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+*** START OF THE PROJECT GUTENBERG EBOOK 77630 ***
+
+
+
+
+  TRANSCRIBER’S NOTE
+
+  Italic text is denoted by _underscores_.
+
+  Some minor changes to the text are noted at the end of the book.
+
+
+
+
+                                   AN
+
+                                  ESSAY
+
+                                   ON
+
+                              _COMBUSTION_,
+
+                            WITH A VIEW TO A
+
+                                 NEW ART
+
+                                   OF
+
+                           DYING AND PAINTING.
+
+                                 WHEREIN
+
+              THE PHLOGISTIC AND ANTIPHLOGISTIC HYPOTHESES
+                          ARE PROVED ERRONEOUS.
+
+
+                            BY MRS. FULHAME.
+
+
+                                 LONDON:
+
+                         PRINTED FOR THE AUTHOR,
+
+                BY J. COOPER, BOW STREET, COVENT GARDEN,
+
+         And Sold by J. JOHNSON, No. 72, St. Paul’s Church Yard;
+               G. G. and J. ROBINSON, Paternoster Row; and
+                 T. CADELL, Jun. and W. DAVIES, Strand.
+
+                                  1794.
+
+                      [ENTERED AT STATIONERS HALL.]
+
+
+
+
+PREFACE.
+
+
+The possibility of making cloths of gold, silver, and other metals, by
+chymical processes, occurred to me in the year 1780: the project being
+mentioned to Doctor Fulhame, and some friends, was deemed improbable.
+However, after some time, I had the satisfaction of realizing the idea,
+in some degree, by experiment.
+
+Animated by this small success, I have, from time to time, ever since,
+prosecuted the subject as far as pecuniary circumstances would permit.
+
+I imagined in the beginning, that a few experiments would determine the
+problem; but experience soon convinced me, that a very great number
+indeed were necessary, before such an art could be brought to any
+tolerable degree of perfection.
+
+A narration of the numerous experiments, which I made with this view,
+would far exceed the bounds, I prescribe myself in this essay; I shall
+therefore present the reader only with a few, selecting such as I judge
+most interesting, and best adapted to illustrate the subject.
+
+Though I was, after some considerable time, able to make small bits of
+cloth of gold, and silver, yet I did not think them worthy of public
+attention; but by persevering, I at length succeeded in making pieces
+of gold cloth, as large as my finances would admit.
+
+Some time after this period, I found the invention was applicable
+to painting, and would also contribute to facilitate the study of
+geography: for I have applied it to some maps, the rivers of which I
+represented in silver, and the cities in gold. The rivers appearing, as
+it were, in silver streams, have a most pleasing effect on the sight,
+and relieve the eye of that painful search for the course, and origin,
+of rivers, the minutest branches of which can be splendidly represented
+in this way.
+
+Notwithstanding this further success, I was dubious about the propriety
+of publishing this Essay; I therefore shewed some specimens of these
+metallic stuffs to persons, whom I thought qualified to judge of them:
+some approved of them very much, and were pleased to say, that the
+invention would make an era in the arts; others thought it a pretty
+conceit; and others were of opinion, that the stuffs had not that
+splendour, or burnished appearance, which could entitle them to public
+notice.
+
+The latter opinion had much weight with me; for it must be allowed,
+that the specimens, which I shewed them, had not that lustre and
+polish, necessary for shoulder-knots, lace, spangles, gold muslins,
+&c.; that some of them had a reddish cast, bordering on the colour of
+copper, some a purple, mixed with gold; and that some of them were
+unequal in the die, and seemed stained; which imperfections were owing
+to a partial reduction of the metal in the fibres of the silk.
+
+But all these imperfections, except the want of that burnished lustre
+so necessary for gold lace, spangles, &c. I knew I could remedy; and
+therefore the criticism, as far as it relates to them, had no great
+influence with me.
+
+I am in possession of some pieces, one of which is about a yard in
+length, which have scarce any of these imperfections.
+
+Moreover, that high polish of burnished gold, so necessary in spangles,
+lace, &c., would, in my opinion, be a great imperfection in gold stuffs
+designed for whole suits; as a person in such a habit, would look like
+a gilded statue.
+
+I saw a piece of gold stuff made for the late King of Spain, which was
+of a purple colour, with gold wire shining through it, though rather
+obscurely; and it was much admired: I was so struck with its beauty,
+that I attempted to imitate it on a small bit of white silk; and
+succeeded, having produced a beautiful purple colour, with gold beaming
+through it.
+
+Therefore, the want of that burnished appearance is no objection to
+this art; for the paler, and cooler, to a certain degree, the colour of
+the gold is, the more lovely do these metallic cloths appear.
+
+I made small bits of gold tiffany, which looked exceedingly beautiful;
+the fineness of the thread contributing much to that effect; and, in my
+opinion, such webs are inimitable by mechanical means.
+
+Beside, though I am not able to make cloths like burnished gold, others
+of greater means and abilities may; for we cannot pretend to prescribe
+any limits to the perfection, at which chymistry, and the arts, may
+arrive.
+
+However, I must acknowledge, that this unfavourable judgement suspended
+my intention of publishing this little work, until a celebrated
+philosopher happening, some time in October 1793, to see some of the
+same pieces, and indeed, some of the worst, viewed the performance in a
+very different light.
+
+This illustrious friend of science not only approved of the specimens
+shewn him, but offered to have a memoir on the subject presented to the
+Royal Society: but different incidents dissuaded me from that mode of
+publication, and induced me to adopt the present.
+
+I now no longer hesitated about the propriety of publishing; for,
+every thing considered, I judged, that though this art could never
+be established, which is by no means my opinion, yet the experiments
+themselves, upon which I attempted to found it, as they are new, and
+seem to throw some light on the theory of combustion, are not unworthy
+the attention of Chymists.
+
+Those who viewed my performance with a favourable eye, were of opinion,
+that I should dedicate this Essay to some patron of the arts; or
+apply for his Majesty’s Royal letters patent, in order to reimburse
+the expence necessarily incurred in this investigation, an expence so
+disproportionate to the fortune which supported it, that nothing but a
+certain fatality, and the hope of reward, could induce me to persevere.
+
+As to patrons, I have heard of such beings on the record of fame; but
+never saw one: on the contrary, it has been my lot to know of many,
+whose malignant breath, as far as its deadly influence can extend,
+never ceases to blast the unsheltered blossoms of science.—And as for a
+patent, had I even the means, I should perhaps never attempt it; for if
+we may judge of the future by the past, I can safely affirm, that such
+an application would be vain.
+
+Thus circumstanced, I publish this Essay in its present imperfect
+state, in order to prevent the furacious attempts of the prowling
+plagiary, and the insidious pretender to chymistry, from arrogating to
+themselves, and assuming my invention, in plundering silence: for there
+are those, who, if they can not by chymical, never fail by stratagem,
+and mechanical means, to deprive industry of the fruits, and fame, of
+her labours.
+
+But the British empire should not forget, that she owes her power and
+greatness to commerce; that she is, as it were, the hive of the arts,
+and should not, by the sulphureous vapour of oppression, and neglect,
+compel her bees to swarm for protection to foreign climes, but rather
+permit them to roam in their native soil, and allow them, in the winter
+of life, to sip a little of the honey of their own industry.
+
+The nation, whose evil genius withholds this protection, only sounds
+the trumpet of emigration; and must erelong lament her cities deserted,
+her fields brown with desolation, and herself the easy prey, and vile
+drudge of surrounding greatness.
+
+I first imagined, that the proper title of this performance, should
+be, an Essay on the Art of making Cloths of Gold, Silver, and other
+Metals, by chymical processes; but reflecting on the imperfect state
+of the art, and that my experiments related not only to the reduction,
+but also to the calcination of metals, and other combustible bodies, I
+determined to entitle it, An Essay on Combustion, with a view to a new
+Art of Dying and Painting, which includes every thing the experiments
+can extend to.
+
+As to the style, I have endeavoured to relate the experiments in a
+plain and simple manner, aiming more at perspicuity, than elegance.
+
+I have adopted the French Nomenclature, as the terms of it are so
+framed, as to prevent circumlocution, assist the memory, by pointing
+out the combination, and state of the elements existing in each
+compound, as far as they are known; advantages to be found in no other
+Nomenclature.
+
+However, the English reader must regret, that the French chymists have
+not preferred the terms _air_, and _ammonia_, to the less harmonious
+sounds, _gas_, and _ammoniac_. I took the liberty of writing the latter
+_ammonia_.
+
+I have not related my experiments in the order, in which they were
+made, sensible that such a narration would be tedious, and that a short
+extract from them would answer every purpose at present intended.
+
+The experiments related I have endeavoured to arrange in such a manner,
+as mutually to illustrate each other, by contrasting the successful
+with those, that failed, thus pointing out a general principle, which
+forms a chain through the whole, connects all the experiments, shows
+their points of coincidence, and disagreement, and by this means
+furnishes us with _data_, by which, I hope, the art may be improved.
+
+This arrangement also facilitates the perusal, and relieves the mind
+of that fatiguing attention, which must necessarily be given to an
+indigested mass of insulated experiments, that have no clew to connect
+them, but has, on the other hand, its disadvantages; for it throws a
+sameness on the work, incompatible with that variety which is often so
+agreeable.
+
+My apparatus consisted chiefly of a few glass vessels for the solution
+of metals, and the formation of such elastic fluids, as I used. The
+cheapest, and the most simple of those described by Dr. Priestley
+answered my purpose.
+
+Dr. Nooth’s machine for combining carbonic acid with water, is very
+convenient for making small experiments with some kinds of gas; as the
+base of that machine serves to contain the materials, from which the
+gas is obtained; and the middle glass the cloth previously dipped in
+the metallic solution, on which the experiment is to be made.
+
+The cloth may be suspended in this part of the machine, by means of a
+thread, and a cork.
+
+As this machine is useful only in experiments on a very small scale, I
+sometimes used tall glass cylinders, in which I suspended the subject
+of the experiment, by means of a thread, a cork, and a bit of cement.
+
+This cylinder I placed over a vessel containing the materials, which
+produced the gas.
+
+It is very convenient to have cylinders of different sizes,
+proportioned to the scale, on which the experiments are to be made.
+
+But machinery for confining elastic fluids is not always necessary; as
+most of the experiments may be performed in the open air.
+
+It may appear presuming to _some_, that I should engage in pursuits of
+this nature, but averse from indolence, and having much leisure, my
+mind led me to this mode of amusement, which I found entertaining, and
+will, I hope, be thought inoffensive by the liberal, and the learned.
+But censure is perhaps inevitable; for some are so ignorant, that they
+grow sullen and silent, and are chilled with horror at the sight of any
+thing, that bears the semblance of learning, in whatever shape it may
+appear; and should the _spectre_ appear in the shape of _woman_, the
+pangs, which they suffer, are truly dismal.
+
+There are others, who suffer the same torture in a still higher degree;
+but by virtue of an _old inspiring tripod_, on which ignorance,
+servility, or chance, has placed them, assume a dictatorship in
+science, and fancying their rights and prerogatives invaded, swell with
+rage, and are suddenly seized with a violent and irresistible desire
+of revenge, manifesting itself by innuendos, nods, whispers, sneers,
+grins, grimace, satanic smiles, and witticisms uttered sometimes in
+the acute, and sometimes in the nasal obtuse twang, with an affected
+hauteur, and contempt of the _spectre_; shrugs, and a variety of other
+contortions, attending.
+
+Sometimes the goblin, which thus agitates them, lurks latent, and
+nothing is perceived but hollow murmurs, portending storms: sometimes
+the lurking fiend darts with sidelong fury at the devoted object,
+which, if unarmed, falls a victim to the grisly monster.
+
+But happily for human kind, the _magic tripod_ drags none into its
+dizzy vortex, but those who are radically stupid, and malicious, who
+are the beasts of prey destined to hunt down unprotected genius, to
+stain the page of biography, or to rot unnoted in the grave of oblivion.
+
+Although the surge of deliberate malice be unavoidable, its force is
+often spent in froth, and bubbles; for this little bark of mine has
+weathered out full many a storm, and stemmed the boisterous tide; and
+though the cargo be not rich, the dangers, which may hereafter be
+pourtrayed on _votive tablet_, may serve as a beacon to future mariners.
+
+But happen what may, I hope I shall never experience such desertion of
+mind, as not to hold the helm with becoming fortitude against the storm
+raised by ignorance, petulant arrogance, and privileged dulness.
+
+However, were I not encouraged by the judgement of some friends, and
+possessed of specimens, to show the progress made in the art, I should
+never perhaps venture to publish this Essay; as I am sensible, it
+labours under many imperfections, which inaccuracy of observation, and
+the drapery of imagination, must spread over the whole, imperfections
+perhaps unavoidable in such a discussion.
+
+Finding, the experiments could not be explained on any theory hitherto
+advanced, I was led to form an opinion different from that of M.
+Lavoisier, and other great names. Persuaded that we are not to be
+deterred from the investigation of truth by any authority however
+great, and that every opinion must stand or fall by its own merits,
+I venture with diffidence to offer mine to the world, willing to
+relinquish it, as soon as a more rational appears.
+
+  November 5th, 1794.
+
+
+
+
+                               CONTENTS.
+
+
+  Introduction                                                         1
+
+  Chap. I.    Reduction of Metals by Hydrogen Gas                     13
+
+  ----  II.   ------------------- Phosphorus                          41
+
+  ----  III.  ------------------- Sulphur                             69
+
+  ----  IV.   ------------------- Alkaline Sulphure                   84
+
+  ----  V.    ------------------- Sulphurated Hydrogen
+                                    Gas                               99
+
+  ----  VI.   ------------------- Phosphorated Hydrogen
+                                    Gas                              113
+
+  ----  VII.  ------------------- Charcoal                           124
+
+  ----  VIII. ------------------- Light                              142
+
+  ----  IX.   ------------------- Acids                              155
+
+  ----  X.    Oxygenation of Combustible Bodies                      161
+
+              -------------- Azote                                 ibid.
+
+              -------------- Hydrogen                                164
+
+              -------------- Phosphorus                              165
+
+              -------------- Sulphur                                 166
+
+              -------------- Charcoal                              ibid.
+
+              -------------- Metals                                  169
+
+              -------------- Light                              168, 169
+
+  ----  XI.   Conclusion                                             178
+
+  Nomenclature                                                       181
+
+
+
+
+INTRODUCTION.
+
+
+Though some of the phenomena of combustion were known from the earliest
+ages, yet no rational attempt to explain them was made till about the
+middle of the 17th century.
+
+Before that period, it was supposed by alchymists and physicians, that
+sulphur was the inflammable principle, on which all the phenomena of
+combustion depended.
+
+But Beecher perceiving, that sulphur did not exist in several
+combustible bodies, asserted it was not the principle of
+inflammability; which, he maintained, was a different substance, common
+to sulphur and other combustible bodies: this principle he supposed to
+be of a dry nature, and called it inflammable Earth.
+
+Stahl refined this hypothesis by supposing the inflammable earth of
+Beccher to be pure fire, fixed in combustible bodies, and constituting
+an essential part of them.
+
+According to Stahl, a combustible body is a compound, containing fixed
+fire, or _phlogiston_; and combustion is the disengagement of this
+phlogiston from a fixed to a free state, attended sometimes with heat
+and light: when these phenomena cease, the body becomes incombustible;
+if this calcined body be now heated with charcoal, or any other
+inflammable substance, capable of giving it phlogiston, or fixed fire,
+it returns again to the class of inflammable bodies.
+
+This hypothesis is so simple and plausible, that, since the year 1736,
+it was received, though differently modified, all over Europe.
+
+The principal objections to it are, that the existence of phlogiston
+cannot be demonstrated; and that it does not explain, why bodies become
+heavier after oxygenation, and lighter after reduction.
+
+M. Lavoisier discovering, that the increase of weight, which bodies
+acquire during combustion, is equal to the weight of the combustible
+substance, and that of the vital air employed, denied the existence
+of phlogiston, or fixed fire, in combustible bodies; though he grants
+the existence of combined _caloric_ in them. He seems then to allow
+the existence of phlogiston, but to have changed its name to that of
+_caloric_, and denied it the power of producing combustion.
+
+However, after discovering that the increase of weight, which bodies
+acquire during combustion, depended on the quantity of the air
+absorbed, he was led to the following beautiful hypothesis, equally
+simple as that of Stahl; and if ever any hypothesis deserved the name
+of theory, surely it is that of M. Lavoisier.
+
+According to M. Lavoisier, “an inflammable body is nothing else but
+a body which has the property of decomposing vital air, and taking
+the base from caloric and light; that is to say, the oxygene, which
+was united to them; and that a body ceases to be combustible when its
+affinity for the oxygene is satisfied, or when it is saturated with
+that principle; but that it becomes again combustible, when the oxygene
+has been taken from it by another body, which has a stronger affinity
+with that principle.
+
+“When this decomposition of the air is rapid, and, as it were,
+instantaneous, there is an appearance of flame, heat, and light; when,
+on the contrary, the decomposition is very slow, and quietly made, the
+heat and light are scarcely perceptible[1].”
+
+Thus all the phenomena of oxygenation, which Stahl ascribed to the
+disengagement of phlogiston, M. Lavoisier ascribes to the union of
+oxygen with combustible bodies.
+
+And, on the other hand, all the phenomena of reduction, which Stahl
+attributed to the union of phlogiston to calcined bodies, M. Lavoisier
+attributes to the separation of oxygen from the same. Combustion,
+then, according to Stahl, is the transition of phlogiston from one
+body to another; and, according to M. Lavoisier, ’tis nothing but the
+transition of oxygen from one substance to another.
+
+Stahl supposed, that the heat, and light, attending combustion proceed
+from the burning body; but M. Lavoisier supposes, that the heat, and
+light, proceed principally, and almost entirely, from the vital air.
+
+However, this opinion of M. Lavoisier is far from being established;
+for Doctor Crawford has shown, that inflammable air contains a much
+greater quantity of heat, than vital air does.
+
+It is evident, then, that the great advantage, which M. Lavoisier’s
+hypothesis has over that of Stahl is, that the former seems to account
+for the increase and decrease of weight, which bodies suffer during
+calcination, and reduction.
+
+Notwithstanding this brilliant discovery, which seems to account, with
+such ease, for the increase of weight, that bodies acquire during
+combustion, M. Macquer was of opinion, that M. Lavoisier’s hypothesis
+was insufficient to explode that of Stahl, and endeavoured to remove
+the objection urged against the nonexistence of phlogiston, by
+supposing it to be light; and that in every case of combustion, light,
+and vital air, mutually precipitate each other: so that, according
+to M. Macquer, when a body is oxygenated, vital air unites to it, and
+disengages light; and, on the other hand, when an oxygenated substance
+is reduced to its inflammable state, light unites to it, and disengages
+vital air.
+
+M. Scheele also modified the hypothesis of Stahl, by supposing that
+heat, light, and inflammable air, were compounds of empyreal, or vital
+air, and phlogiston. Light, he thought, contained more phlogiston than
+heat did; and inflammable air more than either: he farther supposed,
+that these compounds of vital air and phlogiston were convertible
+into one another, by the addition, or subtraction, of phlogiston; and
+that, when a metal was reduced by them, they were decomposed; their
+phlogiston uniting to the substance reduced.
