two delivery tubes, and a central safety tube +dipping into the liquid, as in Figures 22 and 23.] partly filled +with water, as in Figure 22. One bottle is enough to collect the +HCl; but in that case it is less pure, since some H2SO4 and other +impurities are carried over. Several may be connected, as in +Figure 23. The water in the first bottle must be nearly saturated +before much gas will pass into the second. Heat the mixture 15 or +20 minutes, not very strongly, to prevent too much foaming. +Notice any current in the first bottle. NaCl + H2SO4 = HNaSO4 + +HCl. Intense heat would have given: 2NaCl + H2SO4 = Na2SO4 + +2HCl. Compare these equations with those for HNO3. In which +equation above is H2SO4 used most economically? Both reactions +take place when HCl is made on the large scale. + +(Fig. 22) + +79. Tests. Experiment 48.--(1) Test with litmus the liquid in +each Woulffbottle. (2) Put a piece of Zn into a t.t. and cover it +with liquid from the first bottle. Write the reaction, and test +the gas. (3) To 2 cc.solution AgNO3 in a t.t. add 2 cc.of the +acid. Describe, and write the reaction. Is AgCl soluble in water? +(4) Into a t.t. pour 5 cc.Pb(NO3)2 solution, and add the same +amount of prepared acid. Give the description and the reaction. +(5) In the same way test the acid with Hg2(NO3)2 solution, giving +the reaction. (6) Drake a little HCl in a t.t., and bring the gas +escaping from the d.t. in contact with a burning stick. Does it +support the combustion of C? (7) Hold a piece of dry litmus paper +against it. [figure 23] (8) Hold it over 2 cc.of NH4OH in an +evaporating-dish. Describe, name the product, and write the +reaction. (3), (4), (5), (8), are characteristic tests for this +acid. + +80. Chlorhydric, Hydrochloric or Muriatic, Acid is a Gas.--As +used, it is dissolved, in water, for which it has great affinity. +Water will hold, according to temperature, from 400 to 500 times +its volume of HCl. Hundreds of thousands of tons of the acid are +annually made, mostly in Europe, as a bye-product in Na2CO3 +manufacture. The gas is passed into towers through which a spray +of water falls; this absorbs it. The yellow color in most +commercial HCl indicates impurities, some of which are Fe, S, As, +and organic matter. As, S, etc., come from the pyrites used in +making H2SO4. Chemically pure (C.P.) acid is freed from these, +and is without color. The gas may be dried by passing it through +a glass tube holding CaCl2 (Fig. 16) and collecting it over +mercury. + +The muriatic acid of commerce consists of about two- thirds water +by weight. HCl can also be made by direct union of its +constituents.81. Uses.--HCl is used to make Cl, and also +bleaching- powder. Its use as a reagent in the laboratory is +illustrated by the following experiment:-- Experiment 49.--Put +into a t.t. 2 cc. AgNO3 solution, add 5 cc. H2O, then add slowly +HCl so long as a ppt. (precipitate) is formed. This ppt. is AgCl. +Now in another t.t. put 2 cc. Cu(NO3)2, solution, add 5 cc. H2O, +then a little HCl. No ppt. is formed. Now if a solution of AgNO3 +and a solution of Cu(NO3)2 were mixed, and HCl added, it is +evident that the silver would be precipitated as chloride of +silver, while the copper would remain in solution. If now this be +filtered, the silver will remain on the filter paper, while in +the filtrate will be the copper. Thus we shall have performed an +analysis, or separated one metal from another. Perform it. Note, +however, that any soluble chloride, as NaCl, would produce the +same result as HCl. + +BROMHYDRIC AND IODIHYDRIC ACIDS. + +82. NaCl, being the most abundant compound of Cl, is the source +of commercial HCl. KCl treated in the same way would give a like +product. Theoretically HBr and HI might be made in the same way +from NaBr and NaI, but the affinity of H for Br and I is weak, +and the acids separate into their elements, when thus prepared. + +83. To make HI. + +Experiment 50.--Drop into a t.t. three or four crystals of I, and +add 10 cc. H2O. Hold in the water the end of a d.t. from which +H2S gas is escaping. Observe any deposit, and write the reaction. + +FLUORHYDRIC ACID. + +84. Preparation and Action. + +Experiment 51.--Put 3 or 4 g. powdered CaF2, i.e. fluor spar or +fluorite, into a shallow lead tray, e.g. 4x5 cm, and pour over it +4 or 5 cc. H2SO4. A piece of glass large enough to cover this +should previously be warmed and covered on one side with a very +thin coat of beeswax. To distribute itevenly, warm the other side +of the glass over a flame. When cool, scratch a design (Fig. 24) +through the wax with a sharp metallic point. Lay the glass, film +side down, over the lead tray. Warm this five minutes or more by +placing it high over a small flame (Fig. 25) to avoid melting the +wax. Do not inhale the fumes. Take away the lamp, and leave the +tray and glass where it is not cold, for half an hour or more. +Then remove the wax and clean the glass with naphtha or benzine. +Look for the etching. + +Two things should have occurred: (1) the generation of HF. Write +the equation for it. (2) Its etching action on glass. In this +last process HF acts on SiO2 of the glass, forming H2O and SiF4. +Why cannot HF be kept in glass bottles? + +A dilute solution of HF, which is a gas, may be kept in gutta +percha bottles, the anhydrous acid in platinum only; but for the +most part, it is used as soon as made, its chief use being to +etch designs on glass-ware. Glass is also often etched by a blast +of sand (SiO2). + +Notice the absence of O in the acids HF, HCI, HBr, HI, and that +each is a gas. HF is the only acid that will dissolve or act +appreciably on glass. + +Chapter XVIII. + +NITRIC ACID. + +85. Preparation. Experiment 52.--To 10 g. KNO3 or NaNO3, in a +flask, add 15 cc. H2SO4. Securely fasten the cork of the d.t., as +HNO3 is likely to loosen it, and pass the other end to the bottom +of a t.t. held deep in a bottle of water (Fig. 26). Apply heat, +and collect 4 or 5 cc.of the liquid. The usual reaction is: KNO3 ++ H2SO4 = HKSO4 + HNO3. With greater heat, 2 KNO3 + H2SO4 = K2SO4 ++ 2HNO3. Which is most economical of KNO3? Of H2SO4? Instead of a +flask, a t.t. may be used if desired (Fig. 27). + +86. Properties and Tests. + +Experiment 53.--(1) Note the color of the prepared liquid. (2) +Put a drop on the finger; then wash it off at once. (3) Dip a +quill or piece of white silk into it; then wash off the acid. +What color is imparted to animal substances? (4) Add a little to +a few bits of Cu turnings, or to a Cu coin. Write the equation. +(5) To 2 cc.indigo solution, add 2 cc. HNO3. State the leading +properties of HNO3, from these tests. + +87. Chemically Pure HNO3 is a Colorless Liquid.-- The yellow +color of that prepared in Experiment 52 is due to liquid NO2 +dissolved in it. It is then called fuming HNO3, and is very +strong. NO2 is formed at a high temperature. + +Commercial or ordinary HNO3, is made from NaNO3, this being +cheaper than KNO3; it is about half water. + +88. Uses. HNO3 is the basis of many nitrates, as AgNO3, used for +photography, Ba(NO3)2 and Sr(NO3)2 for fire-works, and others for +dyeing and printing calico; it is employed in making aqua regia, +sulphuric acid, nitro-glycerine, gun-cotton, aniline colors, +zylonite, etc. + +Enough experiments have been performed to answer the question +whether some acids can be prepared from their salts. H2SO4 is not +so made, because no acid is strong enough to act on its salts. In +making HCl, HNO3, etc., sulphuric acid was used, being the +strongest. + +AQUA REGIA. + +89. Preparation and Action. Experiment 54.--Into a t.t. put 2 cc. +HNO3, and 14 qcm. of either Au leaf or Pt. Warm in a flame. If +the metal is pure, no action takes place. Into another tube put 6 +cc. HCl and add a similar leaf. Heat this also. There should be +no action. Pour the contents of one t.t. into the other. Note the +effect. Which is stronger, one of the acids, or the combination +of the two? Note the odor. It is that of Cl. 3HCl + HNO3 = NOCl + +2H2O + Cl2. This reaction is approximate only. The strength is +owing to nascent chlorine, which unites with Au. Au + 3Cl = +AuCl3. If Pt be used, PtCl4 is produced. No other acid except +nitro-hydrochloric will dissolve Au or Pt; hence the ancients +called it aqua regia, or king of liquids. It must be made as +wanted, since it cannot be kept and retain its strength. + +CHAPTER XIX. + +SULPHURIC ACID. + +90. Preparation. + +Experiment 55.--Having fitted a cork with four or five +perforations to a large t.t., pass a d.t. from three of these to +three smaller t.t., leaving the others open to the air, as in +Figure 28. Into one t.t. put 5 cc. H2O, into another 5 g. Cu +turnings and 10 cc. H2SO4, into the third 5 g. Cu turnings and 10 +cc. dilute HNO3, half water. Hang on a ring stand, and slowly +heat the tubes containing H2O and H2SO4. Notice the fumes that +pass into the large t.t. + +Trace out and apply to Figure 28 these reactions:-- + +(1) Cu + 2 H2SO4 = CuSO4 + 2 H2O + SO2. + +(2) 3 Cu + 8 HNO3 = 3 Cu(NO3)2+ 4 H2O + 2 NO. + +(3) NO + O = NO2. + +(4) SO2 + H2O + NO2 =H2SO4 + NO. + +(4) comes from combining the gaseous products in (1), (2), (3). +In (3), NO takes an atom of O from the air, becoming NO2, and at +once gives it up, to the H2SO3 (H2O + SO2), making H2SO4, and +again goes through the same operation of taking up O and passing +it along. NO is thus called a carrier of O. It is a reducing +agent, while NO2 is an oxidizing agent. This is a continuous +process, and very important, since it changes useless H2SO3 into +valuable H2SO4. If exposed to the air, H2SO3 would very slowly +take up O and become H2SO4. + +Instead of the last experiment, this may be employed if +preferred: Burn a little S in a receiver. Put into an +evaporating-dish, 5 cc. HNO3, and dip a paper or piece of cloth +into it. Hang the paper in the receiver of SO2, letting no HNO3 +drop from it. Continue this operation till a small quantity of +liquid is found in the bottle. The fumes show that HNO3 has lost +O. 2 HNO3 + SO2 = H2SO4 + 2 NO2. + +91. Tests for H2SO4. + +Experiment 56.--(1) Test the liquid with litmus. (2) Transfer it +to a t.t., and add an equal volume of BaCl2 solution. H2SO4 + +BaCl2 = ? Is BaSO4 soluble? (3) Put one drop H2SO4 from the +reagent bottle in 10 cc. H2O in a clean t.t., and add 1 cc. BaCl2 +solution. Look for any cloudiness. This is the characteristic +test for H2SO4 and soluble sulphates, and so delicate that one +drop in a liter of H2O can be detected. (4) Instead of H2SO4, try +a little Na2SO4 solution. (5) Put two or three drops of strong +H2SO4 on writing-paper, and evaporate, high over a flame, so as +not to burn the paper. Examine it when dry. (6) Put a stick into +a t.t. containing 2 cc. H2SO4, and note the effect. (7) Review +Experiment 5. (8) Into an e.d. pour 5 cc. H2O, and then 15 cc. +H2SO4. Stir it meantime with a small t.t. containing 2 or 3 cc. +NH4OH, and notice what takes place in the latter; also note the +heat of the e.d. + +The effects of (5), (6), (7), and (8) are due to the intense +affinity which H2SO4 has for H2O. So thirsty is it that it even +abstracts H and O from oxalic acid in the right proportion to +form H2O, combines them, and then absorbs the water. + +92. Affinity for Water.--This acid is a desiccator or dryer, and +is used to take moisture from the air and prevent metallic +substances from rusting. In this way it dilutes itself, and may +increase its weight threefold. In diluting, the acid must always +be poured into the water slowly and with stirring, not water into +the acid, since, as H2O is lighter than H2SO4, heat enough may be +set free at the surface of contact to cause an explosion. +Contraction also takes place, as may be shown by accurately +measuring each liquid in a graduate, before mixing, and again +when cold. The mixture occupies less volume than the sum of the +two volumes. For the best results the volume of the acid should +be about three times that of the water. + +93. Sulphuric Acid made on a Large Scale involves the same +principles as shown in Experiment 55, excepting that S02 is +obtained by burning S or roasting FeS2 (pyrite), + +[Fig. 29.] + +and HNO3 is made on the spot from NaNO3 and H2SO4. SO2 enters a +large leaden chamber, often 100 to 300 feet long, and jets of +steam and small portions of HNO3 are also forced in. The "chamber +acid" thus formed is very dilute, and must be evaporated first in +leaden pans, and finally in glass or platinum retorts, since +strong H2SO4, especially if hot, dissolves lead. See Experiment +124. Study Figure 29, and write the reactions. 2 HNO3 breaks up +into 2 NO2, H2O, and O. 94. Importance.--Sulphuric acid has been +called, next to human food, the most indispensable article known. +There is hardly a product of modern civilization in the +manufacture of which it is not directly or indirectly used. +Nearly a million tons are made yearly in Great Britain alone. It +is the basis of all acids, as Na2CO3 is of alkalies. It is the +life of chemical industry, and the quantity of it consumed is an +index of a people's civilization. Only a few of its uses can be +stated here. The two leading ones are the reduction of Ca3(PO4)2 +for artificial manures and the sodium carbonate manufacture. +Foods depend on the productiveness of soils and on fertilizers, +and thus indirectly our daily bread is supplied by means of this +acid; and from sodium carbonate glass, soap, saleratus, baking- +powders, and most alkalies are made directly or indirectly. H2SO4 +is employed in bleaching, dyeing, printing, telegraphy, +electroplating, galvanizing iron and wire, cleaning metals, +refining Au and Ag, making alum, blacking, vitriols, glucose, +mineral waters, ether, indigo, madder, nitroglycerine, gun- +cotton, parchment, celluloid, etc., etc. + +FUMING SULPHURIC ACID. + +95. Nordhausen or Fuming Sulphuric Acid, H2S207 used in +dissolving indigo and preparing coal-tar pigments, is made by +distilling FeSO4. 4FeSO4 + H2O = H2S207 + 2Fe203 + 2S02. This was +the original sulphuric acid. It is also formed when S03 is +dissolved in H2SO4. When exposed to the air, S03 escapes with +fuming. + +CHAPTER XX. + +AMMONIUM HYDRATE. + +96. Preparation of Bases.--We have seen that many acids are made +by acting on a salt of the acid required, with a stronger acid. +This is the direct way. The following experiments will show that +bases may be prepared in a similar way by acting on salts of the +base required with other bases, which we may regard as stronger +than the ones to be obtained. + +97. Preparation of NH4OH and NH3. + +Experiment 57.--Powder 10 g. ammonium chloride, NH4Cl, in a mortar +and mix with 10 g. calcium hydrate, Ca(OH)2; recently slaked lime +is the best. Cover with water in a flask, and connect with Woulff +bottles, as for making HCl (Fig. 22); heat the flask for fifteen +minutes or more. The experiment may be tried on a smaller scale +with a t.t. if desired. + +The reaction is: 2NH4Cl + Ca(OH)2 = CaCl2 + 2NH4OH. NH4OH is +broken up into NH3, ammonia gas, and water. NH4OH = NH3 + H2O. +These pass over into the first bottle, where the water takes up +the NH3, for which it has great affinity. One volume of water at +0° will absorb more than 1000 volumes of NH3. Thus NH4OH may be +called a solution of NH3, in H2O. Write the reaction. + +Experiment 58.--Powder and mix 2 or 3 g. each of ammonium +nitrate, NH4NO3, and Ca(OH)2; put them into a t.t., and heat +slowly. Note the odor. 2NH4NO3 + Ca(OH)2 = ? + +98. Tests. + +Experiment 59.--(1) Generate a little of the gas in a t.t., and +note the odor. (2) Test the gas with wet red litmus paper. (3) +Put a little HCl into an e.d., and pass over it the fumes of NH3 +from a d.t. Note the result, and write the equation. (4) Fill a +small t.t. with the gas by upward displacement; then, while still +inverted, put the mouth of the t.t. into water. Explain the rise +of the water. (5) How might NH4Cl be obtained from the NH4OH in +the Woulff bottles? (6) Test the liquid in each bottle with red +litmus paper. (7) Add some from the first bottle to 5 or 10 cc. +of a solution of FeSO4 or FeCl2, and look for a ppt. State the +reaction. + +99. Formation.--Ammonia, hartshorn, exists in animal and +vegetable compounds, in salts, and, in small quantities, in the +atmosphere. Rain washes it from the atmosphere into the soil; +plants take it from the soil; animals extract it from plants. +Coal, bones, horns, etc., are the chief sources of it, and from +them it is obtained by distillation. It results also from +decomposing animal matter. NH3 can be produced by the direct +union of N and H, only by an electric discharge or by ozone. It +may be collected over Hg like other gases that are very soluble +in water. + +100. Uses. --Ammonium hydrate, NH4OH, and ammonia, NH3, are used +in chemical operations, in making artificial ice, and to some +extent in medicine; from them also may be obtained ammonium +salts. State what you would put with NH4OH to obtain (NH4)2SO4. +To obtain NH4NO3. The use of NH4OH in the laboratory may be +illustrated by the following experiment:-- + +Experiment 60.--Into a t.t. put 10 cc. of a solution of ferrous +sulphate, FeSO4. Into another put 10 cc. of sodium sulphate +solution, Na2SO4. Add a little NH4OH to each. Notice a ppt. in +the one case but none in the other. If solutions of these two +compounds were mixed, the metals Fe and Na could be separated by +the addition of NH4OH, similar to the separation of Ag and Cu by +HCl. Try the experiment. + +CHAPTER XXI. + +SODIUM HYDRATE. + +101. Preparation. + +Experiment 61.--Dissolve 3 g. sodium carbonate, Na2CO3, in 10 or +15 cc. H2O in an e.d., and bring it to the boiling-point. Then +add to this a mixture of 1 or 2 g. calcium hydrate, Ca(OH)2, in 5 +or 10cc. H2O. It will not dissolve. Boil the whole for five +minutes. Then pour off the liquid which holds NaOH in solution. +Evaporate if desired. This is the usual mode of preparing NaOH. + +The reaction is Na2CO3 + Ca(OH)2 = 2NaOH + CaCO3. The residue is +Ca(OH)2 and CaCO3; the solution contains NaOH, which can be +solidified by evaporating the water. Sodium hydrate is an +ingredient in the manufacture of hard soap, and for this use +thousands of tons are made annually, mostly in Europe. It is an +important laboratory reagent, its use being similar to that of +ammonium hydrate. Exposed to the air, it takes up water and CO2, +forming a mixture of NaOH and Na2CO3. It is one of the strongest +alkalies, and corrodes the skin. + +Experiment 62.--Put 20 cc. of H2O in a receiver. With the forceps +take a piece of Na, not larger than half a pea, from the naphtha +in which it is kept, drop it into the H2O, and at once cover the +receiver loosely with paper or cardboard. Watch the action, as +the Na decomposes H2O. HOH + Na = NaOH + H. If the water be hot +the action is so rapid that enough heat is produced to set the H +on fire. That the gas is H can be shown by putting the Na under +the mouth of a small inverted t.t., filled with cold water, in a +water-pan. Na rises to the top, and the t.t. fills with H, which +can be tested. NaOH dissolves in the water.102. Properties. + +Experiment 63.--(1) Test with red litmus paper the solutions +obtained in the last two experiments. (2) To 5cc.of alum +solution, K2A12(SO4)4, add 2cc.of the liquid, and notice the +color and form of the ppt. + +POTASSIUM HYDRATE. + +103. KOH is made in the Same Way as NaOH. + +Describe the process in full (Experiment 61), and give the +equation. + +Experiment 64.--Drop a small piece of K into a receiver of H2O, +as in Experiment 62. The K must be very small, and the experiment +should not be watched at too close a range. The receiver should +not be covered with glass, but with paper. The H burns, uniting +with O of the air. The purple color is imparted by the burning, +or oxidation of small particles of K. Write the equation for the +combustion of each. + +H2O might be considered the symbol of an acid, since it is the +union of H and a negative element; or, if written HOH, it might +be called a base, since it has a positive element and the (OH) +radical. It is neutral to litmus, and on this account might be +called a salt. It is better, however, to call it simply an oxide. + +Potassium hydrate, caustic potash, is employed for the +manufacture of soft soap. As a chemical reagent its action is +almost precisely like that of caustic soda, though it is usually +considered a stronger base, as K is a more electro-positive +element than Na. + +CALCIUM HYDRATE. + +104. Calcium Hydrate, the Most Common of the Bases, is nearly as +important to them as H2SO4 is to acids. Since it is used to make +the other bases, it might be called the strongest base; as H2SO4 +is often called the strongest acid. The strength of an acid or +base, however,depends on the substance to which it is applied, as +well as on itself, and for most purposes this one is classified +as a weaker base than the three previously described. + +Sulphuric acid, the most useful of the acids, is not made +directly from its salts, but has to be synthesized. Calcium +hydrate is also made by an indirect process, as follows: + +CaCO3, i.e. limestone, marble, etc., is burnt in kilns with C, a +process which separates the gas, CO2, according to the reaction: +CaCO3 = CaO + CO2. CaO is unslaked lime, or quick-lime. On +treating this with water, slaked lime, Ca(OH)2 is formed, with +generation of great heat. CaO + H2O = Ca(OH)2. Its affinity for +H2O is so great that it takes the latter from the air, if +exposed. + +Experiment 65.--Saturate some unslaked lime with water, in an +e.d., and look for the results stated above, leaving it as long +as may be necessary. + +105. Resume.--From the experiments in the last few chapters on +the three divisions of chemical compounds, acids, bases and +salts, we have seen (1) that acids and bases are the chemical +opposites of each other; (2) that salts are formed by the union +of acids and bases; (3) that some acids can be obtained from +their salts by the action of a stronger acid; (4) that some bases +can be got from salts by the similar action of other bases; (5) +that the strongest acids and bases, as well as others, may be +obtained in an indirect way by synthesis. + +CHAPTER XXII. + +OXIDES OF NITROGEN. + +106. There are five oxides of N, only two of which are important. + +NITROGEN MONOXIDE (N2O). + +107. Preparation. + +Experiment 66.--Put into a flask, holding 200cc, lOg of ammonium +nitrate, NH4NO3; heat it over wire gauze or asbestus in an iron +plate, having a d.t. connected with a large t.t., which is held +in a receiver of water, and from this t.t., another d.t. passing +into a pneumatic trough, so as to collect the gas over water +(Fig. 30). Have all the bearings tight. The reaction is NH4NO3 = +2H2O + N2O. The t.t. is for collecting the H2O. + +[Fig. 30.] + +Note the color of the liquid in the t.t.; taste a drop, and test +it with litmus. If the flask is heated too fast, some NO is +formed, and this taking O from the air makes NO2, which liquefies +and gives an acid reaction and a red color. Some NH4NO3 is also +liable to be carried over. + +108. Properties. + +Experiment 67.--Test the gas in the receiver with a burning stick +and a glowing one, and compare the combustion with that in O. +N20may also be tested with S and P, if desired. N is set free in +each case. Write the reactions. + +Nitrogen monoxide or protoxide, the nitrous oxide of dentists, +when inhaled, produces insensibility to pain,-- anaesthesia,-- +and, if continued, death from suffocation. Birds die in half a +minute from breathing it. Mixed with one-fourth O, and inhaled +for a minute or two, it produces intoxication and laughter, and +hence is called laughing gas. As made in Experiment 66, it +contains Cl and NO, as impurities, and should not be breathed. + +NITROGEN DIOXIDE (NO, OR N2O2). + +109. Preparation. + +Experiment 68.--Into a t.t. or receiver put 5g Cu turnings, add 5 +cc. H2O and 5 cc. HNO3. Collect the gas like H, over water. 3Cu + +8HNO3 = ? What two products will be left in the generator? Notice +the color of the liquid. This color is characteristic of Cu +salts. Notice also the red fumes of NO2. + +110. Properties. + +Experiment 69.--Test the gas with a burning stick, admitting as +little air as possible. Test it with burning S. NO is not a +supporter of C and S combustion. Put a small bit of P in a +deflagrating-spoon, and when it is vigorously burning, lower it +into the gas. It should continue to burn. State the reaction. +What combustion will NO support? Note that NO is half N, while +N2O is two-thirds N, and account for the difference in supporting +combustion. + +NITROGEN TETROXIDE (NO2 or N2O4). + +111. Preparation. + +Experiment 70.--Lift from the water-pan a receiver of NO, and +note the colored fumes. They are NO2, or N2O4, nitrogen +tetroxide. NO + O = NO2. Is NO combustible? What is the source of +O in the experiment?OXIDES OF NITROGEN. + +NITROGEN TRIOXIDE (N2O3). + +112. Preparation. + +Experiment 71.--Put into a t.t. 1 g. of starch and 1 cc. of HNO3. +Heat the mixture for a minute. The red fumes are N2O3 and NO2. + +Nitrogen pentoxide, N2O5, is an unimportant solid. United with +water it forms HNO3. N2O5 + H2O = 2HNO3. + +CHAPTER XXIII. + +LAWS OF DEFINITE AND OF MULTIPLE PROPORTION. + +113. Weight and Volume.--We have seen that water contains two +parts of H by volume to one part of O; or, by weight, two parts +of H to sixteen of O. These proportions are invariable, or no +symbol for water would be possible. Every compound in the same +way has an unvarying proportion of elements. + +114. Law of Definite Proportion.--In a given compound the +proportion of any element by weight, or, if a gas, by volume is +always constant. Apply the law, by weight and by volume, to +these: HCl, NH3, H2S, N2O. + +There is another law of equal importance in chemistry, which the +compounds of N and O well illustrate. + + + Weight. Volume. + N. O. N. O. +Nitrogen protoxide N2O 28 16 2 1 +Nitrogen dioxide N2O2 28 32 2 2 +Nitrogen trioxide. N2O3 28 48 2 3 +Nitrogen tetroxide N2O4 28 64 2 4 +Nitrogen pentoxide N2O5 28 80 2 5 + + +Note that the proportion of O by weight is in each case a +multiple of the first, 16. Also that the proportion by volume of +O is a multiple of that in the first compound. In this example +the N remains the same. If that had varied in the different +compounds, it would also havevaried by a multiple of the smallest +proportion. This is true in all compounds. + +115. Law of Multiple Proportion.--Whenever one element combines +with another in more than one proportion, it always combines in +some multiple, one or more, of its least combining weight, or, if +a gas, of its least combining volume. + +The least combining weight of an element is its atomic weight; +and it is this fact of a least combining weight that leads us to +believe the atom to be indivisible. + +Apply the law in the case of P2O, P2O3, P2O5; in HClO, HClO2, +HClO3, HClO4, arranging the symbols, weights, and volumes in a +table, as above. + +The volumetric proportions of each element in the oxides of +nitrogen are exhibited below. + + +_ + _ + _ = __ +N + N + O = N2O + +_ + _ + _ + _ = __ +N + N + O + O = N2O2 + +_ + _ + _ + _ + _ = __ +N + N + O + O + O = N2O3 + +_ + _ + _ + _ + _ + _ = __ +N + N + O + O + O + O = N2O4 + +_ + _ + _ + _ + _ + _ + _ = __ +N + N + O + O + O + O + O = N2O5 + +CHAPTER XXIV. + +CARBON PROTOXIDE. + +116. Preparation. + +Experiment 72.--Put into a flask, of 200 cc., 5 g. of oxalic acid +crystals, H2C2O4, and 25 cc. H2SO4. Have the d.t. pass into a +solution of NaOH in a Woulff bottle (Fig. 31), and collect +the gas over water. Heat the flask slowly, and avoid inhaling the +gas. + +117. Tests. + +Experiment 73.--Remove a receiver of the gas, and try to light +the latter with a splinter. Is it combustible, or a supporter of +(C) combustion? What is the color of the flame? When the +combustion ceases, shake up a little lime water with the gas left +in the receiver. What gas has been formed by the combustion, as +shown by the test? See page 80. Give the reaction for the +combustion. + +We have seen that H2SO4 has great affinity for H2O. Oxalic acid +consists of H, C, O in the right proportion to form H2O, CO2, and +CO. H2SO4 withdraws H and O in the right proportion to form +water, unites them, and then absorbs the water, leaving the C and +O to combine and form CO2 and CO. NaOH solution removes CO2 from +the mixture, forming Na2CO3, and leaves CO. Write both reactions. + +118. Carbon Protoxide, called also carbon monoxide, carbonic +oxide, etc., is a gas, having no color or taste, butpossessing a +faint odor. It is very poisonous. Being the lesser oxide of C, it +is formed when C is burned in a limited supply of O, whereas CO2 +is always produced when O is abundant. The formation of each is +well shown by tracing the combustion in a coal fire. Air enters +at the bottom, and CO2 is first formed. C + 2O = CO2. As this gas +passes up, the white-hot coal removes one atom of O, leaving CO. +CO2 + C - 2CO. At the top, if the draft be open, a blue flame +shows the combustion of CO. CO + O = CO2. The same reduction of +CO2 takes place in the iron furnace, and whenever there is not +enough oxygen to form CO2, the product is CO. + +Great care should be taken that this gas does not escape into the +room, as one per cent has proved fatal. Not all of it is burned +at the top of the coal; and when the stove door is open, the +upper drafts should be open also. It is the most poisonous of the +gases from coal; hence the danger from sleeping in a room having +a coal fire. + +119. Water Gas.--CO is one of the constituents of "water gas," +which, by reason of its cheapness, is supplanting gas made from +coal, as an illuminator, in some cities. It is made by passing +superheated steam over red-hot charcoal or coke. C unites with +the O of H2O, forming CO, and sets H free, thus producing two +inflammable gases. C + H2O --? As neither of these gives much +light, naphtha is distilled and mixed with them in small +quantities to furnish illuminating power See page 183. + +CHAPTER XXV. + +CARBON DIOXIDE. + +120. Preparation. + +Experiment 74.--Put into a t.t., or a bottle with a d.t. and a +thistle-tube, 10 or 20 g. CaCO3, marble in lumps; add as many +cubic centimeters of H2O, and half as much HCl, and collect the +gas by downward displacement (Fig. 39). Add more acid as needed. +CaCO3 + 2 HCl = CaCl2 + H2CO3. H2CO3 = H2O + CO2. H2CO3 is a very +weak compound, and at once breaks up. By some, its existence as a +compound is doubted. + +121. Tests. + +Experiment 75.--(1) Put a burning and a glowing stick into the +t.t. or bottle. (2) Hold the end of the d.t. directly against the +flame of a small burning stick. Does the gas support combustion? +(3) Pour a receiver of the gas over a candle flame. What does +this show of the weight of the gas? (4) Pass a little CO2 into +some H2O (Fig. 32), and test it with litmus. Give the reaction +for the solution of CO2 in H2O. + +Experiment 76.