+
+His idea of calcination is, that metals either attract empyreal air by
+means of their phlogiston, and thus form heat, or that they communicate
+their phlogiston to the air, and attract heat from the fire; and that,
+either way, there is empyreal air in the calces, which makes the
+overplus of their weight[2].
+
+The last modification of Stahl’s hypothesis is that of M. Kirwan, who
+supposes that inflammable air exists in a fixed, or concrete, state
+in all combustible bodies, and is the true phlogiston of the antient
+chymists; and, as it can be exhibited in the form of air, its existence
+is no longer doubtful.
+
+M. Kirwan supposes, that, when combustible bodies are calcined, or
+changed into acids, they combine most commonly with fixed air, formed
+during the operation, by the union of their phlogiston to vital air;
+and sometimes to other substances, and water, which is either absorbed
+_in specie_, or formed by the union of their phlogiston to vital air,
+during calcination.
+
+He supposes, that some of these are restored to their combustible
+state by the decomposition of their fixed air; some partly by the
+decomposition of their fixed air, and partly by its expulsion, and
+that of the other foreign bodies, they had absorbed; and lastly, that
+some recover their combustibility by the expulsion of water, and
+others possibly by its decomposition in high degrees of heat. In all
+these reductions he supposes a simultaneous reunion of these bodies to
+phlogiston, or the inflammable principle[3].
+
+Though M. Kirwan’s hypothesis seems to account for the increase
+of weight, which bodies acquire during combustion, yet he has not
+proved the existence of inflammable air, in a concrete state, in all
+combustible bodies; nor has he shown, that fixed air is a compound of
+inflammable, and vital air; neither has he proved, that fixed air is
+the acidifying principle.
+
+All these objections have been made, with great justice, to his
+hypothesis, by the antiphlogistians; who also object, that M. Kirwan’s
+account of calcination, and reduction, is complex, and repugnant to the
+simplicity of nature; “for,” says M. De Fourcroy, “as the author had
+admitted three general species of calcination, it was necessary, that
+he should, likewise, admit three kinds of reduction[4].”
+
+This criticism is very just; but it will appear, that the
+antiphlogistic account of calcination, and reduction, is no less
+complex, erroneous, and repugnant to the simplicity of nature: for when
+we consider the various sources, whence they derive the oxygen, which
+oxygenates bodies; and the long list of metallic reducers, which they
+suppose; it must be allowed, that if simplicity be a recommendation,
+their hypothesis is destitute of that advantage.
+
+Thus, according to M. Lavoisier, the oxygen, which oxygenates
+combustible bodies, is sometimes derived from vital air; sometimes
+from atmospheric air; sometimes from acids; sometimes from water; and
+sometimes from metallic oxids, &c.
+
+On the other hand, the catalogue of substances, which reduce bodies to
+their combustible state, is no less numerous.
+
+“Heat,” says M. De Fourcroy, “separates oxygene from some; one metal
+takes it from another; hydrogene, or inflammable gas, takes it from
+most metals; and carbone perhaps from all[5].”
+
+To this list, may be added phosphorus, sulphur, and compounds of these
+with hydrogen; also light, and the electric fluid, &c., as will appear
+in the sequel.
+
+But, I shall endeavour to show, that the hydrogen of water is the only
+substance, that restores oxygenated bodies to their combustible state;
+and that water is the only source of the oxygen, which oxygenates
+combustible bodies.
+
+Want of simplicity is not the only defect in Mr. Lavoisier’s
+hypothesis: for he supposes, that the increase of weight, which bodies
+acquire during combustion, depends on the absorption of the oxygenous
+principle alone.
+
+Thus, when a bit of phosphorus, sulphur, or charcoal, is burnt in vital
+air; the increase of weight, which these bodies acquire, he attributes
+entirely to oxygen, or the base of vital air.
+
+These combustions he explains, by supposing, that the phosphorus,
+sulphur, and charcoal, decompose oxygen gas, by absorbing its base
+from caloric, and light, which are set free.
+
+“There is,” says M. Lavoisier, “a total absorption of vital air, or
+rather of the oxygene, which forms its base in the combustion of
+phosphorus, and the weight of the phosphoric acid obtained, is found to
+be rigorously equal to the weight of the phosphorus, added to that of
+the vital air employed in its combustion. The same agreement of weights
+is observed in the combustion of inflammable gas and vital air, in the
+combustion of charcoal[6]”, &c.
+
+His idea of the calcination of metals is the same.
+
+“We do not,” says M. Lavoisier, “affirm that vital air combines with
+metals to form metallic calces, because this manner of enunciating
+would not be sufficiently accurate: but we say, when a metal is heated
+to a certain temperature, and when its particles are separated from
+each other to a certain distance by heat, and their attraction to each
+other is sufficiently diminished, it becomes capable of decomposing
+vital air, from which it seizes the base, namely oxygene, and sets the
+other principle, namely caloric, at liberty.
+
+“This explanation of what passes during the calcination is not an
+hypothesis, but the result of facts. It is upwards of twelve years,
+since the proofs have been laid by one of us, before the eyes of the
+academy, and have been verified by a numerous commission. It was then
+established, that when the calcination of metals is effected beneath
+an inverted glass vessel, or in closed vessels containing known
+quantities of air, the air itself is decomposed, and the weight of the
+metal becomes augmented by a quantity accurately equal to that of the
+air absorbed. It has since been found, that when the operation was
+performed in very pure vital air, the whole might be absorbed.”
+
+“No supposition enters into these explanations; the whole is proved by
+weight and measure[7].”
+
+Hence it is evident, that M. Lavoisier confounds oxygen with oxygen
+gas; and considers the latter as a compound of oxygen, light, and
+caloric.
+
+But since the dryest oxygen gas contains a large proportion of water,
+as Dr. Priestley and M. Kirwan have shown[8]; and since the whole of
+the gas, except the caloric, and light, is absorbed, it necessarily
+follows, that the increase of weight, which bodies acquire during
+combustion, depends not only on the oxygen, but also on the water,
+contained in vital air.
+
+Therefore oxids are compounds of combustible bodies united to oxygen,
+and water.
+
+Another great objection to M. Lavoisier’s hypothesis, is, that he
+supposes both oxygenation, and reduction, effected by a single affinity.
+
+Thus, according to him, when iron reduces a sulphate of copper, the
+iron does nothing more, than separate the oxygen from the copper, by
+its superior attraction for that principle.
+
+From this view of combustion, grounded on the most accurate experiments
+in chymistry, it is manifest, that the antiphlogistic hypothesis does
+not account fully for the increase of weight, which bodies acquire
+during combustion; and consequently, that it cannot be admitted as a
+just theory.
+
+
+
+
+CHAPTER I.
+
+REDUCTION OF METALS
+
+BY
+
+HYDROGEN GAS.
+
+
+As Hydrogen, or the base of inflammable air, seems to act an important
+part in the following experiments, and is, according to some chymists,
+pure phlogiston itself; I have therefore assigned the first chapter in
+this essay to hydrogen gas, this being the most simple form, in which
+hydrogen has hitherto been obtained.
+
+But I had not the means of procuring this gas free of carbone, and
+other impurities, that it dissolves and elevates during its formation;
+or of excluding atmospheric air, which circumstances, I am sensible,
+must, in some measure, influence the result; as it cannot be supposed,
+that these extraneous bodies would remain inactive during the process
+of reduction. However, as such exactness is not in the power of every
+experimenter, I was under a necessity of using hydrogen gas, with the
+disadvantages here mentioned.
+
+Though most of the experiments in this essay were made on a variety of
+white and coloured silks, I shall relate only those made on the former,
+as it exhibits the changes produced more distinctly, and contains less
+foreign matter to modify the result of experiment; and, for brevity’s
+sake, I shall use the term _silk_, by which _white silk_ is always
+designed.
+
+
+EXP. 1. GOLD.
+
+I poured a quantity of sulphuric ether on a solution of gold in
+nitro-muriatic acid, and, by this means, obtained a solution of gold in
+ether, which I separated from the acid.
+
+In this ethereal solution of gold, I dipped a piece of silk, after it
+was taken out, and the ether evaporated, it was suspended in a tall
+glass cylinder, placed over a vessel, containing a mixture of diluted
+sulphuric acid, and iron filings.
+
+The silk thus exposed to a rapid current of hydrogen gas acquired,
+after some time, a purple colour, and a large spangle of gold, of an
+irregular figure, appeared on the upper end of the silk, and looked
+very brilliant.
+
+The silk was kept exposed to the gas about four months, and frequently
+observed, but no other remarkable change was perceived, except
+that the purple colour became more intense: the experiment was now
+discontinued; and on taking out the silk, and examining it in the light
+of the sun, I observed many particles of reduced gold; but they were
+very small, and by no means so brilliant, as that, which first appeared.
+
+During the experiment, fresh quantities of materials for supplying
+hydrogen gas were occasionally added.
+
+From the brilliant spangle of reduced gold observed in this experiment,
+I concluded, that there was a sufficient quantity of the metal in the
+fibres of the silk, could it be reduced.
+
+This spot of reduced gold was very permanent, and adhered firmly to the
+silk.
+
+
+EXP. 2. GOLD.
+
+In order to determine, whether a solution of gold in ether, or one
+in water, were best adapted to the object of these experiments; I
+evaporated to dryness a solution of gold in nitro-muriatic acid, and
+dissolved the salt in distilled water: in this solution, I immersed a
+piece of silk, which, after it was dried in the air, was suspended in
+a glass cylinder, like the former piece, and exposed to the action of
+hydrogen gas about two months.
+
+The silk after some time assumed a purple colour, and five or six
+specks of reduced gold, of the size of pin heads, and one much larger,
+were observed. Examining the silk in the sun-beams, I perceived the
+whole of it spangled with minute particles of reduced gold.
+
+After many experiments with these two solutions of gold, I was led to
+conclude, that the solution in water answered best.
+
+
+EXP. 3. SILVER.
+
+Having dissolved some pure silver in diluted nitric acid, and
+evaporated some of the water by a gentle heat, I placed it in the dark
+to crystallize. The crystals were separated from the solution, and
+dissolved in distilled water; to one measure of this solution, which
+was saturated with the nitrate of silver, ten or twelve measures of
+distilled water were added.
+
+In this diluted solution, a piece of silk was dipped; after it was
+taken out, it was dried at the fire: the silk dried in this manner,
+retained its white colour; whereas, were it dried gradually in the air;
+and especially, were the light considerable, its white colour would
+be changed to a reddish brown, more or less intense, according to the
+quantity of light present.
+
+Some kinds of silk, on being immersed in a solution of nitrate of
+silver, have some of their threads immediately coloured brown: but I
+often got white silk, which would retain its pure white colour, if
+dried at the fire, or in the dark.
+
+The piece of silk dried, as above, was suspended in the middle glass of
+Dr. Nooth’s machine; and into the lower glass were introduced a diluted
+solution of sulphuric acid, and some small iron nails.
+
+The machine was now placed in a dark closet, to exclude the action of
+light; after some time, the silk, thus exposed to hydrogen gas, put
+on a light brown colour, which gradually became deeper, until it was
+changed to a disagreeable black, with some mixture of brown: then very
+small particles of reduced silver began to appear, which increased by
+degrees, in number, and brightness.
+
+The experiment was continued four months; after which time, the silk
+was taken out of the machine: it had a gray metallic appearance,
+intermixed with a considerable tinge of brown.
+
+This experiment was repeated on another piece of silk, every
+circumstance being the same, except that a quantity of water was put in
+the middle glass of the machine, over which the silk was suspended; the
+intention of interposing the water in this experiment was to purify the
+gas.
+
+The appearances were much the same, as in the last experiment; except
+that the silk became black sooner; and that some spangles of the
+silver were larger, and better reduced.
+
+The specks of reduced silver were permanent, and adhered firmly to the
+silk.
+
+
+EXP. 4. LEAD.
+
+In a solution of acetite of lead in distilled water I dipped a piece of
+silk, and dried it in the air; it was then suspended over a quantity of
+water in Dr. Nooth’s machine, and exposed to hydrogen gas about three
+months.
+
+The appearances were much the same as in the last experiment, except
+that the silk was not so black: the particles of reduced lead resembled
+silver.
+
+Similar experiments were made in this machine on bits of silk imbued
+with a solution of nitro-muriate of gold in water; but the appearances
+being much the same as those mentioned in the first and second
+experiments, it is unnecessary to repeat them here.
+
+It is much easier to imagine, than express my anxiety, to discover
+the cause of the brilliant specks of reduced gold and silver, with
+which the pieces of silk in these experiments were sometimes spangled;
+concluding, that were the cause ascertained, it would be a considerable
+step towards accomplishing the object in view.
+
+But many and diversified were the experiments I made before the
+circumstance, on which these spangles depended, was perceived.
+
+At length, I found it depended on the presence of moisture; and that
+the spangles of reduced metal were owing to small drops of water
+carried up by the elastic fluid, and deposited on the silk.
+
+The experiments, which led to this conclusion, shall be related in
+their proper places. I shall now proceed to recite the remainder of the
+experiments in this essay, conformable to the plan laid down in the
+preface, premising an occurrence observed in the course of them.
+
+I sometimes found, that the production of hydrogen gas from a mixture
+of acid, water, and iron nails, would unexpectedly stop, which induced
+me to add more acid; this not succeeding, I added more water; but
+still no gas was formed: the proportions of acid and water were varied
+without effect. Thinking the mixture of acid and water unfit for the
+purpose, I poured it off, and repeatedly washed and agitated the nails
+with more water, which was also poured off; but happening inadvertently
+to add some of the mixture of acid and water, which I had before poured
+off as unfit for use, I was surprised to find the gas produced with
+great rapidity.
+
+Reflecting on the cause of this odd circumstance, I concluded that it
+depended on a crust of superoxygenated iron, formed on the surface of
+the nails, which defended them from the action of the water and acid,
+and that this crust was removed by the agitation and washing, which
+enabled the diluted acid to act again on the iron.
+
+
+EXP. 5. GOLD.
+
+I immersed a bit of silk in a solution of nitro-muriate of gold in
+distilled water, and dried it in the air; it was then placed over a
+cylindrical glass vessel, containing a mixture of diluted sulphuric
+acid and iron nails, for about half an hour; but no reduction of the
+metal could be observed.
+
+I dipped another bit of silk in the same solution of gold, and exposed
+it, while wet, to the same current of hydrogen gas, and instantly
+signs of reduction appeared; for the yellow colour, which the solution
+imparts to silk, began to change to a green, and very soon a film of
+reduced gold glittered on the surface opposed to the gas: shortly
+after, a beautiful blue spot, fringed with orange and purple, was
+formed on the middle of the silk. During the experiment, which lasted
+about half an hour, the silk was kept constantly wet with distilled
+water.
+
+When experiments are made with this preparation of gold, it is
+necessary to evaporate the solution to dryness, before the salt be
+dissolved in the water; as an excess of acid prevents the reduction in
+a great measure. Solutions of gold in these experiments do not admit of
+being so largely diluted, as solutions of silver, and other metals do.
+
+
+EXP. 6. SILVER.
+
+I immersed a piece of silk in a solution of nitrate of silver, and
+dried it in a dark place; it was then exposed to a current of hydrogen
+gas about twenty minutes; but no reduced silver appeared, the only
+change observable was a brown stain.
+
+I immersed another bit of the same silk in the same solution of
+silver, and having exposed it, while wet, to a stream of hydrogen gas,
+I soon observed evident signs of reduction; the white colour of the
+silk was changed to a brown, which became gradually more intense; and
+the surface of the silk, opposed to the gas, was coated with reduced
+silver: various colours, as blue, purple, red, orange, and yellow,
+attended the reduction. These colours often change, and are succeeded
+by others in the progress of the reduction. The threads of the silk
+look like silver wire, tarnished in some parts, but of great lustre in
+others.
+
+The silk was kept wet with distilled water during the experiment. When
+the silk happened to be too much wetted, the under surface opposed to
+the gas was often covered with scales of a dull blue colour: these,
+after the silk dries, may be brushed off, and another coat of reduced
+silver, which adheres firmly, but has no considerable brightness, is
+left behind.
+
+These experiments on the reduction of gold, and silver, were often
+repeated with nearly the same result.
+
+
+EXP. 7. SILVER.
+
+Thinking some other preparation of silver might answer better than a
+nitrate, I precipitated some of the latter with a solution of muriate
+of soda, and poured the whole on a filter; the precipitate was well
+washed with distilled water, and dissolved in ammonia. In this solution
+I immersed a piece of silk, and dried it in the air; and having
+exposed it to the action of hydrogen gas, I could perceive no signs of
+reduction, except a faint brown colour.
+
+I dipped another bit of silk in the same solution of silver, and in
+order to determine if water had the power of promoting the reduction of
+the silver in this preparation, as it had in the former experiments, I
+exposed the silk, while wet, to the same current of hydrogen gas; and
+in a few seconds the metallic lustre was evident on the surface opposed
+to the current. After some little time, a blue speck and a faint trace
+of yellow appeared, but soon vanished.
+
+This preparation of silver does not stain white silk so much as a
+nitrate does; the reduced silver was indeed very brilliant, but soon
+grew dull, and disappeared; a brown stain only remaining; so that
+it seems rather inferior to nitrate of silver, which also, after
+reduction, tarnishes, grows dull, and often disappears; but sometimes
+part of it remains permanently reduced.
+
+
+EXP. 8. PLATINA.
+
+With much difficulty I procured a small quantity of the ore of platina,
+and dissolved it in nitro-muriatic acid. The solution was evaporated to
+dryness, and the salt was then dissolved in distilled water.
+
+A bit of silk was dipped in part of this solution, and dried in the
+air; it was then exposed to a brisk current of hydrogen gas about
+twenty minutes, but no signs of reduction appeared.
+
+Another bit of silk was immersed in the solution of platina, and
+exposed, while wet, to the same current of hydrogen gas; in five or
+six minutes the platina was reduced, exhibiting a livid white metallic
+appearance on the surface of the silk opposed to the current. No
+colours attended the reduction. This solution imparts a yellowish brown
+colour to silk.
+
+After some time, the whole of the metallic lustre disappeared, in
+proportion as the silk became dry.
+
+The solution of platina requires more time, and a stronger current of
+hydrogen gas for its reduction, than solutions of silver and gold do.
+
+
+EXP. 9. MERCURY.
+
+I immersed a bit of silk in a solution of oxygenated muriate of mercury
+in distilled water, and dried it in the air: it was then exposed to a
+stream of hydrogen gas; but underwent no visible change.
+
+I dipped another bit of silk in the same solution of mercury, and
+exposed it, while wet, to the same current of gas; the metal was soon
+reduced in a beautiful manner, and resembled silver.
+
+The reduction began suddenly, with scarce any appearance of previous
+stain; some very faint, but at the same time transparent colours
+attended it: the most remarkable of these were a light orange, with a
+fringe of blue, and a yellow verging on a faint green. These colours
+soon disappeared.
+
+After the silk was turned, I observed, that its texture was, in some
+parts, concealed by a thin film, which, as the reduction proceeded,
+was perceived to dart along the threads of the silk, gilding them in a
+beautiful manner, and exhibiting the texture very distinctly.