--Put into a t.t. 51 cc. of clear Ca(OH)2 solution, +i.e. lime water; insert in this the end of a d.t. from a CO2 +generator (Fig. 32). Notice any ppt. formed. It is CaCO3. Let the +action continue until the ppt. disappears and the liquid is +clear. Then remove the d.t., boil the clear liquid for a minute, +and notice whether the ppt. reappears. + +122. Explanation. + +Ca(OH)2 + CO2 = CaCO3 + H2O. The curious phenomena of this +experiment are explained by the solubility of CaCO3 in water +containing CO2, and its insolu-bility in water, having no CO2. +When all the Ca(OH)3 is combined, or changed to CaCO3, the excess +of CO2 unites with H2O, forming the weak acid H2CO3, which +dissolves the precipitate, CaCO3, and gives a clear liquid. On +heating this, H2CO3 gives up its CO2, and CaCO3 is +reprecipitated, not being soluble in pure water. + +Lime water, Ca(OH)2 solution, is therefore a test for the +presence of CO2. To show that carbon dioxide is formed in +breathing, and in the combustion of C, and that it is present in +the air, perform the following experiment: + +Experiment 77.--(1) Put a little lime water into a t.t., and blow +into it through a piece of glass tubing. Any turbidity shows +what? (2) Burn a candle for a few minutes in a receiver of air, +then take out the candle and shake up lime water with the gas. +(3) Expose some lime water in an e.d. to the air for some time. + +133. Oxidation in the Human System.--Carbon dioxide, or carbonic +anhydride, carbonic acid, etc., CO2, is a heavy gas, without +color or odor. It has a sharp, prickly taste, and is commonly +reckoned as poisonous if inhaled in large quantities, though it +does not chemically combine with the blood as CO does. Ten per +cent in the air will sometimes produce death, and five per cent +produces drowsiness. It exists in minute portions in the +atmosphere, and often accumulates at the bottom of old wells and +caverns, owing to its slow diffusive power. Before going down +into one of these, the air should always be tested by lowering a +lighted candle. If this is extinguished, there is danger. CO2 is +the deadly "choke damp" after a mine explosion, CH4 being +converted into CO2 and H2O; a great deal is liberated during +volcanic eruptions, and it is formed in breathing by the union of +O in the air with C in the system. This union of C and O takes +place in the lungs and in all the tissues of the body, even on +the surface. Oxygen is taken into the lungs, passes through the +thin membrane into the blood, forms a weak chemical union with +the red corpuscles, and is conveyed by them to all parts of the +system. Throughout the body, wherever necessary, C and H are +supplied for the O, and unite with it to form CO2 and H2O. These +are taken up by the blood though they do not form a chemical +union with it, are carried to the lungs, and pass out, together +with the unused N and surplus O. The system is thus purified, and +the waste must be supplied by food. The process also keeps up the +heat of the body as really as the combustion of C or P in O +produces heat. The temperature of the body does not vary much +from 99 degrees F., any excess of heat passing off through +perspiration, and being changed into other forms of energy. + +If, as in some fevers, the temperature rises above about 105 +degrees F., the blood corpuscles are killed, and the person dies. +During violent exercise much material is consumed, circulation is +rapid, and quick breathing ensues. Oxygen is necessary for life. +A healthy person inhales plentifully; and this element is one of +nature's best remedies for disease. Deep and continued +inhalations in cold weather are better than furnace fires to heat +the system. All animals breathe O and exhale CO2. Fishes and +other aquatic animals obtain it, not by decomposing H2O, but from +air dissolved in water. Being cold-blooded, they need relatively +little; but if no fresh water is supplied to those in captivity, +they soon die of O starvation. + +124. Oxidation in Water.--Swift-running streams are clear and +comparatively pure, because their organic impurities are +constantly brought to the surface and oxidized, whereas in +stagnant pools these impurities accumulate. Reservoirs of water +for city supply have sometimes been freed from impurities by +aeration, i.e. by forcing air into the water. + +125. Deoxidation in Plants.--Since CO2 is so constantly poured +into the atmosphere, why does it not accumulate there in large +quantity? Why is there not less free O in the air to-day than +there was a thousand years ago? The answer to these questions is +found in the growth of vegetation. In the leaf of every plant are +thousands of little chemical laboratories; CO2 diffused in small +quantities in the air passes, together with a very little H2O, +into the leaf, usually from its under side, and is decomposed by +the radiant energy of the sun. The C is built into the woody +fiber of the tree, and the O is ready to be re-breathed or burned +again. CO2 contributes to the growth of plants, O to that of +animals; and the constituents of the atmosphere vary little from +one age to another. The compensation of nature is here well +shown. Plants feed upon what animals discard, transforming it +into material for the sustenance of the latter, while animals +prepare food for plants. All the C in plants is supposed to come +from the CO2 in the atmosphere. Animals obtain their supply from +plants. The utility of the small percentage of CO2 in the air is +thus seen. + +126. Uses.--CO2 is used in making "soda-water," and in chemical +engines to put out fires in their early stages. In either case it +may be prepared by treating Na2CO3 or CaCO3 with H2SO4. Give the +reactions. On a small scale CO2 is made from HNaCO3. CO2 has a +very weak affinity for water, but probably forms with it H2CO3. +Much carbon dioxide can be forced into water under pressure. This +forms soda-water, which really contains no soda. The +justification for the name is the material from which it is +sometimes made. Salts from H2CO3, called carbonates, are +numerous, Na2CO3 and CaCO3 being the most important. + +Chapter XXVI. + +OZONE. + +127. Preparation. + +Experiment 78.--Scrape off the oxide from the surface of a piece +of phosphorus 2 cm long, put it into a wide-mouthed bottle, half +cover the P with water, cover the bottle with a glass, and leave +it for half an hour or more. + +128. Tests. + +Experiment 79.--Remove the glass cover, smell the gas, and hold +in it some wet iodo-starch paper. Look for any blue color. Iodine +has been set free, according to the reaction, 2 KI + 03= K20 + O2 ++ I2, and has imparted a blue color to the starch, and ordinary +oxygen has been formed. Why will not oxygen set iodine free from +KI?. What besides ozone will liberate it? + +129. Ozone, oxidized oxygen, active oxygen, etc., is an +allotropic form of O. Its molecule is 03, while that of ordinary +oxygen is 02. + +Three atoms of oxygen are condensed into the space of two atoms +of ozone, or three molecules of O are condensed into two +molecules of ozone, or three liters of O are condensed into two +liters of ozone. Ozone is thus formed by oxidizing ordinary +oxygen. 02 + O = 03. This takes place during thunder storms and +in artificial electrical discharges. The quantity of ozone +produced is small, five per cent being the maximum, and the usual +quantity is far less than that. + +Ozone is a powerful oxidizing agent, and will change S, P, and As +into their ic acids. Cotton cloth was formerly bleached, and +linen is now bleached, by spreading it on the grass and leaving +it for weeks to be acted on by ozone, which is usually present in +the air in small quantities, especially in the country. Ozone is +a disinfectant, like other bleaching agents, and serves to clear +the air of noxious gases and germs of infectious diseases. So +much ozone is reduced in this way that the air of cities contains +less of it than country air. A third is consumed in uniting with +the substance which it oxidizes, while two-thirds are changed +into oxygen, as in Experiment 79. + +It is unhealthful to breathe much ozone, but a little in the air +is desirable for disinfection. + +Ozone will cause the inert N of the air to unite with H, to form +ammonia. No other agent capable of doing this is known, so that +all the NH3 in the air, in fact all ammonium compounds taken up +by plants from soils and fertilizers, may have been made +originally through the agency of ozone. At a low temperature +ozone has been liquefied. It is then distinctly blue. + +Electrolysis of water is the best mode of preparing this +substance in quantity. When prepared from P it is mixed with +P2O3. + +Chapter XXVII. + +CHEMISTRY OF THE ATMOSPHERE. + +130. Constituents.--The four chief constituents of the atmosphere +are N, O, H2O, CO2, in the order of their abundance. What +experiments show the presence of N, O, and CO2 in the air? Set a +pitcher of ice water in a warm room, and the moisture that +collects on the outside is deposited from the air. This shows the +presence of H2O. Rain, clouds, fog, and dew prove the same. H2SO4 +and CaCl2, on exposure to air, take up water. Experiment 18 shows +that there is not far from four times as much N as O by volume in +air. Hence if the atmosphere were a compound of N and O, and the +proportion of four to one were exact, its symbol would be N4O. + +131. Air not a Compound.--The following facts show that air is +not a compound, but rather a mixture of these gases. + +1. The proportion of N and O in the air, though it does not vary +much, is not always exactly the same. This could not be true if +it were a compound. Why? + +2. If N4O were dissolved in water, the N would be four times the +O in volume; but when air is dissolved, less than twice as much N +as O is taken up. + +3. No heat or condensation takes place when four measures of N +are brought in contact with one of O. It cannot then be N4O, for +the vapor density of N4O would be 36--i.e. (14 x 4 + 16) / 2; but +that of air is 14 1/2 nearly --i.e. (14 x 4 + 16) / 5. Analysis +shows about 79 parts of N to 21 parts of O by volume in air. + +132. Water.--The volume of H2O, watery vapor, in the atmosphere +is very variable. Warm air will hold more than cold, and at any +temperature air may be near saturation, i.e. having all it will +hold at that temperature, or it may have little. But some is +always present; though the hot desert winds of North Africa are +not more than 1/15 saturated. A cubic meter of air at 25 degrees, +when saturated, contains more than 22 g. of water. + +133. Carbon Dioxide.--Carbon dioxide does not make up more than +three or four parts in ten thousand of the air; but, in the whole +of the atmosphere, this gives a very large aggregate. Why does +not CO2 form a layer below the O and N? + +134. Other Ingredients.--Other substances are found in the air in +minute portions, e.g. NH3 constitutes nearly one-millionth. Air +is also impregnated with living and dead germs, dust particles, +unburned carbon, etc., but these for the most part are confined +to the portion near the earth's surface. In pestilential regions +the germs of disease are said sometimes to contaminate the air +for miles around. + +Chapter XXVIII. + +THE CHEMISTRY OF WATER. + +135. Pure Water.--Review the experiments for electrolysis, and +for burning H. Pure water is obtained by distillation. + +Experiment 80.--Provide a glass tube 40 or 50 cm long and 3 or 4 +cm in diameter. Fit to each end a cork with two perforations, +through one of which a long tube passes the entire length of the +larger tube (Fig. 32a). Connect one end of this with a flask of +water arranged for heating; pass the other end into an open +receptacle for collecting the distilled water. Into the other +perforations lead short tubes,-- the one for water to flow into +the large tube from a jet; the other, for the same to flow out. +This condenses the steam by circulating cold water around it. The +apparatus is called a Liebig's condenser. Put water into the +flask, boil it, and notice the condensed liquid. It is +comparatively pure water; for most of the substances in solution +have a higher boiling-point than water, and are left behind when +it is vaporized. + +(Fig. 32a.) + +136. Test. + +Experiment 81.--Test the purity of distilled water by slowly +evaporating a few drops on Pt foil in a room free from dust. +There should be no spot or residue left on the foil. Test in the +same way undistilled water. 137. Water exists in Three States,-- +solid, liquid, and vaporous. It freezes at 0 degrees, suddenly +expanding considerably as it passes into the solid state. It +boils, i.e. overcomes atmospheric pressure and is vaporized, at +100 degrees (760 mm pressure). If the pressure is greater, the +boiling-point is raised, i.e. it takes a higher temperature to +overcome a greater pressure. If there be less pressure, as on a +mountain, the boiling-point is lowered below 100 degrees. Salts +dissolved in water raise its boiling-point, and lower its +freezing-point to an extent depending on the kind and quantity of +the salt. Water, however, evaporates at all temperatures, even +from ice. + +Pure water has no taste or smell, and, in small quantities, no +color. It is rarely if ever found on the earth. What is taken up +by the air in evaporation is nearly pure; but when it falls as +rain or snow, impurities are absorbed from the atmosphere. Water +falling after a long rain, especially in the country, is +tolerably free from impurities. Some springs have also nearly +pure water; but to separate all foreign matter from it, water +must be distilled. Even then it is liable to contain traces of +ammonia, or some other substance which vaporizes at a lower +temperature than water. + +138. Sea-Water.--The ocean is the ultimate source of all water. +From it and from lakes, rivers, and soils, water is taken into +the atmosphere, falls as rain or snow, and sinks into the ground, +reappearing in springs, or flowing off in brooks and rivers to +the ocean or inland seas. Ocean water must naturally contain +soluble salts; and many salts which are not soluble in pure water +are dissolved in sea-water. In fact, there is a probability that +all elements exist to some extent in sea-water, but many of them +in extremely minute quantities. Sodium and magnesium salts are +the two most abundant, and the bitter taste is due to MgSO4 and +MgCl2. A liter of sea- water, nearly 1000 g., holds over 37 g. of +various salts, 29 of which are NaCl. See Hard Water. + +139. River Water.--River water holds fewer salts, but has a great +deal of organic matter, living and dead, derived from the regions +through which it flows. To render this harmless for drinking, +such water should be boiled, or filtered through unglazed +porcelain. Carbon filters are now thought to possess but little +virtue for separating harmful germs. + +140. Spring Water.--The water of springs varies as widely in +composition as do the rocks whence it bubbles forth. Sulphur +springs contain much H2S; many geysers hold SiO2 in solution; +chalybeate waters have compounds of Fe; others have Na2SO4, MgSO4 +NaCl, etc. + +CHAPTER XXIX. + +THE CHEMISTRY OF FLAME. + +141. Candle Flame. + +Experiment 82.--Examine a candle flame, holding a dark object +behind it. Note three distinct portions: (1) a colorless interior +about the wick, (2) a yellow light-giving portion beyond that, +(3) a thin blue envelope outside of all, and scarcely +discernible. Hold a small stick across the flame so that it may +lie in all three parts, and observe that no combustion takes +place in the inner portion. + +142. Explanation.--A candle of paraffine, or tallow, is chiefly +composed of compounds of C and H, in the solid state. The burning +wick melts the solid; the liquid is then drawn up by the wick +till the heat vaporizes and decomposes it, and O of the air comes +in contact with the outer heated portion of gas, and burns it +completely. Air tends to penetrate the whole body of the flame, +but only N can pass through uncombined, for the O that is left +after combustion in the outer portion seizes upon the compounds +of C and H in the next, or yellow, part. There is not enough O +here for complete combustion; at this temperature H burns before +C, and the latter is set free. In that state it is of course a +solid. Now an incandescent solid, or one glowing with heat, gives +light, while the combustion of a gas gives scarcely any light, +though it may produce great heat. While C in the middle flame is +glowing, during the moment of its dissociation from H, it gives +light. In the outer flame the temperature is high enough to burn +entirely the gaseous compounds of C and H together, so that no +solid C is set free, and hence no light is given except the faint +blue. No combustion takes place in the inner blue cone, because +no O reaches there. + +By packing a wick into a cylindrical tin cup 5 or 10 cm high and +4 cm in diameter, containing alcohol, and lighting it, gunpowder +can be held in the middle of the flame in a def. spoon, without +burning. This shows the low temperature of that portion. Burning +P will also be extinguished, thus showing the exclusion of O. + +143. Bunsen Flame. + +Experiment 83.--Examine a Bunsen burner. Unscrew the top, and +note the orifices for the admission of gas and of air. Make a +drawing. Replace the parts; then light the gas at the top, +opening the air-holes at the base. Notice that the flame burns +with very little color. Try to distinguish the three parts, as in +the candle flame. These parts can best be seen by allowing direct +sunlight to fall on the flame and observing its shadow on a white +ground. Make a drawing of the flame. Hold across it a Pt wire and +note at what part the wire glows most. Also press down on the +flame for an instant with a cardboard or piece of paper; remove +before it takes fire, and notice the charred circle. Put the end +of a match into the blue cone, and note that it does not burn. +Put the end of a Pt wire into this blue cone, and observe that it +glows when near the top of the cone. What do these experiments +show? Ascertain whether this inner portion contains a combustible +material, by holding in it one end of a small d.t., and trying to +ignite any gas escaping at the other end. It should burn. This +shows that no combustion takes place in the interior of the +flame, because sufficient free O is not present. + +Next, close the air-holes, and note that the flame is yellow and +gives much light. From this we infer the presence of solid +particles in an incandescent state. But these could not come from +the air. They must be C particles which have been set free from +the C and H compounds of the gas, just as in the candle flame. +The smoke that rises proves this. Hold an e.d. in the flame and +collect some C. Try the same with the air-holes open. 144. Light +and Heat of Flame.--Which of the two flames is hotter, the one +with the air-holes open, or that with them closed? Evidently the +former; for air is drawn in and mixes with the gas as it rises in +the tube, and, on reaching the flame at the top, the two are well +mingled, and the gaseous compounds of C and H burn at so high a +temperature that solid C is not freed; hence there is little +light. On closing the air-holes, no O can reach the flame except +from the outside, and the heat is much less intense. + +(Fig 33.) (Fig 34.) + +The H burns first, and sets the C free, which, while glowing, +gives the light. This again illustrates the facts (1) that flame +is caused by burning gas; (2) that light is produced by +incandescent solids. Charcoal, coke, and anthracite coal burn +without flame, or with very little, because of the absence of +gases. + +145. Temperature of Combustion. + +Experiment 84.--Light a Bunsen flame, with the basal orifices +open, and hold over it a fine wire gauze. Notice that the flame +does not rise above the gauze. Extinguish the light, and try to +ignite the gas above the gauze, holding the latter within 5 or 6 +cm of the burner tube. Notice that it does not burn below the +gauze (Fig. 33). + +Gas and O are both present. Evidently, then, the only condition +wanting for combustion is a sufficiently high temperature. The +gauze cools the gas below its kindling- point. + +This principle is made use of in the miner's lamp of Davy (Fig. +34). In coal mines a very inflammable gas, CH4, called fire-damp, +issues from the coal. If this collects in large quantities and +mixes with O of the air, a kindling-point is all that is needed +to make a violent explosion. An ordinary lamp would produce this, +but the gauze lamp prevents it; for, though the inside may be +filled with burning gas, CH4, the flame cannot communicate with +the outside. + +(Fig 35.) (Fig 36.) +a, reducing flame b, oxidizing flame + +146. Oxidizing and Reducing Flames.--The hottest part of a Bunsen +flame is just above the inner blue cone (b, Fig. 36). Evidently +there is more O at that point. If a reducing agent, i.e. a +substance which takes up O, be put into this part of the flame, +the latter will remove the O and appropriate it, forming an +oxide. Cu heated there would become copper oxide. This part is +called the oxidizing flame. The inner blue part of the Bunsen +flame is devoid of O. It ought to remove O from an oxidizing +agent, i.e. a substance which supplies O. If copper oxide be +heated there (a, Fig. 36) by means of a mouth blow-pipe (Fig. +35), the flame will appropriate the O and leave the copper. This +is called the reducing flame. Only the upper part of this blue +central cone has heat enough to act in this way. By using a +prepared piece of metal, to make the flame thin and to shut off +the air, and then blowing the flame with a blow-pipe, greater +strength can be obtained in both oxidizing and reducing flames +(Fig. 36). + +147. Combustible and Supporter Interchangeable.-- H was found to +burn in O. H was the combustible, O the supporter. Would O itself +burn in H?--i.e. would the combustible become the supporter, and +the supporter the combustible? As illuminating gas consists +largely of H, and as air is part O, we may try the experiment +with gas and air. Gas will burn in air. Will air burn in gas? + +Experiment 85.--Fit a cork with two holes in it to the large end +of a lamp chimney. Through each hole pass a short piece of +tubing, and connect one of these with a rubber tube leading to a +gas-jet. Pass a metallic tube, long enough to reach the top of +the chimney, through the other, so that it will move easily up +and down. Turn on the gas, and light it at the top of the +chimney. Hold the end of the tube passing through the cork in the +flame for a minute, then draw it down to the middle of the +chimney (Fig. 37, a) and finally slowly remove it (b). Note that +O from the air is burning in the gas. Which is the supporter, and +which the combustible in this case? O will burn equally well in +an atmosphere of H, as can be shown by experiment. + +148. Explosive Mixture of Gases. + +Experiment 86.--Slowly turn down the burning gas of a Bunsen +lamp, having the orifices open, and notice that it suddenly +explodes and goes out at the top, but now burns at the base. As +the gas was gradually turned off, more air became mixed with it, +until there was the right proportion of each gas for an +explosion. Figure 38 shows the same thing. Light the gas at the +top a, when the tube c covers the jet b. Then gradually raise the +tube c. At a certain place there is the same explosion as with +the lamp. + +149. Generalizations.--These experiments show (1) that three +conditions are necessary for combustion,--a combustible, a +supporter, and a burning temperature which varies for different +substances. Given these, "a fire" always results. The conditions +for "spontaneous combustion" do not differ from those of any +combustion. See Experiments 34, 112, 113, 114. (2) That +combustible and supporter are interchangeable. If H burns in O, O +will burn in H, the product, being the same in each case. (3) For +any combustion there must be a certain proportion of combustible +and of supporter. Twenty per cent of CO2 in the air dilutes the O +to such an extent that C will not burn. Hence the utility of the +chemical engine for putting out fires. (4) When two + +gases, a combustible and a supporter, are mixed in the requisite +proportion, they form an explosive mixture, needing only the +kindling temperature to unite them. + +Chemical combination is always accompanied by disengagement of +heat. Chemical dissociation is always accompanied by absorption +of heat. The disengagement, or the absorption, is not always +evident to the senses. + +Combustion is the chemical combination of two or more substances +with the self-evident disengagement of great heat, and usually of +light. + +The temperature of ignition varies greatly with different +substances. PH3 burns spontaneously at the usual temperatures of +the air. P takes fire at 60 degrees, but even at 10 degrees it +oxidizes with rapidity enough to produce phosphorescence. The +vapor of CS2 may be set on fire by a glass rod heated to 150 +degrees, but a red-hot iron will not ignite illuminating gas. + +Spontaneous combustion often takes place in woolen or cotton rags +which have been saturated with oil. The oil rapidly absorbs O, +and sets fire to the cloth. This is thought to be the origin of +some very destructive fires. + +CHAPTER XXX. + +CHLORINE. + +150. Preparation. + +Experiment 87.--Put into a t.t. 5 g. of fine granular MnO2 and 10 +cc. HCl. Apply heat carefully, and collect the gas by downward +displacement in a receiver loosely covered with paper (Fig. 39). +Add more HCl if needed. Have a good draft of air, and do not +inhale the gas. If you have accidentally breathed it, inhale +alcohol vapor from a handkerchief; alcohol has great affinity for +Cl. Note the color of the gas, and compare its weight with that +of air. + +MnO2 + 4 HCl = MnCl2 + 2 H2O + 2 Cl. How much Cl can be separated +with 5 g. MnO2? + +If preferred, a flask may be used for a generator instead of a +t.t. Cl can be obtained directly from NaCl by adding H2SO4 (which +produces HCl) and MnO2. 2 NaCl + 2 H2SO4 + MnO2 = MnSO4 + Na2SO4 ++ 2 H2O + 2 Cl. Try the experiment, using a t.t. and adding +water. + +151. Cl from Bleaching-Powder. + +Experiment 88.--Put a few grams of bleaching- powder into a small +beaker, and set this into a larger one. Cover the latter with +pasteboard or paper, through which passes a thistle-tube reaching +into the small beaker (Fig. 40). Pour through the tube a little +H2SO4 dilated with its volume of H2O. + +152. Chlorine Water.--A solution of Cl in water is often useful, +and may be made as follows:-- Experiment 89.--To 3 or 4 crystals +of KClO3 add a few drops of HCl. Heat a minute, and when the gas +begins to disengage, pour in 10 cc. H2O, which dissolves the gas. +2 KClO3 + 4 HCl = 2 KCl + Cl2O4 + 2 H2O + 2 Cl. + +153. Bleaching Properties. + +Experiment 90.--Put into a receiver of Cl, preferably before +generating it, two pieces of Turkey red cloth, one wet, the other +dry; a small piece of printed paper and a written one; also a red +rose or a green leaf, each wet. Note from which the color is +discharged. If it is not discharged from all, put a little H2O +into the receiver, shake it well, and state what ones are +bleached. + +Experiment 91.--(1) Add 5 cc. of Cl water to 5 cc. of indigo +solution. (2) Treat in the same way 5 cc. K2Cr2O7 (potassium +dichromate) solution, and record the results. + +Indigo, writing-ink, and Turkey red or madder, are vegetable +pigments; printer's ink contains C, and K2Cr2O7 is a mineral +pigment. State what coloring matters Cl will bleach. + +154. Disinfecting Power. + +Experiment 92.--Pass a little H2S gas from a generator into a +t.t. containing Cl water. Look for a deposit of S. Notice that +the odor of H2S disappears. H2S + 2 Cl = 2 HCl + S. + +155. A Supporter of Combustion. + +Experiment 93.--Sprinkle into a receiver of Cl a very little fine +powder or filings of Cu, As, or Sb, and notice the combustion. +Observe that here is a case of combustion in which O does not +take part. Chlorides of the metals are of course formed. Write +the reactions. See whether Cl will support the combustion of +paper or of a stick of wood. + +Experiment 94.--Warm 2 or 3 cc. of oil of turpentine (C1OH16) in +an evaporating-dish; dip a piece of tissue paper into it, and +very quickly thrust this into a receiver of Cl. It should take +fire and deposit carbon. C1OH16 + 16 Cl = ? Test the moisture on +the sides of the receiver with litmus. Clean the receiver with a +little petroleum. + +Experiment 95.--Prepare a H generator with a lamp-tube bent as in +Figure 41. Light the H, observing the cautions in Experiment 23, +and when well burning, lower the flame into a receiver of Cl. +Observe the change of color which the flame undergoes as it comes +in contact with Cl. Give the reaction for the burning. Test with +litmus any moisture on the sides of the receiver. A mixture of Cl +and H, in direct sunlight combines with explosive violence; +whereas in diffused sunlight it combines slowly, and in darkness +it does not combine. From these experiments state the chief +properties of Cl, and what combustion it will support. + +[Figure 41.] + +156. Sources and Uses.--The great source of Cl is NaCl, though it +is often made from HCl. Its chief use is in making bleaching- +powder, one pound of which will bleach 300 to 500 pounds of +cloth. Cl is very easily liberated from this powder by a dilute +acid, or, slowly, by taking moisture from the air. Hence its use +as a disinfectant in destroying noxious gases and the germs of +infectious diseases. Cl attacks organic matter and germs as it +does the membrane of the throat or lungs, owing to its affinity +for H. + +Cl is the best bleaching agent for cotton goods. It is not +suitable for animal materials, such as silk and wool, as it +attacks their fiber. It does not discharge either mineral or +carbon colors. The chemistry of bleaching is obscure. + +As dry material will not bleach, Cl seems to unite with H in H2O +and to set O free. The O then unites with some portion of the +coloring matter, oxidizing it, and breaking up its molecule. +Colors bleached by Cl cannot be restored. + +Chapter XXXI. + +BROMINE. + +Examine bromine, potassium bromide, sodium bromide, magnesium +bromide. + +157. Preparation. + +Experiment 96.--Pulverize 2 or 3 g. KBr, and mix it with about +the same bulk of MnO2. After putting this into a t.t, add as much +H2SO4, mix them together by shaking, attach a d.t., and conduct +the end of it into a t.t. that is immersed in a bottle of cold +water. Slowly heat the contents of the t.t., and notice the color +of the escaping vapor, and any liquid that condenses in the +receiver. Avoid inhaling the fumes, or getting them into the +eyes. + +MnO2 + 2 KBr + 2 H2SO4 = ? Compare this with the equation for +making Cl from NaCl. + +158. Tests. + +Experiment 97.