+
+After some time, the mercury seemed to disappear, so as to render it
+doubtful whether any of it remained in the silk; but shaking it in the
+sunbeams, I perceived bright atoms fly off; and rubbing the silk on a
+bit of blue paper, I observed shining metallic particles, which seemed
+to have lost their affinity of aggregation, for they did not unite.
+
+One remarkable difference between this preparation of mercury and
+nitrate of silver, is, that no black or brown stain preceded, attended,
+or followed, the reduction of the mercury.
+
+Mr. Scheele reduced a prussiate of mercury, dissolved in water, by
+adding iron filings and a small quantity of sulphuric acid to the
+solution[9].
+
+
+EXP. 10. COPPER.
+
+A piece of silk was immersed in a solution of sulphate of copper, then
+taken out, and dried, and exposed for a considerable time to a brisk
+current of hydrogen gas; but no signs of reduction could be perceived.
+
+Another bit of silk was dipped in the same solution of copper, and
+exposed, while wet, to the same rapid current of hydrogen gas; the
+appearances were the following.
+
+After a minute, or two, the silk assumed a faint brown colour, and, on
+the surface opposed to the gas, a white metallic pellicle appeared,
+which vanished in proportion as the silk became dry: wetting the silk
+again, I perceived a similar pellicle appear, which also vanished, as
+soon as the silk dried. If the silk be kept constantly wet, the brown
+colour becomes much more intense, attended with a very slight tinge of
+red. The margins of the silk projecting beyond the verge of the glass
+cylinder, and therefore not exposed to the current of the gas, retained
+the blue colour, which the solution imparts.
+
+In some of these white metallic pellicles there appeared a faint brown
+inclining to yellow, which reflected the light, though obscurely.
+
+After the silk dried, nothing remained, but a brown stain.
+
+
+EXP. 11. LEAD.
+
+A piece of silk was immersed in a solution of acetite of lead in
+distilled water; it was then dried, and exposed for some time to a
+stream of hydrogen gas; but underwent no perceptible change.
+
+Another bit of silk was dipped in the same solution of lead, and
+exposed, while wet, to the same current of hydrogen gas; in a second,
+or two, the surface of the silk, opposed to the current, was coated
+with reduced lead, which looked like silver.
+
+The reduction was accompanied with a brown stain, but by no means so
+intense as that, which attends the reduction of nitrate of silver.
+
+The other side of the silk was opposed to the current of hydrogen gas,
+and soon acquired a metallic coat of the same brilliant appearance,
+exhibiting the texture of the silk, in a very striking manner.
+
+It is remarkable, that lead exhibits no colour, but a light brown,
+during its reduction; whereas gold, silver, and mercury, display a
+great variety of colours, especially the two former.
+
+After some time the lead reduced in this manner loses its metallic
+splendour considerably; and that in proportion as the silk dries.
+
+
+EXP. 12. TIN.
+
+I dissolved some crystals of muriate of tin in distilled water; dipped
+a bit of silk in the solution; and dried it in the air: it was then
+exposed to a stream of hydrogen gas a considerable time; but no change,
+or appearance of reduction, could be observed.
+
+Another bit of silk was immersed in the same solution of tin, and
+exposed, while wet, to the same current of gas; after some little time,
+the reduction commenced, attended with a great variety of beautiful
+colours; as red, yellow, orange, green, and blue, variously intermixed.
+
+The reduced tin disappears along with these colours, as the silk dries;
+nothing remaining but a feuille-morte colour.
+
+The same solution of tin was also reduced by hydrogen gas, obtained
+from tin, and the muriatic acid.
+
+These experiments do not succeed well with muriate of tin containing an
+excess of acid.
+
+
+EXP. 13. ARSENIC.
+
+A muriate of arsenic, which was prepared by digesting white oxid of
+arsenic in muriatic acid, and continuing the heat, till most of the
+acid evaporated, and left behind a soft mass of the consistence of tar,
+was dissolved in distilled water.
+
+In this solution a bit of silk was immersed, and dried in the air: it
+was exposed to a brisk stream of hydrogen gas, obtained from zinc, and
+muriatic acid; but no reduction took place.
+
+Another bit of silk was dipped in the same solution, and exposed, while
+wet, to the same current of hydrogen gas; and instantly, the surface of
+the silk, opposed to the gas, was covered with a bright coat of reduced
+arsenic, accompanied with a yellow stain. In a short time the metallic
+lustre vanished; and nothing remained but the yellow stain.
+
+M. Pelletier restored the acid of arsenic to its metallic state, by
+passing hydrogen gas through a solution of that acid, in twice its
+weight of water[10].
+
+
+EXP. 14. BISMUTH.
+
+A bit of silk, which was immersed in a solution of nitrate of bismuth
+in distilled water, and exposed dry to hydrogen gas, obtained from
+zinc, and muriatic acid, underwent no visible change.
+
+Another bit of silk was dipped in the same solution of bismuth, and
+placed over a languid stream of hydrogen gas; the bismuth was soon
+restored to its metallic form, on the surface of the silk opposed to
+the elastic fluid. The reduction was attended with a reddish brown
+stain, intermixed with a tinge of violet.
+
+
+EXP. 15. ANTIMONY.
+
+A bit of silk was immersed in a solution of tartarite of antimony in
+distilled water; and dried in the air. It was then exposed to hydrogen
+gas, obtained from zinc, and muriatic acid; but suffered no visible
+alteration.
+
+Another bit of silk, which was dipped in the same solution of antimony,
+was exposed wet to a weak stream of the gas; and, in a short time, the
+metallic lustre appeared, accompanied by a light yellow colour.
+
+
+EXP. 16. IRON.
+
+A bit of silk, which was immersed in a largely diluted solution of
+sulphate of iron, and dried in the air, was exposed to a strong
+current of hydrogen gas, obtained from iron nails, and diluted
+sulphuric acid; but no visible change was produced on the silk.
+
+Another bit of silk was dipped in the same solution of iron, and placed
+wet over the same stream of hydrogen gas; but no reduced iron could be
+perceived. The silk was then immersed in a glass of clear water, and
+transferred a very minute metallic film to the surface of that fluid.
+
+This experiment was repeated with a rapid current of hydrogen gas,
+obtained from zinc, and muriatic acid; and, in about a minute, small
+films of reduced iron were visible on the surface of the silk, opposed
+to the gas.
+
+The silk was then immerged in water, and transferred to its surface a
+large metallic pellicle; parts of which were very brilliant; but other
+parts were dull, and much more imperfectly reduced.
+
+
+EXP. 17. ZINC.
+
+A bit of silk, which was dipped in a muriate of zinc, largely diluted
+with water, and dried in the air, was exposed to a rapid current of
+hydrogen gas, obtained from zinc, and muriatic acid; but suffered no
+visible alteration.
+
+Another piece of silk was immersed in the same solution of zinc, and
+exposed, while wet, to the same rapid current of hydrogen gas: in
+about half a minute, the metal was reduced in a very evident manner, on
+part of the silk. The silk was then dipped in a glass of clear water,
+and transferred a bright metallic film to its surface.
+
+As these reductions of iron, and zinc, by hydrogen, are contrary to M.
+Lavoisier’s table of the affinities of the oxygenous principle; I began
+to suspect, that the films, which were so evident, both on the silk,
+and the water, might be abraded, or torn from the zinc, by the muriatic
+acid; and elevated, and deposited on the silk by the gas.
+
+In order to remove this doubt, I dipped a bit of the same silk in
+distilled water; and exposed it, while wet, to the same current of
+hydrogen gas, but nothing metallic could be seen on the silk; nor did
+it when immersed in water transfer a film, or the smallest appearance
+of a metal, to the surface of that fluid: and, therefore, there can be
+no doubt of the reality of these reductions.
+
+Dr. Priestley restored iron, and lead, to their metallic state, by
+heating their oxids with a burning glass in hydrogen gas.
+
+These experiments point out an error in M. Bergman’s table of elective
+attractions in the humid way; for he assigned the last place in that
+table to phlogiston, which he considered as the base of inflammable
+air; because he was unacquainted with any metallic reductions effected
+by hydrogen in the humid way[11].
+
+Having found, that water promoted, and accelerated, these reductions in
+a very remarkable manner; I was curious to know, if alcohol, and ether,
+would produce the same effect. With this view, I evaporated a solution
+of gold in nitro-muriatic acid to dryness; when the vessel cooled, some
+alcohol was poured on to dissolve the salt; and immediately the vessel
+containing the salt, became so hot, that it could be scarcely endured
+by the hand; and diffused a fragrant smell, like that of ether, which,
+no doubt, was a species of that fluid.
+
+
+EXP. 18. GOLD.
+
+In this solution of gold in alcohol, a bit of silk was dipped, and
+exposed to a stream of hydrogen gas, obtained from diluted sulphuric
+acid, and iron nails; and kept wet with alcohol: in about two minutes,
+the silk began to assume a brown colour, and white metallic films
+appeared on some parts of the surface opposed to the gas; some of these
+disappeared in a short time; and were succeeded by a few very small
+spangles of the proper colour of gold. These also soon vanished; and
+nothing remained but a disgreeable brown stain, intermixed with specks
+of a dull blue.
+
+I sometimes found, on repeating this experiment, that no yellow films
+or spangles appeared; and am persuaded, that their appearance, and
+that of the white pellicles also, depends on the presence of water,
+contained in the alcohol, or the gas, and deposited on the silk.
+
+
+EXP. 19. GOLD.
+
+A bit of silk was immersed in a solution of gold in ether, and exposed
+to a stream of hydrogen gas, and kept wet with ether. The silk
+underwent no alteration for a few minutes; at length, it began to
+assume a faint brown colour, but no white, or yellow films appeared.
+
+If this experiment be continued till the silks collects a sufficient
+quantity of water from the gas, some films will appear.
+
+
+EXP. 20. SILVER.
+
+I procured some nitrate of silver, which had been fused in order to
+expell as much of its water as possible; and dissolved it in alcohol. I
+immersed a bit of silk in this solution, and exposed it to a stream of
+hydrogen gas, and kept it wet with alcohol: in a few seconds, the silk
+assumed a brown colour, which gradually became more intense: but no
+reduced silver appeared for several minutes; at length, a few metallic
+films appeared on part of the surface opposed to the gas.
+
+
+EXP. 21. MERCURY.
+
+A bit of silk was dipped in a solution of oxygenated muriate of
+mercury, and dried; it was then exposed to hydrogen gas about ten or
+fifteen minutes, and kept constantly wet with alcohol. The silk, during
+the first minutes, suffered no perceptible alteration: at length, a few
+small films were visible on the side of the silk opposed to the current.
+
+
+EXP. 22. LEAD.
+
+A bit of silk, which was immersed in a solution of acetite of lead,
+and dried, was exposed about fifteen minutes to a stream of the gas;
+and kept constantly wet with alcohol; but suffered no visible change;
+except that a very minute film was reduced on one of its margins, which
+did not project beyond the verge of the glass vessel on which it was
+placed.
+
+When we compare these experiments with those, in which water was
+used, to wet the silk, ’tis evident, that alcohol, and ether, do not
+promote the reduction of metals, as water does; and that the few films,
+which appear, when the silk is kept wet with ether or alcohol, depend
+entirely on water collected from the gas, or deposited by them on the
+silk during their evaporation.
+
+In order to compare the effects of hydrogen gas, obtained from water,
+iron nails, and muriatic acid, with that, procured from the same
+materials, by means of the sulphuric; I made some experiments on gold,
+silver, mercury, and lead, in the same manner, as the preceding; and
+the principal difference was, that the colours produced in all the
+pieces of silk, except that, which was dipped in acetite of lead,
+were much brighter, and more beautiful, than any produced, when the
+sulphuric acid was used.
+
+The reduction of the lead was accompanied with its usual brown colour.
+
+On the upper surface of a bit of silk, which was dipped in a solution
+of gold, a green colour instantly appeared; and soon changed to a deep
+olive, in proportion as the reduction advanced: now examining the
+under surface, I saw it coated with a bright film of reduced gold, in
+the middle of which a blue spangle, mixed with purple, soon began to
+appear: I then moistened the upper surface of the silk with water; and
+in a few seconds, it also was coated with reduced gold.
+
+The blue on the other side of the silk became much more intense: the
+piece was now turned; and on each colour I let fall a drop of water:
+the drop on the blue had a blue film, the drop on the purple, had a
+purple film, and the drop on the yellow, a film of reduced gold.
+
+After some time, these drops of water evaporated, and the films came
+again in contact with the silk: some parts of which were left bare, as
+generally happens, when too much water is applied.
+
+On the under surface of a bit of silk, which was immersed in a solution
+of nitrate of silver in water, a coat of reduced metal was formed, with
+various colours, as green, blue, orange, and yellow, the beauty and
+brightness of which were remarkable.
+
+In some time a muriate of silver is formed in the fibres of the silk,
+which on exposure to light becomes of a bluish black colour: but the
+whole of the silver does not undergo this change; for part of it
+remains in its metallic state. The colours remain a considerable time,
+if the silk be removed from the gas before this muriate is formed.
+
+Hence it appears, that hydrogen gas should not be prepared with an
+acid, which forms an insoluble compound with the metal to be reduced.
+
+I also found, that hydrogen gas produces different effects not only
+according to the difference of the acid, but also according to the
+difference of the metal employed to obtain it: for this gas procured
+from zinc or tin, and muriatic acid, did not restore gold to its proper
+metallic lustre; but formed on the silk, a white metalline coat like
+silver.
+
+The experiments related in this chapter indicate the following
+conclusions.
+
+1. Hydrogen is capable of reducing the metals in the ordinary
+temperature of the atmosphere.
+
+2. Water promotes, and accelerates, these reductions, in a very
+remarkable manner.
+
+3. Ether, and alcohol, do not promote these reductions, without the aid
+of water.
+
+4. A variety of colours accompanies these reductions, similar to what
+appears, during the calcination of metals by heat and air; and depends
+on the same cause: viz. the quantity of oxygen combined with the metal.
+
+These colours have not been observed hitherto; nor indeed could they;
+as the metals were reduced in close vessels, and in high degrees of
+heat.
+
+5. These reductions often disappear.
+
+This is commonly owing to an imperfect, and partial reduction of the
+metal: for the acid, and water, remaining in that part of the metallic
+solution, not reduced, recalcines these delicate films: sometimes the
+disappearance of the metallic lustre depends on the nature of the
+metal itself: thus arsenic, lead, silver, &c., suffer some degree of
+calcination by water and atmospheric air.
+
+Messrs. Bergman and Keir relate instances, in which silver after being
+precipitated in its metallic state, was recalcined, and disappeared.
+
+I first imagined, that water promoted these reductions by minutely
+dividing the particles of the metallic salt, and by condensing the
+gas, and bringing its hydrogen, and the metallic oxid, within the
+sphere of attraction; the hydrogen either uniting to the metallic
+earth and reducing it, as the Phlogistians suppose; or uniting with,
+and separating the oxygen of the metal, and thus restoring it to the
+metallic form, as the Antiphlogistians maintain.
+
+But it is evident from the experiments related, that water does not
+promote these reductions solely, by minutely dividing the particles of
+the metallic salt: for were this the case; ether, and alcohol, should
+promote the reduction of the metallic salts, which they dissolve, since
+they divide their particles, as minutely as water can.
+
+Since then metallic solutions in ether, and alcohol, cannot be reduced
+by hydrogen gas; it follows that the above supposition concerning the
+mode of agency of water does not account for the reduction of metals in
+this way.
+
+And indeed were it true that hydrogen condensed by water reduced metals
+in the manner above mentioned, it would follow, that the reduction was
+effected by a single affinity, which cannot be admitted; 1st. because
+the existence of a single affinity in such cases has not been proved;
+2dly, because a double affinity always takes place in preference to
+a single affinity, which is demonstrated by the following facts,
+transcribed from the works of Mr. Kirwan.
+
+“If a solution of silver in the nitrous acid be thrown into a mixed
+solution of fixed alkali and common salt, the silver will be
+precipitated by the marine acid of the common salt, and not by the free
+alkali, contained in the liquor: for a luna cornea is found[12].”
+
+“I repeated the experiment with a solution of lead, and also of mercury
+in the nitrous acid, and the result was similar: both lead and marine
+salt of mercury were formed[13].”
+
+In these experiments of Messrs. Monnet and Kirwan, ’tis evident that
+a double affinity takes place in preference to a single one: for the
+nitrous acid of these different nitrates unites with the alkali of the
+common salt, while the muriatic acid of the latter seizes the silver,
+mercury, and lead, of the nitrates, and forms muriates of silver,
+mercury, and lead: the free alkali remaining passive in the mixture.
+
+M. Lavoisier says, “There exists only in nature, as far as we can
+observe them, cases of double affinity, often triple, and others
+perhaps still more complicated[14].”
+
+Now as water does not promote these reductions merely by dissolving,
+and minutely dividing, the particles of the metallic salts, and
+condensing the hydrogen gas; and since a double affinity takes place in
+preference to a single affinity; it is obvious that the water must be
+decomposed in these reductions in the following manner.
+
+The hydrogen of the gas unites to the oxygen of the water, while the
+hydrogen of the latter unites in its nascent state to the oxygen of the
+metal, reduces it, and forms water.
+
+Thus what could never be effected by a single, is readily performed by
+a double affinity.
+
+Hence it follows, that the hydrogen of the gas is oxygenated by the
+oxygen of the water, while the metal is, at the same time, restored
+to its combustible state. It also follows, that the quantity of water
+formed is double that decomposed.
+
+
+
+
+CHAPTER II.
+
+_Reduction of Metals by Phosphorus._
+
+
+The next substance, of whose effects in reducing metals in the fibres
+of silk, I shall treat, is Phosphorus, one of the most inflammable
+substances, we are acquainted with.
+
+I was for some time at a loss, how to apply it to this purpose; but
+learning from a note of Mr. Lewis, that it is soluble in ether; I
+dissolved a small quantity of it in that fluid, which can be easily
+effected, if the ether be good. The solution is considerably promoted
+by a gentle heat, as that of the hand, and may be made in a small
+phial, which should be nearly filled with the ether, and accurately
+corked: a common cork is preferable, for this purpose, to a glass
+stopper; and a single grain of phosphorus is sufficient for a great
+number of experiments.
+
+I sometimes applied a much greater degree of heat than the above, by
+placing the phial in hot sand, pressing on the cork at the same time
+with my finger, to prevent its being forced out by the expansion of the
+ether, part of which is converted into an elastic fluid, and holds some
+phosphorus in solution: the ether soon begins to boil; the phosphorus
+melts; and a strong solution is obtained in a few minutes by shaking
+the phial. If the solution be removed to a cool place it frequently
+deposits crystals.
+
+This manner of preparing the solution is attended with some danger; for
+should the phial burst, or the cork be extruded, the contents will be
+thrown out with considerable force, and that part of the phosphorus not
+dissolved by the ether burn with great violence.
+
+The only objection to this preparation of phosphorus is the ether,
+which must necessarily modify the result, and prevent that simplicity
+so desirable in experiment.