--Try the bleaching action of Br vapor as in the +case of Cl. Bleach a piece of litmus paper, and try to restore +the color with NH4OH. Explain its bleaching and disinfecting +action. Try the combustibility of As, Sb, and Cu. + +159. Description.--Bromine at usual temperatures is a liquid +element; it is the only common one except Hg; it. quickly +evaporates on exposure to air. The chemistry of its manufacture +is like that of Cl; its bleaching and disinfecting powers are +similar to the latter, though they are not quite so strong as +those of Cl. Its affinity for H and for metals is also strongly +marked. A drop of Br on the skin produces a sore slow to heal. +Bromine salts are mainly KBr, NaBr, MgBr2. These in small +quantities accompany NaCl, and are most common in brine springs. +The world's supply of Br comes chiefly from West Virginia and +Ohio, over 300,000 pounds being produced from the salt (NaCl) +wells there in 1884. The water taken from these wells is nearly +evaporated, after which NaCl crystallizes out, leaving a thick +liquid--bittern, or mother liquor--which contains the salts of +Br. The bittern is treated with H2SO4 and Mn02, as above. + +For transportation in large quantities, Br has to be made into +the salts NaBr and KBr, on account of the danger attending +leakage or breakage of the receptacles for Br. + +160. Uses.--Its chief uses are in photography (page 167), +medicine, as KBr, and analytical chemistry. + +Chapter XXXII. + +IODINE. + +Examine iodine, potassium iodide. + +161. Preparation of I. + +Experiment 98.--Put into a t.t. 2 or 3 g. of powdered KI mixed +with an equal bulk of MnO2, add H2SO4 enough to cover well, shake +together, complete the apparatus as for making Br, and heat. +Notice the color of the vapor, and any sublimate. The direct +product of the solidification of a vapor is called a sublimate. +The process is sublimation. Observe any crystals formed. Write +the reaction, and compare the process with that for making Br and +Cl. Compare the vapor density of I with that of Br and of Cl. +With that of air. What vapor is heavier than I? What acid and +what base are represented by KI? + +162. Tests. + +Experiment 99.--(1) Put a crystal of I in the palm of the hand +and watch it for a minute. (2) Put 2 or 3 crystals into a t.t., +and warm it, meanwhile holding a stirring-rod half-way down the +tube. Notice the vapor, also a sublimate on the sides of the t.t. +and rod. (3) Add to 2 or 3 crystals in a t.t. 5 cc. of alcohol, +C2H5OH; warm it, and see whether a solution is formed. If so, add +5 cc. H2O and look for a ppt. of I. Does this show that I is not +at all soluble in H2O, or not so soluble as in alcohol? + +163. Starch Solution and Iodine Test. + +Experiment 100.--Pulverize a gram or two of starch, put it into +an evaporating-dish, add 4 or 5 drops of water, and mix; then +heat to the boiling-point 10 cc. H2O in a t.t., and pour it over +the starch, stirring it meanwhile. + +(1) Dip into this starch paste a piece of paper, hold it in the +vapor of I, and look for a change of color. (2) Pour a drop of +the starch paste into a clean t.t., and add a drop or two of the +solution of I in alcohol. Add 5 cc. H2O, note the color, then +boil, and finally cool. (3) The presence of starch in a potato or +apple can be shown by putting a drop of I solution in alcohol on +a slice of either, and observing the color. (4) Try to dissolve a +few crystals of I in 5 cc. H2O by boiling. If it does not +disappear, see whether any has dissolved, by touching a drop of +the water to starch paste. This should show that I is slightly +soluble in water. + +164. Iodo-Starch Paper. + +Experiment 101.--Add to some starch paste that contains no I 5 +cc. of a solution of KI, and stir the mixture. Why is it not +colored blue? Dip into this several strips of paper, dry them, +and save for use. This paper is called iodo-starch paper, and is +used as a test for ozone, chlorine, etc. Bring a piece of it in +contact with the vapor of chlorine, bromine, or ozone, and notice +the blue color. + +Experiment 102.--Add a few drops of chlorine water to 2cc. of the +starch and KI solution in 10 cc. H2O. This should show the same +effect as the previous experiment. + +165. Explanation.--Only free I, not compounds of it, will color +starch blue. It must first be set free from KI. Ozone, chlorine, +etc., have a strong affinity for K, and when brought in contact +with KI they unite with K and set free I, which then acts on the +starch present. Com- plete the equation: KI + Cl = ? + +166. Occurrence.--The ultimate source of I is sea water, of which +it constitutes far too small a percentage to be separated +artificially. Sea-weeds, or algae, especially those growing in +the deep sea, absorb its salts--NaI, KI, etc.--from the water. It +thus forms a part of the plant, and from this much of the I of +commerce is obtained. Algae are collected in the spring, on the +coasts of Ireland, Scotland, and Normandy, where rough weather +throws them up. They are dried, and finally burned or distilled; +the ashes are leached to dissolve I salts; the water is nearly +evaporated, and the residue is treated with H2SO4, and MnO2, as +in the case of Br and Cl. I also occurs in Chili, as NaI and +NaIO3, mixed with NaNO3. This is an important source of the I +supply. + +167. Uses.--I is much used in medicine, and was formerly employed +in taking daguerreotypes and photographs. Its solution in alcohol +or in ether is known as tincture of iodine. + +168. Fluorine.--F, Cl, Br, I, are called halogens or haloids, and +exist in compounds--salts--in sea water. F is the most active of +all elements, combining with every element except O. Until +recently it has never been isolated, for as soon as set free from +one compound it attacks the nearest substance, and seems to be as +much averse to combining with itself, or to existing in the +elementary state, as to uniting with O. It is supposed to be a +gas, and, as is claimed, has lately been isolated by electrolysis +from HF in a Pt U-tube. Fluorite (CaF2) and cryolite (Al2F6 + 6 +NaF) are its two principal mineral sources. The enamel of the +teeth contains F in composition. + +CHAPTER XXXIII. + +THE HALOGENS. + +169. Halogens Compared.--The elements F, Cl, Br, I, form a +natural group. Their properties, as well as those of their +compounds, vary in a step-by-step way, as seen below. F is +sometimes an exception. They are best remembered by comparing +them with one another. Notice: + +1. Similarity of name-ending. Each name ends in ine. + +2. Similarity of origin. Salt water is the ultimate source of +all, except F. + +3. Similarity of valence. Each is usually a monad. + +4. Similarity of preparation. Cl, Br, I, are obtained from their +salts by means of MnO2 end H2SO4. + +5. Variation in occurrence. Cl occurs in sea-salt, Br in sea- +water, I in sea-weed. + +6. Variation in color; F being colorless, Cl green, Br red, I +violet. + +7. Gradation in sp. gr.; F 19, Cl 35.5, Br 80, I 127. + +8. Gradation in state, corresponding to sp. gr.; F being a light +gas, Cl a heavy gas, Br a liquid, I a solid. + +9. Corresponding gradation in their usual chemical activity; F +being most active, then Cl, Br, and I. + +10. Corresponding gradation in the strength of the H acids; the +strongest being HF, the next, HCl, etc. + +11. Corresponding gradation in the explosibility of their N +compounds; the strongest NCl3, the next, NBr3, etc. + +12. Corresponding gradation in the number of H and O acids; Cl 4, +Br 3, I 2. + +170. Compounds.--The following are some of the oxides, acids, and +salts of the halogens. Name them. + + +CI2O (+H2O=) 2 HClO. The salts are hypochlorites, as Ca(ClO)2. +Cl2O3 (+H20=) 2 HClO2. The salts are chlorites, as KClO2. +Cl2O4 +-- HClO3 The salts are chlorates, as KClO3. +-- HClO4 The salts are perchlorates, as KClO4, +-- HBrO The salts are ? KBrO, +-- -- The salts are wanting. +-- HBrO3. The salts are ? KBrO3, +-- HBrO4. The salts are ? KBrO4, +-- -- The salts are wanting. +-- -- The salts are wanting. +I2O5 (+H2O=) 2 HIO3. The salts are ? KIO3. +-- HIO4. The salts are ? KIO4. + + +F forms no oxides, and no acids except HF. HF, HCl, HBr, HI, are +striking illustrations of acids with no O. HClO4 is a very strong +oxidizing agent. A drop of it will set paper on fire, or with +powdered charcoal explode violently. This is owing to the ease +with which it gives up 0. Notice why its molecule is broken up +more readily than HC103. The higher the molecular tower, or the +more atoms it contains, the greater its liability to fall. Some +organic compounds contain hundreds of atoms, and hence are easily +broken down, or, as we say, are unstable. Inorganic compounds +are, as a rule, much more stable than organic ones. It is not +always true, however, that the compound with the least number of +atoms is the most stable. SO2 is more stable than SO3, but H2SO3 +is less so than H2SO4. +Chapter XXXIV. + +VAPOR DENSITY AND MOLECULAR WEIGHT. + +Examine a liter measure, in the form of a cube,--cubic decimeter, +--and a cubic centimeter. + +171. Gaseous Weights and Volumes.--A liter of H, at 0 degrees +and 760 mm., weighs nearly 0.09 g. This weight is called a crith. +Find the weight of H in the following, in criths and in grams: 15 +1., 0.07 1., 50.3 1., 0.035 1., 0.6 1.. + +It has been estimated that there are (10) 24. molecules of H in a +liter. Does the number vary for different gases? The weight of a +molecule of H in parts of a crith is 1/(10) 24.; in parts of a +gram .09/(10) 24.. If the H molecule is composed of 2 atoms, what +is the weight of its atom in fractions of a crith? What in +fractions of a gram? The weight of the H atom is a microcrith. +What part of a crith is a microcrith? + +172. Vapor Density.--Vapor density, or specific gravity referred +to H as the standard, (Physics) is the ratio of the weight of a +given volume of a gas or vapor to the weight of the same volume +of H. A liter of steam weighs nine times as much as a liter of H. +Its vapor density is therefore nine. For convenience, a definite +volume of H is usually taken as the standard, viz., the H atom. +The volume of the H atom and that of the half-molecule of H2O, or +of any gas are identical, each being represented by one square. +If, then, the standard of vapor density is the H atom, half the +molecular weight of a gas must be its vapor density, since it is +evident that we thus compare the weights of equal volumes. The +vapor density of H2O, steam, is found from the symbol as follows: +(2 + 16) / 2 = 9. To obtain the vapor density of any compound +from the formula, we have only to divide its molecular weight by +two. Find the vapor density of HCl, N2O, NO, C12H22O11, Cl, CO2, +HF, SO2. Explain each case. + +The half-molecule, instead of the whole, is taken; because our +standard is the hydrogen atom, the smallest portion of matter, by +weight, known to science. + +How many criths in a liter of HCl? How many grams? Compute the +number of criths and of grams in one liter of the compounds whose +symbols appear above. + +PROBLEMS. + +(1) A certain volume of H weighs 0.36 g. at standard temperature +and pressure. How many liters does it contain? If one liter +weighs 0.09 g., to weigh 0.36 g. it will take 0.36 / 0.09 = 4 +liters. + +(2) How many liters, or criths, of H in 63 g.? 2.7 g.? 1 g.? 5 +g.? 250 g.? Explain each. + +(3) Suppose the gas to be twice as heavy as H, how many liters in +0.36 g.? A liter of the gas will weigh 0.18 g. (0.09 X 2). In +0.36 g. there will be 0.36 / 0.18 = 2. Answer the question for 63 +g., 2.7 g., etc. + +(4) How many liters of Cl in each of the above numbers of grams? + +(5) How many of HCl? H2O (steam)? CO2? Explain fully every case. + +Vapor density is very easily determined from the formula by the +method given above. But in practice the formula is obtained from +the vapor density, and hence the method there given has to be +reversed. + +173. Vapor Density of Oxygen.--Suppose we were to obtain the +vapor density of O. We should carefully seal and weigh a given +volume, say a liter, at a noted temperature and barometric +pressure, which are reducedto 0 degrees and 760 mm, and compare +it with the weight of the same volume of H. This has been done +repeatedly, and O has been found to weigh 16 times as much as H, +volume for volume, or, more exactly, 15.96+. Now a liter of each +gas has the same number of molecules, therefore the O molecule +weighs 16 times the H molecule. The half-molecule of each has the +same proportion, and the vapor density of O is 16. Atomic weight +is obtained in a very different way. + +PROBLEMS. + +(1) A liter of Cl is found to weigh 3.195 g. Compute its vapor +density, and explain fully. + +(2) A liter of Hg vapor, under standard conditions, weighs 9 g. +Find its vapor density, and explain. + +The vapor density of only a few elements has been satisfactorily +determined. See page 12. Some cannot be vaporized; others can be, +but only under conditions which prevent weighing them. The vapor +density of very many compounds also is unknown. + +(3) A liter of CO2 weighs 1.98 g. Find the vapor density, and +from that the molecular weight, remembering that the latter is +twice the former. See whether it corresponds to that obtained +from the formula, CO2. This is,in fact, the way a formula is +ascertained, if the atomic weights of its elements are known. + +(4) A liter of a compound gas weighs 2.88 g. Analysis shows that +its weight is half S and half O. As the atomic weight of S is 32, +and that of O is 16, what is the symbol for the gas? + +Solution. Its molecular weight is 64, i.e. (2.88=0.09) X 2, of +which 32 is S and 32 O. The atomic weight of S is 32, hence there +is one atom of S, while of O there are two atoms. The formula is +SO2. + +(5) A liter of a compound gas, which is found to contain 1 C and +3 O by weight, weighs 1.26 g. What is its formula? Atomic weights +are taken from page 12. Prove your answer. + +(6) A liter of a compound of N and O weighs 1.98 g. The N is +7/11; and the O 4/11. What is the gas? + +(7) A compound of N and H gas weighs 0.765 g. to the liter. The N +is 14/17 of the whole, the H 3/17. What gas is it? CHAPTER XXXV. + +ATOMIC WEIGHT. + +174. Definition.--We have seen that the molecular weight of a +compound, as well as of most elements, is obtained from the vapor +density by doubling the latter. It remains to explain how atomic +weights are obtained. The term is rather misleading. The atomic +weight of an element is its least combining weight, the smallest +portion that enters into chemical union, which is, of course, the +weight of an atom. + +175. Atomic Weight of Oxygen.--Suppose we wish to find the atomic +weight of oxygen. We must find the smallest proportion by weight +in which it occurs in any compound. This can only be done by +analyzing all the compounds of O that can be vaporized. As +illustrative of these compounds take the six following:-- + + + Wt. of other +Names. V. d. Mol. Wt. Wt. of O. Elem. Symbol. +Carbon monoxide... 14 28 16 12 ? +Carbon dioxide.... 22 44 32 12 ? +Hydrogen monoxide... 9 18 16 2 ? +Nitrogen monoxide... 22 44 16 28 ? +Nitrogen trioxide... 38 76 48 28 ? +Nitrogen pentoxide... 54 108 80 28 ? + + +176. Molecular Symbols.--From the vapor density of the gases-- +column 2--we obtain their molecular weight-- column 3. To find +the proportion of O, it must be separated by chemical means from +its compounds and separately weighed. These relative weights are +given in column 4. Now the smallest weight of O which unites in +any case is its atomic weight. If any compound of O should in +future be found in which its combining weight is 8 or 4, that +would be called its atomic weight. By dividing the numbers in +column 4, wt. of O, by 16, the atomic weight of O, we obtain the +number of O atoms in the molecule. Subtracting the weights of O +from the molecular weights, we have the parts of the other +elements, column 5, and dividing these by the atomic weight of +the respective elements, we have the number of atoms of those +elements, these last, combined with the number of O atoms, give +the symbol. In this way complete the last column. + +Show how to get the atomic weight of Cl from these compounds, +arranging them in tabular form, and completing as above: HCl, +KCl, NaCl, ZnCl2, MgCl2; the atomic weight of N in these: N2O, +NO, NH3. + +177. Molecular and Atomic Volumes.--We thus see that vapor +density and atomic weight are obtained in two quite different +ways. In the case of elements the two are usually identical, i.e. +with the few whose vapor density is known; but this is not always +true, and it leads to interesting conclusions regarding atomic +volume. In O both vapor density and atomic weight are 16. This +gives 2 atoms of O to the molecule, i.e. the molecular weight / +the atomic weight. The size of an O atom is therefore half the +gaseous molecule, and is represented by one square. S has a vapor +density and an atomic weight of 32 each. Compute the number of +atoms in the molecule. Compute for I, in which the two are +identical, 127. P has an atomic weight of 31, while its vapor +density is 62. Its molecule must consist of 4 atoms, each half +the size of the H atom, The vapor density of As is 150, the +atomic weight 75. Compute the number of atoms in its molecule, +and represent their relative size. Hg has an atomic weight of +200, a vapor density of 100. Compute as before, and compare the +results with those on page 12. Ozone has an atomic weight of 16, +a vapor density 24. Compute. + +Chapter XXXVI. + +DIFFUSION AND CONDENSATION OF GASES. + +178. Diffusion of Gases.--Oxygen is 16 times as heavy as H. If +the two gases were mixed, without combining, in a confined space, +it might be supposed that O would settle to the bottom and H rise +to the top. This would, in fact, take place at first, but only +for an instant, for all gases tend to diffuse or become +intimately mixed. The lighter the gas the more quickly it +diffuses. + +179. Law of Diffusion of Gases.--The diffusibility of gases +varies inversely as the square roots of their vapor densities. +Compare the diffusibility of H with that of O. dif. H:dif. O:: +sqrt(16): sqrt(1), or dif: H: dif. O:: 4: 1. + +That is to say, if H and O be set free from separate receivers in +a room, the H will become intermingled with the atmosphere four +times as quickly as the O. Compare the diffusibility of O and N; +of Cl and H. Take the atomic weights of these, since they are the +same as the vapor densities. In case of a compound gas, half the +molecular weight must be taken for the vapor density; e.g. dif. +N20: dif. O.:: sqrt(16): sqrt(22). + +180. Cause.--Diffusion is due to molecular motion; the lighter +the gas the more rapid the vibration of its molecules. Compare +the diffusibility of CO2 and that of Cl; of HCl and SO2; of HF +and I. + +181. Liquefaction and Solidification of Gases.--Water boils at +100 degrees, under standard pressure, though evaporating at all +temperatures; it vaporizes at a lower point if the pressure be +less, as on a mountain, and at a higher temperature if the +pressure be greater, as at points below the sea level. Alcohol +boils at 78 degrees, standard pressure, and every liquid has a +point of temperature and pressure above which it must pass into +the gaseous state. Likewise every gas has a critical temperature +above which it cannot be liquefied at any pressure. + +This condition was not recognized formerly, and before 1877, O, +H, N, C4, CO, NO, etc., had not been liquefied, though put under +a pressure of more than 2,000 atmospheres. They were called +permanent gases. In 1877 Cailletet and Pictet liquefied and +solidified these and others. The lowest temperature, about -225 +degrees, was produced by suddenly releasing the pressure from +solid N to 4mm, which caused it rapidly to evaporate. +Evaporation, especially under diminished pressure, always lowers +the temperature by withdrawing heat. + +These low degrees are indicated by a H thermometer, or if too low +for that, by a "thermo-electric couple" of copper and German +silver. + +The pupil can easily liquefy SO, by passing it through a U-tube +which is surrounded by a mixture of ice and salt in a large +receiver. At the meeting of the American Association for the +Advancement of Science in 1887, a solid brick of CO2 was seen and +handled by the members, Liquid H is steel blue. + +A few results obtained under a pressure of one atmosphere are:-- +Boiling Points: C2H4--102 degrees; CH4--184 degrees; O--181 +degrees; N --194 degrees; CO--190 degrees; NO--154 degrees; Air-- +191 degrees. + +Solidifying Points: Cl -102 degrees; HCl -115 degrees; Ether -129 +degrees; Alcohol -130 degrees. + +Chapter XXXVII. + +SULPHUR. + +Examine brimstone, flowers of sulphur, pyrite, chalcopyrite, +sphalerite, galenite, gypsum, barite. + +182. Separation. + +Experiment 103.--To a solution of 2 g. of sodium sulphide,, Na2S2 +in 10 cc. H2O add 3 or 4cc. HCl, and look for a ppt. Filter, and +examine the residue. It is lac sulphur, or milk of sulphur. + +183. Crystals from Fusion. + +Experiment 104.--In a beaker of 25 or 50 cc. capacity put 20 g. +brimstone. Place this over a flame with asbestos paper +interposed, and melt it slowly. Note the color of the liquid, +then let it cool, watching for crystals. When partly solidified +pour the liquid portion into an evapo- rating-dish of water, and +observe the crystals of S forming in the beaker (Fig. 42). The +hard mass may be separated from the glass by a little HNO3 and a +thin knife-blade, or by CS2. + +184. Allotropy. + +Experiment 105.--Place in a t.t. 15g of brimstone, then heat +slowly till it melts. Notice the thin amber-colored liquid. The +temperature is now a little above 100 degrees. As the heat +increases, notice that it grows darker till it becomes black and +so viscid that it cannot be poured out. It is now above 200 +degrees. Still heat, and observe that it changes to a slightly +lighter color, and is again a thin liquid. At this time it is +above 300 degrees. Now pour a little into an evaporating dish +containing water. Examine this, noticing that it can be stretched +like rubber. Leave it in the water till it becomes hard. Continue +heating thebrimstone in the t.t. till it boils at about 450 +degrees, and note the color of the escaping vapor. Just above +this point it takes fire. Cool the t.t., holding it in the light +meantime, and look for a sublimate of S on the sides. + +185. Solution. + +Experiment 106.--Place in an evaporating-dish a gram of powdered +brimstone, and add 5cc, CS2, carbon disulphide. Stir, and see +whether S is dissolved. Put this in a draft of air, and note the +evaporation of the liquid CS2, and the deposit of S crystals. +These crystals are different in form from those resulting from +cooling from fusion. + +186. Theory of Allotropy.--The last three experiments well +illustrate allotropy. We found S to crystallize in two different +ways. Substances can crystallize in seven different systems, and +usually a given substance is found in one of these systems only; +e.g. galena is invariably cubical. An element having two such +forms is said to be dimorphous. If it crystallizes in three +systems, it is trimorphous. A crystal has a definite arrangement +of its molecules. If without crystalline form, a substance is +called amorphous. An illustration of amorphism was S after it had +been poured into water. Thus S has at least three allotropic +forms, and the gradations between these probably represent +others. Allotropy seems to be due to varied molecular structure. +We know but little of the molecular condition of solids and +liquids, since we have no law to guide us like Avogadro's in +gases; but, from the density of S vapor at different +temperatures, we infer that liquids and solids have their +molecules very differently made up from those of gases. The least +combining weight of S is 32. Its vapor density at 1,000 degrees +is 32; hence its molecular weight is 64, i.e. vapor density x 2; +and there are 2 atoms in its molecule at that temperature, +molecular weight / atomic weight. At 500 degrees, however, the +vapor density is 96and the molecular weight 192. At this degree +the molecule must contain 6 atoms. How many it has in the +allotropic forms, as a solid, is beyond our knowledge; but it +seems quite likely that allotropy is due to some change of +molecular structure. + +The above experiments show two modes of obtaining crystals, by +fusion and by solution. + +187. Occurrence and Purification.--Sulphur occurs both free and +combined, and is a very common element. It is found free in all +volcanic regions, but Sicily furnishes most of it. Great +quantities are thrown up from the interior of the earth during an +eruption. The heat of volcanic action probably separates it from +its compound, which may be CaSO4. Vast quantities of the +poisonous SO2 gas are also liberated during an eruption, this +being, in volume of gases evolved, next to H2O. S is crudely +separated from its earthy impurities in Sicily by piling it into +heaps, covering to prevent access of air, and igniting, when some +of the S burns, and the rest melts and is collected. After +removal from the island it is further purified by distilling in +retorts connected with large chambers where it sublimes on the +sides as flowers of sulphur (Fig. 43). This is melted and run +into molds, forming roll brimstone. S also occurs as a +constituent of animal and vegetable compounds, as in mustard, +hair, eggs, etc. The tarnishing of silver spoons by eggs is due +to the formation of silver sulphide, Ag2S. The yellow color of +eggs, however, is due to oils, not to S. + +The main compounds of S are sulphides and sulphates. What acids +do they respectively represent? Metallic sulphides are as common +as oxides; e.g. FeS2, or pyrite, PbS, or galenite, ZnS, or +sphalerite, CuFeS2, or chalcopyrite, etc. The most abundant +sulphate is CaSO4, or gypsum. BaSO4, or barite, and Na2SO4, or +Glauber's salt, are others. + +The only one of these compounds that is utilized for its S is +FeS2. In Europe this furnishes a great deal of the S for H2SO4. S +is obtained by roasting FeS2. 3 FeS2 = Fe3S4 + 2 S. + +188. Uses. -The greatest use of S is in the manufacture of H2SO4. +A great deal is used in making gunpowder, matches, vulcanized +rubber, and the artificial sulphides, like HgS, H2S, CS2, etc. +The last is a very volatile, ill- smelling liquid, made by the +combination of two solids, S being passed over red-hot charcoal. +It dissolves S, P, rubber, gums, and many other substances +insoluble in H2O. + +189. Sulphur Dioxide, SO2, has been made in many experiments. It +is a bleaching agent, a disinfectant, and a very active compound, +having great affinity for water, but it will not support +combustion. Like most disinfectants, it is very injurious to the +system. It is used to bleach silk and wool--animal substances-- +and straw goods, which Cl would injure; but the color can be +restored, as the coloring molecule seems not to be broken up, but +to combine with SO2, which is again separated by reagents. Goods +bleached with SO2 often turn yellow after a time. + +190. SO2 a Bleacher. + +Experiment 107.-Test its bleaching power by burning S under a +receiver under which a wet rose or a green leaf is also placed. + +Chapter XXXVIII. + +HYDROGEN SULPHIDE. + +Examine ferrous sulphide, natural and artificial. + +191. Preparation. + +Experiment 108.--Put a gram of ferrous sulphide (FeS) into a t.t. +fitted with a d.t., as in Figure 32. Add 10cc. H2O and 5cc. +H2SO4. H2S is formed. Write the equation, omitting H2O. What is +left in solution? + +192. Tests. + +Experiment 109.-(1) Take the odor of the escaping gas. (2) Pour +into a t.t. 5cc.solution AgNO3, and place the end of the d.t. +from a H2S generator into the solution and note the color of the +ppt. What is the ppt.? Write the equation. (3) Experiment in the +same way with Pb(NO3)2 solution. Write the equation. (4) Let some +H2S bubble into a t.t. of clean water. To see whether H2S is +soluble in H2O, put a few drops of the water on a silver coin. +Ag2S is formed. Describe, and write the equation. Do the same +with a copper coin. (5) Put a drop of lead acetate solution, +Pb(C2H3O2)2, on a piece of unglazed paper, and hold this before +the d.t. from which H2S is escap- ing. PbS is formed. Write the +equation. This is the characteristic test of H2S. + +193. Combustion of H2S + +Experiment 110.--Attach a philosopher's lamp tube to the H2S +generator, and, observing the same precautions as with H, light +the gas. What two products must be formed? State the reaction. +The color of the flame. Compute the molecular weight and the +vapor density of H2S. 194. Uses. -Hydrogen sulphide or +sulphuretted hydrogen, H2S, is employed chiefly as a reagent in +the chemical laboratory. It forms sulphides with many of the +metals, as shown in the last experiment. These are precipitated +from solution, and may be separated from other metals which are +not so precipitated, as was found in the case of HCl and NH4OH. +The subjoined experiment will illustrate this. Suppose we wished +to separate Pb from Ba, having salts of the two mixed together, +as Pb(NO3)2 and Ba(NO3)2. + +195. H2S an Analyzer of Metals. + +Experiment 111.--Pass Some H2S gas in to 5cc.solution Ba(NO3)2. +No ppt. is formed. Do the same with Pb(NO3)2 solution. A ppt. +appears. Now mix 5cc.of each of these solutions in a t.t. and +pass the gas from a H2S generator into the liquid. What is +precipitated, and what is unchanged? When fully saturated with +the gas, as indicated by the smell, filter. Which metal is on the +filter and which is in the filtrate? Other reagents, as Na2CO3 +solution, would precipitate the latter. + +196. Occurrence and Properties. -- H2S is an ill-smell- ing, +poisonous gas, formed in sewers, rotten eggs, and other decaying +albuminous matter. It is formed in the earth, probably from the +action of water on sulphides, and issues with water from sulphur +springs. + +A characteristic property is the formation of metallic sulphides, +as above. A skipper one night anchored his newly painted vessel +near the Boston gas-house, where the refuse was deposited, with +its escaping H2S. In the morning, to his consternation, the craft +was found to be black. H2S had come in contact with the lead in +the white paint, forming black PbS. This gradually oxidized after +reaching the open sea, and the white color reappeared. + +Chapter XXXIX. + +PHOSPHORUS. + +NOTE.--Phosphorus should be kept in water, and handled with +forceps, never with the fingers, except under water, as it is +liable to burn the flesh and produce ulcerating sores. Pieces not +larger than half a pea should be used, and every bit should +finally be burned. + +197. Solution and Combustion. Experiment 112. -Put 1 or 2 pieces +of P into an evaporating- dish, and pour over them 5 or 10cc.CS2 +carbon disulphide. This will be enough for a class. When +dissolved, dip pieces of unglazed paper into it, and hold these +in the air, looking for any combustion as they dry. The P is +finely divided in solution, which accounts for its more ready +combustion then. Notice that the paper is not destroyed. This is +an example of so-called "spontaneous combustion." The burning- +point of P, the combustible, in air, the supporter, is about 60 +degrees. + +198. Combustion under Water. + +Experiment 113. -Put a piece of P in a t.t. which rests in a +receiver, add a few crystals KClO3 and 5cc. H2O. Now pour in +through a thistle-tube 1cc.or more of H2SO4. Look for any flame. +H2SO4 acts very strongly on KClO3. What is set free? From this +fact explain the combustion in water. + +199. Occurrence.--P is very widely disseminated, but not +abundant, and is found only in compounds, the chief of which is +calcium phosphate Ca3(PO4)2. It occurs in granite and other +rocks, as the mineral apatite, in soils, in plants, particularly +in seeds and grains, and in the bones, brains, etc., of +vertebrates. From the human system it is excreted by the kidneys +as microcosmic salt, HNaNH4PO4; and when the brain is hard- +worked, more than usual is excreted. Hence brain-workers have +been said to "burn phosphorus." + +200. Sources.--Rocks are the ultimate source of this element. +These, by the action of heat, rain, and frost, are disintegrated +and go to make soils. The rootlets of plants are sent through the +soil, and, among other things, soluble phosphates in the earth +are absorbed, circulated by the sap, and selected by the various +tissues. Animals feed on plants, and the phosphates are +circulated through the blood, and deposited in the osseous +tissue, or wherever needed. + +Human bones contain nearly 60 per cent of Ca3(PO4)2; those of +some birds over 80 per cent. + +The main sources of phosphates and P are the phosphate beds of +South Carolina, the apatite beds of Canada, and the bones of +animals. + +201. Preparation of Phosphates and Phosphorus.--Bone ash, +obtained by burning or distilling bones, and grinding the +residue, is treated with H1SO4, and forms soluble H4Ca(PO4)2, +superphosphate of lime, and insoluble CaSO4. + +Ca3(PO4)2 + 2 H2SO4 = H4Ca(PO04)2 + 2 CaSO4. This completes the +process for fertilizers. If P is desired, the above is filtered; +charcoal, a reducing agent, is added to the filtrate; the +substance is evaporated, then very strongly heated and distilled +in retorts, the necks of which dip under water. It is then +purified from any uncombined C by melting in hot water and +passing into molds in cold water. + +The work is very dangerous and injurious, on account of the low +burning-point of P, and its poisonous properties. While its +compounds are necessary to human life, P itself destroys the +bones, particularly the jaw bones, of the workers in it. + +Between 1,000 and 2,000 tons are made yearly, mostly for matches, +but almost all at two factories, one in England, and one in +France. 202. Properties.--P is a colorless, transparent solid, +when pure; the impure article is yellowish, translucent, and +waxy. It is insoluble in water, slightly soluble in alcohol and +ether, and it readily dissolves in CS2, oil of turpentine, etc. +Fumes, having a garlic odor, rise when it is exposed to the air, +and in the dark it is phosphorescent, emitting a greenish light. + +203. Uses. -The uses of this element and its compounds are for +fertilizers, matches, vermin poisons, and chemical operations. + +204. Matches.-The use of P for matches depends on its low +burning-point. Prepared wood is dipped into melted S, and the end +is then pressed against a stone slab having on it a paste of P, +KClO3, and glue. KNO3 is often used instead of KClO3. In either +case the object is to furnish O to burn P. Matches containing +KClO3 snap on being scratched, while those having KNO3 burn +quietly. The friction from scratching a match generates heat +enough to ignite the P, that enough to set the S on fire, and the +S enough to burn the wood. Give the reaction for each. Paraffine +is much used instead of S. Safety matches have no P, and must be +scratched on a surface of red P and Sb2S3, or on glass. + +205. Red Phosphorus.-Two or three allotropic forms of P are +known, the principal one being red. If heated between 230 degrees +and 260 degrees, away from air, the yellow variety changes to +red, which can be kept at all temperatures below 260 degrees. +Above that it changes back. Red P is not poisonous, ignites only +at a high temperature, and is not phosphorescent, like the +yellow. 206. Spontaneous Combustion of Phosphene, or Hydrogen +Phosphide, PH3. + +Experiment 114.--Put into a 20cc.flask 1 g. P and 50cc.saturated +solution NaOH or KOH. Connect with the p.t. by a long d.t., as in +Figure 44, the end of which must be kept under water. Pour 3 or +4cc.of ether into the flask, to drive out the air. It is +necessary to exclude all air, as a dangerously explosive mixture +is formed with it. Heat the mixture, and as the gas passes over +and into the air, it takes fire spontaneously, and rings of smoke +successively rise. It will do no harm if, on taking away the +lamp, the water is drawn back into the flask; but in that case +the flask should be slightly lifted to prevent breakage by the +sudden rush of water. On no account let the air be drawn over. + +The experiment has no practical value, but is an interesting +illustration of the spontaneous combustion of PH3 and of vortex +rings. What are the products of the combustion? An admixture of +another compound of P and H causes the combustion. + +Chapter XL. + +ARSENIC. + +Examine metallic arsenic, realgar, orpiment, arsenopyrite, +arsenic trioxide, copper arsenite. + +The compounds of arsenic are very poisonous if taken into the +system, and must be handled with care. + +207. Separation. Experiment 115.--Draw out into two parts in the +Bunsen flame a piece of glass tubing 20cm long and 1 or 2cm in +diameter. Into the end of one of the ignition tubes thus formed, +when it is cool, put one-fourth of a gram of arsenic trioxide, +As2O3, using paper to transfer it. Now put into the tube a piece +of charcoal, and press it down to within 2 or 3cm of the AS2O3 +(Fig. 45). Next heat the coal red-hot, and then at once heat the +As203. Continue this process till you see a metallic sublimate- +metallic mirror-on the tube above the coal. Break the tube and +examine the sublimate. It is As. Heat vaporizes the As2O;3. +Explain the chemical action. What is the agency of C in the +experiment? Of As2O3? 2 As2O3 + 3 C = ? + +208. Tests.-Experiments 115 and 116 are used as tests for the +presence of arsenic. + +Experiment 116.--Prepare a H generator, - a flask with a thistle- +tube and a philosopher's lamp tube (Fig. 46), put in some +granulated Zn, water, and HCl. Test the purity of the escaping +gas (Experiment 23), and when pure, light the jet of H. H is now +burning in air. To be sure that there is no As in the ingredients +used, hold the inside of a porcelain evaporating-dish directly +against the flame for a minute. If no silvery-white mirror is +found, the chemicals are free from As. Then pour through the +thistle-tube, while the lamp is still burning, 1cc.solution of +AS2O3 in HCl or H2O a bit of As2O3 not larger than a grain of +wheat in 10 cc. HCl. + +See whether the color of the flame changes; then hold the +evaporating-dish once more in the flame, and notice a metallic +deposit of As. Set away the apparatus under the hood and leave +the light burning. + +This experiment must not be performed unless all the cautions are +observed, since the gas in the flask (AsH3) is the most poisonous +known, and a single bubble of it inhaled is said to have killed +the discoverer. By confining the gas inside the flask there is no +danger. + +Instead of using As2O3 solution, a little Paris green, wall paper +suspected of containing arsenic, green silk, or green paper +labels, etc., may be soaked in HCl, and tested. + +209. Explanation.--The chemical changes are as follows: The +compounds of As, in this case As2O3, in presence of nascent H, +are immediately converted into the deadly hydrogen arsenide +(arsine, arseniuretted hydrogen), AsH3. As2O3 + 12 H = 2 AsH3 + 3 +H2O. The AsH3 mixed with excess of H tends to escape and is +burned to As2O3 and H2O, and thus is rendered comparatively +harmless as it passes into the air. This is why the flame must be +burning when the arsenic compound is introduced. 2 AsH3 + 6 O = +As2O3 + 3 H2O. + +In the combustion of AsH3, H burns at a lower point than As. The +introduction of a cold body like porcelain cools the flame below +the kindling-point of As, and this is deposited, while H burns, +in exactly the same way as lamp- black was collected in +Experiment 26. + +210. Expert Analysis.--A modification of this experiment is +employed by experts to test for AS2O3 poisoning. The organs.-- +stomach or liver--are cut into small pieces dissolved by nascent +Cl, or HClO, made from KC1O3 and HCl, and the solution is +introduced into a H generator, as above. AS2O3 preserves the +tissues it comes in contact with, for a long time, and the test +can be made years after death. All the chemicals must be pure, +since As is found in small quantities in most ores, and the Zn, +HCl, and H2SO4 of commerce are very likely to contain it. The +above is called Marsh's test, and is so delicate that a mere +trace of arsenic can be detected. + +211. Properties and Occurrence.--As is a grayish white solid, of +metallic luster, while a few of its characters are non-metallic. +It is very widely distributed, being sometimes found native, and +sometimes combined, as AsS, realgar, As2S8, orpiment, and FeAsS, +arsenopyrite. Its chief source is the last, the fine powder of +which is strongly heated, when As separates and sublimes. It has +the odor of garlic, as may be observed by heating a little on +charcoal with the blow-pipe. + +212. Atomic Volume.--As is peculiar in that its atomic volume, so +far as the volume can be determined, is only half that of the H +atom. Its vapor density is 150, which gives 300 for the molecular +weight, while its least combining or atomic weight is 75. 300, +the molecular weight = 75, the atomic weight =4, the number of +atoms in the molecule. All gaseous molecules being of the same +size, represented by two squares, the atomic volume of As must be +one-fourth of this size, represented by half of one square. Of +what other element is this true? 213. Uses of As2O3.-Arsenic is +used in shot-manufacture, for hardening the metal. Its most +important compound is As2O3, arsenic trioxide, called also +arsenious anhydride, arsenious acid, white arsenic, etc. So +poisonous is this that enough could be piled on a one-cent piece +to kill a dozen persons. Taken in too large quantities it acts as +an emetic. The antidote is ferric hydrate Fe2(OH)6 and a mustard +emetic, followed by oil or milk. + +The vapor density of this compound shows that its symbol should +be As4O6, but the improper one, As2O3, is likely to remain in +use. Another oxide, As2O5, arsenic pentoxide, exists, but is less +important. Show how the respective acid formulae are obtained +from these anhydrides. See page 50. + +AS2O3 is used in making Paris green; in many green coloring +materials, in which it exists as copper arsenite; in coloring +wall papers, and in fly and rat poisons. It is employed for +preserving skins, etc. Fashionable women sometimes eat it for the +purpose of beautifying the complexion, to which it imparts a +ghastly white, unhealthy hue. Mountaineers in some parts of +Europe eat it for the greater power of endurance which it is +supposed to give them. By beginning with small doses these +arsenic-eaters finally consume a considerable quantity of the +poison with apparent impunity; but as soon as the habit is +stopped, all the pangs of arsenic-poisoning set in. Wall paper +containing arsenic is said to be injurious to some people, while +apparently harmless to others. + +Chapter XLI. + +SILICON, SILICA, AND SILICATES. + +214. Comparison of Si and C.--The element Si resembles carbon in +valence and in allotropic forms. It occurs in three forms like C, +a diamond form, a graphite, and an amorphous. C forms the basis +of the vegetable and animal world; Si, of the mineral. Most soils +and rocks, except limestone, are mainly compounds of O, Si, and +metals. While O is estimated to make up nearly one- half of the +known crust of the earth, Si constitutes fully a third. The two +are usually combined, as silica, SiO2, or silicates, SiO2 +combined with metallic oxides. This affinity for O is so strong +that Si is not found uncombined, and is separated with great +difficulty and only at the highest temperatures. No special use +has yet been found for it, except as an alloy with Al. Its +compounds are very important. + +215 Silica.--Examine some specimens of quartz, rock crystal, +white and colored sands, agate, jasper, flint, etc.; test their +hardness with a knife blade, and see whether they will scratch +glass. Notice that quartz crystals are hexagonal or six-sided +prisms, terminated by hexagonal pyramids. The coloring matters +are impurities, often Fe and Mn, if red or brown. When pure, +quartz is transparent as glass, infusible except in the oxy- +hydrogen blow- pipe, and harder than glass. Rock crystal is +massive Si02. Sand is generally either silica or silicates. + +The common variety of Si02 is not soluble in water or in acids, +except HF. An amorphous variety is to some extent soluble in +water. Most geysers deposit the latter in successive layers about +their mouths. Agate, chalcedony, and opal have probably an origin +similar to this. A solution of this variety of SiO2 forms a +jelly-like masscolloid--which will not diffuse through a membrane +of parchment -dialyzer--when suspended in water. Crystalloids +will diffuse through such a membrane, if they are in solution. +This principle forms the basis of dialysis. + +All substances are supposed to be either crystalloids, i.e. +susceptible of crystallization, or colloids-jelly-like masses. +HCl is the most diffusible in liquids of all known substances; +caramel is one of the least so. To separate the two, they would +be put into a dialyzer suspended in water, when HCl will diffuse +through into the water, and caramel will remain. As2O3, in cases +of suspected poisoning, was formerly separated from the stomach +in this way, as it is a crystalloid, whereas most of the other +contents of the stomach are colloidal. + +216. Silicates.--Si is a tetrad. SiO2 + 2 H2O =? Si02 + H2O =? In +either case the product is called silicic acid. Replace all the H +with Na, and name the product. Replace it with K; Mg; Fe; Ph; Ca. +Na4SiO4 and Na2SiO3 are typical silicates of Na, but others +exist. + +217. Formation of SiO2 from Sodium Silicate. Experiment 117.--To +5cc.Na4SiO4 in au evaporating-dish add 5cc. HCl. Describe the +effect. Pour away any extra HCl. Heat the residue gently, above a +flame, till it becomes white, then cool it and add water. In a +few minutes taste a drop of the water, then pour it off, leaving +the residue. Crush a little in the fingers, and compare it with +white sand, SiO2. Apply to the experiment these equations: - +Na4SiO4 + 4 HCl = 4 NaCl + H4SiO4. H4SiO4 + 2 H2O = Si02. Why was +H4Si04 heated? Why was water finally added? + +Water glass, sodium or potassium silicate, used somewhat for +making artificial stone, is made by fusing SiO2 with Na2CO3 or +K2CO3, and dissolving in water. Silicic acid forms the basis of a +very important series of compounds, - the silicates. The above +two are the only soluble ones, and may be called liquid glass. + +Chapter XLII. + +GLASS AND POTTERY. + +Examine white sand, calcium carbonate, sodium carbonate, smalt; +bottle, window, Bohemian and flint glass. + +218. Glass is an Artificial Silicate.--Si02 alone is almost +infusible, as is also Ca0; but mixed and heated the two readily +fuse, forming calcium silicate. Ca0 + SiO2 = ? Notice that Si02 +is the basis of an acid, while CaO is essentially a base, and the +union of the two forms a salt. There are four principal kinds of +glass: (1) Bohemian, a silicate of K and Ca, not easily fused, +and hence used for chemical apparatus where high temperatures are +required; (2) window or plate glass, a silicate of Na and Ca; (3) +bottle glass, a silicate of Na, Ca, Al, Fe, etc., a variety which +is impure, and is tinged green by salts of Fe; (4) flint glass, a +silicate of K and Pb, used for lenses in optical instruments, cut +glass ware, and, with B added, for paste, or imitation diamonds, +etc. Pb gives to glass high refracting power, which is a valuable +property of diamonds, as well as of lenses. + +219. Manufacture.--Pure white sand, Si02, is mixed with CaCO3 and +Na2CO3, some old glass - cullet - is added, and the mixture is +fused in fire-clay crucibles. For flint glass, Pb304, red lead, +is employed. If color is desired, mineral coloring matter is also +added, but not always at this stage. CoO, or smalt, gives blue; +uranium oxide, green; a mixture of Au and Sn of uncertain +composition, called the "purple of Cassius," gives purple. MnO2 +is used to correct the green tint caused by FeO, which it is +supposed to oxidize. Opacity, or enamel, as in lamp-shades, is +produced by adding As2O3, Sb2O3, SnO2, cryolite, etc. The glass- +worker dips his blowpipe--a hollow iron rod five or six feet +long--into the fused mass of glass, removes a small portion, +rolls it on a smooth surface, swings it round in the air, blowing +meanwhile through the rod, and thus fashions it as desired, into +bottles, flasks, etc. For some wares, e.g. common goblets, the +glass is run into molds and stamped; for others it is blown and +welded. All glass must be annealed, i.e. cooled slowly, for +several days. The molecules thus arrange themselves naturally. If +not annealed, it breaks very easily. It may be greatly toughened +by dipping, when nearly red-hot, into hot oil. Cut glass is +prepared at great expense by subsequent grinding. Glass may be +rendered semi-opaque by etching either with HF, or with a blast +of sand. + +220. Importance.--Few manufactured articles have more importance +than glass. Without it the sciences of chemistry, physics, +astronomy, microscopic anatomy, zoology, and botany, not to +mention its domestic uses, would be almost impossible. + +221. Porcelain and Pottery.--Genuine porcelain and china-ware are +made of a fine clay, kaolin, which results from the +disintegration of feldspathic rocks. Bricks are baked clay. The +FeO in common clay is oxidized to Fe2O3, on heating, a process +which gives their red color. Some clay, having no Fe, is white; +this is used for fire-bricks and clay pipes. That containing Fe +is too fusible for fire-clay, which must also have much SiO2. The +electric arc, however, will melt even this, and the most +refractory vessels are of calcium oxide or of graphite. Pottery +is clay, molded, baked, and either glazed, like crockery, or +unglazed, like flower-pots. Jugs and coarse earthenware are +glazed by volatilizing NaCl in an oven which holds the porous +material. This coats the ware with sodium silicate. To glaze +china, it is dipped into a powder of feldspar and SiO2 suspended +in water and vinegar, and then fused. If the ware and glaze +expand uniformly with heat, the latter does not crack. + +Chapter XLIII. + +METALS AND THEIR ALLOYS. + +222. Comparison of Metals and Non-Metals.--The majority of +elements are metals, only about a dozen being non-metallic in +their properties. The division line between the two classes is +not very well defined; e.g. As has certain properties which ally +it to metals; it has other properties which are non-metallic. H +occupies a place between the two classes. The following are the +more marked characteristics of each group: - + +METALS. + +1. Metals are solid at ordinary temperatures, and usually of high +specific gravity. + +Exceptions: Hg is liquid above -39.5 degees; Li is the lightest +solid known; Na and K will float on water. + +2. Metals reflect light in a way peculiar to themselves. They +have what is called a metallic luster. + +3. They are white or gray. Exceptions: Au, Ca, Sr are yellow; Cu +is red. + +4. In general they conduct heat and electricity well. + +NON-METALS. 1. Non-metals are either gaseous or solid at ordinary +temperatures, and of low specific gravity. Exceptions: Br is a +liquid; I has the heaviest known vapor. + +2. Non-metallic solids have different lusters, as glassy, +resinous- silky, etc. Exceptions: I, B, and C have metallic +luster. + +3. Non-metals have no characteristic color. + +4. They are non-conductors of heat and electricity. Exceptions: C +and some others are conductors. 5. They are usually malleable and +ductile. + +6. They form alloys, or "chemical mixtures," with one another, +similar to other solutions. Exceptions: Some, as Ph and Zn, will +not alloy with one another. + +7. Metals are electro-positive elements, and unite with O and H +to form bases. Exceptions: Some of the less electro-positive +metals, with a large quantity of O, form acids, as Cr, As, etc. + +Numbers 2, 6, and 7 are the most characteristic and important +properties. + +5. They are deficient in malleability and ductility. + +6. They often form liquid solutions, similar to alloys in metals. + +7. Non-metals are electronegative, and with H, or with H and O, +form acids. + +Examine brass, bronze, bell-metal, pewter, German silver, solder, +type-metal. + +223. Alloys.-An alloy is not usually a definite chemical +compound, but rather a mixture of two or more metals which are +melted together. One metal may be said to dissolve in the other, +as sugar dissolves in water. The alloy has, however, different +properties from those of its elements. For example, plumber's +solder melts at a lower temperature than either Ph or Sn, of +which it is composed. Some metals can alloy in any proportions. +Solder may have two parts of Sn to one of Pb, two of Pb to one of +Sn, or equal parts of each, or the two elements may alloy in +other proportions. Not all metals can be thus fused together +indefinitely; e.g., Zn and Pb. Nickel and silver coins are +alloyed with Cu, gold coins with Cu and Ag. + +Gun-metal, bell-metal, and speculum-metal are each alloys of Cu +and Sn. Speculum-metal, used for reflectors in telescopes, has +relatively more Sn than either of the others; gun-metal has the +least. An alloy of Sb and Pb is employed for type-metal as it +expands at the instant of solidification. Pewter is composed of +Sn and Pb; brass, of Cu and Zn; German silver, of brass and Ni; +bronze, of Cu, Sn, and Zn; aluminium bronze, of Cu and Al. + +224. Low Fusibility is a feature of many alloys. Wood's metal, +composed of Pb eight parts, Bi fifteen, Sn four, Cd three, melts +at just above 60 degrees, or far below the boiling-point of +water. By varying the proportions, different fusing-points are +obtained. This principle is applied in automatic fire alarms, and +in safety plugs for boilers and fire extinguishers. Water pipes +extend along the ceiling of a building and are fitted with plugs +of some fusible alloy, at short distances apart. When, in case of +fire, the heat becomes sufficiently intense, these plugs melt and +the water flows out. + +225. Amalgams.--An amalgam is an alloy of Hg and another metal. +Mirrors are "silvered" with an amalgam of Sn. Tin-foil is spread +on a smooth surface and covered with Hg, and the glass is pressed +thereon. + +Various amalgams are employed for filling teeth, a common one +being composed of Hg, Ag, and Sn. Au or Ag, with Hg, forms an +amalgam used for plating. Articles of gold and silver should +never be brought in contact with Hg. If a thin amalgam cover the +surface of a gold ring or coin, Hg can be removed with HNO3, as +Au is not attacked by it. Would this acid do in case of silver +amalgam? Heat will also quickly cause Hg to evaporate from Au. + +CHAPTER XLIV. + +SODIUM AND ITS COMPOUNDS. + +Examine NaCl, Na2SO4, Na2CO3, Na, NaOH, HNaCO3, NaNO3. + +226. Order of Derivation.--Though K is more metallic, or electro- +positive, than Na, the compounds of Na are more important, and +will be considered first. The only two compounds of Na which +occur extensively in nature are NaCl and NaNO3. Almost all others +are obtained from NaCl, as shown by this table, which should be +memorized and frequently recalled. + + + ) Na +NaCl ) Na2SO4) Na2CO3) NaOH +NaNO3) ) ) HNaCO3 + + + +From what is Na2SO4 prepared, as shown by the table? Na2CO3? Na? + +227. Occurrence and Preparation of NaCl.--NaCl occurs in sea +water, of which it constitutes about three per cent, in salt +lakes, whose waters sometimes hold thirty per cent, or are nearly +saturated, and, as rock salt, in large masses underground. Poland +has a salt area of 10,000 square miles, in some parts of which +the pure transparent rock salt is a quarter of a mile thick. In +Spain there is a mountain of salt five hundred feet high and +three miles in circumference. France obtains much salt from sea +water. At high tide it flows into shallow basins, from which the +sun evaporates the water, leaving NaCl to crystallize. In Norway +it is separated by freezing water, and in Poland it is mined like +coal. In New York and Michigan it is obtained by evaporating the +brine of salt wells, either by air and the sun's heat, or by +fire. Slow evaporation gives large crystals; rapid, small ones. + +228. Uses.--The main uses are for domestic purposes and for +making the Na and Cl compounds. In the United States the +consumption amounts to more than forty pounds per year for every +person. + +229. Sodium Sulphate.--What acid and what base are represented by +Na2SO4? Which is the stronger acid, HCl or H2SO4? Would the +latter be apt to act on NaCl? Why? + +230. Manufacture.--This comprises two stages shown by the +following reactions, in which the first needs moderate heat only; +the last, much greater. + +(1) 2 NaCl + H2SO4 = HNaSO4 + NaCl + HCl: +(2) NaCl + HNaSO4 = Na2S4 + HCl. + +The operation is carried on in large furnaces. The gaseous HCl is +passed into towers containing falling water in a fine spray, for +which it has great affinity. The solution is drawn off at the +base of the tower. Thus all commercial HCl is made as a by- +product in manufacturing Na2SO4. + +When crystalline, sodium sulphate has ten molecules of water of +crystallization (Na2SO4, 10 H2O); it is then known as Glauber's +salt. This salt readily effloresces; i.e. loses its water of +crystallization, and is reduced to a powder. Compute the +percentage of water. + +231. Uses.--The leading use of Na2SO4 is to make Na2CO3; it is +also used to some extent in medicine, and in glass manufacture. +232. Sodium Carbonate.--Note the base and the acid which this +salt represents. Test a solution of the salt with red and blue +litmus, and notice the alkaline reaction. Do you see any reason +for this reaction in the strong base and the weak acid +represented by the salt? + +233. Manufacture.--Na2CO3 is not made by the union of an acid and +a base, nor is H2CO3 strong enough to act on many salts. The +process must be indirect. This consists in reducing Na2SO, to +Na2S, by taking away the O with C, charcoal, and then changing +Na2S to Na2O3 by CaCO3, limestone. The three substances, Na2SO4, +C, CaCO3, are mixed together and strongly heated. The reactions +should be carefully studied, as the process is one of much +importance. + +(1) Na2SO4 + 4 C = Na2S + 4 CO. +(2) Na2S + CaCO3 = CaS + Na2CO3. + +Observe that C is the reducing agent. The gas CO escapes. The +solid products Na2CO3 and CaS form black ash, the former being +very soluble, the latter only sparingly soluble in water. Na2CO3 +is dissolved out by water, and the water is evaporated. This +gives commercial soda. CaS, the waste compound in the process, +contains the S originally in the H2SO4 used. This can be +partially separated and again made into acid. Describe the +manufacture of NaCO3 in full, starting with NaCl. This is called +the Le Blanc process, but is not the only one now employed to +produce this important article. + +234. Occurrence.-Sodium carbonate is found native in small +quantities. It forms the chief surface deposit of the "alkali +belt" in western United States, where it often forms +incrustations from an inch to a foot in thickness. It was +formerly obtained from sea-weeds, by leaching their ashes, as, by +a like process, K2CO3 was obtained from land plants. + +235. Uses.--Na2CO3 forms the basis of many alkalies, as H2SO4 +does of acids. Of all chemical compounds it is one of the most +important, and its manufacture constitutes one of the greatest +chemical industries. Its economical manufacture largely depends +on the demand for HCl, which is always formed as a by-product. As +but little HCl is used in this country, Na2CO3 is mostly +manufactured in Europe. The chief uses are for glass and +alkalies. + +236. Sodium.--Na must always be kept under naphtha, or some other +liquid compound containing no O, since it oxidizes at once on +exposure to the air. For this reason it never occurs in a free +state. + +237. Preparation.-By depriving Na2CO3 of C and O, metallic sodium +is formed. As usual, heated charcoal is the reducing agent. The +end of the retort, which holds the mixture, dips under naphtha. + +Na2CO3 + 2 C = 2 Na + 3 CO. The process is a difficult one, and +Na brings five dollars per pound, though in its compounds it is a +third as common as Fe. K is as abundant as Na, but more difficult +of separation, and is worth three dollars per ounce. Notice the +position of K and Na at the positive end of the elements. + +238. Uses.--Na is used to reduce Al, Ca, Mg, Si, which are the +most difficult elements to separate from their compounds. It acts +in these cases as a reducing agent. + +239. Sodium Hydrate. Review Experiment 62. + +Experiment 118.--Put into a t.t. 10cc. H2O and 2 or 3 g. NaOH. +Note its easy solubility. Test with litmus. Will it neutralize +any acids? + +240. Preparation. -- Sodium hydrate, caustic soda, or soda by +lime, is made by treating a solution of Na2CO3 with milk of lime. +CaCO3 is precipitated and al- lowed to settle, the solution is +poured off, and NaOH is obtained by evaporating the water and +running the residue into molds. + +241. Use.--NaOH is a powerful caustic, but its chief use is in +making hard soap. + +242. Hydrogen Sodium Carbonate.