+
+But, after some observation, it was perceived, that the ether flies
+off, and leaves the phosphorus pure, and minutely divided in the fibres
+of the silk: the ether, from its great volatility, first evaporates,
+and, at the same time, produces a very considerable degree of cold,
+which effectually prevents the evaporation, and combustion, of the
+phosphorus.
+
+After the ether evaporates; the cold ceases, and the combustion of the
+phosphorus commences, attended with white fumes, which continue till
+the whole is consumed, if no other power intervene.
+
+Hence it is evident, that this preparation of phosphorus has a
+simplicity, and elegance, not always to be obtained.
+
+It has also another great advantage in experiments of this kind; for
+it does not change, in the smallest degree, the white colour of silk,
+during its slow combustion, which is not attended with heat sufficient
+to affect the most delicate colour. This property of not affecting the
+colour of the silk renders observation, and experiment, more accurate;
+as whatever change supervenes, must depend either on the metallic
+solution itself, or on the action of the phosphorus on the same. But
+this advantage is confined to a certain range of the thermometer; for
+if the heat be increased to about 86° of Fahrenheit, and the silk be
+dry, the phosphorus is apt to set fire to it.
+
+
+EXP. 1. GOLD.
+
+I immersed a bit of silk in a solution of gold in ether, and after the
+ether evaporated, dropped on it some of the solution of phosphorus,
+which diffused itself through the silk, like a drop of oil, and formed
+a circumscribed spot, whose limits, as the ether evaporated, assumed
+a brown colour, which soon diffused itself equally over every part,
+to which the solution of phosphorus was applied; but the parts of the
+silk, to which the latter did not reach, retained the yellow colour,
+which the solution of gold gave them.
+
+The silk viewed by transmitted light presented the same colours, except
+that the limits of the brown appeared more intense, and seemed to
+border on a faint purple.
+
+Examining the silk next day, I found, that the whole of the brown stain
+acquired a faint shade of purple, which was most evident on the margins
+of the stain.
+
+
+EXP. 2. GOLD.
+
+I dipped a bit of silk in the solution of gold in ether, and after it
+was well dried, half of it was wetted with distilled water; the other
+half remaining dry: the solution of phosphorus was applied to both the
+moist and dry parts of the silk: instantly the part wetted with the
+water began to acquire a purple colour; and, soon after, the metallic
+splendour of the gold appeared; but that part, which was kept dry,
+acquired only a brown stain, similar to that described in the preceding
+experiment.
+
+I repeated these experiments many times, and always found, that the
+gold was reduced only in proportion to the water applied.
+
+Finding water promoted the reduction of gold by phosphorus, I began to
+form various conjectures about its mode of action: I first supposed,
+it acted by holding the particles of the salt minutely divided, thus
+diminishing their attraction of cohesion, and consequently increasing
+their chymical attraction.
+
+The truth of this supposition might, I thought, be decided by using
+ether, and alcohol, instead of water, to wet the silk, avoiding
+aqueous moisture, as much as possible; accordingly, I made the
+following experiments, which were frequently repeated with nearly the
+same result.
+
+
+EXP. 3. GOLD.
+
+A piece of silk was immersed in the solution of phosphorus; as soon as
+the ether evaporated, and the phosphorus began to fume, an ethereal
+solution of gold was dropped on the silk, which immediately got a brown
+colour; the piece was kept constantly wet with ether; in some time a
+purple tinge appeared on parts of the silk; and, shortly after, small
+films of reduced gold appeared: the silk was now remarkably wet, and
+seemed to have a great power of collecting water; this, I supposed, was
+partly attracted from the air by the salt, and phosphorous acid formed
+during the combustion, which has a powerful attraction for water; and
+partly deposited in the silk by the ether during its evaporation.
+
+In order to determine if the ether during its evaporation deposited
+water in the silk, I kept a bit of silk wet with ether for a few
+minutes, and found, that, after the evaporation ceased, the silk was
+moist: but this humidity was not so great, as that observed in the
+silk, to which the ethereal solutions of phosphorus, and gold, were
+applied.
+
+Another bit of silk was dipped in the ethereal solution of gold, and
+after the ether evaporated, the solution of phosphorus was applied: a
+brown colour was produced; the silk was kept wet with ether, and, in a
+short time, a purple tinge appeared on parts of it; but chiefly at the
+margin of the stain, which gradually diffused itself over the whole.
+
+The only difference between this and the preceding experiment on gold
+is the order, in which the solution of gold, and phosphorus, were
+applied to the silk; but there is a considerable difference in the
+result; for in this the brown and purple colours were formed much more
+slowly, and no particles of reduced gold appeared till after a much
+longer time.
+
+
+EXP. 4. GOLD.
+
+A piece of silk was immersed in the solution of phosphorus, and when
+the white fumes began to rise, a solution of gold in alcohol was
+applied to the silk, which was kept wet with alcohol; a brown tinge,
+which soon changed to a purple, appeared on different parts; and, in a
+little time after, a very small film of reduced gold was visible on a
+part of the margin.
+
+In another experiment, conducted in the same manner, the reduction was
+more evident.
+
+The solution of gold used in this experiment was very rich; and had
+a great attraction for water; for bits of silk tinged with it, could
+not be dried without difficulty; and after they were removed to a cool
+place, they very soon became moist again. This is more or less the case
+with solutions of gold in general.
+
+
+EXP. 5. GOLD.
+
+A bit of silk was dipped in a solution of gold in alcohol, and dried;
+then some of the solution of phosphorus was poured on the silk; a
+brown, and then a purple colour, appeared; and in some parts a small
+portion of the gold was reduced: the reduction was very obscure; but
+became gradually more evident, in proportion as it attracted water from
+the air. The silk was occasionally wetted with alcohol.
+
+This experiment was repeated, with this difference, that the silk was
+not kept wet with alcohol; and no reduced gold could be perceived.
+
+
+EXP. 6. GOLD.
+
+In order to exclude water more effectually, a small phial was carefully
+dried by placing it in hot sand, and then corked, to prevent the access
+of moisture from the air; when the phial cooled, it was nearly filled
+with ether, and a small bit of phosphorus dropped into it; it was then
+corked, and replaced on the hot sand; the phosphorus soon melted, and
+a strong solution was obtained by shaking the phial.
+
+Into this solution a small bit of silk, which was dipped in a rich
+solution of gold, and carefully dried, was introduced: the silk
+immediately got a brown tinge; but not a particle of reduced gold could
+be perceived. The solution in a short time became turbid, and deposited
+a brown powder. The colour of the precipitate was exactly the same, as
+that which the silk acquired. The experiment was continued about three
+months, and carefully observed; but no other change could be perceived:
+at the end of this time the silk was taken out of the phial; and the
+solution of phosphorus was found capable of reducing gold and silver by
+the aid of water.
+
+
+EXP. 7. GOLD.
+
+In order to contrast the effects of water with those of ether, and
+alcohol, more fully, a piece of silk was immersed in a solution of
+nitro-muriate of gold in water, and dried in the air about twelve
+hours; during which time the yellow tinge, the solution of gold gave
+the silk, remained unchanged: the solution of phosphorus was then
+applied; a brown stain appeared; the ether soon evaporated; the
+phosphorus began to fume; and the silk acquired a purple colour; but
+not a particle of reduced gold could be perceived. The purple tinge
+in this bit of silk was much more intense, and more equal, than in the
+pieces, in which ether and alcohol were used.
+
+
+EXP. 8. GOLD.
+
+I dipped a piece of silk in the solution of phosphorus, when the ether
+evaporated, and the phosphorus began to fume, a solution of gold in
+water was applied; instantly the silk was covered with a splendid coat
+of reduced gold.
+
+Nothing can be more striking than this experiment, which was repeated
+times without number, or demonstrates the necessity of water in these
+reductions in a more convincing manner.
+
+This piece, viewed by transmitted light, had a purple colour with a
+considerable tinge of blue; and the margin of the reduced gold was
+fringed with purple.
+
+
+EXP. 9. GOLD.
+
+Thinking that phosphorus applied in the form of vapour through the
+medium of water might be more effectual than a solution of it in ether,
+I immersed a small bit of silk in an aqueous solution of gold, and
+suffered it to dry a little; it was then suspended in a phial over
+a little water, into which a small bit of phosphorus was previously
+introduced: the phial was then corked, and placed on hot sand: the
+phosphorus began to melt, and ascend in white vapours, which, as soon
+as they reached the lower end of the silk, gave it a brown tinge,
+succeeded by a purple; and the gold began to assume its metallic
+splendour: in a short time these appearances were evident over the
+whole silk.
+
+The following propositions are deducible from these experiments.
+
+1. Water does not promote the reduction of gold merely by dissolving,
+and minutely dividing, the particles of the salt, and thus diminishing
+their attraction of cohesion, and consequently increasing their
+chymical attraction, as I first supposed; for were this the case, ether
+and alcohol, which equally dissolve, and divide, the salt, should
+produce the same effect.
+
+2. Ether and alcohol do not promote these reductions without the aid
+of water; for it is evident from the experiments related, that the few
+particles of reduced gold, which appear, when they are employed, depend
+entirely on the quantity of water, which they leave in the silk during
+their evaporation, and that attracted from the air by the solution of
+gold, and by the phosphorus during its combustion, both of which have a
+strong attraction for water.
+
+3. Phosphorus does not reduce gold by giving the metallic earth
+phlogiston, as the Phlogistians suppose; for were this opinion true,
+a solution of gold in ether, or alcohol, should be reduced by the
+phosphorus as effectually as a solution of gold in water is.
+
+4. Phosphorus does not reduce gold, by combining with, and separating,
+the oxygen of the gold, as the Antiphlogistians assert; for were
+this the case, the particles of the phosphorus so attenuated by the
+ether, should reduce a solution of gold in ether, or alcohol, as well
+as a solution of gold in water, since the impediment opposed by the
+attraction of cohesion is equally removed in both cases.
+
+I shall conclude these remarks on the reduction of gold with the
+following experiment, which often amused me.
+
+
+EXP. 10. GOLD.
+
+A small bit of silk was immersed in a solution of gold in ether, and
+dried; then the solution of phosphorus was applied, which changed the
+yellow colour of the silk to a brown: when the phosphorus began to
+fume, I placed the silk on the palm of my hand, and breathed on it a
+considerable time; a purple tinge gradually succeeded the brown, and,
+in some little time after, the metallic lustre of the gold began to
+appear.
+
+The same experiment succeeds with a solution of gold in alcohol.
+
+Another bit of silk, treated in the same manner, was placed over the
+vapour of warm water for some time; the same appearances took place,
+and particles of reduced gold were evident in the silk.
+
+If the water, whence the vapour arises, be too hot; the heat retards,
+and sometimes prevents, the reduction, by volatilizing the phosphorus.
+
+
+EXP. 11. SILVER.
+
+I dipped a bit of silk in a solution of fused nitrate of silver
+in alcohol, and dried it in the air: then some of the solution of
+phosphorus was applied, which produced a brown stain, whose margin,
+after a few minutes exposure to the air, acquired a livid white
+appearance, caused by a partial and imperfect reduction of the silver.
+
+This, however, would not be taken by a person unacquainted with
+experiments of this kind for reduced silver.
+
+
+EXP. 12. SILVER.
+
+A bit of silk was immersed in the solution of phosphorus; as soon as
+the ether evaporated, and the phosphorus began to fume; a few drops of
+the solution of silver in alcohol were applied: immediately a black
+stain, intermixed with some brown, appeared: and, after some time,
+obscure films of reduced silver presented themselves; these appeared
+on different parts of the stain; but were so minute as to be scarce
+visible. The only difference between this and the preceding experiment
+is the order, in which, the solutions were applied; but even this
+modifies the result in some measure.
+
+That these imperfect reductions depended on water, deposited in the
+silk, by the alcohol during its evaporation, or attracted from the air
+by the phosphorus during its combustion, will appear from the following
+experiment.
+
+
+EXP. 13. SILVER.
+
+A small phial was well dried in hot sand, then corked, and removed to
+a cool place; after the phial cooled, it was nearly filled with ether,
+and a small bit of phosphorus, which was repeatedly washed in alcohol
+to free it from any aqueous moisture, that might adhere to it, was
+introduced; the phial was then corked, and placed in hot sand; when the
+phosphorus melted, I shook the phial, and obtained a strong solution.
+
+Into this solution a small bit of silk, which was dipped in a solution
+of silver in alcohol, and dried, was introduced: the phial was corked;
+the silk instantly assumed a brown colour; but not a particle of
+reduced silver could be seen, though the experiment was continued about
+three months; nor did the solution of phosphorus become turbid, or
+deposit any precipitate, as happened in similar experiments on gold.
+
+At the end of this period the silk was taken out of the phial, wetted
+with water, and suspended in a window; and, after a considerable time,
+reduced silver was manifest on different parts of the silk.
+
+With the solution of phosphorus, in which the silk stood during that
+time, I reduced gold, and silver, with the assistance of water.
+
+In order to compare the effects of water with those of ether and
+alcohol, I made the following experiments.
+
+
+EXP. 14. SILVER.
+
+I dipped a bit of silk in a solution of nitrate of silver in water,
+and dried it at the fire: the silk thus dried retained its white
+colour: the solution of phosphorus was then applied, and immediately
+produced a brown colour, which soon, in proportion as the phosphorus
+fumed, acquired a deeper tinge, verging on black; and slight signs of
+reduction appeared after a little time on the margin of the stain.
+
+Another bit of silk, treated in the same manner, but dried much better,
+exhibited still fainter signs of reduction: for the brown stain did not
+appear on this piece as soon as on the former, nor was it so intense;
+however, after some minutes exposure to the air, the stain became
+deeper, and its margin acquired a livid white appearance, owing to a
+partial reduction of the silver.
+
+It has been often remarked, that the reduction commences first on the
+margin of the stain, which the solution of phosphorus, and that of the
+metal, produce in the silk: I was a long time at a loss to account
+for this appearance; but the cause was accidentally discovered; for
+happening to spill a few drops of the solution of phosphorus on a
+table, I observed, that, as they evaporated, watery circles were formed
+round the spaces, on which the drops fell; and, that all the parts
+within the circles were dry.
+
+This explains why the reduction begins on the margin of the stain.
+
+I observed the same of alcohol; for if it be dropped on a level
+surface, it leaves a watery ring behind, though not near so soon, as a
+solution of phosphorus in ether does: this is the reason why alcohol
+seems to promote the reduction of some metals; I say seems; for it
+does not promote it, but in proportion to the quantity of water it
+contains, or attracts from the air, and deposits in the silk during its
+evaporation.
+
+How essential water is to the reduction of metals will appear from the
+following experiment.
+
+
+EXP. 15. SILVER.
+
+I immersed a piece of silk in the solution of phosphorus, and after
+the ether evaporated, and the phosphorus began to fume, a solution
+of nitrate of silver in water was applied; instantly the silver was
+restored to its metallic splendour.
+
+This experiment is very amusing, and well calculated to strike the
+beholder with surprise.
+
+The reduction is sometimes attended with spangles of a beautiful blue,
+which appear chiefly where the solution of silver is most abundant.
+
+The solution of silver is commodiously applied by a camel hair pencil.
+
+I also tried the effects of the vapour of phosphorus on bits of silk
+dipped in a solution of nitrate of silver in water, and exposed to the
+vapour, in the same manner as in experiment the 9th; and the silver was
+always reduced: but a solution of phosphorus in ether seems preferable
+to the vapour.
+
+A small glass tube, resembling a thermometer, with its bulb terminating
+in a smaller and nearly capillary tube, I found useful, and economic,
+especially in experiments on gold: by immersing the smaller end in the
+metallic solution, and inspiring through the tube at the same time, the
+bulb may be filled: by this means a single drop, or more, if necessary,
+may be applied to the silk; and, thus, a great number of experiments
+can be made on a single grain, or a much less quantity, of gold, or any
+other metal.
+
+This little instrument may be used also to apply the solution of
+phosphorus to the silk; and it was by using it for this purpose,
+I discovered, that phosphorus has not the power of reducing silver
+without the aid of water; for blowing the solution of phosphorus from
+the tube on bits of silk, which had been dipped in a solution of
+silver, and dried, I was surprised to find films of reduced silver
+frequently appear; whereas none appeared, when I applied the solution
+of phosphorus in a different manner: this unexpected event often
+occurred, before I learned the cause; at length I suspected, it might
+depend on the moisture of the breath; and I was soon convinced by
+moistening the silk with water, that the suspicion was well founded.
+
+It is evident from these experiments on silver, that water is essential
+to the reduction of this metal by phosphorus; and that ether, and
+alcohol, do not promote it.
+
+It is also evident, that these experiments, and those, made on the
+reduction of gold, mutually illustrate each other; and confirm the
+conclusions drawn from them.
+
+
+EXP. 16. PLATINA.
+
+I immersed a bit of silk in a solution of nitro-muriate of platina in
+distilled water, and dried it in the air; the solution of phosphorus
+was then applied to the silk; but no appearance of reduction could be
+perceived.
+
+Another bit of silk was dipped in the solution of phosphorus; when the
+ether evaporated, and the phosphorus began to fume, the solution of
+platina was applied to the silk; and, in some time, delicate films of
+reduced platina were visible where the water was most abundant. These
+films of platina commonly disappear; and nothing remains but a brown
+tinge, which, however, is more intense, than what the solution of
+platina alone gives the silk.
+
+To succeed in this experiment, the silk should be replete with
+phosphorus; which is easily done by applying the solution twice or
+thrice, and waiting after each application, till the fumes begin to
+appear. It is also necessary to keep the silk constantly wet with
+water. Sometimes it requires from ten to twenty minutes to reduce
+platina in this manner.
+
+
+EXP. 17. MERCURY.
+
+I dipped a bit of silk in a solution of oxygenated muriate of mercury,
+and dried it in the air; then the solution of phosphorus was applied;
+when the ether evaporated, and the phosphorus began to fume, a yellow
+stain commenced on the margin, and gradually appeared over the whole.
+
+To compare the effects of different degrees of moisture, I immersed a
+bit of silk in the same solution of mercury, and dried it carefully at
+the fire; the solution of phosphorus was then applied; the silk began
+to fume; but no change, except a very slight ring of a yellow hue,
+appeared. The rest of the silk retained its white colour.
+
+Another bit of silk was immersed in the solution of phosphorus, when
+the ether evaporated, and the phosphorus began to fume, the same
+solution of mercury in distilled water was applied; and, in a few
+seconds, a bright film of reduced mercury was visible on the margin of
+the part, to which the metallic solution was applied, and after some
+time appeared on the whole. The reduction was attended with the colours
+of the rainbow.
+
+After a little time, these colours vanish, and the metallic film
+becomes much more obscure, according as the silk dries, and is
+succeeded by a yellow stain.
+
+
+EXP. 18. MERCURY.
+
+A bit of silk was dipped in a solution of nitrate of mercury in
+distilled water, and dried at the fire; then the solution of phosphorus
+was applied; and, when it began to fume, a brown stain commenced at
+the margin, which soon diffused itself over the whole, and gradually
+acquired a faint tinge of black.
+
+Another piece of silk, treated in the same manner, but dried in the
+air, exhibited the same appearances; except that the brown tinge verged
+more on black.
+
+Another bit of silk was immersed in the solution of phosphorus, and
+when it began to fume, the solution of nitrate of mercury was applied;
+a brown colour instantly appeared, accompanied with a film of reduced
+mercury, which was most evident where the metallic solution was most
+abundant. This film soon disappeared, and was succeeded by a black
+stain, in which, however, reduced mercury was visible. No colours but
+black, and brown, appeared in this experiment.
+
+It appears from these experiments on mercury, that the reduction kept
+pace with the quantity of water present.
+
+
+EXP. 19. COPPER.
+
+A piece of silk was immersed in a solution of sulphate of copper, and
+dried in the air: then a strong solution of phosphorus was applied; the
+silk acquired a brown colour; but no other visible alteration occurred.
+
+Another piece of silk was dipped in the same solution of copper, and
+dried at the fire much better than the preceding; the solution of
+phosphorus was applied; when the ether evaporated, and the phosphorus
+began to fume, a brown tinge commenced on the margin of the silk, and
+gradually diffused itself over the whole; but the stain was by no means
+so intense as that produced in the preceding piece: so that there can
+be no doubt that the difference was owing to the different degrees of
+moisture in the silk.
+
+After this piece remained in the air for some time, the brown tinge
+became more intense, a proof that it attracted water from the air. This
+difference in the appearances of pieces dried in the air, and at the
+fire, I frequently remarked.
+
+
+EXP. 20. COPPER.
+
+A strong solution of phosphorus was applied to a piece of silk, when
+the ether evaporated, and the phosphorus began to fume, a solution of
+sulphate of copper was applied; a brown stain was instantly produced,
+and its margins were soon covered with a _white_ metallic film, parts
+of which, after some time, verged on the colour of copper, intermixed
+with purple, green, and blue. If the solution of phosphorus be weak,
+which is always the case, when the ether is bad, nothing appears on
+the silk but the brown stain, and the _white_ metallic film. As the
+silk dries most of these appearances vanish; but some of the blue tinge
+survives; and the silk looks very unseemly.
+
+A bit of silk was immersed in the same solution of copper, and exposed
+to the vapour of phosphorus, as in experiment the 9th; but no change
+was produced on the silk, except a few brown spots, though the heat
+was such that the vapour filled the phial, and circulated through it:
+the vapour corroded a brass pin, which was used to suspend the silk
+in the phial. This induced me to try its effects on copper, which
+was corroded by it in a remarkable manner, and changed into a black
+substance resembling a mixture of charcoal and oil. It appears then
+that phosphorus is ill adapted to the reduction of this metal.
+
+
+EXP. 21. TIN.
+
+A bit of silk was immersed in a solution of muriate of tin in distilled
+water, and dried in the air; the solution of phosphorus was then
+applied to the silk, and though it fumed considerably, no change
+whatever could be perceived in the colour of the silk; nor was there
+the smallest appearance of reduction.
+
+I poured some of the solution of phosphorus on a bit of silk, and when
+it began to fume, the solution of tin was applied: after a few seconds,
+white metallic films appeared, first on the margin, and were gradually
+diffused over that part of the silk, to which the muriate of tin was
+applied: a yellow colour intermixed with red sometimes attends the
+reduction. After some little time these films of reduced tin vanish,
+and scarcely leave a stain behind.
+
+I did not succeed in reducing acetite of lead, muriate of arsenic, or
+sulphates of iron, and zinc, in this way.
+
+These experiments on tin shew that water is essential to its reduction
+by phosphorus, and give additional force to the preceding conclusions.
+
+M. Sage discovered that gold, silver, &c. are precipitated from their
+solutions in the metallic form, by pieces of phosphorus, which are
+covered at the same time with bright coats of gold, silver, &c.
+
+To determine if water were essential to these reductions performed by
+M. Sage, I made the following experiments.
+
+
+EXP. 22. GOLD.
+
+Some solution of phosphorus in ether was poured into a china cup, and
+a few drops of the ethereal solution of gold were added; instantly a
+brown powder was precipitated similar to what appeared in experiment
+the 6th, but no gold in its metallic form could be perceived.
+
+
+EXP. 23. GOLD.
+
+A solution of nitro-muriate of gold in water was poured into a china
+cup, containing a solution of phosphorus in ether; instantly the
+gold began to assume its metallic splendour, attended with a variety
+of colours, as purple, blue, and red, the beauty of which cannot be
+described: the quantity of the blue was gradually diminished, and what
+remained, was dispersed over the surface in small films, intermixed
+with spangles of reduced gold. Most of the blue films were of a
+circular figure; some had a central speck of ruby red, and were fringed
+with purple; some had a round central speck of a darker blue than the
+surrounding parts: and some were of an irregular figure, fringed with
+purple, or ruby red. I often observed these blue films assume the real
+colour of gold without suffering any intermediate change of colour;
+and, I think, I observed the same of one of the largest specks of ruby
+red, that appeared in this experiment. All these colours disappeared,
+when the reduction was completed.
+
+The variety of colours, which those films assume, depends on the
+different degrees of reduction; that is to say, on the quantity of
+oxygen combined with the metal: in proportion as the metal is deprived
+of the oxygen, it assumes various colours, which often succeed
+each other in a regular order, showing the different stages of the
+reduction: thus when gold is reduced; the first perceptible change is a
+green, which soon becomes olive; this is succeeded by blue, and purple;
+and sometimes by a ruby red: the purple tinge is a mixture of blue, and
+red.
+
+The various colours, which metals, and their calces, communicate to
+glass, and other substances, are explicable on these principles: and
+the difficulty of obtaining a ruby-coloured glass by gold is readily
+understood from the facility, with which that metal parts with oxygen.
+
+
+EXP. 24. GOLD.
+
+A thread was passed by means of a needle through a small bit of
+phosphorus, which was freed from any moisture, that might adhere to
+it, by immersing it for some time in alcohol; it was then suspended
+by means of the thread in a solution of gold in ether, contained in
+a phial, which was carefully dried in hot sand: in a few minutes,
+the solution became turbid, an effervescence commenced, and a brown
+precipitate was formed: according as the precipitate fell, the solution
+became clear, lost its yellow colour; and the whole of the gold seemed
+to have been precipitated: but not a particle of reduced gold could be
+seen.
+
+Another bit of phosphorus was suspended in the same manner in a
+solution of nitro-muriate of gold in water; and in a few minutes got a
+splendid coat of reduced gold.
+
+
+EXP. 25. SILVER.
+
+A few drops of a solution of fused nitrate of silver in alcohol were
+poured into a china cup containing a solution of phosphorus in ether:
+instantly a black precipitate, with a tinge of brown, was formed; but
+no silver in its metallic state could be perceived.
+
+After some time the precipitate attracted moisture from the air; and
+some films of reduced silver appeared.
+
+The same experiment was made in a phial, which was corked, to exclude
+the moisture of the air; and nothing, but the black precipitate,
+appeared.
+
+Some of the same solution of silver was diluted with water, and dropped
+on a solution of phosphorus in ether; and instantly films of reduced
+silver floated on the surface.
+
+
+EXP. 26. SILVER.
+
+A bit of phosphorus was suspended by a thread in some of the same
+solution of silver in alcohol, contained in a phial carefully dried: a
+black precipitate with a tinge of brown soon appeared; but no silver in
+its metallic state could be observed; part of the precipitate adhered
+to the phosphorus, and part fell to the bottom of the phial.
+
+In another experiment made in a phial not sufficiently dried, a few
+small films of reduced silver were observed on the sides of the phial;
+but not a particle of silver in its metallic form could be seen on the
+phosphorus.
+
+Another bit of phosphorus was suspended in a diluted solution of
+nitrate of silver in water: and in some hours, the phosphorus was
+covered with reduced silver.
+
+The case of silver, which covered the phosphorus, prevented its
+spontaneous combustion in the air; the same was observed of the bit of
+phosphorus coated with gold.
+
+Hence it appears, that M. Sage’s success in reducing metals by
+phosphorus depended on the water of the metallic solution.
+
+These experiments were often repeated with nearly the same result; but
+some variety often occurs, depending on various circumstances; as the
+strength of the metallic solution, and that of the phosphorus; the
+quantity of water present, and the purity of the materials employed.
+
+It is difficult to obtain ether, or alcohol, with the least possible
+quantity of water; and equally difficult to expel all moisture from
+the surface of glass; for this reason, the bits of phosphorus in the
+experiments made with alcohol and ether were suspended by threads, so
+as not to touch the sides of the glass.
+
+I shall conclude this chapter with a general view of the inferences,
+which seem naturally to flow from these experiments with phosphorus.
+
+1. Water is essential to the reduction of metals by phosphorus;
+for these experiments show that the reduction is effected only in
+proportion to the quantity of water present.
+
+2. Phosphorus does not reduce the metals by giving them phlogiston.
+
+3. Phosphorus does not reduce the metals by uniting with, and
+separating, their oxygen.
+
+How then is the reduction effected? are we not to conclude, that it is
+effected by the decomposition of the water, in the following manner?
+
+The phosphorus attracts the oxygen of the water, while the hydrogen of
+the latter unites, in its nascent state, with the oxygen of the metal,
+and effects the reduction.
+
+Hence it follows, that the phosphorus is oxygenated by the oxygen of
+the water, while the metal is restored to its combustible state.
+
+Thus what could never be effected by a single, is readily performed by
+a double affinity; which always takes place in preference to a single
+affinity, as the experiments of Messrs. Monnet, and Kirwan, mentioned
+in the preceding chapter, show.
+
+It is well known, that phosphorus kept in water acquires an oxygenated
+crust, which could not happen without a decomposition of the water:
+this fact serves to confirm the explanation here offered.
+
+And indeed the decomposition of water in these experiments must be
+granted, or it must be supposed, that water itself reduces the metals,
+by uniting with their earths, and constituting their phlogiston; or by
+uniting with, and separating, their oxygen; suppositions repugnant to
+our present knowledge of chymistry.
+
+
+
+
+CHAPTER III.
+
+_Reduction of Metals by Sulphur._
+
+
+Though Sulphur, as far as my reading extends, has seldom been
+considered as a reducer of the metals, yet as it holds a distinguished
+rank among combustible bodies, analogy led me to examine its powers in
+reducing and fixing the metals in the fibres of silk.
+
+The vapour of sulphur appeared to be the most simple form, in which
+it could be applied to this purpose; and may be obtained by placing a
+phial containing flowers of sulphur in hot sand: as the sulphur melts,
+it assumes the form of vapour, which soon fills the phial, expels the
+atmospheric air, and bears a considerable heat, before it inflames; a
+bit of silk, prepared for the experiment, may be held over the vapour,
+as it issues from the phial, or immersed in it. The neck of the phial
+should be of a convenient size for this purpose.
+
+But these experiments are more conveniently made by means of a
+sulphurous match, and a glass funnel, in which the silk imbued with the
+metallic solution may be suspended by a thread passed through it, and
+made fast with a cork, which also serves to confine the vapour.
+
+The glass is then placed on a table, and by moving it a little beyond
+the verge of the same, a lighted match is readily introduced, which, as
+soon as the glass is filled with vapour, may be withdrawn; the vapour
+is confined by making the glass glide back on the table; and thus the
+phenomena of the experiment can be easily observed.
+
+Though the vapour obtained in this manner be chiefly sulphurous acid
+gas; yet its effects are not less interesting on that account.
+
+
+EXP. 1. GOLD.
+
+A bit of silk was dipped in a solution of gold in ether, and dried:
+it was then suspended in the glass funnel, and exposed for some time
+to the vapour obtained from a burning match: but no change could be
+perceived, except that the silk became a little brown.
+
+Another bit of silk, prepared in the same manner, was immersed in the
+vapour of sulphur, formed in a phial placed in hot sand, with the same
+result.
+
+
+EXP. 2. GOLD.
+
+A piece of silk was immersed in a solution of nitro-muriate of gold in
+water, suspended in the glass funnel, and exposed, while wet, to vapour
+of sulphur, formed by a burning match; no sooner did the vapour touch
+the silk, than the reduction commenced; and in a few seconds the whole
+piece was covered with a splendid coat of reduced gold, permanent, and
+retentive of its lustre; but had a few specks of a dull violet hue.
+
+The silk viewed by transmitted light appeared of a beautiful blue
+colour; and being removed from the vapour, and suspended in the air,
+began in about ten minutes to exhale a vapour, which continued about
+two hours, and smelled acid, and pungent.
+
+Another bit of silk, dipped in the same solution of gold, and dried,
+was wetted with alcohol, and exposed to the same vapour: the silk
+acquired a brownish hue; and a small white metallic film appeared on
+its lower end, where the alcohol most abounded: the silk was then
+wetted with water, and replaced in the vapour; instantly a lively
+purple with a bright pellicle of reduced gold appeared.
+
+
+EXP. 3. SILVER.
+
+A piece of silk was immersed in a solution of nitrate of silver in
+water, and suspended in the air of a dark closet to dry; the silk
+retained its white colour, though it remained in the air twenty-four
+hours; it was then exposed fourteen hours to the vapour obtained from a
+burning match; but suffered no change, except that it acquired a brown
+tinge: it was now wetted with alcohol, and replaced in the vapour for
+some time; no signs of reduction appearing, it was wetted again with
+the alcohol, and exposed to the vapour; but still no signs of reduction
+could be perceived: I then wetted the silk with distilled water,
+replaced it in the sulphureous vapour; and in about a minute reduced
+silver appeared.
+
+
+EXP. 4. SILVER.
+
+I dipped a bit of silk in a solution of nitrate of silver in distilled
+water, and exposed it, while wet, to the vapour of sulphur, as in the
+preceding experiment; in a few seconds the silver appeared in its
+metallic form, attended with a variety of lively colours: the most
+remarkable of these were a pleasant blue, orange, purple, and yellow,
+which soon disappeared: the reduced silver also disappeared in a
+great measure, some faint traces only remaining. The silk was removed
+from the vapour into the air, but exhaled no vapour, as happened in
+experiment the second.
+
+A small bit of sulphur was suspended in a phial containing a solution
+of nitrate of silver in water; and after some weeks the sulphur was
+coated with reduced silver of no great lustre.
+
+
+EXP. 5. PLATINA.
+
+A bit of silk was immersed in a solution of nitro-muriate of the ore
+of platina in distilled water, and dried in the air; it was then
+suspended in the glass funnel, and exposed to the vapour of a burning
+match: but no signs of reduction could be observed: the silk retained
+the colour, the solution gave it.
+
+Another bit of silk was dipped in the same solution of platina, and
+exposed, while wet, to the sulphureous vapour; in a few seconds the
+reduction was very evident. The silk was immerged in a glass of clear
+water, and transferred bright films of reduced platina to the surface
+of that fluid; most of them were of the same colour as the spangles
+in the ore of platina; and some were distinguished by lively blue and
+purple colours.
+
+Another bit of silk, dipped in the same solution of platina, was
+immersed, while wet, in the vapour of sulphur, formed in a phial placed
+in hot sand; the reduction soon commenced, and was much more perfect,
+and permanent, than in pieces exposed to the vapour obtained from
+ignited matches.
+
+It is remarkable that sulphur reduced this metal much better, than
+phosphorus or hydrogen gas did: but the reduced platina disappears
+after some time, and leaves nothing behind but a brown stain.
+
+If the films be transferred from the silk to water, they may be
+preserved in their metallic form.
+
+
+EXP. 6. MERCURY.
+
+A bit of silk was immersed in a solution of nitrate of mercury in
+distilled water, and dried; parts of the silk immediately acquired
+a slate colour: the silk was then exposed to the vapour of sulphur,
+obtained from a burning match; but it suffered no change, except that
+the colour became a little more intense.
+
+Another bit of silk was dipped in the same solution of mercury, and
+exposed, while wet, to the same vapour: the reduction instantly
+commenced in a very evident manner, accompanied with several colours,
+as blue, purple, and yellow.
+
+The silk was removed from the vapour, and soon lost most of its lustre,
+which was succeeded by a slate colour, through which some particles of
+reduced mercury were observed to shine.
+
+
+EXP. 7. MERCURY.
+
+A bit of silk was immersed in a solution of oxygenated muriate of
+mercury in water, and dried in the air: it was then exposed to the
+sulphureous vapour obtained from a burning match; but the silk
+underwent no visible change. This solution of mercury does not change
+the white colour of silk, as that of nitrate does.
+
+Another bit of silk was dipped in the same solution of oxygenated
+muriate of mercury, and exposed, while wet, to the vapour; in a few
+seconds reduced mercury appeared, unattended by any colour, except a
+slight tinge of citron yellow on part of the silk. After some time the
+whole of the reduced mercury vanished.
+
+
+EXP. 8. COPPER.
+
+A piece of silk was immersed in a solution of sulphate of copper, and
+dried; it was then suspended in the glass funnel, and exposed to the
+vapour obtained from a burning match; but the silk suffered no change,
+retaining the colour, which the solution gave it.
+
+Another bit of silk was dipped in the same solution of copper, and
+exposed, while wet, to the vapour of an ignited match; in a short
+time a white metallic film appeared, accompanied with a brown tinge;
+the silk becoming dry, was wetted with water, and exposed to a brisk
+vapour from another match: the film became more evident, and parts of
+it verged on yellow, bordering on a copper colour. After some time this
+white metallic film disappears, and nothing remains but a light brown
+stain.
+
+
+EXP. 9. LEAD.
+
+A bit of silk was immersed in a solution of acetite of lead in
+distilled water, and dried in the air: it was then exposed to the
+sulphureous vapour of a burning match; but underwent no visible change
+whatever.
+
+Another bit of silk was dipped in the same solution of lead, and
+exposed, while wet, to the vapour; reduced lead soon appeared all over
+the silk; but after some time this reduced lead disappears, unless it
+be transferred to the surface of water.
+
+
+EXP. 10. TIN.
+
+A bit of silk was immersed in a solution of muriate of tin in distilled
+water, and dried in the air: it was then exposed to the vapour obtained
+from a burning match, which soon filled the glass; but produced no
+visible change on the silk.
+
+Another bit of silk was dipped in the same solution of tin, and
+exposed, while wet, to the sulphureous vapour; and in a few seconds
+reduced tin appeared all over the silk; but the tin soon disappears, if
+not transferred to water.
+
+
+EXP. 11. ARSENIC.
+
+A bit of silk was immersed in a solution of muriate of arsenic in
+distilled water, and dried in the air; it was then exposed to the
+vapour of sulphur, obtained from a burning match; but the silk suffered
+no apparent alteration.
+
+Another bit of silk was dipped in the same solution of arsenic, and
+exposed, while wet, to the vapour: in a few seconds the arsenic was
+reduced, but not in a very evident manner; the silk was immerged in
+water, and several bright films of reduced arsenic floated on the
+surface of that fluid.
+
+
+EXP. 12. BISMUTH.
+
+A bit of silk was immersed in a solution of nitrate of bismuth in
+distilled water, and dried in the air; it was then exposed to the
+vapour of sulphur obtained from a burning match; but no signs of
+reduction appeared.
+
+Another bit of silk was dipped in the same solution of bismuth, and
+exposed, while wet, to the sulphureous vapour; the bismuth was soon
+reduced, accompanied with a brown stain: but the metallic lustre soon
+disappeared.
+
+
+EXP. 13. ANTIMONY.