--Hydrogen so- dium carbonate, +bicarbonate of sodium, acid sodium carbonate, cooking-soda, etc., +HNaCO3, is prepared by passing CO2 into a solution of Na2CO3. +Na2CO3 + H2O + CO2 = 2 HNaCO3. Test a solution of it with litmus. +Account for the result. Its use in bread-making depends on the +ease with which CO2 is liberated. Even a weak acid, as the lactic +acid of sour milk, sets this free, and thus causes the dough to +rise. + +243. Sodium Nitrate.--Sodium nitrate occurs in Chili and Peru. It +is the main source of HNO3. + +Review Experiments 46 and 52. From NaNO3 is also made KNO3, +(NaNO3 + KCl = NaCl + KNO3), one of the ingredients of gunpowder. +By reason of its deliqcescence NaNO3 is not suitable for making +gunpowder, though it is sometimes used for blasting-powder. The +action of the latter is slower than that made from KNO3. NaNO3 is +cheaper and more abundant than KNO3; this is true of most Na +compounds in comparison with those of K. + +Chapter XLV. + +POTASSIUM AND AMMONIUM. + +POTASSIUM AND ITS COMPOUNDS. + +Examine K, KCl, K2SO4, K2CO3, KOH, HKCO3, KCLO3, KCN. + +244. Occurrence and Preparation.--Potassium occurs only in +combination, chiefly as silicates, in such minerals as feldspar +and mica. By their disintegration it forms a part of soils from +which such portions as are soluble are taken up by plants. The +ashes of land-plants are leached in pots to dissolve K2CO3; hence +it is called potash. Sea-plants likewise give rise to Na2CO3. +Wood ashes originally formed the main source of K2CO3. From +plants this substance is taken into the animal system, and makes +a portion of its tissue. Sheep excrete it in sweat, which is then +absorbed by their wool. Large quantities are now obtained by +washing wool and evaporating the water. K2CO3 and other compounds +of K are mainly derived from KCl, beds of which exist in Germany. + +In the following list each K compound is prepared like the same +Na compound, and the uses of each of the former are similar to +those of the latter. K compounds are made in much smaller +quantities than those of Na, as KCl is far less common than NaCl. + + + { K + KCl { K2SO4 { K2CO3 { KOH + KNO3 { { HKCO3 + + + +Examine specimens of each, side by side with like Na compounds. +Describe in full their preparation, giving the reactions. Also, +perform theexperiments given under Na, substituting K therefor. +From KOH are made KClO3 and KCN. + +KOH {KCl03 + {KCN + + +245. Potassium Chlorate.--KCl03 is made by passing Cl into a hot +concentrated solution of KOH. + +6 KOH + 6 Cl = KCl03 + 5 KCl + 3 H2O + +Its uses are making O, and as an oxidizing agent. + +246. Potassium Cyanide, KCN, is a salt from HCN--hydrocyanic or +prussic acid. Each is about equally poisonous, and more so than +any other known substance. A drop of pure HCN on the tongue will +produce death quickly by absorption into the system. In examining +these compounds take care not to handle them or to inhale the +fumes. KCN is used as a solvent for metals in electro-plating, +and is the source of many cyanides, i.e. compounds of CN and a +metal. KCN is employed to kill insects for cabinet specimens. In +a wide-mouthed bottle is placed a little KCN, which is covered +with cotton, and over this a perforated paper. The bottle is +inverted over the insect, and the fumes destroy life without +injuring the delicate parts. HCN is made from KCN and H2SO4. + +247. Gunpowder.--Gunpowder is a mixture of KNO3, C, and S. Heat +or concussion causes a chemical change, and transforms the solids +into gases. These gases at the moment of explosion occupy 1500 or +more times the volume of the solids. Hence the great rending +power of powder. If not confined, powder burns quietly but +quickly. The appended reaction is a part of what takes place, but +it by no means represents all the chemical changes. + +2KNO3 + S + 3C =K2S + 2N + 3CO2. + +From this equation compute the percentage, by weight, of each +substance used to make gunpowder economically. + +Thoroughly burned charcoal, distilled sulphur, and the purest +nitre are powdered and mixed in a revolving drum,made into a +paste with water, put under great pressure between sheets of gun +metal, granulated, sifted, to separate the coarse and fine +grains, and glazed by revolving in a barrel which sometimes +contains a little powdered graphite. + +Experiment 119.--Pulverize and mix intimately 4 g. KNO3, l/2 g. +S, 1/2 g. charcoal. Pile the mixture on a brick, and apply a +lighted match. The adhering product can be removed by soaking in +water. + +AMMONIUM COMPOUNDS. + +248. Read the chapter on NH3. Also, review the experiments on +bases. Examine NH4Cl, NH4NO3, (NH4)2SO4, (NH4)2CO3. + +Ammonium, NH4, is too unstable to exist alone, but it forms salts +similar to those of K and Na. NH3 dissolved in water forms NH4OH. + +The food of plants, as well as that of animals, must contain N. +It has not yet been shown that they can make use of that +contained in the air, but they do absorb its compounds from the +soil. All fertilizers and manures contain a soluble compound of +NH4. All NH4 compounds are now obtained either from coal, in +making illuminating-gas, or from bones, by distillation. + +Suppose the product obtained from the gas-house to be NH4OH, how +would NH4Cl be made? (NH4)2SO4? NH4NO3? Write the reactions. +(NH4)2CO3 is made by heating NH4Cl with CaCO3. Give the reaction. + +Chapter XLVI. + +CALCIUM COMPOUNDS. + +Examine CaCO3--marble, limestone, chalk, not crayon,--CaSO4 -- +gypsum or selenite--CaCl2, CaO. + +249. Occurrence.--The above are the chief compounds of Ca. The +element itself is not found uncombined, is very difficult to +reduce (page 141), is a yellow metal, and has no use. Its most +abundant compound is CaCO3. Shells of oysters, clams, snails, +etc., are mainly CaCO3, and coral reefs, sometimes extending +thousands of miles in the ocean, are the same. CaCO3 dissolves in +water holding CO2, and thence these marine animals obtain it and +therefrom secrete their bony framework. All mountains were first +laid down on the sea bottom layer by layer, and afterwards lifted +up by pressure. Rocks and mountains of CaCO3 were formed by +marine animals, and all large masses of CaCO3 are thought to have +been at one time the framework of animals. Marble is +crystallized, transformed limestone. The process, called +metamorphism, took place in the depths of the earth, where the +heat is greater than at the surface. + +250. Lime.--If CaCO3 be roasted with C, CO2 escapes and CaO is +left. CaCO3 - CO2 = ? This is called burning lime, and is a large +industry in limestone countries. CaO is unslaked lime, quicklime +or calcium oxide. It may be slaked either by exposure to the +air, air-slaking, when it gradually takes up H2O and CO2; or by +mixing with H2O, water-slaking. Ca0 + H2O = Ca(OH)2. + +Great heat is generated in the latter case, though not so much as +in the formation of KOH and NaOH. Like them, Ca(OH)2 dissolves in +water, forming lime-water. Milk of lime, cream of lime, etc., +consist of particles of Ca(OH)2 suspended in H2O. + +251. Uses of Lime--CaO is infusible at the highest temperatures. +If it be introduced into the oxy-hydrogen blow-pipe (page 28), a +brilliant light, second only to the electric, is produced. Mortar +is made by mixing CaO, H2O, and Si02. It hardens by evaporating +the extra H2O, absorbing CO2 from the air, and uniting with Si02 +to form calcium silicate. It often continues to absorb CO2 for +hundreds or thousands of years before being saturated, as is +found in the Egyptian pyramids. Hence the tenacity of old mortar. +Hydraulic mortar contains silicates of Al and Ca, and is not +affected by water. What are the uses of mortar? Being the +important constituent of mortar and plaster, lime is the most +useful of the bases. + +252. Hard Water.--Review Experiment 76. The solubility of CaCO3 +in water that contains CO2 leads to important results. Much +dissolves in the waters of all limestone countries; and the +water, though perfectly transparent, is hard; i.e. soap has +little action on it. See page 187. Such water may be softened by +boiling, a deposit of CaCO3 being formed as a crust on the +kettle. Such water is called water of temporary hardness. MgCO3 +produces a similar effect, and water containing it is softened in +the same way. Permanently hard waters contain the sulphates of Ca +and Mg, which cannot be removed by boiling, but may be by adding +(NH4)2CO3. 253. The Formation of Caves in limestone rocks is due +also to the solubility of CaCO3. Water collects on the mountains +and trickles down through crevices, dissolving, if it contains +CO2, some of the CaCO3, and thus making a wider opening, and +forcing its way along fissures and lines of least resistance into +the interior of the earth, or out at the base of the mountain. +Its channel widens as it dissolves the rock, and the stream +enlarges until in the course of ages an immense cavern may be +formed, with labyrinths extending for miles, from the entrance of +which a river often issues. In the long ages which elapsed during +the slow formation of Mammoth Cave its denizens lost many of the +characters of their ancestors, and eyeless fish and also eyeless +insects now abound there. + +254. Reverse Action.--Drops of water on the roofs of these +caverns lose their CO2, and deposit CaCO3. Thus long, pendant +masses of limestone, called stalactites, are slowly formed on the +roofs like icicles. From these, water charged with CaCO3 drops to +the bottom, loses CO2 and deposits CaCO3, which forms an upward- +growing mass, called stalagmite. In time it may meet the +stalactite and form a pillar. Notice that the same action which +formed the cave is filling it up; i.e. the solubility of CaCO3 in +water charged with CO2. + +255. Famous Marbles.--The marble from Carrara, Italy, is most +esteemed on account of a pinkish tint given by a trace of oxide +of iron. The best of Grecian marble was from Paros, one of the +Cyclades. The isles of the Mediterranean are of limestone, or of +volcanic, origin, often of both. 256. Calcium Sulphate occurs in +two forms, (1) with water of crystallization--gypsum, CaSO4 + 2 +H2O, --(2) without it--anhydrite, CaSO4. The former, on being +strongly heated, gives up its water, and is reduced to a powder-- +plaster of Paris. This, on being mixed with water, again takes up +2 H2O, and hardens, or sets, without crystallizing. If once more +heated to expel water, it will not again absorb it. When plaster +of Paris sets, it expands slightly, and on this account is +admirable for taking casts. + +257. Uses.--Gypsum finds use as a fertilizer and as an adulterant +in coloring-materials, etc. CaSO4 is employed in making casts, +molds, statuettes, wall-plaster, crayons, etc. + +How can CaCl2 be made? What is its use? See page 27. What else +is used for a similar purpose? + +Symbolize and name the acid represented by Ca(ClO)2, and name +this salt (page 107). It is one of the constituents of bleaching- +powder, the symbol of which, though still under discussion, may +be considered Ca(ClO)2 + CaCl2. This is made by passing Cl over +Ca(OH)2 2 Ca(OH)2 + 4 Cl = Ca(ClO)2 + CaCl2 + 2 H2O. + +CHAPTER XLVII. + +MAGNESIUM, ALUMINIUM, AND ZINC. + +MAGNESIUM AND ITS COMPOUNDS. + +Examine magnesite, dolomite, talc, serpentine, hornblende, +meerschaum, magnesium ribbon, magnesia alba, Epsom salt. + +258. Occurrence and Preparation.--Mg is very widely distributed, +but does not occur uncombined. Its salts are found in rocks and +soils, in sea water and in the water of some springs, to which +they impart a brackish taste. + +The most common minerals containing Mg are magnesite, MgCO3, +dolomite, MgCO3 + CaCO3, and talc, serpentine, hornblende, and +meerschaum. The last four are silicates, and often are unctious +to the touch. What proportion of the earth's crust is composed of +Mg? See page 173. + +259. Metallic Mg is prepared by fusing MgCl2 with Na. Why is the +process expensive? Write the reaction. + +Experiment 120.--With forceps hold a short strip of Mg ribbon in +a flame. Note the brilliancy of the light, and give the reaction. +Examine and name the product. + +Photographs of the interior of caverns, where sunlight does not +penetrate, are taken by Mg light. Gun-cotton sprinkled with +powdered Mg has recently been employed for that purpose. Mg +tarnishes slightly in moist air. Compounds of Mg.--MgO, magnesia, +like CaO, is very infusible, and is used for crucibles. Magnesia +alba, a variable mixture of MgCO2 and Mg(OH)2, is employed in +medicine, as is also Epsom salt, MgSO4 + 7 H2O. + +ALUMINIUM AND ITS COMPOUNDS. + +Examine aluminium, aluminium bronze, corundum, emery, feldspar, +argillite, clay. Note especially the color, luster, specific +gravity and flexibility of Al. + +What elements are more common in the earth than Al? What metals? +Compare the abundance of Al with that of Fe. + +260. Compounds of Al.--Al occurs only in combination with other +elements. Feldspar, mica, slate, and clay are silicates of it. It +occurs in all rocks except CaCO3 and SiO2, and in nearly 200 +minerals. Though found in all soils, its compounds are not taken +up by plants, except by a few cryptogams. Corundum, Al2O3, is the +richest of its ores. Compute its percent of Al. Compounds of Al +are very infusible and difficult of reduction. + +261. Reduction.--Like most other metals not easily reducible by C +or H, it was originally obtained by electrolysis, but more +recently from its chloride, by the reducing action of strongly +heated K or Na. Al2Cl6 + 6 Na = 6 NaCl + 2 Al. + +What is the chief use of Na? As it takes three pounds of Na to +make one pound of Al, the cost of the latter has been fifteen +dollars or more per pound. Its use has thus been restricted to +light apparatus and aluminium bronze, an alloy of Cu 90, Al 10, +which is not unlike gold in appearance. + +Al2O3 has lately been reduced by C. Higher temperatures than have +heretofore been known are obtained by means of the electric arc +and large dynamo machines. Afurnace made of graphite, because +fire-clay melts like wax at such a high temperature, is filled +with Al2O3--corundum, --C, and Cu. In the midst of this are +embedded large carbon terminals, connected with dynamos. The +reduction takes several hours. + +The following reaction takes place: Al2O3 + 3 C = 2 Al + 3 CO. Cu +is also added, and an alloy of Al and Cu is thus formed. This +alloy is not easily separable into its elements. Explain the +action of the C. CO escapes through perforations in the top of +the furnace, burning there to CO2. Only alloys of Al have yet +been obtained by this process. This method has not been employed +before, simply because the highest temperatures of combustion, +2000 degrees or 2500 degrees, would not effect a reduction. In +the same way Si, B, K, Na, Ca, Mg, Cr, have recently been reduced +from their oxides; but a process has yet to be found for +separating them easily from their alloys. + +262. Properties and Uses.--Al is a silvery white metal, lighter +than glass, and only one-third the weight of iron. It does not +readily rust or oxidize, it fuses at 1000 degrees (compare with +Fe), is unaffected by acids, except by HCl and, slightly, by +H2SO4, is a good conductor of electricity, can be cast and +hammered, and alloys with most metals, forming thus many valuable +compounds. Every clay-bank is a mine of this metal, which has so +many of the useful properties of metals and has so few defects +that, if it could be obtained in sufficient quantities, it might, +for many purposes, take the place of iron, steel, tin, and other +metals. From its properties state any advantages which it would +have over iron in ocean vessels, railroads, and bridges. Why is +it better than Sn or Cu for culinary utensils? An alloy of Al, +Cu, and Si is used for telephone wires in Europe, and the +Bennett-Mackay cable is of the same material. Washington +monument, the tallest shaft in the world, is capped with a +pyramid of Al,ten inches high. + +For the uses of alumina, Al2O3, and its silicates, see page 133. + +ZINC AND ITS COMPOUNDS. + +Examine zincite, sphalerite, Smithsonite, sheet zinc, galvanized +iron, granulated zinc, zinc dust. + +263. Compounds.--The compounds of zinc are abundant. Its chief +ores are zincite, ZnO, sphalerite or blende, ZnS, Smithsonite, +ZnCO3. For their reduction these ores are first roasted, i.e. +heated in presence of air. With ZnS this reaction takes place: +ZnS + 3 O = Zn0 + S02. The oxide is reduced with C, and then Zn +is distilled. State the reaction. Zinc is sublimed-in the form of +zinc dust-like flowers of S. Granulated Zn is made by pouring a +stream of the molten metal into water. + +Experiment 121.--Burn a strip of Zn foil, and note the color of +the flame and of the product. State the reaction. The red color +of zincite is supposed to be imparted by Mn present in the +compound. + +264. Uses.--Name any use of Zn in the chemical laboratory. It is +employed for coating wire and sheet iron --galvanized iron. This +is done by plunging the wire or the sheets of iron into melted +Zn. Describe the use of Zn as an alloy. See page 136. + +ZnO forms the basis of a white paint called zinc white. White +vitriol, ZnSO4 + 7 H2O, is employed in medicine. Name two other +vitriols. + +CHAPTER XLVIII. + +IRON AND ITS COMPOUNDS. + +Examine magnetite, hematite, limonite, siderite, pig-iron, +wrought-iron, steel. + +265. Ores and Irons.--As Fe occurs native only in meteorites and +in small quantities of terrestrial origin, it is obtained from +its ores. There are four of these ores--magnetite (Fe3O4), +hematite (Fe2O3), limonite (2 Fe2O3 + 3 H2O), and siderite +(FeCO3). Which is richest in Fe? Compute the proportion. FeCO3 +occurs mostly in Europe. The reduction of these ores, as well as +of other metallic oxides, consists in removing O by C at a high +tempera- ture. As ordinarily classified there are three kinds of +iron,--pig- or cast-iron, steel, and wrought-iron. + +Study this table, noting the purity, the fusing-point, and the +per cent of C in each case. + + + Per Cent Fe Fusibility. Per Cent + (general). C. +Pig......... 90 1200 degrees 2-6 +Steel........ 99 1400 degrees 0.5-2 +Wrought....... 99.7 1500 degrees Fraction. + + +Pure iron melts at about 1800 degrees. Pig-iron is obtained from +the ore by smelting, and from this are made steel and wrought- +iron. + +266. Pig-Iron.--The ore is reduced in a blast furnace (Fig. 47), +in some cases eighty or one hundred feet high, and having a +capacity of about 12,000 cubic feet. The reducing agent is either +charcoal, anthracite coal, or coke,bituminous coal being too +impure. Charcoal is the best agent, and is used in preparing +Swedish iron; but it is too expensive for general use. + +Fig. 47. Blast furnace. F, entrance of tuyeres, or blast-pipes. +E, F, hottest part. C, conductor for gases, which are +subsequently used to heat the air going into the tuyeres. G, +upper portion, slag, lower portion, melted iron. + +Were ores absolutely pure, only C would be needed to reduce them. +Complete: Fe3O4 + 4 C =? Fe3O4 + 2C=? + +Much earthy material--gangue--containing silica and silicates is +always found with iron ores. These are infusible, and something +must be added to render them fusible. CaO forms with SiO2 just +the flux needed. See page 132. Ca0 + Si02 = ? Which of these is +the basic, and which the acidic compound? CaO results from +heating CaCO3; hence the latter is employed instead of the +former. In what case would Si02 be used as the flux? + +Into the blast furnace are put, in alternate layers, the fuel, +the flux, and the ore. The fire, once kindled, is kept burning +for months or years. Hot air is driven in through the tuyeres +(tweers). O unites with C of the fuel, forming CO2 and CO. The C +also reduces the ore. Fe2O3 + 3 C = ? CO accomplishes the same +thing. 3 CO + Fe2O3 = ? The intense heat fuses CaO and SiO2 to a +silicate which, with other impurities, forms a slag; this, rising +to the surface of the molten mass, is drawn off. The iron is +melted, falls in drops to the bottom, and is drawn off into sand +molds. See Figure 47. This is pig-iron. It contains as +impurities, C, Si, S, P, Mn, etc. If too much S or P is present +in an ore, it is worthless. This is why the abundant mineral FeS2 +cannot be used as a source of iron. From the top of the furnace +N, CO, CO2, H2O, etc., escape. These gases are used to heat the +air which is forced through the tuyeres, and to make steam in +boilers. + +267. Steel.--The manufacture of steel and wrought-iron consists +in removing most of the impurities from pig-iron. It will be seen +that the most common compounds of C, S, Si, and P, are their +oxides, and these are for the most part gases. Hence these +elements are removed by oxidation. + +Bessemer steel is prepared by melting pig-iron and blowing hot +air through it. A converter (Fig. 48) lined with siliceous sand, +and holding several tons, is partially filled with the molten +metal; blasts of hot air are driven into it, and the C and other +impurities, together with a little of the Fe, are oxidized. The +exact moment when the process has gone far enough, and most of +the impurities have been removed, is indicated by the appearance +of the escaping flame. It usually takes from five to ten minutes. +The blast is then stopped, and the metal has about the +composition of wrought-iron; it contains some uncombined O. A +white pig-iron (spiegeleisen), which contains a known quantity of +C and of Mn, is at once added. Mn removes part of the extra O, +and, though it remains, does not injure the metal. The C is +"dissolved" by the Fe, which is then run into molds (ingots). +This process, the Bessemer, invented in 1856, has revolutionized +steel manufacture. No less than ten tons of iron have been +converted into steel, in five minutes, in a single converter. + +268. Wrought-Iron.--The chemical principle involved in making +wrought-iron is the same as that in making steel, but the process +is different. Impurities are burned out from pig-iron in an open +reverberatory furnace, by constantly stirring the metal in +contact with air. This is called puddling. A reverberatory +furnace is one in which the fuel is in one compartment, and the +heat is reflected downward into another, that holds the substance +to be acted upon (Fig. 49). + +Steel may also be made by carburizing wrought-iron. Iron and +charcoal are packed together and heated for days, without +melting, when it is found that, in some unknown way, solid C has +penetrated solid Fe. The finer kinds of steel are made in this +way, but they are very expensive. + +Wrought-iron may also be made directly from the ore in an open +hearth furnace, with charcoal. This was the original mode. + +269. Properties.--The varying properties of pig-iron, steel, and +wrought-iron are due in part to the proportion of C and of other +elements present, either as mixtures or as compounds, and in part +to other causes not well understood. Wrought-iron is fibrous, as +though composed of fine wires, and hence is ductile, malleable, +tough, and soft, and cannot be hardened or tempered, but it is +easily welded. Pig-iron is crystalline, and so is not ductile or +malleable; it is hard and brittle, and cannot be welded. On +account of its low melting-point it is generally employed for +castings. Steel is crystalline in structure, and when suddenly +cooled from red heat by plunging into cold water, becomes hard +and brittle. The tempering can be varied by afterwards heating to +any required degree, indicated by the color of the oxide formed +on the exterior. The higher temperatures give the softer steel. + +270. Salts of Iron.--Examine FeSO4, FeS, FeS2. + +Fe has a valence of 2 or 4. This gives rise to two kinds of +salts, ferrous and ferric, as in FeCl2 and Fe2Cl6 The valence of +Fe in ferric salts is 4. Ferrous sulphate is FeSO4; ferric +sulphate, Fe2(SO4)3. Write the symbols for ferrous and ferric +hydrate; for the oxides; for the nitrates. Write the graphic +symbols for each. + +271. Colors.--The characteristic color of ferrous salts is green, +as in FeSO4. These salts give the green color to the chlorophyll +in leaves and grass, and bottle glass owes its green color to +ferrous silicate. Ferric salts are a brownish red, as shown in +hematite and limonite, and in some bottles. Red sandstone, and +most soils and earths, are illustrations of this coloring action. +The blood of vertebrates owes its color to ferric salts. Bricks +are made from a greenish blue clay in which iron exists in the +ferrous state. On being heated, ferrous salts are oxidized to +ferric, and their color is changed to red. Iron rust is hydrated +ferric oxide, Fe2O3 and Fe2(OH)6. + +272. Change of Valence. + +Experiment 122.--Dissolve 2 g. of iron filings in diluted HCl. +Filter or pour off the clear liquid, divide it into two parts, +and add NH4OH to one part till a ppt. occurs. Notice the greenish +color of Fe(OH)2. Oxidize the other part by adding a few drops of +HNO3 and boiling a minute. Now add NH4OH, and observe the reddish +color of the ppt., Fe2(OH)6. + +Solutions of ferrous salts will gradually change to ferric, if +allowed to stand, thus showing the greater stability of the +latter. In changing from FeCl2 to Fe2Cl6 oxidation does not +consist in adding O, but in increasing the negative element or +radical. This is possible only by changing the valence of Fe from +2 to 4. Hence oxidation, in its larger sense, means increasing +the valence of the positive element. To oxidize FeSO4 is to make +it Fe2(SO4)3, changing the valence of Fe as before. Reduction or +deoxidation diminishes the valence of the positive element. +Illustrate this by the same iron salts. Illustrate it by PbO and +Pb02; AuCl and AuCl3; Sb2S3 and Sb2S5. In this sense define an +oxidizing agent. A reducing agent. + +273. Ferrous Sulphate. + +Experiment 123.--Dissolve a few iron filings in dilute H2SO4, and +slowly evaporate for a few minutes. Write the equation. + +Ferrous sulphate, green vitriol, or copperas, FeSO4 + 7 H2O, is +the source of what acid? See page 66. It is also one of the +ingredients in many writing inks. On being heated, or exposed to +the air, it loses its water of crystallization and becomes a +white powder. It is prepared as above, or by oxidizing moistened +FeS2 by exposure to the air. + +Ferrous sulphide, protosulphide of iron, FeS, is how prepared? +See Experiment 6. State its use. See Experiment 108. It also +occurs native. + +Ferric sulphide, pyrite, FeS2, occurs native in large quantities. +What is its use? See page 65. + +CHAPTER XLIX. + +LEAD AND TIN. + +LEAD. + +Examine galena, lead protoxide and dioxide, red-lead, lead +carbonate, acetate, and nitrate. Note especially the colors of +the oxides, the cubical crystallization and cleavage of galena, +the specific gravity of the compounds, the softness of Pb, and +the tarnish, Pb2O, which covers it,if long exposed. + +274. Distribution of Pb.--Pb is widely distributed, occurring as +PbS and PbCO3. PbS, galenite or galena, is its main source. By +heating it in air, SO2 is formed, and Pb liberated and drawn off. + +Pb is but little acted on by cold H2SO4, unless concentrated. +Describe its use in making that acid. See page 65. To show that a +little Pb has been dissolved, as PbSO4, in the manufacture of +that acid, perform this experiment. + +Experiment 124.--To 5cc. of water in a clean t.t. add the same +volume of H2SO4, not C.P.; shake, and notice any fine powder +suspended. PbSO4, being insoluble in water, is precipitated. What +is the test for Pb? See Experiment 109. + +275. Poisonous Properties.--Ph is very flexible and soft, and is +much used for water pipes. In moist air it is soon coated with +suboxide, Pb20, as may be seen by exposing a fresh surface. Some +portion of this is liable to dissolve in water, and, as all +soluble salts of Pb are poisonous, water that has stood in pipes +should not be used fordrinking. Lead is employed as an alloy of +tin for covering sheet-iron in "terne plate." T his plate is +rarely used except for roofing. The "bright plate," used for tin +cans and other purposes, scarcely ever contains any lead except +the small portion in solder. In soldering, ZnCl2 is employed for +a flux. Sn, Pb, and Zn are somewhat soluble in vegetable acids. +If citric acid be present, as it usually is, citrates of these +metals are formed, and all of them are poisonous. The action is +far more rapid after opening the can, since oxidation is +hastened. Hence the contents should be taken out directly after +opening. + +Lead poisons seem to have an affinity for the tissues of the +body, and accumulate little by little. Painter's colic results +from lead poisoning. Epsom salt, or other soluble sulphate, is an +antidote, since with Pb it makes insoluble PbSO4. + +276. Some Lead Compounds.--Lead salts form the basis of many +paints. White paint is a mixture of PbCO3 and Pb(OH)2 suspended +in linseed oil. It is often adulterated with BaSO4, ZnO, CaCO3. +Other lead compounds are used for colored paints. The two chief +soluble salts are Pb(NO3)2 and lead acetate, Pb(C2H302)2. + +Red-lead, Pb3O4, and, to some extent, litharge, PbO, are employed +in glass manufacture. Name the kind of glass in which it is used, +describe its manufacture, and write a symbol for lead silicate. +What is the characteristic of lead glass? See page 132. + +Experiment 125.--Put a small fragment of Pb on a piece of +charcoal, and blow the oxidizing flame against it for some time +with a mouth blow-pipe. Note the color of the coating on the +coal. PbO has formed. + +Experiment 126.--Dissolve a small piece of lead in dilute HNO3. +Pour off the solution into a t.t. and add HCl or other soluble +chloride. Pb(NO3)2 + 2 HCl = ? What is the insoluble product? + +Experiment 127.--Add to a solution of Pb(C2H3O2)2 some H2SO4. +Give the reaction and the explanation. TIN. + +Examine cassiterite, tin foil, "terne plate," "bright plate." + +277. Sn occurs as the mineral cassiterite, tin stone, Sn02, and +is found in only a few localities, as Banca, Malacca, and +England. It does not readily tarnish, and is used to cover thin +plates of copper and iron. Tin foil is generally an alloy of Pb +and Sn. + +Sn is sometimes a dyad, at others a tetrad. Write symbols for its +two chlorides, stannous and stannic, also for its sulphides and +oxides. + +CHAPTER L. + +COPPER, MERCURY, AND SILVER. + +COPPER. + +Examine native copper, chalcopyrite, malachite, azurite, copper +acetate, copper nitrate, copper sulphate. + +278. Occurrence.--Copper occurs both native and in many +compounds, being diffused in rocks and, in minute quantities, in +soils, waters, plants, and animals. Spain, Chili, and the United +States are the chief Cu producing countries. The extensive mines +of Michigan yield the native ore. The Calumet and Heela mine +alone produces 4,000,000 pounds per month. The most abundant +compound of Cu is chalcopyrite, or copper pyrites, CuFeS2. +Malachite, which is green, and azurite, which is blue, are +carbonates, the former being used for ornamental purposes. + +Cu is, next to Ag, the best conductor of electricity and heat +among the elements; it is very ductile, malleable, and tenacious. + +Cu has two valences, 1 and 2. Symbolize and name its chlorides, +iodides, sulphides, and oxides. Cupric compounds, as a rule, are +more stable than cuprous. + +279. Uses.