+
+A piece of silk was immersed in a solution of tartarite of antimony in
+water, and dried; it was then exposed to the vapour of a burning match;
+but no change could be observed; nor did the silk immerged in water
+deposit any films on its surface.
+
+Another piece of silk was dipped in the same solution of antimony, and
+exposed, while wet, to the vapour: the silk, in a few seconds, acquired
+a yellow colour, and a bright bluish film of reduced antimony appeared
+on the lower end of the silk, where the water was most abundant: the
+silk was then immerged in a glass of water, and transferred a large
+pellicle of reduced antimony to the surface of that fluid.
+
+
+EXP. 14. IRON.
+
+A bit of silk was immersed in a largely diluted solution of sulphate of
+iron in distilled water, and dried in the air; it was then exposed to
+the vapour of sulphur obtained from a burning match; after some time
+the colour of the silk became a little brown; but no reduced iron could
+be seen; nor did the silk immerged in a glass of clear water transfer
+any thing metallic to its surface.
+
+Another bit of silk was dipped in the same solution of iron, and
+exposed, while wet, to the sulphureous vapour; in a short time the silk
+was withdrawn, and a minute shining film, of a livid white colour, was
+visible on its lower margin, where the water most abounded: the silk
+was then immerged in a glass of water, and transferred a large film of
+reduced iron to its surface.
+
+This experiment succeeded also with the vapour of sulphur formed in a
+phial placed on hot sand. The films of reduced iron were seldom visible
+on the silk; but were soon rendered visible, by transferring them to
+water.
+
+
+EXP. 15. ZINC.
+
+A piece of silk was dipped in a diluted solution of sulphate of zinc,
+and dried; it was then exposed to the vapour obtained from a burning
+match; no change whatever could be perceived: the silk was immerged in
+a glass of water, but deposited no film on its surface.
+
+Another piece of silk was dipped in the same solution of zinc, and
+immersed while wet in the vapour of sulphur formed in a phial placed
+on hot sand; in about half a minute the silk was withdrawn from the
+vapour, and some parts of it had a shining livid appearance, which I
+took for reduced zinc: in order to determine if the reduction were
+real, the silk was immerged in a glass of clear water, and transferred
+to its surface a bright film of reduced zinc.
+
+If the silk be kept too long in the vapour, some sulphur will be
+condensed on its surface, and give it a yellow colour: if it be then
+dipped in a glass of water, it will deposit both the sulphur, and
+the metallic films on its surface; but the appearance of the sulphur
+is so different from that of the reduced metal, that they are easily
+distinguished.
+
+Another bit of silk was immersed in a largely diluted solution of
+muriate of zinc, and exposed, while wet, to the vapour obtained from a
+burning match: the silk being withdrawn exhibited a few minute shining
+films on its lower end, and on immersion in water, left bright films of
+reduced zinc floating on the surface of that fluid.
+
+Very often these films cannot be seen, until they are transferred to
+water, which I found a very useful test in doubtful cases: they are
+better seen in the gray light than in sunshine.
+
+These experiments on the reduction of metals by sulphur were often
+repeated with nearly the same result: but some variety occurs depending
+on the quantity of water present, the strength of the metallic
+solution, and sulphureous vapour, and also on the time the silk is
+exposed to the vapour.
+
+When the experiments are made in a phial placed in hot sand, part of
+the metallic solution frequently drops from the silk, and falling on
+the bottom, or sides of the phial, is reduced, covering these parts
+with a metallic crust; on which the sulphur soon reacts, and changes
+the greater part into a sulphure. The phial commonly cracks.
+
+The following conclusions are deducible from the experiments related in
+this chapter.
+
+1. Water is essential to the reduction of metals by sulphur; for this
+effect is always in proportion to the quantity of water present.
+
+2. Alcohol does not promote these reductions without the aid of water.
+
+3. Sulphur does not reduce the metals by giving them phlogiston;
+nor by uniting with and separating their oxygen; for were either of
+these opinions just, the sulphur, so minutely divided by heat, should
+reduce metallic solutions in alcohol as effectually as it does metallic
+solutions in water.
+
+When we compare these reductions by sulphur, with those effected by
+phosphorus, and consider that water is essential to both; we must
+conclude, that the reduction is effected in the same manner, viz. by
+the decomposition of water; which may be thus explained.
+
+The sulphur attracts the oxygen of the water, while the hydrogen of the
+latter unites, in its nascent state, to the oxygen of the metal, and
+restores it to the metallic form.
+
+Hence it follows, that the sulphur is oxygenated by the oxygen of the
+water, while the metal is restored to its combustible state.
+
+It also follows, that a quantity of water equal to that consumed is
+formed by the hydrogen of the water, and the oxygen of the metal.
+
+This explanation is supported by a fine experiment of Dr. Priestley,
+who obtained inflammable air by passing the vapour of water through
+sulphur heated in an earthen tube[15]; and farther confirmed by the
+experience of some judicious makers of oil of vitriol, who always
+sprinkle the sulphur with a certain proportion of water, before they
+inflame it.
+
+The decomposition of water in these reductions must be granted, or it
+must be supposed, that a single takes place in preference to a double
+affinity; which cannot be admitted.
+
+These experiments point out several errors in M. Lavoisier’s Table of
+the Affinities of the Oxygenous Principle; for he has placed sulphur
+at a much greater distance from that principle than any of the metals
+treated of in this chapter, except gold; and even in this instance his
+table is erroneous, unless it be proved, that sulphur reduces metals
+by directly uniting with, and separating their oxygen; a supposition
+which implies, that the reduction is effected by a single affinity; and
+therefore inadmissible.
+
+I shall close this chapter with a short extract from the chemical
+essays of Bishop Watson; as it seems to have some relation to the
+experiments related here.
+
+His lordship says, that his experiments on “the Derbyshire lead ore
+instruct us to believe, that the lead in this kind of ore is in its
+metallic state; as the ore was changed into lead without the addition
+of any substance containing the inflammable principle[16].”
+
+But the reduction of lead by sulphur and water, related in this
+chapter, points out an evident source of the inflammable principle;
+for the ore itself must contain some water, a constituent part of
+which is hydrogen, or the base of inflammable air: beside his lordship
+thinks, no appearance of lead would have taken place, had there been no
+communication with the external air: but as air always holds water in
+solution, an ample source of the inflammable principle is evident.
+
+
+
+
+CHAPTER IV.
+
+_Reduction of Metals by Alkaline Sulphure._
+
+
+The Sulphure, I made use of, was prepared by fusing equal parts of
+carbonate of potash, and flowers of sulphur, till the effervescence
+ceased.
+
+M. Gengembre has made a very important observation on alkaline
+sulphure, prepared in this way, which is, that this substance has no
+smell, and that it exhales no gas, while it continues dry; but that,
+when it is dissolved in water, or attracts humidity from the air, it
+diffuses an offensive smell.
+
+From this circumstance M. Gengembre inferred, that the disengagement of
+this gas depended on the decomposition of water; for he discovered both
+by analysis, and synthesis, that this air consists of hydrogen, one of
+the principles of water, combined with sulphur, and caloric.
+
+There can then be no doubt, but alkaline sulphure has the power of
+decomposing water; and may therefore be happily employed to illustrate
+the mode of action of sulphur, and other combustible substances,
+treated of in this essay.
+
+When dilated acids are poured on solid alkaline sulphure, the
+decomposition of the water is promoted, and accelerated, sulphurated
+hydrogen gas being formed in great abundance.
+
+I made two solutions of this alkaline sulphure, one in water, and the
+other in alcohol.
+
+
+EXP. 1. GOLD.
+
+A bit of silk was immersed in the solution of sulphure in alcohol, and
+then a solution of gold in ether was applied: a brown matter was formed
+in the silk; but no reduced gold could be perceived.
+
+Another bit of silk was dipped in the same solution of sulphure in
+alcohol, and a solution of nitro-muriate of gold in water was applied;
+a white metallic film was slowly formed; but no other signs of
+reduction were visible.
+
+This experiment was repeated on another bit of silk, with this
+difference, that the solutions of the gold, and sulphure, were both in
+water; and the white metallic film was instantly formed, accompanied by
+a considerable precipitate of a brown matter.
+
+It is obvious then, that water accelerates, and is necessary to the
+appearance of this film: for when both solutions were in water, it
+appeared much sooner.
+
+
+EXP. 2. GOLD.
+
+A piece of silk was immersed in an aqueous solution of gold, in which
+the acid predominated, then a few drops of the aqueous solution of
+sulphure were applied: a white pellicle, which looked like silver, was
+immediately formed, and the silk got a deep brown colour.
+
+To another piece of silk, dipped in the same solution of gold,
+the solution of sulphure in alcohol was applied, a white metallic
+film appeared; but not so evident, or so soon, as in the preceding
+experiment, wherein the solution of sulphure in water was used:
+beside the film produced by the aqueous solution of sulphure was more
+permanent, and the stain, which the silk acquired, was more intense,
+than those produced by the solution of sulphure in alcohol.
+
+
+EXP. 3. SILVER.
+
+I immersed a piece of silk in a solution of the sulphure in alcohol,
+and after most of the spirit evaporated, a solution of nitrate of
+silver in alcohol was applied: nothing appeared on the silk, but a
+brown stain. The nitrate of silver, used in this experiment, was fused,
+to expel as much water as possible.
+
+Another piece of silk was dipped in the same solution of sulphure; when
+most of the alcohol evaporated, a solution of crystallized nitrate of
+silver in water was applied to the silk; and instantly the metallic
+lustre of the silver appeared, attended with a brown stain.
+
+
+EXP. 4. SILVER.
+
+A piece of silk was dipped in the solution of alkaline sulphure in
+water, and an aqueous solution of crystallized nitrate of silver was
+applied; the silver was immediately reduced in greater quantity than
+in the preceding experiment, in which the alkaline sulphure employed
+was dissolved in alcohol. The stain produced in the silk was also more
+intense.
+
+
+EXP. 5. SILVER.
+
+A bit of silk was immersed in a solution of the sulphure in water,
+and then a solution of nitrate of silver in alcohol was applied: but
+nothing appeared on the silk, except a brown stain. The nitrate of
+silver, used in this experiment, was fused, which deprived it of a
+great part of its acid. That this was the circumstance, which prevented
+the reduction of the silver, appears from the following experiment.
+
+A bit of silk was immersed in the same solution of silver in alcohol,
+then some diluted nitric acid was applied, lastly the aqueous solution
+of sulphure was dropped on the silk: and instantly the silver was
+restored to its metallic splendour. It is evident then, that acids
+contribute to the reduction of silver by alkaline sulphure, which they
+effect by promoting the decomposition of water.
+
+In some time the reduced silver disappears for the most part: and
+indeed the white metallic films, which were produced in the experiments
+on gold, totally disappeared.
+
+
+EXP. 6. PLATINA.
+
+A bit of silk was immersed in a solution of nitro-muriate of the ore of
+platina in distilled water, and dried; then the solution of sulphure in
+alcohol was dropped on the silk: nothing appeared but a brown stain.
+
+Another bit of silk was dipped in the aqueous solution of sulphure, and
+a little of the solution of platina applied; in a short time, a film of
+reduced platina appeared.
+
+To another bit of silk, which was dipped in the solution of platina, a
+few drops of distilled vinegar were applied, and then the solution of
+sulphure in water was added; a brown stain was immediately produced,
+and more platina reduced than in the preceding experiment.
+
+
+EXP. 7. MERCURY.
+
+To a bit of silk, which was immersed in a solution of oxygenated
+muriate of mercury in water, and dried in the air; some of the solution
+of sulphure in alcohol was applied; but no change, except a light
+yellowish brown, was produced.
+
+After the silk was some time exposed to the air, some very faint shades
+of black were visible on parts of it.
+
+To a piece of silk, which was immersed in the solution of sulphure in
+water, some of the same solution of mercury was applied; immediately
+the metal was restored to its metallic lustre, in a very striking
+manner; and it was remarkable, that the precipitate on the silk was
+very small.
+
+This experiment was repeated with this difference, that the silk
+was first wetted with distilled vinegar: and more of the mercury
+was reduced, than in the preceding experiment, attended with an
+olive precipitate, which gradually turned blackish: the quantity
+of precipitated matter in this was much greater than in the former
+experiment; but the reduced metal was not so bright.
+
+
+EXP. 8. MERCURY.
+
+A bit of silk, which was dipped in a solution of nitrate of mercury,
+and dried in the air, had no change produced on it by a solution of
+sulphure in alcohol, except a stain compounded of the slate colour,
+which the nitrate imparts, and the yellow of the sulphure.
+
+To another bit of silk, which was immersed in the aqueous solution of
+sulphure, some of the same solution of mercury was applied: the metal
+was immediately reduced; and a very black stain attended the reduction.
+
+
+EXP. 9. COPPER.
+
+A piece of silk was dipped in a solution of sulphate of copper, and
+dried in the air; a solution of the sulphure in alcohol was applied to
+it; but no change, except a brown stain, was produced.
+
+To another bit of silk, immersed in the aqueous solution of sulphure,
+some of the same solution of copper was applied: a white metallic film
+was slowly formed, attended with a brown colour.
+
+On another bit of silk, which was dipped in the same solution of
+copper, and placed on a saucer, some distilled vinegar was dropped,
+and then a few drops of the aqueous solution of sulphure were added:
+immediately a white metallic film appeared in greater quantity than in
+the preceding experiment.
+
+
+EXP. 10. LEAD.
+
+A piece of silk was immersed in a solution of acetite of lead in
+distilled water, and dried in the air; then the solution of sulphure in
+alcohol was applied: but nothing appeared on the silk, except a brown
+stain.
+
+A bit of the same silk was dipped in the same solution of lead, then
+the solution of sulphure in water was applied: the lead was soon
+reduced to its metallic state: a brown stain, and precipitate of the
+same colour, attending the reduction.
+
+The same experiment was repeated with this difference, that the silk
+was first wetted with distilled vinegar, and instantly the lead was
+reduced of greater lustre, and in greater quantity, than in the
+preceding experiment.
+
+This experiment was tried on a bit of white calico, dipped in distilled
+vinegar, and placed on the palm of my hand; and instantly the metallic
+lustre of the lead, which was reduced in great quantity, appeared in a
+very remarkable manner, attended with a brown stain.
+
+
+EXP. 11. TIN.
+
+To a bit of silk dipped in a solution of muriate of tin in distilled
+water, and dried in the air, the solution of sulphure in alcohol was
+applied: nothing appeared but a brown stain.
+
+Another bit of silk was immersed in the solution of sulphure in water,
+then the same solution of muriate of tin was applied; in a short time
+some reduced tin appeared on the silk. Vinegar promoted the reduction
+of this metal also, in a remarkable manner.
+
+
+EXP. 12. ARSENIC.
+
+A bit of silk was immersed in a solution of muriate of arsenic in
+distilled water, and dried in the air: the solution of sulphure in
+alcohol was then applied: the silk first looked yellow, in a short
+time the yellow colour almost entirely disappeared, leaving behind a
+whitish precipitate; but no other change was produced.
+
+Another bit of silk was dipped in the solution of sulphure in water;
+then some of the same solution of arsenic was applied; a yellow
+precipitate was formed; and shortly after, this precipitate was
+surrounded by a violet margin; but no other change could be observed.
+
+I immersed another bit of the same silk in the same solution of
+arsenic, some distilled vinegar was then dropped on it; and lastly the
+aqueous solution of sulphure was applied: after some time, a few minute
+films of reduced arsenic bright as silver were visible.
+
+Some attention is necessary to discover the reduced arsenic, as the
+particles reduced are few, and minute; and sometimes none can be seen.
+
+
+EXP. 13. BISMUTH.
+
+To a bit of silk, which was dipped in a solution of nitrate of Bismuth
+in distilled water, and dried in the air, the solution of sulphure in
+alcohol was applied: the silk appeared first yellow, then brown; but no
+farther change could be observed.
+
+Another bit of silk was immersed in the solution of sulphure in water;
+some of the same solution of bismuth was then applied to it; the metal
+was immediately reduced; and a brown precipitate was formed. Vinegar
+seems neither to promote, nor retard the reduction.
+
+Two bits of white calico were dipped in the same solution of bismuth;
+to one of these placed on a saucer some distilled vinegar was added;
+then a single drop of the solution of sulphure in water was applied;
+and the whole of the calico, except that part on which the drop fell,
+was covered with reduced bismuth, which looked exceedingly bright: the
+same appearance was observed on the other bit, to which no vinegar was
+added.
+
+
+EXP. 14. ANTIMONY.
+
+To a bit of silk, which was dipped in a solution of tartarite of
+antimony in distilled water, and dried in the air, the solution of
+sulphure in alcohol was applied; the silk got a yellow colour, whose
+margins, some time after, acquired an orange hue; but no other change
+was perceived.
+
+Another bit of the same silk was immersed in the aqueous solution of
+sulphure, the same solution of antimony was then applied: part of the
+metal was reduced, though in small quantity, attended with an orange
+precipitate.
+
+The acids of vinegar, and tartar, seemed to impede the reduction; the
+muriatic acid also seemed to have the same effect, though not in so
+great a degree as the two former.
+
+
+EXP. 15. COBALT.
+
+To a bit of silk, which was dipped in a solution of nitrate of cobalt,
+and dried in the air, the solution of sulphure in alcohol was applied;
+the silk soon became brown; but no farther change could be perceived.
+
+To another bit of silk, which was immersed in the solution of sulphure
+in water, a few drops of the same solution of cobalt were applied: the
+silk immediately acquired a dark colour, and, in a little time, some
+of the metal was reduced, attended with a dull blue precipitate, which
+changed to a blackish brown.
+
+Muriate of cobalt was reduced in the same manner: vinegar promoted the
+reduction of both these preparations of cobalt.
+
+EXP. 16. IRON.
+
+To a piece of silk, which was immersed in a solution of sulphate of
+iron largely diluted, and dried in the air, the solution of sulphure in
+alcohol was applied: the silk soon became black; but no other change
+could be perceived.
+
+Another bit of silk was dipped in the solution of sulphure in water,
+some of the same solution of iron was then applied: the silk instantly
+assumed a black colour; but no reduced iron appearing, it was immerged
+in a glass of water, and transferred a bright film of reduced iron to
+the surface of that fluid.
+
+Sometimes part of the film has not the metallic lustre, which is very
+evident in other parts of it; so that the parts completely reduced can
+be easily distinguished from the dull and imperfectly reduced black
+oxid of iron, intermixed with these bright films.
+
+The same experiments were repeated on bits of calico with the same
+result: the calico from its spongy texture is better suited to produce
+strong films than silk is.
+
+Vinegar did not promote the reduction of iron in these experiments.
+
+
+EXP. 17. ZINC.
+
+To a bit of silk, which was immersed in a largely diluted solution of
+muriate of zinc, and dried in the air, some of the solution of sulphure
+in alcohol was applied; nothing appeared on the silk, but the yellow
+colour, which the solution of sulphure imparts.
+
+Another bit of silk was dipped in the solution of sulphure in water,
+and some of the same solution of zinc was applied: the yellow colour,
+which the solution of sulphure gave the silk, soon became white; but
+no reduced zinc could be seen. The silk was then immerged in a glass
+of clear water, and transferred a bright film of reduced zinc to its
+surface.