--Thousands of tons of Cu find use in domestic +utensils, ocean vessels, electric wires, batteries, and plating. +Name the chief alloys of Cu and their uses. See page 136. How may +CuS be obtained? See Experiment 7. Cu2O, cuprous oxide, is used +to color glass red. CUSO4 is employed in calico-printing, +electric batteries, etc. It is called blue vitriol. + +Paris green, used for killing potato-beetles, is composed chiefly +of copper arsenite. Write the symbol for this compound. All +soluble salts of Cu are poisonous; hence care should be taken not +to bring any acid in contact with copper vessels of domestic use. +With acetic acid, what would be formed? + +MERCURY AND ITS COMPOUNDS. + +Examine cinnabar, vermilion, mercury, red oxide, mercurous and +mercuric chloride. + +280. Cinnabar, HgS, is practically the only source of mercury-- +quicksilver. Austria, Spain, and California contain nearly all +the mines. In these mines the metal also occurs native to a small +extent. It is the only commonly occurring metal that is liquid at +ordinary temperatures; it solidifies at about -40 degrees. What +other common liquid element? See page 12. Hg is reduced from the +ore by Fe, Hg being distilled over and collected in water. Heat +regularly expands the metal. + +281. Uses.--For uses see Reduction of Ag and Au, pages 165 and +170; amalgams, page 137; laboratory work, page 68. It is also +employed for thermometers and barometers, and as the source of +the red pigment vermilion, which is artificial HgS. + +Compare the vapor density and the atomic weight of Hg, and +explain. See page 12. Hg is either a monad or a dyad. Symbolize +its ous and ic oxides and chlorides. Which of the following are +is salts, and which are ous, and why? HgNO3, Hg(NO3)2, HgCl, +HgCl2? Calomel, HgCl or Hg2Cl2, used in medicine, and corrosive +sublimate, HgCl2, are illustrations of the ous and ic salts. The +former is insoluble, the latter soluble. All soluble compounds of +Hg are virulent poisons, for which the antidote is the white of +egg, albumen. With it they coagulate or form an insoluble mass. + +SILVER AND ITS COMPOUNDS. + +282. Occurrence and Reduction.--Silver is found uncombined, and +combined, as Ag2S, argenite, and AgCl, horn silver. It occurs +usually with galena, PbS. It is abundant in the Western States, +Mexico, and Peru. Silver is separated from galena by melting the +two metals. As they slowly cool, Pb crystallizes, and is removed +by asieve, while Ag is left in the liquid mass. The principle is +much like crystallizing NaCl from solution and leaving behind the +salts of Mg, etc., in the mother liquor. When, by repeating the +process, most of the Pb is eliminated, the rest is oxidized by +heating in the air. Pb + O = PbO. Ag does not oxidize, and is +left in the metallic state. + +Another mode of reduction is to change the silver salt to its +chloride, and then remove the Cl with Fe. Roasting with NaCl +makes the first change, 2 NaCl + Ag2S = Na2S + 2 AgCl, and with +Fe the second, 2 AgCl + Fe = FeCl2 + 2 Ag. Ag is separated from +the other products by adding Hg, with which it forms an amalgam. +By distilling this, Hg passes over and Ag remains. This is the +amalgamating process. + +283. Salts of Silver are much employed in organic chemistry, and +AgCl, AgBr, and AgNO3 are used in photography. AgNO3 is a +soluble, colorless crystal, and is the basis of the silver salts. +It blackens when in contact with organic matter. Stains on a +photographer's hands are due to this substance, and the use of +AgNO3 in indelible inks depends on the same property. This may be +due to a reduction of AgNO3 to Ag4O. Stains can be removed from +the skin or from linen by a solution of Kl, or of CuCl2 followed +by sodium hyposulphite. Lunar caustic is made by fusing AgNO3 +crystals, and is used for cauterizing (burning) the flesh. Much +AgCN finds use in electroplating. + +Experiment 128.--Put 5 cc. AgNO3 solution in each of three t.t. +To the first add 3 cc. HCl, to the second 3cc.NaCl solution, and +to the third 3 cc. KBr solution. Write the reaction for each +case, and notice that the first two give the same ppt., as in +fact any soluble chloride would. Filter the second and third, on +separate filter papers, and expose half the residue to direct +sunlight, observing the change of color by occasionally stirring. +Solar rays reduce AgCl and AgBr, it is thought, to Ag2Cl and +Ag2Br. Try to dissolve the other half in Na2S2O3, sodium +thiosulphate solution. This experiment illustrates the main facts +of photography. + +CHAPTER LI. + +PHOTOGRAPHY. + +284. Descriptive.--The silver halogens, AgCI, AgBr, AgI, are very +sensitive to certain light rays. Red rays do not affect them; +hence ruby glass is used in the "dark room." + +Photography involves two processes. The negative of the picture +is first taken upon a prepared glass plate, and the positive is +then printed on prepared paper. The negative shows the lights and +shades reversed, while the positive gives objects their true +appearance. + +Few photographers now make their own plates, these being prepared +at large manufactories. The glass is there covered on one side +with a white emulsion of gelatine and AgBr, making what are +called gelatine-bromide plates. This is done in a room dimly +lighted with ruby light. The plates are dried, packed in sealed +boxes, and thus sent to photographers. The artist opens them in +his dark room, similarly lighted, inserts the plates in holders, +film side out, covers with a slide, adjusts to the camera, +previously focused, and makes the exposure to light. The time of +exposure varies with the kind of plate, the lens, and the light, +from several seconds, minutes, or hours, to 1/250 part of a +second in some instantaneous work. In the dark room the plates +are removed and can be at once developed, or kept for any time +away from the light. No change appears in the plate until +development, though the light has done its work. + +To develop the plate, it is put into a solution of pyrogallic +acid, the developer, and carbonate of sodium, the motive power in +the process. Other developers are often used. The chemical action +here is somewhat obscure, but those parts of the plates which +were affected by the light are made visible, a part of the AgzBr +being reduced to Ag by the affinity which sodium pyrogallate has +for Br. Ag2Br = 2 Ag + Br. Br is dissolved and Ag is deposited. +When the rather indistinct image begins to fade out, the plate is +dipped for a minute into a solution of alum to harden the +gelatine and prevent it from peeling off (frilling). It is +finally soaked in a solution of sodium thiosulphate (hyposulphite +or hypo), Na2S208. This removes the AgBr that the light has +failed to reduce. The processis called fixing, as the plate may +thereafter be exposed to the light with impunity. It must be left +in this bath till all the white part, best seen on the back of +the plate, disappears. 2AgBr + 3Na2S2O3 = Ag2Na4(S2O3) + 2 NaBr. +Both products are dissolved. It is then thoroughly washed. Any +dark objects become light in the negative, and vice versa. Why? + +For the positive, the best linen paper is covered on one side +with albumen, soaked in NaCl solution, dried, and the same side +laid on a solution of AgNO3. What reaction takes place? What is +deposited on the paper, and what is dissolved? This sensitized +paper, when dry, is placed over a negative, film to film, and +exposed in a printing frame to direct sunlight till much darker +than desired in the finished picture. What is dark in the +negative will be light in the positive. Why? The reducing action +of sunlight is similar to that in the negative. Explain it. + +After printing, the picture is toned and fixed. Toning consists +in giving it a rich color by replacing part of the Ag2Cl with +gold from a neutral solution of AuCl3. 3 Ag2Cl+ AUCl3 = 6AgCI + +Au. Fixing removes the unaffected AgCl, as in the negative, the +same substance being used. Describe the action. 2 AgCI + 3 +Na2S203 = Ag2Na4(S203) + 2 NaCl. Both the positive and the +negative must be well washed after each process, particularly +after the last. The picture is then ready for mounting. In fine +portrait work both the negative and the positive are retouched. +This consists in removing blemishes with colored pencils or India +ink. + +The negative--No. 1. Dissolve: sulphite soda crystals, 2 oz. (57 +g) in 8 oz. (236 cc.) water (distilled); citric acid, 60 grains +(4 g) in 1/2 oz. (15 cc.) water; bromide ammonium, 25 grains (1 +1/2 g) in 1/2 oz. water; pyrogallic acid, 1 oz. (28 g) in 3 oz. +(90 cc.) water. After dissolving, mix in the order named, and +filter. No. 2. Dissolve: sulphite soda, 2 oz. (57 g) in 4 oz. +(118 cc.) water; carbonate potash, 4 oz. (113 g) in 8 oz. (236 +cc.) water. Dissolve separately, mix, and filter. To develop +plates, mix 1 dram (3 2/3 cc.) of No. 1 and 1 dram of No. 2 with +2 oz. (60 cc.) water. Cover the plate with the mixture, and leave +as long as the picture increases in distinctness. Remove, wash, +and put it into a saturated solution of alum for a minute or two, +then wash and put it into a half-saturated solution of hypo. +Leave till no white AgCl is seen through the back of the plate. +Wash it well. + +The positive.--1. Dissolve 30 grains (2 g.) pure gold chloride in +15 oz. (450 cc.) water. This forms a stock solution. 2. Make a +saturated solution of borax. 3. Prepare a toning bath by adding +1/2 oz. (15 cc.) of the gold chloride solution and 1 oz. (30 cc.) +of the borax solution to 7 oz. (210 cc.) water. After printing +the picture, wash it in 3 or 4 waters, put it into the toning +bath, and leave it till considerably darker than desired; wash, +and put it for 15 minutes into a hypo solution that has been, +after saturation, diluted with 3 or 4 volumes of water. Then wash +repeatedly. + +CHAPTER LII. + +PLATINUM AND GOLD. + +PLATINUM. + +Examine platinum foil and wire. + +285. Platinum is much rarer than gold, and is about two-thirds as +costly as the latter. It is found alloyed with other metals, as +An, and is obtained from sand, in which it occurs, by washing. +Aqua regia is the only acid which dissolves it, and the action is +much slower than with Au. Pt is one of the heaviest metals, +having a specific gravity three times that of Fe, or twenty-one +and a half times that of water. Its fusing-point is about 1600 +degrees, or just below the temperature of the oxy-hydrogen flame. +Like Au it has little affinity for other elements, but alloys +with many metals. Pt is so tenacious that it can be drawn into +wire invisible to the naked eye, being drawn out in the center of +a silver wire, which is afterwards dissolved away from the Pt by +HNO3. Noting its valences, 2 and 4, write the symbols for the ous +and ic chlorides and oxides. + +286. Uses.--Pt is much used in chemistry in the form of foil, +wire, and crucibles. On what properties does this use depend? +Describe its use in making H2SO4. + +PtCl4 is made by dissolving Pt in aqua regia, and evaporating the +liquid. On heating PtCl4, half of its Cl is given up, leaving +PtCl2. If it be still more strongly heated, the Cl all passes +off, leaving spongy Pt. By fusing this in the oxy-hydrogen flame, +ordinary Pt is obtained. Spongy Pt has a remarkable power of +absorbing, or occluding, O without uniting with it. This O it +gives up to some other substances, and thus becomes indirectly an +oxidizing agent. What other element has this property of +occluding gases? + +GOLD. + +Examine auriferous quartz, gold chloride, yellow and ruby glass +colored with gold. 287. Gold is rarely found combined, and has +small affinity for other elements, though forming alloys with Cu, +Ag, and Hg. Its source is usually either quartz rock, called +auriferous quartz, or sand in placer mines. The element is widely +distributed, occurring in minute quantities in most soils, sea +water, etc. California and Australia are the two greatest gold- +producing countries. That from California has a light color, due +to a slight admixture of Ag. Australian gold is of a reddish hue, +due to an alloy of Cu. Gold-bearing quartz is pulverized, and +treated with Hg to dissolve the precious metal, which is then +separated from the alloy by distillation. Compare this with the +preparation of Ag. + +Such is the malleability of Au that it has been hammered into +sheets not over one-millionth of an inch thick; it is then as +transparent as glass. Gold does not tarnish or change below the +melting-point. On account of its softness it is usually alloyed +with Cu, sometimes with Ag. Pure gold is twenty-four carats fine. +Eighteen carat gold has eighteen parts Au and six Cu. Gold coin +has nine parts Au to one part Cu. The most important compound is +AuCl3. Describe a use of it. This metal is much employed in +electroplating, and somewhat in coloring glass. + +CHAPTER LIII. + +CHEMISTRY OF ROCKS. + +288. Classification.--Rocks may be divided, according to their +origin, into three classes: (1) Aqueous rocks. These have been +formed by deposition of sedimentary material, layer by layer, on +the bottoms of ancient oceans, lakes, and rivers, from which they +have gradually been raised, to form dry land. (2) Eruptive or +volcanic rocks. These have been forced, as hot fluids, through +rents and fissures from the interior of the earth. (3) +Metamorphic rocks. These, by the combined action of heat, +pressure, water, and chemical agents, have been crystallized and +chemically altered. The rocks of the first class, such as chalk, +limestone, shale, and sandstone, are distinguished by the +existence of fossils in them, or by the successive layers of the +material which goes to make up their structure and to give them a +stratified appearance. The rocks of the second class are +recognized by their resemblance to the products of modern +volcanoes and their non-stratified appearance. Rocks of the third +class are composed of crystals, which, though often very minute, +are minerals having a definite chemical composition. Examples of +the third class are gneiss, slate, schist, and marble. The last +two classes abound on the Eastern sea-board, while the interior +of our continent is composed almost exclusively of stratified +sedimentary rocks. + +289. Composition.--Rocks are not definite compounds, but variable +mixtures of minerals. Some, however, are tolerably pure, as +limestone (CaCO3) and sand-stone. + +Granite is mainly made up of three minerals,--quartz, feldspar, +and mica. Quartz, when pure, is SiO2. Feldspar is a mixed +silicate of K and Al, and often several other metals, K2Al2Si6O16 +(=K2O, Al2O3, 6 SiO2) symbolizing one variety, while a variety of +mica is H8Mg5Fe7Al2Si3O18. + +The pupil should learn to distinguish the different minerals in +granite. Quartz is glassy, mica is in scales, usually white or +black, and feldspar is the opaque white or red mineral. + +290. Importance of Siliceous Rocks.--Slate and schist are also +mixed silicates. Pure sandstone is SiO2, the red variety being +colored by iron. Igneous rocks are always siliceous. Obsidian is +a glassy silicate. A mountain of very pure glass, obsidian, two +hundred feet high, has lately been found in the Yellow-stone +region. We see how important Si is, in the compounds Si02 and the +silicates, as a constituent of the terrestrial crust. Limestone +is the only extensive rock from which it is absent. Always +combined with O, it is, next to the latter, the most abundant of +elements. Silicates of Al, Fe, Ca, K, Na, and Mg are most common, +and these metals, in the order given, rank next in abundance. + +291. Soils.--Beds of sand, clay, etc., are disintegrated rock. +Sand is chiefly SiO2; clay is decomposed feldspar, slatestone, +etc. Soils are composed of these with an added portion of +carbonaceous matter from decaying vegetation, which imparts a +dark color. The reddish brown hue so often observed in soils and +rocks results from ferric salts. + +292. Minerals, of which nearly 1000 varieties are now known, may +be simple substances, as graphite and sulphur, or compounds, as +galena and gypsum. Only seven systems of crystallizations are +known, but these are so modified as to give hundreds of forms of +crystals. See Physics. A given chemical substance usually occurs +in one system only, but we saw in the case of S that this was not +always true. + +Crystals of some substances deliquesce, or take water from the +air, and thus dissolve themselves. Some compounds cannot exist in +the crystalline form without a certain percentage of water. This +is called "water of crystallization"; if it passes into the air +by evaporation, the crystal crumbles to a powder- and is then +said to effloresce. + +293. The Earth's Interior.--We are ignorant of the chemistry of +the earth's interior. The deepest boring is but little more than +a mile, and volcanic ejections probably come from but a very few +miles below the surface. The specific gravity of the interior is +known to be more than twice that of the surface rock. From this +it has been imagined that towards the center heavy metals like Fe +and Au predominate; but this is by no means certain, since the +greater pressure at the interior would cause the specific gravity +of any substance to increase. + +294. Percentage of Elements.--Compute the percentage of O in the +following rocks, which compose a large proportion of the earth's +crust: SiO2, Al2SiO4, CaCO3. Find the percentage of O in pure +water. In air. Taking cellulose, C16H30O15, as the basis, find +the percentage of O in vegetation. + +An estimate, based on Bunsen's analysis of rocks, of the chief +elements in the earth's crust, is as follows:-- + + +O, 46 per cent Ca, 3 per cent +Si, 30 per cent Na, 2 per cent +Al, 8 per cent K, 2 per cent +Fe, 6 per cent Mg, 1 per cent + + +More than half the elements are known to exist in sea-water, and +the rest are thought to be there, though dissolved in such small +quantity as to elude detection. What four are found in the +atmosphere?CHAPTER LIV. + +ORGANIC CHEMISTRY. + +295. General Considerations.--Inorganic chemistry is the +chemistry of minerals, or unorganized bodies. Organic chemistry +was formerly defined as the chemistry of the compounds found in +plants and animals; but of late it has taken a much wider range, +and is now defined as the chemistry of the C compounds, since C +is the nucleus around which other elements centre, and with which +they combine to form the organic substances. New organic +compounds are constantly being discovered and synthesized, so +that nearly 100,000 are now known. The molecule of organic matter +is often very complex, sometimes containing hundreds of atoms. + +In organic as in inorganic chemistry, atoms are bound together by +chemical affinity, though it was formerly supposed that an +additional or vital force was instrumental in forming organic +compounds. For this reason none of these substances, it was +thought, could be built up in the laboratory, although many had +been analyzed. In 1828 the first organic compound, urea, was +artificially prepared, and since then thousands have been +synthesized. They are not necessarily manufactured from organic +products, but can be made from mineral matter. + +296. Molecular Differences.--Molecules may differ in three ways: +(1) In the kind of atoms they contain. Compare CO2 and CS2. (2) +In the number of atoms. Compare CO and CO2. (3) In the +arrangement of atoms, i.e. the molecular structure. Ethyl alcohol +and methyl ether have the same number of the same elements, +C2H6O, but their molecular structure is not the same, and hence +their properties differ. + +Qualitative analysis shows what elements enter into a compound; +quantitative analysis shows the proportion of these elements; +structural analysis exhibits molecular structure, and is the +branch to which organic chemists are now giving particular +attention. ` + +A specialist often works for years to synthesize a series of +compounds in the laboratory. + +297. Sources.--Some organic products are now made in a purer and +cheaper form than Nature herself prepares them. Alizarine, the +coloring principle of madder, was until lately obtained only from +the root of the madder plant; now it is almost wholly +manufactured from coal-tar, and the manufactured article serves +its purpose much better than the native product. Ten million +dollars' worth is annually made, and Holland, the home of the +plant, is giving up madder culture. Artificial naphthol-scarlet +is abolishing the culture of the cochineal insect. Indigo has +also been synthesized. Certain compounds have been predicted from +a theoretical molecular structure, then made, and afterwards +found to exist in plants. Others are made that have no known +natural existence. The source of a large number of artificial +organic products is coal-tar, from bituminous coal. Saccharine, a +compound with two hundred and eighty times the sweetening power +of sugar, is one of its latest products. Wood, bones, and various +fermentable liquids are other sources of organic compounds. + +298. Marsh-Gas Series.--The chemistry of the hydro-carbons +depends on the valence of C, which, in most cases, is a tetrad. +Take successively 1, 2, and 3 C atoms, saturate with H, and note +the graphic symbols:-- + + + H H H H H H + | | | | | | +H-C-H, or CH4. H-C-C-H, or? H-C-C-C-H, or ? + | | | | | | + H H H H H H + +Write the graphic and common symbols for 4, 5, and 6 C atoms, +saturated with H. Notice that the H atoms are found by doubling +the C atoms and adding 2. Hence the general formula for this +series would be CnH2n+2. Write the common symbol for C and H with +ten atoms of C; twelve atoms; thirteen. This series is called the +marsh-gas series. The first member, CH4 methane, or marsh gas, +may be written CH3H, methyl hydride, CH3 being the methyl +radical. C2H6, ethane, the second one, is ethyl hydride, C2H5H. +Theoretically this series extends without limit; practically it +ends with C35H72. + +In each successive compound of the following list, the C atoms +increase by unity. Give the symbols and names of the compounds, +and commit the latter to memory:-- + + + Boiling-point. +1. CH4 methane, or CH3H, methyl hydride, gas. +2. C2H6 ethane, C2H5H, ethyl hydride, gas +3. C3H8 propane, C3H7H, propyl hydride, gas +4. ? butane, ? ? 1 degree +5. ? pentane ? ? 38 degrees +6. ? hexane, ? ? 70 degrees +7. ? heptane, ? ? 98 degrees +8. ? octane, ? ? 125 degrees +9. ? nonane, ? ? 148 degrees +10.? dekane, ? ? 171 degrees + + +Note a successive increase of the boiling-point of the compounds. +Crude petroleum contains these hydro-carbons up to 10. +Petroleumissues from the earth, and is separated into the +different oils by fractional distillation and subsequent +treatment with H2SO4, etc. Rhigoline is mostly 5 and 6; gasoline, +6 and 7; benzine, 7; naphtha, 7 and 8; kerosene, 9 and 10. Below +10 the compounds are solids. None of those named, however, are +pure compounds. Explosions of kerosene are caused by the presence +of the lighter hydro-carbons, as naphtha, etc. Notice that, in +going down the list, the proportion of C to H becomes much +greater, and the lower compounds are the heavy hydro-carbons. To +them belong vaseline, paraffine, asphaltum, etc. + +299. Alcohols.--The following replacements will show how the +symbols for alcohols, ethers, etc., are derived from those of the +marsh-gas series. Notice that these symbols also exhibit the +molecular structure of the compound. In CH3H by replacing the +last H with the radical OH, we have CH3OH, methyl hydrate. By a +like replacement C2H5H becomes C2H5OH, ethyl hydrate. These +hydrates are alcohols, and are known as methyl alcohol, ethyl +alcohol, etc. The common variety is C2H5OH. How does this symbol +differ from that for water, HOH? Notice in the former the union +of a positive, and also of a negative, radical. + +Complete the table below, making a series of alcohols, by +substitutions as above from the previous table. + + + +1. CH3OH, methyl hydrate, or methyl alcohol. +2. C2H5OH, ethyl hydrate, or ethyl alcohol. +3. ? ? ? +4. ? ? ? +5. ? ? ? + +Continue in like manner to 10. + +The graphic symbol for CH3OH is--- + + H + | +H-C-OH; + | + H + +for C2H5OH it is-- + + H H + | | +H-C-C-OH. + | | + H H + +Write it for the next two. + + +300. Ethers.--Another interesting class of compounds are the +oxides of the marsh-gas series. In this series, O replaces H. +CH3H becomes (CH3)2O, and C2H5H becomes (C2H5)2O. Why is a double +radical taken? These oxides are ethers, common or sulphuric ether +being (C2H5)2O. Complete this table, by substituting O in place +of H, in the table on page 176. + + +1. (CH3)2O, methyl oxide, or methyl ether. +2. (C2H5)2O, ethyl oxide, or ethyl ether. +3. ? ? ? +4. ? ? ? +5, etc. ? ? ? + +Graphically represented the first two are:-- + + H H H H H H + | | | | | | +(1) H-C-O-C-H. (2) H-C-C-O-C-C-H. + | | | | | | + H H H H H H + + +301. Substitutions.--A large number of other substitutions can be +made in each symbol, thus giving rise to as many different +compounds. + + +In CH4, by substituting 3 Cl for 3 H,-- + + + H Cl + | | +H-C-H becomes H-C-CI, or CHCl3,the symbol for chloroform. + | | + H Cl + + +Replace successively one, two, and four atoms with Cl, and write +the common symbols. Make the same changes with Br. For each atom +of H in CH4 substitute the radical CH3, giving the graphic and +common formulae. Also substitute C2H5. Are these radicals +positive or negative? From the above series of formulae, of which +CH4 is the basis, are derived, in addition to the alcohols and +ethers, the natural oils, fatty acids, etc. + +302. Olefines.--A second series of hydro-carbons is represented +by the general formula CnH2n. The first member of this series is +C2H4 or, graphically,-- + + + H H + | | + C = C. + | | + H H + +Compare it with that for C2H6, in the first series, noting +the apparent molecular structure of each. + +H H +| | +C = C - C - H, or C3H6 is the second member. +| | | +H H H + + +Write formulae for the third and fourth members. + +Write the common formulae for the first ten of this series. This +is the olefiant-gas series, and to it belong oxalic and tartaric +acids, glycerin, and a vast number of other compounds, many of +which are derived by replacements. + +303. Other Series.--In addition to the two series of hydro- +carbons above given, CnH2n+2 and CnH2n, other series are known +with the general formulm CnH2n-2, CnH2n-4, CnH2n-6, CnH2n-8, +etc., as far as CnH2n-32, or C26H2O. Each of these has a large +number of representatives, as was found in the marsh-gas series. +Not far from two hundred direct compounds of C and H are known, +not to mention substitutions. The formula CnH2n-6 represents a +large and interesting group of compounds, called the benzine +series. This is the basis of the aniline dyes, and of many +perfumes and flavors. + +Chapter LV. + +ILLUMINATING GAS. + +304. Source.--The three main elements in combustion are O, H, C. +Air supplies O, the supporter; C and H are usually united, as +hydro-carbons, in luminants and combustibles. H gives little +light in burning; C gives much. The fibers of plants contain +hydro-carbons, and by destructive distillation these are +separated, as gases, from wood and coal, and used for +illuminating purposes. Mineral coal is fossilized vegetable +matter; anthracite has had most of the volatile hydro-carbons +removed by distillation in the earth; bituminous and cannel coals +retain them. These latter coals are distilled, and furnish us +illuminating gas. + +Experiment 129.--Put into a t.t. 20 g. of cannel coal in fine +pieces. Heat, and collect the gas over H2O. Test its +combustibility. Notice any impurities, such as tar, adhering to +the sides of the t.t., or of the receiver after combustion. Try +to ignite a piece of cannel coal by holding it in a Bunsen flame. +Is it the C which burns, or the hydrocarbons? Distil some wood +shavings in a small ignition-tube, and light the escaping gas. + +305. Preparation and Purification.--To make illuminating gas, +fire-clay retorts filled with coal are heated to 1100 degrees or +more, over a fire of coke or coal. Tubes lead the distilled gas +into a horizontal pipe, called the hydraulic main, partly filled +with water, into which the ends of the gas-pipe dip. The gas then +passes through condensers consisting of several hundred feet of +vertical pipe, through high towers, called washers, in which a +fine spray Fig. 60. Gas Works. + +A, furnace; C, retorts containing coal; T, gas-tubes leading to +B, the hydraulic main; D, condensers; O, washers, with a spray of +water, and sometimes coke; M, purifiers-ferric oxide or lime; G, +gas-holder. In C remain the coke and gas carbon. At B, D, E, and +O, coal tar, H2O, NH3, CO2, and SO2 are removed. At M are taken +out H2S and CO2.of water falls, into chambers with shelves +containing the purifiers CaO or hydrated Fe2O3, and finally into +a gas-holder, whence it is distributed. At the hydraulic main, +condensers, washers, and purifiers, certain impurities are +removed froth the gas. Coke is the solid C residue after +distillation. Gas-carbon, also a solid, is formed by the +separation of the heavier hydro-carbons at high temperature, and +is deposited on the sides of the retort. + +Coal gas, as it leaves the retort, has many impurities. It is +accompanied with about 3 its weight of coal tar, 1/2 its weight +of H2O vapor, 1/50 NH3, 1/20 CO2, 1/20 to 1/50 H2S, 1/300 to +1/600 S in other forms. The tar is mostly taken out at the +hydraulic main, which also withdraws some H2O with other +impurities in solution. The condensers remove the rest of the +tar, and the H2O, except what is necessary to saturate the gas. +At the main, the condensers, and the washers, NH3 is abstracted, +CO2 and H2S are much reduced, and the other S compounds are +diminished. Lime purification removes CO2 and H2S, and, to some +extent, other S compounds. Iron purification removes H2S. Fe2O3 + +3 H2S = 2 FeS + S + 3 H2O. + +The FeS is revivified by exposure to the air. 2 FeS + O3 = Fe2O3 ++ 2S. It can then be used again. H2S, if not separated, burns +with the gas, forming H2S03, which oxidizes in the air to H2SO4; +hence the need of removing it. CO2 diminishes the illuminating +power. + +306. Composition.--Even when freed from its impurities coal-gas +is a very complex mixture, the chief components being nearly as +follows:-- + + +Percent Diluents, having little C, give +H 45) very little light. Notice the small +CH, 41) diluents. percentage of luminants, or light- +CO 5 ) giving compounds, also the proportion +C,HB 1.3) of C to H in them. +C,H6 1.2)luminants. +CZH4 2.5) Cannel coal contains more of +C02 2) impurities. the heavy bydro-carbons, CnH2n, +N, etc. 2) etc., than the ordinary bituminous + 100 coal. Ten per cent of the coal should be +cannel; naphtha is, however, often employed to subserve the same +purpose, one ton of ordinary bituminous coal requiring four gallons +of oil. + +In Boston, 7,000,000 cubic feet of gas have been burned in one +day, consuming 500 tons of coal; the average is not more than +half that quantity. Of the other products, coke is employed for +heating purposes, gas carbon is used to some extent in electrical +work, and coal-tar is the source of very many artificial products +that were formerly only of natural origin. NH3, is the main +source of ammonium salts, and S is made into H2SO4. + +307. Natural Gas occurs near Pittsburg, Pa., and in many other +places, in immense quantities. It is not only employed to light +the streets and houses, but is used for fires and in iron and +glass manufactories. It is estimated that 600,000,000 cubic feet +are burned, saving 10,000 tons of coal daily in Pittsburg, Only +half a dozen factories now use coal. More than half the gas is +wasted through safety valves, on account of the great pressure on +the pipes as it issues from the earth. + +These reservoirs of natural gas very frequently occur in +sandstone, usually in the vicinity of coal-beds, but sometimes +remote from them. In all cases the origin of the gas is thought +to be in the destructive distillation, extending through long +geological periods, of coal or of other vegetable or animal +matter in the earth's interior. + +Natural gas varies in composition, and even in the same well, +from day to day; it consists chiefly of CH4, with some other +hydro-carbons. + +CHAPTER LVI. + +ALCOHOL. + +308. Fermented Liquor. + +Experiment 130.--Introduce 20 cc.of molasses into a flask of 200 +cc, fill it with water to the neck, and put in half a cake of +yeast. Fit to this a d.t., and pass the end of it into a t.t. +holding a clear solution of lime water. Leave in a warm place for +two or three days. Then look for a turbidity in the lime water, +and account for it. See whether the liquid in the flask is sweet. +The sugar should be changed to alcohol and CO2. This is fermented +liquor; it contains a small percentage of alcohol. + +309. Distilled Liquor. Experiment 131.--Attach the flask used in +the last experiment to the apparatus for distilling water (Fig. +32), and distil not more than one-fifth of the liquid, leaving +the rest in the flask. The greater part of the alcohol will pass +over. To obtain it all, at least half of the liquid must be +distilled; what passes over towards the last is mostly water. +Taste and smell the distillate. Put some into an e.d. and touch a +lighted match to it. If it does not burn, redistil half of the +distillate and try to ignite the product. Try the combustibility +of commercial alcohol; of Jamaica ginger, or of any other liquid +known to contain alcohol. + +310. Effect on the System. + +Experiment 132.--Put a little of the white of egg into an e.d. or +a beaker; cover it with strong alcohol and note the effect. +Strong alcohol has the same coagulating action on the brain and +on the tissues generally, when taken into the system, absorbing +water from them, hardening them, and contracting them in bulk. + +311. Affinity for Water. + +Experiment 133.--To show the contraction in mixing alcohol and +water, measure exactly 5cc.of alcohol and 5cc.of water. Pour them +together, and presently measure the mixture. The volume is +diminished. A strip of parchment soaked in water till it is limp, +then dipped into strong alcohol, becomes again stiff, owing to +the attraction of alcohol for water. + +312. Purity.--The most important alcohols are methyl alcohol and +ethyl alcohol. The former, wood spirit, is obtained in an impure +state by distilling wood; it is used to dissolve resins, fats, +oils, etc., and to make aniline. It is poisonous, as are the +others. + +Ethyl alcohol, spirit of wine, is the commercial article. It is +prepared by fermenting glucose, and distilling the product. It +boils at 78 degrees, vaporizing 22 degrees lower than water, from +which it can be separated by fractional distillation. By +successive distillations of alcohol ninety-four per cent can be +obtained, which is the best commercial article, though most +grades fall far below this. Five per cent more can be removed by +distilling with CaO, which has a strong affinity for water. The +last one per cent is removed by BaO. One hundred per cent +constitutes absolute alcohol, which is a deadly poison. Diluted, +it increases the circulation, stimulates the system, hardens the +tissues by withdrawing water, and is the intoxicating principle +in all liquors.--It is very inflammable, giving little light, and +much heat, and readily evaporates. + +Beer has usually three to six per cent of alcohol; wines, eight +to twenty per cent. The courts now regard all liquors having +three per cent, or less, of alcohol, as not intoxicating. In +Massachusetts it is one per cent. + +CHAPTER LVII. + +OILS, FATS, AND SOAPS. + +313. Sources and Kinds of Oils and Fats.--Oils and fats are +insoluble in water; the former are liquid, the latter solid. Most +fats are obtained from animals, oils from both plants and +animals. Oils are classified as fixed and essential. Castor oil +is an example of the former and oil of cloves of the latter. +Fixed oils include drying and non-drying oils. They leave a stain +on paper, while essential, or volatile oils, leave no trace, but +evaporate readily. Essential oils dissolved in alcohol furnish +essences. They are obtained by distilling with water the leaves, +petals, etc., of plants. Drying oils, as linseed, absorb O from +the air, and thus solidify. Non-drying ones, as olive, do not +solidify, but develop acids and become rancid after some time. + +Oils and fats are salts of fatty acids and the base glycerin. The +three most common of these salts are olein, found in olive oil, +palmitin, in palm oil and human fat, and stearin, in lard. The +first is liquid, the second semi-solid, the last solid. Most fats +are mixtures of these and other salts. + + +Olefin = Glyceryl) ( oleic) + oleate ) ( ) +Pahnitin = Glyceryl)salts from (palmitic)acid and glyceryl hydrate. + palmitate) ( ) +Stearin = Glyceryl) (stearic ) + stearate) + + +314. Saponification consists in separating these salts +into their acids and the base glycerin; soap-making is the best +illustration. To effect this separation, a strong soluble base is +used, KOH for soft, and NaOH for hard soap. Study this reaction: + + +Glyceryl oleate ) (sodium ) (oleate ) +Glyceryl palmitate) + (hydrate) = sodium (palmitate) + (glyceryl +Glyceryl stearate ) (stearate ) (hydrate + + +Soaps are thus salts of fatty acids and of K or Na. + +315. Soap is soluble in soft water, but the sodium stearate +probably unites with water to form hydrogen sodium stearate and +NaOH. The grease which exudes from the skin, or appears in +fabrics to be washed, is attacked by this NaOH and removed, +together with the suspended dirt, and a new soap is formed and +dissolved in the water. Hard water contains salts of Ca and Mg, +and when soap is used with it the Na is at once replaced by these +metals, and insoluble Ca or Mg soaps are formed. Hence in hard +water soap will not cleanse till all the Ca and Mg compounds have +combined. + +316. Glycerin, C3H5(OH)3, is a sweet, thick, colorless, unctuous +liquid, used in cosmetics, unguents, pomades, etc. It is prepared +in quantity by passing superheated steam over fats when under +pressure. + +317. Dynamite.--Treated with HNO3 and H2SO4 glycerin forms the +very explosive and poisonous liquid nitro-glycerin. In this +process the C3H5(OH)3 becomes C3H5(NO3)3. C3H5(OH)3 + 3HNO3 = +C3H5(NO3)3+3 H2O. H2SO4 is used to absorb the H2O which is +formed. Nitro-glycerin, absorbed by gunpowder, diatomaceous +earth, sawdust, etc., forms dynamite. For obvious reasons the +pupil should not experiment with these substances. + +318. Butter and Oleomargarine.--Milk contains minute particles of +fat, about 1/500 of an inch in diameter, which give it the +whitecolor. These particles are lighter than the containing +liquid, and rise to the top as cream. Churning unites the +particles more closely, and separates them from the buttermilk. +The flavor of butter is due to the presence of five or ten per +cent of butyric and other acids of the same series. + +It was found that cows gave milk after they ceased to have food; +hence it was inferred that the milk was produced at the expense +of the cows' fat. Why could not butter be artificially made from +the same fat? It was but a step from fat to milk, as it was from +milk to butter. Oleomargarine, or butterine, was the result. Beef +fat, suet, is washed in water, ground to a pulp, and partially +melted and strained, the stearin is separated from the filtered +liquid and made into soap, and an oily liquid is left. This is +salted, colored with annotto, mixed with a certain portion of +milk, and churned. The product is scarcely distinguishable from +butter, and is chemically nearly identical with it, though less +likely to become rancid from the absence of certain fatty acids; +its cost is perhaps one-third as much as that of butter. + +Chapter LVIII + +CARBO-HYDRATES. + +319. Carbon and Water.--Some very important organic compounds +have H and O, in the proper proportion to form water, united with +C. The three leading ones are sugar, C12H22O11 or C12(H2O)11, +starch, C6H10O6, or ?, and cellulose, C18H30O15 or ?. Note the +significance of the name carbo-hydrates as applied to them. + +320. Sugars may be divided into two classes,--the sucroses, +C12H22O11, and the glucoses, C6H12O6. Sucrose, the principal +member of the first class, is obtained from the juice of the +maple, the palm, the beet and the sugarcane; in Europe largely +from the beet, in America from cane. Granulated sugar is that +which has been refined; brown sugar is the unrefined. From the +sap evaporated by boiling, brown sugar crystallizes, leaving +molasses, which contains glucose and other substances. Good +molasses has but a small percentage of glucose. To refine brown +sugar it is dissolved in water, a small quantity of blood is +added to remove certain vegetable substances, after which it is +filtered through animal charcoal, i.e. bone-black, a process +which takes out the coloring-matter. The water is then evaporated +in vacuum-pans, so as to boil at about 74 degrees and to prevent +conversion into grape sugar. By this process much glucose or +syrup is formed, which is separated from the crystalline sucrose +by rapidly revolving centrifugal machines. Great quantities of +sucrose are used for food by all civilized nations. A single +refinery in New York purifies 2,000,000 pounds per day. + +321. Glucose, or invert sugar, the principal member of the second +class, consists of two distinct kinds of sugar, --dextrose and +levulose. These differ in certain properties, but have the same +symbol. Both are found in equal parts in ripe fruits, while +sucrose occurs in the unripe. Honey contains these three kinds of +sugar. + +Sucrose, by the action of heat, weak acids, or ferments, may be +resolved into the other two varieties. C12H22O11 + H2O = C6H12O6 ++ C6H12O6. No mode of reversing this process, or of transforming +glucose into sucrose is known. Glucose is easily made from starch +or from the cellulose in cotton rags, sawdust, etc. If boiled +with dilute H2SO4 starch takes up water and becomes glucose. +C6H10O5 + H2O = C6H12O6. + +CaCO3 is added to precipitate the H2SO4, which remains unchanged. +State the reaction. The product is filtered and the filtrate is +evaporated. Much glucose is made from the starch of corn and +potatoes. + +322. Starch is found in all plants, especially in grains, seeds, +and tubers. Green plants--those containing chlorophyll-- +manufacture their own starch from CO2 and H2O. These chlorophyll +grains are the plant's chemical laboratories, and hundreds of +thousands of them exist in every leaf. CO2 and a very little H2O +enter the leaf from the air, H2O being also drawn up through the +root and stem from the earth. In some unknown way in the leaf, +light has the power of synthesizing these into starch and setting +free O, which is returned to the atmosphere.6 CO2 + 5 H2O = +C6H10O5 + 12 O. As no such change takes place in darkness, all +green plants must have light. Parasitic plants, which are usually +colorless, obtain starch ready-made from those on which they +feed. + +323. Uses.--Glucose is used in the manufacture of alcohol and +cheap confectionery, and in adulterating sucrose. It is only two- +thirds as sweet as the latter. The seeds of all plants contain +starch for the germinating sprout to feed upon; but starch is +insoluble, and hence useless until it is converted into glucose. +This is effected by the action of warmth, moisture, and a ferment +in the seed. Glucose is soluble and is at first the plant's main +food. + +Commercial starch is made in the United States chiefly from corn; +in Europe, from potatoes. Differences in the size of starch +granules enable microscopists to determine the plant to which +they belong. + +324. Cellulose, or woody fiber, is the basis of all vegetable +cell walls. Cotton fiber represents almost pure cellulose. From +it are made paper and woven tissues. In paper manufacture, woody +fiber is made into a pulp, washed, bleached, filtered, hot- +pressed, and sometimes glazed. Parchment paper, vegetable +parchment, is made by dipping unglazed paper for half a minute +into cold dilute H2SO4, 1 part H2O, 2 1/2 parts H2SO4, and then +washing. The fiber, by chemical change, is thus toughened. The +cell walls of wood are impure cellulose; hence the inferior +quality of paper made from wood-pulp. Paper is now employed for a +large number of purposes for which wood has heretofore been used, +such as for barrels, pails, and other hollow ware, wheels, +etc. + +325. Gun-cotton is made by treating cotton fiber with H2SO4 +and HNO3, washing and drying. To all appearances no change has +taken place, but the substance has become an explosive compound. + +326. Dextrin, a gummy substance used for the backs of postage +stamps, is a carbo-hydrate, as in fact are gums in general. +Dextrin is made by heating starch with H2SO4 at a lower +temperature than for dextrose. + +327. Zylonite and Celluloid. -These two similar substances embody +the latest use of cellulose in manufactured articles. For +zylonite, linen paper is cut into strips two feet by one inch, +soaked ten minutes in a mixture of H2SO4 and HNO3, a process +called nitration, washed for several hours, then ground to a fine +pulp, and thoroughly dried. It is then similar to pyroxiline. +Aniline coloring-matter of any desired shade is added, after +which it is dissolved by soaking some hours in alcohol and +camphor, the liquid is evaporated, and the substance is kneaded +between steam-heated iron rollers, dried with hot air, and +finally subjected to great pressure, to harden it, and cut into +sheets. Zylonite is combustible at a low temperature, and when in +the pyroxiline stage, explosively so. Ivory, coral, amber, bone, +tortoise shell, malachite, etc., are so closely imitated that the +imitation can only be detected by analysis. Collars, combs, +canes, piano-keys, and jewelry, are manufactured from it, and it +can be made transparent enough for windows. + + CHAPTER LIX + +CHEMISTRY OF FERMENTATION. + +328. Ferments.--A large number of chemical changes are brought +about through the direct agency of bodies called ferments; their +action is called fermentation. Ferments are sometimes lifeless +chemical products found in living bodies; but in other cases they +are humble plants. + +329. Yeast is one of the most common of living ferments, wild +yeast being a microscopic plant found on the ground near apple- +trees and grape-vines, and often in the air. The cultivated +variety is sold by grocers. The temperature best suited to the +rapid multiplication of the germs forming the ferment plant is 25 +degrees to 35 degrees. + +330. Alcoholic and Acetic Fermentation.--The changes which the +juice of the apple undergoes in forming cider and vinegar are a +good illustration of fermentation by a living plant. Apple-juice +contains sucrose. Yeast germs from the air, getting into this +unfermented liquor, cause it to "work." This process changes +sucrose to glucose, and glucose to alcohol and CO2, and is known +as alcoholic fermentation. The latter reaction, C6H12O6 = 2 C2H6O ++ 2 CO, is only partially correct, as other products are formed. +The juice has now become cider; the sugar alcohol. After a time, +if left exposed, another organism finds its way to the alcohol, +and transforms it into acetic acid, HC2H8O2, and H2O. This +process is called acetic fermentation. C2H6O + O2 = HC2H3O2 + +H2O. For this fermentation, a liquor should not have over ten per +cent of alcohol. Mother of vinegar consists of the germs that +caused the fermentation. Still a third species of ferment may +cause another action, changing acetic acid to H2O and CO2. The +vinegar then tastes flat. HC2H3O2 + 4 O = 2H2O + 2 CO2. + +Some mineral acids, as H2SO4 and HCl, and some organic acids, are +regarded as lifeless ferments. To this class are thought to +belong the diastase of malt and the pepsin of the stomach. This +variety of ferments exists in the seeds of all plants, and +changes starch to glucose. + +331. Bread which is raised by yeast is fermented, the object +being to produce CO2, bubbles of which, with the alcohol, cause +the dough to rise and make the bread light. + +Grapes and other fruits ferment and produce wines, etc., from +which distilled liquors are obtained. + +332. Lactic Fermentation changes the sugar of milk, lactose, to +lactic acid, i.e. sour milk. In canning fruit, any germs present +are killed by heating, and those from the air are excluded by +sealing the can. Milk has been kept sweet for years by boiling, +and tightly covering the receptacle with two or three folds of +cotton cloth. + +333. Putrefaction is fermentation in which the products of decay +are ill-smelling. Saprophytes attack the dead matter, feed on it, +and cause it to putrefy. This action, as well as that of ordinary +fermentation, used to be attributed solely to oxygen. Germs bring +back organic matter to a more elementary state, and so have a +very important function. By some scientists, digestion is +regarded as a species of fermentation, probably due to the action +of lifeless ferments; e.g. sucrose cannot be taken into the +system, but is first fermented to glucose. + +334. Most Infectious Diseases are now thought to be due to +parasites of various kinds, such as bacteria, microbes, etc., +with which the victim often swarms, and which feed on his +tissues, multiplying with enormous rapidity. Such diseases are +small-pox, intermittent and yellow fevers, etc. Consumption, or +tuberculosis, is believed to be caused by a microbe which +destroys the lungs. In some diseases not less than fifteen +billions of the organisms are estimated to exist in a cubic inch. +These multiply so rapidly that from a single germ in forty-eight +hours may be produced nearly three hundred billions. These germs +do not spring into life spontaneously from inorganic matter, but +come from pre-existent similar forms. Parasites are not so rare +in the system even of a healthy person as is generally supposed. +They are found on our teeth and in many of the tissues of the +body. + +Several infectious diseases are now warded off or rendered less +virulent by vaccination, the philosophy of which is that the +organisms are rendered less dangerous by domestication; several +crops, or generations, are grown in a prepared liquid, each less +injurious than its parent. Some of the more domesticated ones are +introduced into the system, and the person has only a modified +form of the disease, often scarcely any at all, and is for a more +or less limited time insured against further danger. + +Dust particles and motes floating in the air are in part germs, +living or dead, often requiring only moisture and mild +temperature for resuscitation. Most of these are harmless. + +Chapter LX. + +CHEMISTRY OF LIFE. + +335. Growth.--The chemistry of organic life is very complex, and +not well understood. A few of the principal points of distinction +between the two great classes of living organisms, plants and +animals, are all that can be noted here. Minerals grow by +accretion, i.e. by the external addition of molecules of the same +material as their interior. A crystal of quartz grows by the +addition of successive molecules of SiO2, arranged in a +symmetrical manner around its axis. The growth of crystals can be +seen by suspending a string in a saturated solution of CuSO4, or +of sugar. In plants and animals the growth is very much more +complex, but is from the interior, and is produced by the +multiplication of cells. To produce this cell-growth and +multiplication, food-materials must be furnished and assimilated. +In plants, sap serves to carry the food-materials to the parts +where they are needed. In the higher animals, vari- ous fluids, +the most important of which is the blood, serve the same purpose. + +336. Chemistry of Plants.--In ultimate analysis, plants consist +mainly of C, H, O, N, P, K. In proximate analysis, as it is +called, they are found to contain these elements combined to form +substances like starch, sugar, etc. Water is the leading compound +in both animals and plants. One of the most important differences +between animals and plants is, that all plants, except parasitic +ones, are capable of building up such compounds as starch from +mineral food-stuffs, while animals have not that power, but must +have the products of proximate analysis ready prepared, as it +were, by the plant. Hence plants thrive on minerals, whereas +animals feed on plants or on other animals. The power which +plants have of transforming mineral matter is largely due to +sunlight, the action of which in separating CO, was described. +The reaction in the synthesis of starch from CO2 and H2O in the +leaf, is thought to be as follows: 6 CO2 + 5 H2O = C6H10O5 + 12 +O. C6H10O5 is taken into the tree as starch; 12 O is given back +to the air. All the constituents, except CO2 and a very small +quantity of H2O, are absorbed by the roots, from the soil, from +which they are soon withdrawn by vegetation. To renew the supply, +fertilizers or manures are applied to the soil. These must +contain compounds of N, P, and K. N is usually applied in the +form of ammonium compounds, e.g. (NH4)2SO4, (NH4)2CO3, and +NH4NO3. The reduction and application of Cas(PO4)2 for this +purpose was described. K is usually applied in the form of KCl +and K2SO4. + +337. Food of Man.--In the higher animals the object is not so much +to increase the size as to supply the waste of the system. The +principal elements in man's body are C, H, O, N, S, P. + +An illustration of the transformation of mineral foods by plants +before they can be used by animals is found in the Ca3(PO4)2 of +bones. This is rendered soluble; plants absorb and transform it; +animals eat the plants and obtain the phosphates. Thus man is +said to "eat his own bones." The food of mankind may be divided +into four classes (1) proteids, which contain C, H, O, N, and +often S and P; (2) fats, and (3) amyloids, both of which contain +C, H, O; (4) minerals. Examples of the first class are the gluten +of flour, the albumen of the white of egg, and the casein of +cheese. To the second class belong fats and oils; to the third, +starch, sugar, and gums; to the fourth, H2O, NaCl and other +salts. Since only proteids contain all the requisite elements, +they are essential to human food, and are the only absolutely +essential ones, except minerals; but since they do not contain +all the elements in the proportion needed by the system, a mixed +diet is indispensable. Milk, better than any other single food, +supplies the needs of the system. The digestion and assimilation +of these food-stuffs and the composition of the various tissues +is too complicated to be taken up here; for their discussion the +reader is referred to works on physiological chemistry. + +338. Conservation.--Plants, in growing, decompose CO2, and +thereby store up energy, the energy derived from the light and +heat of the sun. When they decay, or are burned, or are eaten by +animals, exactly the same amount of energy is liberated, or +changed from potential to kinetic, and the same amount of CO2 is +restored to the air. The tree that took a hundred years to +complete its growth may be burned in an hour, or be many years in +decaying; but in either case it gives back to its mother Nature, +all the matter and energy that it originally borrowed. The ash +from burning plants represents the earthy matter, or salts, which +the plant assimilated during its growth; the rest is volatile. In +the growth and destruction of plants or of animals, both energy +and matter have undergone transformation. Animals, in feeding on +plants, transform the energy of sunlight into the energy of +vitality. Thus "we are children of the sun." + +CHAPTER LXI. + +THEORIES. + +339. The La Place Theory.--This theory supposes that at one time +the earth and the other planets, together with the sun, +constituted a single mass of vapor, extending billions of miles +in space; that it rotated around its center; that it gradually +shrank in volume by the transformation of potential into kinetic +energy; that portions of its outer rim were thrown off, and +finally condensed into planets; that our sun is only the +remainder of that central mass which still rotates and carries +the planets around with it; that the earth is a cooling globe; +that the other planets are going through the same phases as the +earth; and finally that the sun itself is destined like them to +become a cold body. + +340. A Cooling Earth.--The sun's temperature is variously +estimated at many thousands, or even millions oŁ degrees. Many +metals which exist on the earth as solids -e.g. iron- are gases +in the dense atmosphere of the sun. Thus the earth, in its early +existence, must have been composed of gases only, which in after +ages condensed into liquids and solids. So intense was the heat +at that time, that substances probably existed as elements +instead of compounds, i.e. the temperature was above the point of +dissociation. We have seen that Al2O3, CaO, SiO2, etc., are +dissociated at the highest temperatures only. If the temperature +were above that of combination, compounds could not exist as +such, but matter would exist in its elemental state. On slowly +cooling, these elements would combine. It is, then, a fair +inference that such compounds as need the highest temperatures to +separate them, as silica, silicates, and some oxides, were formed +from their elements at a much earlier stage of the earth's +history than were those compounds that are more easily separable, +such as water, lead sulphide, etc., and that the most infusible +substances were solidified first. + +341. Evolution.--As the earth slowly cooled, elements united to +form compounds, gases condensed to liquids, and these to solids. +At one time the entire surface of our planet may have been +liquid. When the cooling surface reached a point somewhat below +that of boiling water, the lowest forms of life appeared in the +ocean. This was many millions of years ago. Most scientists +believe that all vegetable and animal life has developed from the +lowest forms of life. There is also a theory that all chemical +elements are derivatives of hydrogen, or of some other element, +and that all the so-called elements are really compounds, which a +sufficiently high temperature would dissociate. As evidence of +this, it is said that less than half as many elements have been +discovered in the sun as in the earth, and that comets and +nebula, which are less developed forms of matter than the sun, +have a few simple substances only. + +It is easy to fancy that all living bodies, both animal and +vegetable, are only natural growths from the lowest forms of +life; that these lowest forms are a development, with new +manifestations of energy, from inorganic matter; that compounds +are derived from elements; and that the last are derivatives of +some one element; but it must be borne in mind that this is only +a theory. + +342. New Theory of Chemistry. We have seen that heat lies at the +basis of chemical as well as of physical changes. By the loss of +heat, or perhaps by the change of potential into kinetic energy, +in a nebulous parent mass, planets were formed, capable of +supporting living organisms. Heat changes solids to liquids, and +liquids to gases; it resolves compounds, or it aids chemical +union. In every chemical combination heat is developed; in every +case of dissociation heat is absorbed. Properly written, every +equation should be: a + b = c + heat; e.g. 2 H + 0 = H2O + heat; +or, c - a = b - heat; e.g. H2O - 2 H = 0 - heat. Another +illustration is the combination of C and O, and the dissociation +of CO2, as given on page 82. C + O2 = CO2 + energy. CO2 - O2 = C +- energy. In fact, there are indications that the present theory +of atoms and molecules of matter, as the foundation of chemistry, +will at no distant day give place to a theory of chemistry based +on the forms of energy, of which heat is a manifestation. + +Chapter, LXII. + +GAS VOLUMES AND WEIGHTS. + +343. Oxygen. + +Experiment 134.--Weigh accurately, using delicate balances, 5 g. +KClO3, and mix with the crystals 1 or 2 g. of pure powdered MnO2. +Put the mixture into a t.t. with a tight-fitting cork and +delivery-tube, and invert over the water-pan, to collect the gas, +a flask of at least one and a half liters' capacity, filled with +water. Apply heat, and, without rejecting any of the gas, collect +it as long as any will separate. + +Then press the flask down into the water till the level in the +flask is the same as that outside, and remove the flask, leaving +in the bottom all the water that is not displaced. Weigh the +flask with the water it contains; then completely fill it with +water and weigh again. + +Subtract the first weight from the second, and the result will +evidently be the weight of water that occupies the same volume as +the O collected. This weight, if expressed in grams, represents +approximately the number of cubic centimeters of water,--since 1 +cc. of water weighs lg,--or the number of cubic centimeters of O. + +At the time the experiment is performed the temperature should be +noted with a centigrade thermometer, and the atmospheric pressure +with a barometer graduated to millimeters. + +Suppose that we have obtained 1450 cc. of O, that the temperature +is 27 degrees, and the pressure 758 mm.; we wish to find the +volume and the weight of the gas at 0 degrees and 760 mm. + +According to the law of Charles--the volume of a given quantity +of gas at constant pressure varies directly as the absolute +temperature. To reduce from the centigrade to the absolute scale, +we have only to add 273 degrees. Adding the observed temperature, +we have 273 degrees + 27 degrees = 300 degrees. Applying the +above law to O obtained at 300 degrees A, we have the proportion +below. Since the volume of O at 273 degrees will be less than it +will at 300 degrees, the fourth term, or answer will be less than +the third, and the second term must be less than the first. 