+
+In another experiment, made with white calico, the pellicle transferred
+to the surface of water was brighter; and more zinc was reduced, than
+in the preceding experiment.
+
+Sulphate of zinc also was reduced both on silk, and calico, with this
+difference that black, and olive, precipitates, attended the reduction.
+
+
+EXP. 18. MANGANESE.
+
+I dipped a bit of silk in a diluted solution of nitrate of manganese,
+and dried it in the air; the solution of sulphure in alcohol was then
+applied: the silk acquired a yellow colour, which soon disappeared; but
+no other change could be observed.
+
+To another bit of silk, which was immersed in the solution of sulphure
+in water, a drop of the same solution of manganese was applied:
+instantly a pearl-white precipitate was formed, the margin of which
+soon acquired a bright film of reduced manganese. Under this film a
+violet tinge was evident.
+
+The nitrate of manganese used in this experiment was very acid.
+
+A solution of alkaline sulphure in water after a certain length of time
+loses the power of reducing the metals, in which respect it resembles
+an old solution of sulphate of iron.
+
+Having procured a more neutral solution of nitrate of manganese, I
+immersed a bit of silk in the solution of sulphure in alcohol, when
+most of the spirit evaporated; a single drop of this solution of
+manganese was applied; instantly a bright film of reduced manganese
+appeared, attended with a violet tinge, and a brown precipitate. After
+some time the violet tinge disappears.
+
+On another bit of silk immersed in the same solution of sulphure in
+alcohol, a drop of a solution of sulphate of manganese in distilled
+water was applied: instantly films of reduced manganese bright
+as silver appeared, accompanied with a faint violet tinge, and a
+pearl-white precipitate. These films soon disappear.
+
+A solution of alkaline sulphure in alcohol does not by age lose its
+power of reducing the metals, as that in water does; I kept the former
+solution more than two years, and found it, at the end of that time, as
+capable of reducing the metals, as when it was made.
+
+It is manifest from the experiments related in this chapter,
+
+1. That water is essential to the reduction of metals by alkaline
+sulphure.
+
+2. That alcohol does not promote these reductions, without the aid of
+water.
+
+3. That alkaline sulphure does not reduce the metals by giving them
+phlogiston; nor by uniting with, and separating, their oxygen; for
+were either of these opinions true, a solution of alkaline sulphure in
+alcohol should reduce them as effectually, as a solution of the same in
+water does.
+
+4. That acids contribute to these reductions by promoting the
+decomposition of water.
+
+Now since M. Gengembre has demonstrated, that water is decomposed
+by alkaline sulphure; who can doubt, that it is decomposed in these
+reductions?
+
+The manner, in which metals are reduced by this substance, seems to be
+the following.
+
+An hydrure of sulphur, that is, a combination of hydrogen, and sulphur,
+is formed: this hydrure of sulphur attracts the oxygen of the water,
+while the hydrogen of the latter unites, in its nascent state, with the
+oxygen of the metal, and reduces it.
+
+The experiments in this chapter leave us no room to doubt of the
+decomposition of water in metallic reductions by alkaline sulphure,
+and serve to illustrate, and confirm, the manner, in which sulphur,
+phosphorus, and other combustible bodies, effect the reduction of
+metals.
+
+
+
+
+CHAPTER V.
+
+REDUCTION OF METALS
+
+BY
+
+_SULPHURATED HYDROGEN GAS_.
+
+
+Having treated of the effects of hydrogen gas, and sulphur, separately,
+I shall next treat of their effects, when combined in the form of
+sulphurated hydrogen gas.
+
+I obtained this elastic fluid by pouring water, acidulated with
+sulphuric acid, on alkaline sulphure, prepared in the manner mentioned
+in the preceding chapter; but had it been prepared with a caustic
+alkali, it is probable, the gas would be more powerful. The sulphure of
+the shops is generally unfit for these experiments.
+
+It is necessary in experiments with sulphurated hydrogen gas, hydrogen
+gas, &c. to have some mode of conveying them into a chimney; as they
+are offensive, and unwholesome.
+
+
+EXP. 1. GOLD
+
+A piece of silk, which was immersed in a solution of nitro-muriate
+of gold in water, and dried in the air, was exposed to sulphurated
+hydrogen gas: the silk got a slight tinge of brown; but no other
+change occurred: it was then wetted with alcohol, and after some time,
+the brown became more intense; and white films appeared on some parts
+of the silk, owing to moisture collected from the gas, which is always
+replete with water.
+
+Another bit of silk was dipped in the same solution of gold, and
+exposed, while wet, to the gas: the yellow colour, which the solution
+of gold gave the silk, was immediately changed to a brown; and a white
+metallic pellicle appeared, and covered the whole surface of the silk
+opposed to the gas; but no purple, or other colours, that usually
+attend the reduction of this metal by other agents, could be perceived.
+This pellicle did not entirely disappear, as the silk became dry;
+though it lost most of its lustre, and looked more like silver, or some
+other white metal imperfectly reduced, than gold.
+
+This elastic fluid, and alkaline sulphure, have an effect on the
+reduction of gold, very different from that of the vapour of sulphur,
+obtained from a burning match, which further appears from the following
+experiment, made with sulphurated hydrogen gas, that happened to be
+mixed with some sulphurous acid gas.
+
+
+EXP. 2. GOLD.
+
+A piece of silk, which was dipped in a solution of gold in ether, and
+dried in the air, was exposed to a current of sulphurated hydrogen
+gas, containing some sulphurous acid gas; but no signs of reduction
+could be perceived: the silk was then wetted with alcohol; still no
+visible change was produced, except a brown stain, where the alcohol
+most abounded: this stain, after some minutes exposure to atmospheric
+air, was covered with a white metallic film, which soon disappeared:
+after some minutes, the silk was wetted with water, and exposed again
+to the gas; a white metallic film immediately appeared, and the brown
+stain began to change slowly to a purple; the silk was soon covered
+with various colours, as blue, red, and orange; and some spots of
+reduced gold of its own proper colour appeared: after some time the
+white film, and all the colours, except the purple, disappeared: some
+specks of the perfectly reduced gold were permanent.
+
+Another bit of silk, which was immersed in an aqueous solution of
+gold, and exposed to the same mixed gas, exhibited nearly the same
+appearances.
+
+
+EXP. 3. GOLD.
+
+Having found that sulphurated hydrogen gas had a powerful effect in
+reducing other metals, I was desirous of trying its effects on a larger
+scale, thinking it might be attended with more success: I therefore
+immersed a quarter of a yard of silk in an aqueous solution of gold,
+and exposed it, while wet, to this gas in close vessels: the silk was
+soon covered with a white metallic pellicle, which disappeared in a
+short time: the experiment was continued about twelve hours, and, on
+withdrawing the silk from the gas, I could not perceive the smallest
+vestige of reduced metal, or purple, or other colours, that constantly
+attend the reduction of gold.
+
+The silk had a dull brown hue verging on a slate colour.
+
+
+EXP. 4. SILVER.
+
+A piece of silk, which was immersed in a solution of nitrate of silver
+in water, and dried in the air, was exposed to a current of sulphurated
+hydrogen gas; but no change could be perceived for some time; at
+length, when the silk collected moisture from the gas, some particles
+of reduced silver were visible, accompanied by a brown stain.
+
+Another piece of silk was dipped in the same solution of nitrate of
+silver, and exposed, while wet, to the gas: the silver was instantly
+reduced all over the side of the silk opposed to the current: a great
+variety of beautiful colours, as red, orange, yellow, green, and blue,
+attended the reduction: most of these disappeared; but part of the
+silver remained permanently reduced.
+
+I found, that, if the silk be immersed in a solution of silver in
+alcohol, and dried, and then moistened with water, and exposed, while
+wet, to the gas, none of these colours appear.
+
+This experiment was repeated on a quarter of a yard of silk in close
+vessels, and immediately both sides of the silk were covered with
+reduced silver, attended with the same beautiful colours: the silk was
+left exposed to the gas seven or eight hours; and being then examined,
+no reduced silver could be seen: nothing remained, but a strange medley
+of colours, chiefly blue, green, purple, and orange, unequally mixed,
+some prevailing more than others in certain parts of the silk: however
+the die is by no means disagreeable.
+
+
+EXP. 5. SILVER.
+
+A piece of silk, which was immersed in a solution of fused nitrate of
+silver in alcohol, and dried in the air, was exposed to a current of
+the gas; but no change could be perceived for some time: it was then
+wetted with alcohol, still no alteration could be observed, till the
+silk attracted moisture from the gas, when small particles of reduced
+silver began to appear, attended with a brown stain.
+
+If the silk immersed in the solution of silver in alcohol, and exposed
+while wet to the gas, be kept constantly wet with alcohol, these
+appearances take place sooner.
+
+A piece of silk, which was dipped in a solution of muriate of silver in
+ammonia, and exposed, while wet, to the gas, had in a short time its
+surface covered with reduced silver: but another piece of silk dipped
+in the same solution of silver, and dried, underwent no such change.
+
+
+EXP. 6. PLATINA.
+
+A bit of silk, which was dipped in a solution of nitro-muriate of the
+ore of platina in distilled water, and dried in the air, was exposed
+to a current of sulphurated hydrogen gas; but underwent no perceptible
+change.
+
+Another bit of silk was immersed in the same solution of platina, and
+exposed, while wet, to the gas; the whole surface of the silk, opposed
+to the current, was instantly covered with reduced platina, which soon
+lost its lustre; nothing remaining but a brown colour, with some faint
+vestiges of the reduced metal.
+
+This experiment was repeated on a bit of linen with the same result.
+
+
+EXP. 7. MERCURY.
+
+A bit of silk, which was dipped in a solution of oxygenated muriate
+of mercury in distilled water, and dried in the air, was exposed to a
+current of the gas; the only visible change produced was a slight shade
+of yellow on part of the silk.
+
+Another bit of silk was immersed in the same solution of mercury, and
+exposed, while wet, to the gas: the mercury was immediately reduced;
+but soon lost its lustre: the gas reacting changed most of it to a
+substance of a dull white colour.
+
+The same experiments were made with nitrate of mercury, with the same
+result.
+
+
+EXP. 8. COPPER.
+
+A bit of silk was immersed in a solution of sulphate of copper in
+distilled water, and suspended in the air to dry; it was then exposed
+to a current of the gas: the silk assumed a brown colour; but no other
+change appeared.
+
+Another bit of silk was dipped in the same solution of copper, and
+exposed, while wet, to the gas: a white metallic film, attended with
+a brown stain, immediately appeared: some parts had a yellow film
+approaching to the colour of copper: these films all disappeared,
+leaving behind a brown stain: the parts, which were covered with the
+yellow film, resembling copper, exhibited, after some time, a dull
+bluish disagreeable matter.
+
+
+EXP. 9. LEAD.
+
+Having dipped a piece of silk in a solution of acetite of lead in
+distilled water, and dried it in the air, I exposed it to a stream of
+the gas: the silk became a little brown; but no other change could be
+observed.
+
+Another bit of silk was immersed in the same solution of lead, and
+exposed while wet to the gas; no sooner did it touch the silk, than
+a brown tinge diffused itself, like a passing shadow, over the whole
+surface of the silk, accompanied with a bright coat of reduced lead,
+which resembled silver.
+
+The brown tinge, which the silk acquires, resembles what happens when
+white paper is slightly singed by holding it near a burning body.
+
+This experiment was repeated on a quarter of a yard of silk in close
+vessels; and the silk was immediately covered with a coat of reduced
+lead, which had the brilliance of silver, and was attended with a brown
+tinge: the experiment was continued several hours, after which the
+silk was examined, and found to have lost all the argentine lustre,
+which was succeeded by a sparkling gray die: a sulphure of lead, or
+galena, being formed in the fibres of the silk. The same experiment was
+repeated on two other pieces of silk with the same result.
+
+This elastic fluid is so powerful a reducer of the metals, that if
+chambers, painted with white lead, have any considerable degree of
+moisture, and are exposed to its influence, the lead on the surface
+of the walls is reduced, and that chiefly where the humidity is most
+abundant: this effect, I observed, was produced, even at the distance
+of three chambers from the place, where the gas was formed: and the
+lead was reduced most evidently behind the window-shutters where the
+moisture of the wall was most considerable.
+
+It is a common experiment with chymists, in order to show the effects
+of this gas, to draw characters with a solution of sugar of lead on
+paper, which they place over a glass of water, containing some alkaline
+sulphure: in some time the characters drawn on the paper acquire a
+brown, or black colour, and become visible; which amuses the spectators.
+
+But it is surprising, that the metal has never been reduced in this
+experiment even by chance; and not less so, why _lead_ should be
+singled out for this trial of skill, in preference to other metals,
+which are equally affected by this gas.
+
+
+EXP. 10. TIN.
+
+A piece of silk was dipped in a solution of muriate of tin in distilled
+water, and dried in the air; the silk, on exposure to a current of the
+gas, scarce underwent any change, except a few brown specks dispersed
+over its surface.
+
+Another bit of silk was immersed in the same solution of tin, and
+exposed, while wet, to the gas, which no sooner touched the silk, than
+the surface opposed to the current was covered with reduced tin of
+great brightness: in some time various colours, as blue, orange, and
+a faint purple, appeared, and became more evident, as the reduction
+proceeded.
+
+The gas does not react on this metal so much as on mercury, and some
+other metals: part of the reduced tin remained permanent; but most of
+it disappeared, and left behind a disagreeable brown stain.
+
+
+EXP. 11. ARSENIC.
+
+A bit of silk was immersed in a solution of muriate of arsenic in
+distilled water, and dried in the air; it was then exposed to a stream
+of sulphurated hydrogen gas; but no change could be observed, except a
+faint tinge of citron yellow, which appeared on some parts of the silk.
+
+Another bit of silk was dipped in the same solution of arsenic, and
+exposed, while wet, to the gas: the arsenic was instantly reduced all
+over the surface, opposed to the gas, attended with a citron yellow
+colour.
+
+The gas soon reacted on the reduced arsenic; and nothing remained but
+the yellow stain.
+
+
+EXP. 12. BISMUTH.
+
+I dissolved some bismuth in nitric acid, and evaporated the solution
+to dryness; the salt was then dissolved in distilled water, and the
+solution deposited a copious white precipitate, but retained a quantity
+of the metal sufficient for these experiments.
+
+In this solution of bismuth a piece of silk was immersed, and dried
+in the air; it was then exposed to a stream of the gas: and the only
+visible effect produced was a very faint tinge of brown.
+
+Another bit of silk was dipped in the same solution of bismuth, and
+exposed wet to the gas: the silk was instantly covered with a bright
+pellicle of reduced bismuth, which soon lost most of its metallic
+lustre, being changed by the reaction of the gas to a sulphure.
+
+Mr. Kirwan in his experiments on hepatic air, found, that nitrous
+solution of bismuth, by mixture with a solution of hepatic air in
+water, changes to a reddish brown, and even assumes a metallic
+appearance.
+
+He also found that nitrates of silver, lead, and acetite of lead, were
+precipitated black.
+
+
+EXP. 13. ANTIMONY.
+
+A piece of silk, which was immersed in a solution of tartarite of
+antimony in distilled water, and dried in the air, was exposed to a
+stream of the gas; but suffered no visible change, except that a few
+specks of yellow, and orange appeared.
+
+A bit of silk was dipped in the same solution of antimony, and exposed,
+while wet, to the gas; the antimony was immediately reduced to its
+metallic form, attended with a deep orange colour: in some time, most
+of the metallic lustre disappeared, a few specks only remaining
+permanent.
+
+
+EXP. 14. IRON.
+
+A piece of silk was immersed in a diluted solution of sulphate of iron
+in distilled water, and dried; it was then exposed to a current of the
+gas; but underwent no visible change.
+
+Another bit of silk was dipped in the same solution of iron, and
+exposed, while wet, to the gas: the silk soon began to acquire a dark
+colour, which gradually increased, and, at length, became black,
+attended with an obscure metallic film. The silk was immersed in water,
+and deposited a bright metallic film on the surface of that fluid.
+
+
+EXP. 15. ZINC.
+
+A bit of silk, which was immersed in a diluted solution of sulphate of
+zinc in distilled water, and dried in the air, was exposed to a current
+of the gas; but underwent no visible change.
+
+Another bit of silk was dipped in the same solution of zinc, and
+exposed, while wet, to the gas; but no change in the colour of the
+silk, or sign of reduction could be perceived: the silk was then
+immerged in a glass of clear water, and transferred to its surface a
+bright metallic film of the colour of zinc.
+
+When a languid stream of gas was employed in these experiments, the
+films transferred to water were scarce visible.
+
+
+EXP. 16. ZINC.
+
+A piece of silk, which was immersed in a largely diluted solution of
+muriate of zinc, and dried in the air, was exposed to a brisk current
+of sulphurated hydrogen gas; but underwent no visible alteration.
+
+Another bit of silk was dipped in the same solution of zinc, and
+exposed, while wet, to the same brisk current of gas; instantly the
+surface of the silk, opposed to the gas, was covered with a bright coat
+of reduced zinc, attended with faint orange, and purple colours.
+
+Though the reduced zinc was quite evident; yet I had the curiosity to
+examine its appearance on the surface of water; I therefore immersed
+the silk in a glass of that fluid, and a bright metallic pellicle,
+which retained the texture of the silk, as wax retains the impression
+of a seal, was transferred to its surface.
+
+Another bit of silk, dipped in the same solution of zinc, and exposed
+for a longer time to the gas, lost its metallic lustre, the zinc being
+changed to a sulphure by the reaction of the gas.
+
+These experiments on sulphate, and muriate of zinc, show, that the
+acid, in which the metal is dissolved, influences the reduction in a
+remarkable manner.
+
+It is evident from the experiments related in this chapter,
+
+1. That water is essential to the reduction of metals by sulphurated
+hydrogen gas.
+
+2. That alcohol does not promote these reductions, without the aid of
+water.
+
+3. That sulphurated hydrogen gas does not reduce the metals by giving
+them phlogiston; nor by uniting with, and separating, their oxygen:
+for were either of these opinions well founded; metallic solutions
+in alcohol should be as effectually reduced by this gas, as metallic
+solutions in water are.
+
+When we consider, that alkaline sulphure reduces the metals by
+decomposing water; we have every reason to conclude, that sulphurated
+hydrogen gas reduces them in the same manner; since the same
+circumstances are necessary to both: the hydrure of sulphur, which
+constitutes the base of this gas, attracts the oxygen of the water,
+while the hydrogen of the latter unites, in its nascent state, with the
+oxygen of the metal, and reduces it.
+
+Hence it follows, that the hydrure of sulphur is oxygenated by the
+oxygen of the water, while the metal is restored to its combustible
+state.
+
+
+
+
+CHAPTER VI.
+
+REDUCTION OF METALS
+
+BY
+
+_PHOSPHORATED HYDROGEN GAS_.
+
+
+The effects of hydrogen gas and phosphorus on the reduction of metals
+in the fibres of silk have been treated of separately in the two
+first chapters; in this, I shall briefly treat of their effects, when
+combined in the form of phosphorated hydrogen gas, which from its high
+degree of inflammability seemed well adapted to this purpose.
+
+The spontaneous inflammation of this kind of air was known to M.