300 : +273 :: 1450 : x. This would give the result dependent upon +temperature alone. + +By the law of Mariotte - Physics, - the volume of a given +quantity of gas at a constant temperature varies inversely as the +pressure. Applying this law to the O obtained at 758mm, we have +the following proportion. The volume at 760mm will be less than +at 758mm; or the fourth term will be less than the third; hence +the second must be less than the first. 760: 758:: 1450: x. This +would give the result dependent on pressure alone. + +Combining the two proportions in one:-- + + 300: 273 ):: 1450: x = 1316cc. + 760: 758 ) + +1316cc=1.316 liters. It remains to find the weight of this gas. A liter of +H weighs 0.0896g. The vapor density of O is 16. Hence 1.316 liters of O +will weigh 1.316 X 16 X 0.0896 =1.89g. + + (KClO3 = KCl + O3) +From the equation (122.5 48) we make a proportion, + ( 5 x) + +122.5: 5:: 48: x = 1.95, and obtain, as the weight of O contained in +5g of KClO3, 1.95g. The weight we actually,obtained was 1.89g. This +leaves an error of 0.06g, or a little over 4 per cent of error (0.06 / 1.95 += 0.03 +). The percentage of error, in performing this experiment, +should fall within 10. + +Some of the liabilities to error are as follows:-- + + +1. Impure MnO2, which sometimes contains C. CO2 is soluble m H2O. + +2. Solubility of O in water. + +3. Escape of gas by leakage. + +4. Moisture taken up by the gas. + +5. Difference between the temperature of the gas and that of the +air in the room. + +6. Errors in weighing. + +7. Want of accuracy in the weights and scales. + +344. Hydrogen. + +Experiment 135.--Weigh 5g, or less of sheet or granulated Zn, and +put it into a small flask provided with a thistle-tube and a +delivery-tube. Cover the Zn with water, and introduce through the +thistle-tube measured quantities of HCl, a few cubic centimeters +at a time. Collect the H over water in large flasks, observing +the same directions as in removing O. Weigh the water, compute +the volume of the gas, reduce it to the standard, and obtain the +weight, as before. Should any Zn or other solid substance be +left, pour off the water or filter it, weigh the dry residue, and +deduct its weight from that of the Zn originally taken. Suppose +the residue to weigh 0.5g. Make and solve the proportion from the +equation:- + + +Zn + 2HCl = ZnCl2 + 2H. +65 2. +4.5 x. + + +Compute the percentage of errcr, as in the case of O. If the +purity of the HCl be known, i.e. the weight of HCl gas in one +cubic centimeter of the liquid, a proportion can be made between +HCl and H, provided no free HCl is left in the flask. State any +liabilities to error in this experiment. + +PROBLEMS. + +(1) A gas occupies 2000cc.when the barometer stands +750mm. What volume will it fill at 760mm? + +(2) At 750mm my volume of O is 4 1/2 liters. What will it be at +730mm? + +(3) At 825mm? + +(4) At 200mm? + +(5) Compute the volume of a gas at 70 degrees, which at 30 +degrees is 150cc. + +(6) At 0 degrees I have 3000cc.of O. What volume will it occupy +at 100 degrees? + +(7) I fill a flask holding 2 litres with H. The thermometer +indicates 26 degrees, the barometer 762mm. What is the volume of +the gas at 0 degrees and 760mm? + +If the volumes of gases vary as above, it is evident that their +vapor densities must vary inversely. A liter of H at 0 degrees +weighs 0.0896. What will a liter of H weigh at 273 degrees? At +273 degrees the one liter has be- come two liters, one of which +weighs 0.0448 (= 0.0896 / 2). The vapor density of a gas is +inversely proportional to the temperature. Also, the vapor +density is directly proportional to the pressure, since a liter +of any gas under a pressure of one atmosphere is reduced to half +a liter under two atmospheres. + +PROBLEMS. + +(1) Find the weight of a liter of O at 0 degrees; then compute the +weight of a liter at 27 degrees. + +(2) Find the weight of 500cc.of N2O at 60 degrees. + +(3) Of 200 cc. of CO at -5 degrees. + +(4) A given volume of O weighs 0.25g at a pressure of 750mm; find +the weight of a like volume of O at 758mm. + +APPENDIX. + +INDIVIDUAL APPARATUS. + +Each pupil should be provided with the apparatus given below, but in +cases where great economy must be exercised different pupils may, by +working at different times, use the same set. The author has selected +apparatus specially adapted, as to exact dimensions, quality, and cheap- +ness, for performing in the best way the experiments herein described, +and sets or separate pieces of this, together with other apparatus and +chemicals, can be had of the L.E. Knott Apparatus Co., 14 Ashburton +Place, Boston, to which firm teachers are referred for catalogs. + +4 wide-mouthed bottles (horse-radish size), with corks. +1 soda-bottle. +4 pieces window-glass (3 in. sq.). +2 pieces thick glass tubing (20 in. long, 4 in. outside diam.). +1 glass stirring-rod. +1 glass funnel (2 1/2 in. wide, 60 degrees). +2 pieces glass tubing (12 in. long; 5/8 in. diam.). +1 porcelain evaporating-dish (3 in. wide). +1 asbestus paper and 1 fine wire gauze (3 in. sq.). +1 iron (or tin) plate. +1 pair forceps. +1 triangular file and 1 round file. +1 copper wire (15 in. long). +6 test-tubes, and corks to fit. +1 wooden test-tube holder. +1 flask with cork (200cc). +1 Bunsen burner (or alcohol lamp). +1 iron ring-stand. +1 piece rubber tubing (18 in. long, +3/8 in. inside diam.). +4 reagent bottles (250cc), HCl, HNO3, H2SO4, NH4OH. +1 pneumatic trough. + +Wherever in this work "Bunsen burner" or "lamp" is mentioned, if +gas is not to be had, an alcohol lamp may be substituted. + +GENERAL APPARATUS. + +The following list includes apparatus needed for occasional +use:-- + +Metric rules (20 or 30cm long). +Scales with metric weights (1-200 g). +Metric graduates (25 or 50cc). +Filter papers. +Metric graduates (500cc). +Reagent bottles (250 and 500cc). +Mouth blowpipes. +Platinum wire and foil. +Mortars and pestles. +Test-tube racks. +Thistle-tubes. +Filter-stands. +Beakers. +Glass tubing (3/16 in., 1/4 in., and 1 in. outside). +Rubber tubing (1/8 in., and 3/8 in. inside). +Hessian crucibles. +Porcelain crucibles. +Electrolytic apparatus, including 2 or more Bunsen cells. +Ignition-tubes. +Steel glass-cutters. +Wire-cutters. +Calcium chloride tubes. +Water baths. +Thermometers. +Barometers, etc. + +APPENDIX. + +CHEMICALS. + +The following estimate is for twenty pupils: - +Alcohol 1 pt +Alum 1 oz +Ammonium chloride 1/2 lb +Ammonium hydrate 1 lb +Ammonium nitrate. 1/2 lb +Antimony (powdered metallic) 1/2 oz. +Arsenic (powdered metallic) 1/2 oz. +Arsenic trioxide..... 1 oz. +Barium chloride..... 1 oz. +Barium nitrate..... 1 oz. +Beeswax....... 1 oz. +Bleaching-powder.... 1/4 lb. +Bone-black...... 1/2 lb. +Bromine....... 1/4 lb. +Calcium chloride.... 1 lb. +Calcium fluoride (powdered) 1 lb. +Cannel coal 1 lb +Carbon disulphide 1/4 lb +Chlorhydric acid 6 lb +Cochineal 1 oz +Copper (filings) 2 lb. +Copper nitrate 1 oz +Copper oxide 1/4 lb. +Ether (sulphuric) 1/4 lb +Ferrous sulphide 1 lb. +Ferrous sulphate 1/4 lb +Indigo 1/4 lb +Iodine 1 oz +Iron (filings or turnings) 1 lb. +Lead (sheet) 4 lb +Lead acetate 1 oz +Lead nitrate 1/4 lb +Litmus 1/2 oz +Litmus paper 3 sheets +Magnesium ribbon.... 3 ft. +Manganese dioxide.... 2 lb. +Mercurous nitrate.... 1/2 oz. +Nitric acid 3 lb. +Oxalic acid 1/4 lb +Phosphorus 1/4 lb +Potassium (metallic) 1/8 oz +Potassium bromide 1/4 lb. +Potassium dichromate 1/4 lb. +Potassium chlorate 2 lb. +Potassium hydrate 1/4 lb. +Potassium iodide 2 oz +Potassium nitrate 1/4 llb +Silver nitrate 1 oz. +Sodium 1/8 oz. +Sodium carbonate 1/4 lb +Sodium hydrate 1 lb. +Sodium nitrate 1/2 lb +Sodium silicate..... 1/2lb +Turkey red cloth.... 1/2yd +Sodium sulphate..... 1/4lb +Turpentine(spirits). 1/4lb +Sodium sulphide..... 1/4lb +Zinc(granulated).... 2lb +Sodium thiosulphate. 1/4lb +Zinc foil........... 3ft +Sulphur............. 2lb +Sulphuric acid...... 12lb + +Additional Material + +These substances are best obtained of local dealers. + +Calcium carbonate(marble)..... 1lb +Molasses...................... 1pt +Calcium oxide(unslaked lime).. 1lb +Sodium chloride(fine)......... 1lb +Charcoal...................... 1lb +Sodium chloride(coarse)....... 1lb +Sheet lead.................... 4lb +Sugar......................... 1/2lb + +FOR EXAMINATION + +Those in capitals are most important + +Rocks and Minerals. +ARGILLITE, +ARESENIC, +ARSENOPYRITE, +Barite, +CALCITE, +CASSITERITE, +CHALCOPYRITE, +CHALK, +CINNABAR, +COPPER (native), +Corundum, +Dolomite, +EMERY, +FELDSPAR, +Flint, +GALENITE, +GRANITE, +GRAPHITE, +GYPSUM, +HEMATITE, +Hornblende, +Jasper, +LIMONITE, +MAGNESITE, +MAGNETITE, +MALACHITE, +Meerschaum, +MICA, +OBSIDIAN, +Orpiment, +PYRITE, +QUARTZ, +Realgar, +SAND, +SERPENTINE, +SIDERITE, +SPHALERITE, +Talc, +ZINCITE + +Metals and Alloys. + +Aluminium, Iron (cast), +Aluminium bronze. Pewter, +Bell metal, Solder, +Brass, Steel, +Bronze, Type metal, +Copper, Tin foil, +Galvanized iron, Tin (bright plate and terne plate), +German silver, Zinc (sheet). +Iron (wrought) + +Additional Compounds, for Examination: + +Copper acetate, Lead carbonate, +Copper arsenite, Red lead, +Copper nitrate, Magnesia alba, +Copper sulphate, Smalt, +Lead dioxide, Vermilion. +Lead protoxide, + +TABLE OF SOLUTIONS. + +Number of grams of solids to be dissolved in 500cc of water. + +AgNO3......... 25 K2Al2(SO4)4...... 50 +BaCl2......... 50 KBr.... 25 +Ba(N0 3)2........ 30 K2Cr207........ 50 +CaClz......... 60 KI.......... 25 +Ca(OH)2...... saturated KOH....... 60 +CaS04....... saturated NaICOS........ 50 +CUC12 50 NaOH 60 +Cu(N03)......... 50 NalSl03....... saturated +FeS04......... 50 NH,N03........ 50 +HgC12......... 30 Pb(C2H302)2...... 50 +HgN03..... 25 + 25 HN03 Pb(NOs)2....... . 50 + + +Other solutions....saturated. + +Indigo solution (sulphindigotic acid) is prepared by heating for +several hours over a water bath, a mixture of ten parts of H 2SO4 +with one of indigo, and, after letting it stand twenty-four +hours, adding twenty parts of water and filtering. + + + +TEXTBOOK ADVERTISEMENTS THAT APPEARED IN THE ORIGINAL EDITION + + + +INTRODUCTION TO CHEMICAL SCIENCE + +By R.P. WILLIAMS, Instructor in Chemistry in the English High +School, Boston. l2mo. Cloth. 216 pages. By mail, 90 cents; for +introduction, 80 cents. + +This work is strictly, but easily, inductive. The pupil is +stimulated by query and suggestion to observe important +phenomena, and to draw correct conclusions. The experiments are +illustrative, the apparatus is simple and easily made. The +nomenclature, symbols, and writing of equations are made +prominent features. In descriptive and theoretical chemistry, the +arrangement of subjects is believed to be especially superior in +that it presents, not a mere aggregation of facts, but the +science of chemistry. Brevity aud concentration, induction, +clearness, accuracy, and a legitimate regard for interest, are +leading characteristics. The treatment is full enough for any +high school or academy. + +Though the method is an advanced one, it has been so simplified +that pupils experience no difficulty, but rather an added +interest, in following it. + +The author himself has successfully employed this method in +classes so large that the simplest and most practical plan has +been a necessity. + +Thomas C. Van Nuys, Professor of Chemistry, Indiana University, +Bloomington, Ind.: + +"I consider it an excellent work for students entering upon the +study of chemistry." + +C.F. Adams, Teacher of Science, High School, Detroit, Mich.: + +"I have carried two classes through Williams's Chemistry. The +book has surpassed my highest expectations. It gives greater +satisfaction with each succeeding class." + +J.W. Simmons, County Superintendent of Schools, Owosso, Mich.: + +"The proof of the merits of a textbook, is found in the crucible +of the class-room work. There are many chemistries, and good +ones; but, for our use, this leads them all. It is stated in +language plain, interesting and not misleading. A logical order +is followed, and the mind of the student is at work because of +the many suggestions offered. We use Williams's work, and the +results are all we could wish. There is plenty of chemistry in +the work for any of our high schools." + +W.J. Martin, Professor of Chemistry, Davidson College, N.C.: + +"One of the most admirable little text-books I have ever seen." + +T.H. Norton, Projessor of Chemistry, Cincinnati University, O.: + +"Its clearness, accuracy, and compact form render it +exceptionally well adapted for use in high and preparatory +schools. I shall warmly recommend it for use, whenever the effort +is made to provide satisfactory training in accordance with the +requirements for admission to the scientific courses of the +University." + + +CHEMICAL EXPERIMENTS + + +General and Analytical. By R.P. WILLIAMS, Instructor in +Chemistry, English High School, Boston. 8vo. Boards. xv + 212 +pages. Fully illustrated. Mailing price, 60 cents; for +introduction, 50 cents. + +This book is for the use of students in the chemical laboratory. +It contains more than one hundred sets of the choicest +illustrative experiments, about half of which belong to General +Chemistry, the rest to Metal and Acid Analysis. + +Great care has been taken to describe accurately and minutely the +methods of performing experiments, and in directing pupils to +observe phenomena and to explain what is seen. The work is amply +illustrated and is replete with questions and suggestions. Blank +pages are inserted for pupils to make a record of their work, for +which careful directions are given, with a model, laboratory +rules, tables of solubilities, etc. + +A new feature is the supplementary and original work, vhich is +given at the end of each set of experiments for such pupils as +complete the prescribed work ahead of others in the class, and a +list of terms to be looked up in some text-book. This gives an +elasticity to the book and fits it for use in schools where much +time is devoted to chemistry, as well as in the most elementary +classes in labortttory work. + +Another original feature which it is believed will be heartily +welcomed by teachers is the method of treating Metal Analysis +successfully used by the author for several years. + +Briefly, the aim of this book is to aid the pupil to do, to +observe, to explain, to record, aud thus to learn the essentials +of chemistry. + + +LABORATORY MANUAL OF GENERAL CHEMISTRY + + +By R.P. WILLIAMS, Instructor in Chemistry, English High School, +Boston. 12mo. Boards. xvi + 200 pages. by mail, 30 cents; for +introduction, 25 cents. + +The book contains one hundred experiments in general chemistry +aNd qualitative analysis, blanks opposite each for pupils to to +take notes, laboratory rules, complete tables of symbols, with +chemical and common names, reagents, solutions, chemicals, and +apparatus, and the plan of a model laboratory. + + +AN ELEMENTARY CHEMISTRY + + +By GEORGE R. WHITE, Instructor in Chemistry at Phillips Academy, +Exeter. 12mo. Cloth. xxix + 272 pages. Mailing price, $1.10; for +introduction, $1.00. + +This is an excellent text-book for High Schools and Academies, +and for elementary classes in Colleges. The strictly inductive +method here followed, together with the insertion of numerous +questions that must cause the student to do his own reasoning +from the observations, renders this book particularly useful. + +T.H. Norton, Professor of Chemistry, University of Cincinnati, +Cincinnati, Ohio.: + +"I am greatly pleased with the plan and its execution. It is an +admirable arrangement for our inductive course in chemistry and +should not fail to yield good results." + + +A STUDENTS' MANUAL OF A LABORATORY COURSE IN PHYSICAL +MEASUREMENTS + + +By Wallace C. Sabine, Assistant Professor of Physics, Harvard +University. 8vo. Cloth. ix + 126 pages. Mailing price, $1.35; for +introduction, $1.25. + +This manual, which is intended for use in supplementing college +courses in physics, contains an outline of seventy experiments, +arranged with special regard to a systematic and progressive +development of the subject. + +Le Roy C. Cooley, Professor of Physics, Vassar College: + +"I have examined it and am ready to commend it." + +J.F. Woodhull, Professor of Sciences, Teachers' College, New +York: + +"I find Sabine's Laboratory Manual a thoroughly good thing." + + +HIGH SCHOOL LABORATORY MANUAL OF PHYSICS + + +By Dudley G. Hays, Charles D. Lowry, and Austin C. Rishel, +Teachers of Physics in the Chicago High Schools. 8vo. Cloth. iv + +154 pages. Mailing price, 60 cents; for introduction, 50 cents. + +This manual has been written: First, to present a logically +arranged course of experimental work covering the ground of +Elementary Physics. Second, to provide sufficient laboratory work +to meet college entrance requirements. + +The experiments are largely quantitative, but qualitative work is +introduced. + +W.S. Jackman, Teacher of Science, Cook Co. Normal School, +Englewood, Ill.: + +"It is a most excellent manual, and I believe it meets the needs +of high schools on this subject better than any other book I have +seen." + + +YOUNG'S LESSONS IN ASTRONOMY + + +Including Uranography. Revised Edition. By CHARLES A. YOUNG, +Professor of Astronomy in the College of New Jersey. 12mo. Cloth. +Illustrated. ix + 357 pages, exclusive of four double-page star +maps. By mail, $1.30; for introduction, $1.20. + +The revised edition of this book has been prepared for schools +that desire a brief course free from mathematics. It is based +upon the author's Elements of Astronomy, but many changes of +arrangement have been made. In fact, everything has been +carefully worked over and re-written to adapt it to the special +requirements. Great pains has been taken not to sacrifice +accuracy and truth to brevity, and no less to bring everything +thoroughly down to date. The latest results of astronomical +investigation will be found here. The author has endeavored, too, +while discarding mathematics, to give the student a clear +understanding and a good grasp of the subject. As a body of +information and as a means of discipline, this book will be +found, it is believed, of notable value. The most important +change in the arrangement of the book has been in bringing the +Uranography, or constellation tracing, into the body of the text +and placing it near the beginning, a change in harmony with the +accepted principle that those whose minds are not mature succeed +best in the study of a new subject by beginning with what is +concrete and appeals to the senses, rather than with the abstract +principles. Brief notes on the legendary mythology of the +constellations have been added for the benefit of such pupils as +are not likely to become familiar with it in the study of +classical literature. + +N.W. Rarrington, President of University of Washington, Seattle, +Wash., formerly chief of the U.S. Weather Bureau, Washington, +D.C.: + +"I shall take pleasure in commending it to schools requiring an +astronomy of this grade. The whole series of Astronomies reflects +credit on their distinguished author and shows that he +appreciates the needs of the schools." + +Clarence E. Kelly, Prin. of High School, Haverhill, Mass.: + +"It seems to me the book is admirably adapted to its purpose, and +that it accomplishes the difficult task of presenting to the +student or reader not conversant with Algebra and Geometry, an +excellent selection of what may with profit be given him as an +introduction to the science of astronomy." + + +YOUNG'S ELEMENTS OF ASTRONOMY + + +With a Uranography. By CHARLES A. YOUNG, Professor of Astronomy +in the College of New Jersey. 12mo. Half leather. x + 472 pages, +and four star maps. Mailing price, $1.55: for introduction, +$1.40. + +Uranography. + +From Youpg's Elements of Astronomy. 12mo. Flexible covers. 42 +pages. besides four star maps. By mail, 35 cents; for +introduction, 30 cents. + +This volume is an independent work, and not an abridgment of the +author's General Astronomy. It is a text-book for advanced High +Schools, Seminaries, and Brief Courses in colleges generally. It +was prepared by one of the most distinguished astronomers of the +world, a most popular lecturer, and most successful teacher. It +had every presumption in its favor, and the event has more than +justified expectations. Special attention has been paid to making +all statements correct and accurate so far as they go. + +In the text no mathematics higher than elementary algebra and +geometry is introduced; in the foot-notes and in the Appendix an +occasional trigonometric formula appears, for the benefit of the +very considerable number of High school students who understand +such expressions. + +G.B. Merriman, formerly Prof. of Mathemutics and Astronomy, +Rutgers College, New Brunswick, N.J.: + +"For a short course in elementary astronomy, it is by far the +best book I have ever examined." + +Warren Mann, State Normal School, Potsdam, N. Y.: + +"Accuracy in use of terms is a marked feature. I consider it the +best text-book on this subject." + +H.N. Chute, High School, Ann Arbor, Mich.: + +"It is just the book the scholars have been waiting for." + +G.H. Howe, State Normal School, Warrensburg, MO.: + +"It is indeed an admirable book, up to the times, clear, and +complete." + +Jeremiah Slocum, South Division High School, C&ugo, Ill.: + +"It is well adapted both as to scope and manner of treatment to +high-school work." + +Ray G. Huling, Prin. of English High School, Cambridge, Mass.: + +"It is delightfully fresh, full, and clear." + +A.S. Roe, recently of High School, Worcester, Muss.: + +"The book is extended enough to please the exacting teacher." + +I.P. Bishop, State Normal School, Buffalo, N.Y.: + +"The book seems to have all the essentials of a first-class text +for high school work; viz., conciseness, clearness, and the +results of recent research." + + +YOUNG'S GENERAL ASTRONOMY + + +A Text-book for Colleges and Technical Schools. By CHARLES A . +YOUNG, Professor of Astronomy in the College of New Jersey. 8vo. +viii + 551 pages. Half morocco. Illustrated with over 250 cuts +and and diagrams, and supplemented with the necessary tables. +Mailing price, $2.50; for introduction, $2.25. + +In amount, the work has been adjusted as closely as possible to +the prevailing courses of study in our colleges. By omitting the +fine print, a briefer course may be arranged. + +The eminence of Professor Young as an original investigator in +astronomy, a lecturer and writer on the subject, and an +instructor of college classes, and his scrupulous care in +preparing this volume, led the publishers to present the work +with the highest confidence; and this confidence has been fully +justified by the event. More than one hundred colleges adopted +the work within a year from its publication, and it is conceded +to be the best astronomical text-book of its grade to be found +anywhere. + +Edw. C. Pickering, Prof. of Astronomy, Harvard University: + +"I think this work the best of its kind, and admirably adapted to +its purpose." + +S.P. Langley, Sec. Smithsonian Inst., Washington, D.C.: + +"I know no better book (not to say as good a one) for its +purpose, on the subject." + + +AN INTRODUCTION TO SPHERICAL AND PRACTICAL ASTRONOMY + + +By DASCOM GREENE, Professor of Mathematics and Astronomy in the +Rensselaer Polytechnic Institute, Troy, N.Y. NW. Cloth. +Illustrated. viii + 158 pages. Mailing price, $1.60; for +introduction, $1.50. + +The book is intended for class-room use and affords such a +preparation as the student needs before entering upon the study +of the larger and more elaborate works on this subject. + +The appendix contains an elementary exposition of the method of +least squares. + +Daniel Carhart, Act. Prof. Mathematics, Western Univ. of Pa., +Allegheny, Pa.: + +"Professor Greene has supplied that which is needed to make the +usual course in Astronomy in our colleges more practical." + +Rodney G. Kimball, Polytechnic Institute, Brooklyn, N.Y.: + +"The hasty examination which I have given it has left a very +favorable impression as to its merits as a judicious compound of +the practical work which it professes to cover." + + +SCHEINER'S ASTRONOMICAL SPECTROSCOPY + + +Department of Special Publication.--Revised Edition. Translated, +revised and enlarged by E.B. FROST, Professor of Astronomy in +Dartmouth College. 8vo. Half leather. Illustrated. xiii + 482 +pages. Price by mail, $5.00; for introdoctiort, $4.75. + +This work aims to explain the most practical and modern methods +of research, and to state our present knowledge of the +constitution, physical condition alld motions of the heavenly +bodies, as revealed by the spectroscope. + +Edward S. Holden, Director of the Lick Observatory, Mt. Hamilton, +California: + +"I congratulate you on the appearance of this very important +book; it is indispensable to all astronomers and students of +spectroscopy." + + +ELEMENTS OF PLANT ANATOMY + + +By EMILY L. GREGORY, Professor of Botany in Barnard College. 8vo. +Cloth. viii + 148 pages. Illustrated. Mailing price, $1.35; for +introduction, $1.25. + +This book is designed as a text-book for students who have +already some knowledge of general botany. It consists of an +outline of the principal facts of plant anatomy, in a form +available not only for those who wish to specialize in botany but +for all who wish to know the leading facts about the inner +structure of plants. It affords a preparation for the study of +the more intricate and difficult questions of plant anatomy and +physiology, while it is especially adapted to the wants of +students, who need a practical knowledge of plant structure. + + +ELEMENTS OF STRUCTURAL AND SYSTEMATIC BOTANY + + +For High Schools and Elementary College Courses. By DOUGLAS H. +CAMPBELL, Professor of Botany in the Leland Stanford Junior +University. 12mo. Cloth. ix + 253 pages. Price by mail, $1.25; +for introduction, $1.12. + +The special merit of this book is that it begins with the simple +forms, and follows the order of nature to the complex ones. + + +PLANT ORGANIZATION + + +By R. HALSTEAD WARD, formerly Professor of Botany in the +Rensselaer Polytechnic Institute, Troy, N.Y. Quarto. 176 pages. +Illustrated. Flexible boards. Mailing price, 85 cents; for +introduction, 75 cents. + + +ELEMENTARY METEOROLOGY + + +By WILLIAM MORRIS DAVIS, Professor of Physical Geography in +Harvard College. With maps and charts. 8vo. Cloth. xi + 355 +pages. Mailing price, $2.70; for introduction, $2.50. + +This work is believed to be very opportune, since no elementary +work on the subject has been issued for over a quarter of a +century. It represents the modern aspects of the science. It is +adapted to the use of advanced students, and will meet the needs +of members of the National and State Weather Services who wish to +acquaint themselves with something more than methods of +observation. + +The essential theories of modern Meteorology are presented in +such form that the student shall perceive their logical +connection, and shall derive from their mastery something of the +intellectual training that comes with the grasp of well-tested +conclusions. + +The charts of temperature, pressure, winds, etc., are reduced +from the latest available sources, while the diagrams freely +introduced through the text are for the most part new. + +A.W. Greeley, retired Brigadier General U.S.A., and formerly +Chief of Signal Office, Washington: + +"A valuable and timely contribution to scientific text-books." + +Winslow Upton, Professor of Astronomy, Brown University: + +"The best general book on the subject in our language." + +Wm. B. Clark, Professor of Geology, Johns Hopkins University: + +"An excellent book and of great value to the teacher of +meteorology." + +David Todd, Professor of Astronomy, Amherst College: + +"Clear, concise, and direct. To teach meteorology with it must be +a delight." + + +MOLECULES AND THE MOLECULAR THEORY OF MATTER + + +Department of Special Publioation. By A. D. RISTEEN. 8vo. Cloth. +Illustrated. viii + 223 pages. Retail price, $2.00 + +This work is a complete popular exposition of the molecular +theory of matter, as it is held by the leading physicists of +today. Considerable space is devoted to the kinetic theory of +gases. Liquids also are discussed, and solids receive much +attention. There is also a division discussing the methods that +have been proposed for finding the sizes of molecules, and here, +as elsewhere throughout the book, the methods described are +illustrated by numerical examples. The last division of the book +touches upon the constitution of molecules. The subject is +everywhere treated from a physical standpoint. + + + +END OF AN INTRODUCTION TO CHEMICAL SCIENCE + + + +INFORMATION ABOUT THIS ELECTRONIC EDITION + +The original edition of this text was published by Ginn and +Company, Publishers, Boston, U.S.A. in 1896. The typography was +by J.S. Cushing and Co., Boston and the Presswork was by Ginn +and Co., Boston. The book was "Entered according to Act of +Congress, in the year 1887, by R.P. Williams, in the Office +of the Librarian of Congress, at Washington." + +This electronic text was prepared by John Mamoun with help from +numerous other proofreaders, including those associated with +Charles Franks' Distributed Proofreaders website. Thanks to +R. Zimmerman, D. Starner, B. Schak, K. Rieff, D. Kokales, +N. Harris, K. Peterson, E. Beach, W.M. Maull, M. Beauchamp +J. Roberts and others for proofing this e-text. + +This e-text is public domain, freely copyable and distributable +for any non-commercial purpose, and may be included without royalty +or permission on a mass media storage product, such as a cd-rom, +that contains at least 50 public domain electronic texts, whether +offered for non-commercial or commercial purposes. Any other +commercial usage requires permission. + +Use of the Project Gutenberg Trademark requires separate +permission. + + + + + +End of Project Gutenberg Etext of An Introduction to Chemical Science + |