+Gengembre in 1783; and his experiments were published in Rosier’s
+journal for October 1785.
+
+Mr. Kirwan also, without any knowledge of M. Gengembre’s experiments,
+discovered the same air, which he calls phosphoric air, and published
+his experiments in the 76th volume of the Philosophical Transactions
+for 1786.
+
+This elastic fluid may be obtained by digesting a solution of potash in
+water with about half its weight of phosphorus in a heat sufficient to
+melt the latter; and may be received in glass vessels over mercury.
+
+But finding it inconvenient to introduce pieces of silk prepared for
+these experiments over mercury in close vessels, I exposed them to the
+gas, as it issued from the neck of the phial in which it was prepared.
+
+Part of this elastic fluid is spontaneously inflammable; but the other
+has not that property, which M. Gengembre imputes to the presence of
+carbonic acid; for the sake of brevity, I shall design the latter by
+the term _gas_, or _phosphorated hydrogen gas_; and the former by the
+epithets _spontaneously inflammable_, or _detonating_ gas, which, I
+found, does not burn or scorch silk wetted with metallic solutions.
+
+
+EXP. 1. GOLD.
+
+A piece of silk, which was immersed in a solution of nitro-muriate of
+gold in distilled water, and suspended in the air twelve hours to dry,
+was divided into three parts.
+
+One of these was exposed to a stream of phosphorated hydrogen gas: the
+silk became brown, and its margins, which happened to touch the sides
+of the phial, acquired a violet tinge: but no reduction took place.
+
+Another of these parts was wetted with alcohol, and exposed to the gas;
+but no signs of reduction could be perceived.
+
+The remaining part was wetted with water, and was no sooner exposed to
+the gas, than the reduction commenced over the whole silk, which was
+soon covered with a bright coat of reduced gold.
+
+
+EXP. 2. SILVER.
+
+A piece of silk was dipped in a solution of fused nitrate of silver in
+alcohol, and dried in the air: it was then divided into three parts.
+
+One of these, in order to dissipate moisture more effectually, was
+dried still better by a gentle heat, and exposed to the gas; the silk
+acquired a brownish dark colour: but no other alteration could be
+perceived.
+
+Another of these parts, which was also better dried by a gentle heat,
+was wetted with alcohol, and exposed to the gas: the silk acquired a
+dark brown colour; but no other change could be observed.
+
+The remaining part was wetted with water, and exposed to the gas: the
+reduction commenced immediately, and in a short time the silk was
+covered with reduced silver.
+
+
+EXP. 3. PLATINA.
+
+A piece of silk was immersed in a solution of nitro-muriate of the
+ore of platina in distilled water, and dried in the air; it was then
+divided into three parts.
+
+One of these parts was exposed to the gas; but suffered no visible
+change.
+
+Another of them was wetted with alcohol, and exposed to the gas; but
+underwent no perceptible change.
+
+The remaining part was wetted with water, and exposed to the gas: in
+about three or four minutes, a bright metallic film, of great lustre,
+appeared on the side of the silk, opposed to the gas.
+
+Another bit of silk, which was dipped in the same solution of platina,
+and exposed, while wet, to the spontaneously inflammable gas, was
+immediately covered with reduced platina, which being transferred
+to the surface of water looked bright as silver, and retained the
+impression of the silk.
+
+
+EXP. 4. MERCURY.
+
+A bit of silk, which was immersed in a solution of nitrate of mercury
+in distilled water, and dried in the air, was exposed to the gas; but
+underwent no visible change.
+
+Another bit of silk was dipped in the same solution of mercury, and
+dried: it was then wetted with alcohol, and exposed to the gas; but no
+sign of reduction appeared.
+
+Another bit of silk was immersed in the same solution of mercury, and
+exposed to the gas; the metal was instantly reduced all over the silk;
+a great variety of beautiful colours attending.
+
+A piece of silk was dipped in a solution of oxygenated muriate of
+mercury in distilled water, and dried in the air: it was then divided
+into two parts.
+
+One of these was exposed to the gas: no change appearing, it was wetted
+with alcohol, and exposed again to the gas; but still no alteration
+could be perceived.
+
+The remaining part was wetted with water, and was no sooner exposed to
+the gas, than the mercury was reduced over the whole silk. No colours
+attended the reduction.
+
+Mr. Kirwan introduced some precipitate per se to a small portion of
+phosphoric air: the precipitate soon grew black; and a white smoke
+appeared; in two days the precipitate remained solid; yet acquired a
+pale white colour, like that of steel: the air lost its spontaneous
+inflammability[17].
+
+
+EXP. 5. COPPER.
+
+A piece of silk, which was immersed in a solution of sulphate of copper
+in distilled water, and dried in the air, was divided into two parts.
+
+One of these was exposed to the gas; but no visible change occurred.
+
+The remaining part was wetted with water, and exposed to the gas: in
+a few minutes a brownish matter appeared in the silk; but nothing
+metallic could be seen: the silk was then dipped in a glass of clear
+water, and transferred a small white metallic pellicle to its surface.
+
+In another experiment, made with the spontaneously inflammable gas,
+a white metallic pellicle was immediately formed, attended with a
+brown stain; this pellicle resembled silver, or a white metal: but the
+gas soon reacted on it, and formed a disagreeable brown matter in the
+fibres of the silk.
+
+
+EXP. 6. LEAD.
+
+A bit of silk, which was dipped in a solution of acetite of lead in
+distilled water, and dried in the air, was exposed to the gas; but
+suffered no visible change.
+
+Another bit of silk was immersed in the same solution of lead, and
+exposed, while wet, to the gas; but nothing metallic could be seen: the
+silk, however, on immersion in water, transferred a few minute bright
+films to the surface of that fluid.
+
+In another experiment, made with the detonating gas, the reduced films
+were more evident.
+
+
+EXP. 7. TIN.
+
+A bit of silk, which was dipped in a solution of muriate of tin in
+distilled water, and dried in the air, was exposed to the action of the
+gas, without suffering any visible alteration.
+
+Another piece of silk was immersed in the same solution of tin, and
+exposed, while wet, to the gas; but no signs of reduction could be
+perceived: the silk was then immersed in water, and transferred a
+delicate metallic film to its surface.
+
+
+EXP. 8. ARSENIC.
+
+A bit of silk, which was immersed in a solution of muriate of arsenic
+in distilled water, and dried in the air, was exposed to the gas; but
+no change could be perceived.
+
+Another bit of silk, immersed in the same solution of arsenic, and
+exposed, while wet, to the gas, acquired in a few minutes a brown
+stain; but nothing metallic could be seen on the silk; which, however,
+on being dipped in water, transferred a very minute film of reduced
+arsenic to its surface.
+
+In another experiment, made with the detonating gas, the films of
+reduced arsenic were much more evident, of greater brilliance, and
+attended with a brown stain produced in the fibres of the silk.
+
+
+EXP. 9. BISMUTH.
+
+A piece of silk, which was dipped in a solution of nitrate of bismuth
+in distilled water, and dried in the air, was exposed to the gas; but
+no alteration could be observed.
+
+Another bit of silk was immersed in the same solution of bismuth, and
+exposed, while wet, to the gas: the silk in two or three minutes got a
+brown stain, which gradually became more intense; and a very delicate
+metallic film appeared: the silk was then immerged in water, and
+transferred a bright film of reduced bismuth to the surface of that
+fluid: the film retained the impression of the silk.
+
+
+EXP. 10. ANTIMONY.
+
+A bit of silk, immersed in a solution of tartarite of antimony in
+distilled water, and dried in the air, was exposed to the gas; but
+suffered no apparent change.
+
+Another piece of silk was dipped in the same solution of antimony, and
+exposed, while wet, to the gas; but no signs of reduction appeared:
+the silk was then immerged in water, to the surface of which, it
+transferred one small spangle.
+
+This experiment was repeated with the detonating gas, which with
+difficulty produced some sparkling films: the silk was immersed in
+water, and transferred the films to its surface.
+
+A white matter was visible in the fibres of the silk.
+
+
+EXP. 11. COBALT.
+
+A piece of silk, immersed in a solution of muriate of cobalt, and dried
+in the air, was exposed to the gas; but suffered no visible alteration.
+
+Another bit of silk was dipped in the same solution of cobalt, and
+exposed, while wet, to the gas: but no sign of reduction appeared; nor
+did the silk transfer a film to water.
+
+Another bit of silk was immersed in a solution of nitrate of cobalt,
+and exposed, while wet, to the detonating gas: no signs of reduction
+were visible for some time; but at length a few small spangles of
+the metal appeared on the silk, and were very brilliant, and when
+transferred to water, were still more so: a white matter could be seen
+in the fibres of the silk.
+
+
+EXP. 12. IRON.
+
+A bit of silk was immersed in a largely diluted solution of sulphate of
+iron in distilled water, and dried: it was then exposed to the action
+of the gas; but no alteration could be perceived.
+
+Another bit of silk was dipped in the same solution of iron, and
+exposed, while wet, to the gas: in a few minutes some parts of the silk
+acquired a light brown colour; but no reduced iron could be seen on the
+silk, which however transferred a very minute, and delicate film to
+water.
+
+This experiment was repeated with a strong detonating gas, and a very
+brilliant metallic film about four lines in diameter was reduced on the
+silk accompanied with a brown stain: but nothing like the black oxid of
+iron appeared.
+
+
+EXP. 13. ZINC.
+
+A bit of silk, which was immersed in a largely diluted solution of
+muriate of zinc, was exposed dry to the gas; but underwent no visible
+alteration.
+
+Another piece of silk was dipped in the same solution of zinc, and
+exposed wet to the gas; no signs of reduction appearing, the silk was
+immerged in water, and left a very minute metallic film on its surface,
+which could with difficulty be seen.
+
+The experiment was repeated with the detonating gas, and a very bright
+metallic film of zinc, four or five lines in diameter, was reduced on
+the silk.
+
+This experiment succeeded also with a largely diluted solution of
+sulphate of zinc.
+
+The silk, viewed by transmitted light, exhibited a brown stain beneath
+these films of iron and zinc.
+
+The experiments detailed in this chapter show,
+
+1. That water is essential to the reduction of metals by phosphorated
+hydrogen gas.
+
+2. That alcohol does not promote these reductions, without the aid of
+water.
+
+3. That this elastic fluid does not reduce metals by giving them
+phlogiston; nor by combining with, and separating, their oxygen; for
+were either of these suppositions true, it should reduce them as well
+with alcohol, as with water.
+
+After explaining the manner, in which sulphurated hydrogen gas reduces
+the metals; the mode of agency of phosphorated hydrogen gas is
+sufficiently obvious.
+
+The gas attracts the oxygen of the water, while the hydrogen of the
+latter unites, in its nascent state, with the oxygen of the metal, and
+reduces it.
+
+Hence it follows, that the hydrure of phosphorus, which constitutes the
+base of this gas, is oxygenated by the oxygen of the water, while the
+metal is, at the same time, restored to its combustible state.
+
+By hydrure of phosphorus is meant, a combination of hydrogen and
+phosphorus, containing less caloric, than is necessary to the gazeous
+state.
+
+
+
+
+CHAPTER VII.
+
+REDUCTION OF METALS
+
+BY
+
+_CHARCOAL_.
+
+
+Finding several combustible bodies, as hydrogen, phosphorus, sulphur,
+and combinations of these, capable of reducing the metals in the
+ordinary temperature of the atmosphere; I was desirous of knowing, if
+Charcoal also possessed that power.
+
+Charcoal may be applied with this view in several forms. M. Rouelle has
+observed that caustic fixed alkali dissolves a considerable quantity of
+this substance.
+
+Charcoal also exists in a very attenuated state in ether, alcohol, gum,
+&c.
+
+I have examined some of its effects on the reduction of metals, in
+these different forms, in which it probably exists combined with
+hydrogen, and also some of its effects in the solid form.
+
+
+EXP. 1. GOLD.
+
+A small bit of well burned charcoal was suspended by a thread in
+a phial containing a diluted solution of nitro-muriate of gold in
+distilled water: some air bubbles soon appeared on the charcoal: and
+in about two hours reduced gold was evident on its lower surface, and
+increased gradually, till the charcoal was nearly coated with gold of
+its proper colour.
+
+This experiment was repeated with a richer solution of gold; the
+reduction did not commence near so soon, nor was the quantity reduced
+so great, or brilliant, as in the preceding experiment.
+
+
+EXP. 2. GOLD.
+
+A small bit of charcoal was suspended in a solution of gold in
+ether: an effervescence immediately commenced, and continued for a
+considerable time: but the solution suffered no change of colour; nor
+was there a particle of the gold reduced.
+
+I should not be surprised, if the gold were reduced in this experiment,
+as charcoal contains a large quantity of water, which it powerfully
+attracts from the surrounding air: however not a vestige of reduced
+gold could be perceived.
+
+Bits of charcoal were suspended in the same manner in most of the
+metallic solutions treated of in this essay: no change was perceived on
+those immersed in solutions of arsenic, manganese, and fused nitrate of
+silver in water: but a bit immersed in a solution of the same nitrate
+in alcohol, had parts of it covered with bright sparkling particles,
+which seemed to vegetate from the charcoal, and were evidently reduced
+silver: for they were not soluble in water, on the surface of which the
+bit of charcoal deposited some small spangles of great lustre. The bits
+immersed in solutions of sulphate of iron and zinc exhibited some very
+faint signs of reduction.
+
+But these experiments were not repeated, nor sufficiently varied, to
+enable us to form a just opinion of the power of charcoal in reducing
+metals in this way.
+
+A small quantity of charcoal, reduced to fine powder, was digested
+several days in a strong solution of caustic potash in alcohol; the
+phial was frequently shaken to promote the solution.
+
+Some of the clear solution, which was of a reddish colour, was poured
+into a phial for use.
+
+
+EXP. 3. GOLD.
+
+A few drops of this solution of charcoal, or carbone, were applied to a
+bit of silk; after the alcohol evaporated, a solution of gold in ether
+was dropped on, and immediately produced a brown, which, in about half
+an hour, was changed to a purple hue, owing to water attracted from the
+air; but no other sign of reduction appeared.
+
+Another bit of silk was immersed in the solution of carbone, and when
+the alcohol evaporated, a few drops of an aqueous solution of gold
+were applied; a brown stain was instantly formed; the silk was kept wet
+with water; the stain gradually assumed a purple tinge, and, in about
+five minutes, some reduced gold of its proper splendour, and colour,
+appeared: and in some time after every part of the silk, to which the
+solutions of carbone and gold were applied, was coated with reduced
+gold, which remained permanent. During the experiment, it is necessary
+to keep the silk constantly wet with water.
+
+If the solution of gold be applied before the alcohol evaporates,
+a black precipitate is formed, along with the brown stain. In an
+experiment made in this manner, a metallic film, whitish, and obscure,
+appeared in the beginning; but soon vanished: and in some time after
+the gold was reduced of its proper colour; and a speck of ruby red
+appeared on the margin.
+
+The silk viewed by transmitted light presented various colours, as
+purple, blue, and some green.
+
+
+EXP. 4. SILVER.
+
+A few drops of the solution of carbone were applied to a bit of silk;
+when the alcohol evaporated, a solution of fused nitrate of silver in
+alcohol was applied: a light brown stain was immediately produced in
+the silk; but no reduced silver could be seen.
+
+The solution of carbone was applied to another bit of silk, and when
+the alcohol evaporated, an aqueous solution of fused nitrate of silver
+was dropped on: a brown stain was instantly formed, and, in about ten
+minutes, minute films of reduced silver were visible.
+
+The silk was kept wet with water during the experiment; and the brown
+stain was gradually changed to black. In some little time the metallic
+films disappeared.
+
+If the solution of silver be applied to the silk, before the alcohol
+evaporates, black and brown precipitates are immediately formed; and
+commonly no reduced silver can be seen; but sometimes very minute films
+appear.
+
+
+EXP. 5. PLATINA.
+
+To a bit of silk, which was immersed in a solution of nitro-muriate of
+platina in distilled water, and dried in the air, a few drops of the
+solution of carbone were applied; but no visible change was produced.
+
+Another bit of silk was dipped in the solution of carbone, and when
+the alcohol evaporated, a few drops of the solution of platina were
+applied: a yellow precipitate was immediately formed, and, in about ten
+minutes delicate films of reduced platina were visible: these metallic
+films soon vanished; and nothing but a yellow stain and the precipitate
+remained.
+
+A bit of calico, on which this experiment was repeated, transferred a
+bright film of reduced platina to the surface of water.
+
+During the experiments, the silk and calico were kept wet with water.
+
+
+EXP. 6. MERCURY.
+
+On a bit of silk, which was immersed in a solution of oxygenated
+muriate of mercury in distilled water, and dried in the air, a little
+of the solution of carbone was dropped; but the silk underwent no
+visible change.
+
+Another bit of silk was dipped in the solution of carbone, and, when
+the alcohol evaporated, a little of the same solution of mercury was
+applied; a yellow precipitate was immediately formed; and soon after
+small films of reduced mercury appeared on the margin of the stain.
+
+This experiment was repeated with a solution of nitrate of mercury, and
+the reduction of the metal was very evident on the margin of the stain,
+which was black: the precipitate on the bit of silk was of the colour
+of sulphur.
+
+
+EXP. 7. COPPER.
+
+To a bit of calico, which was immersed in a solution of acetite of
+copper in distilled water, and dried in the air, a few drops of the
+solution of carbone were applied; but no visible change was produced.
+
+On another bit of calico, which was dipped in the same solution
+of copper, some of the solution of carbone was dropped: the calico
+acquired a slight tinge of brown; it was kept wet with water; and, in
+about twenty minutes, several white metallic films were evident.
+
+A bit of silk, on which this experiment was made, acquired a beautiful
+red colour, similar to the ruby red, with which copper tinges glass,
+and depending on the same cause, viz. the quantity of oxygen combined
+with the metal.
+
+
+EXP. 8. LEAD.
+
+A bit of white calico was immersed in a solution of acetite of lead in
+distilled water, and dried in the air: then a few drops of the solution
+of carbone were applied; but no visible alteration took place.
+
+On another bit of the same calico, which was dipped in the solution
+of carbone, a little of the same solution of lead was dropped; and
+in a few seconds films of reduced lead, bright as silver, appeared:
+the calico was then immerged in water, and transferred a continuous
+pellicle of reduced lead to its surface.
+
+This experiment was often repeated both on silk, and calico: sometimes
+the lead is reduced in an instant; but at other times five or six
+seconds elapse, before any reduced lead becomes visible.
+
+I also found, that a solution of potash in alcohol reduces lead;
+but not so soon, or effectually, or in such quantity, as the former
+solution does; but it is evident, that these solutions differ only in
+the quantity of carbone, which they contain.
+
+
+EXP. 9. TIN.
+
+To a bit of calico, which was immersed in a solution of muriate of
+tin in distilled water, and dried in the air, some of the solution of
+carbone was applied: but no signs of reduction appeared, nor was the
+colour of the calico much altered.
+
+On another bit of calico, which was dipped in the solution of carbone,
+some of the same solution of tin was dropped: a white precipitate was
+instantly formed, attended with bright films of reduced tin: the calico
+was immerged in water; and left a bright metallic film on the surface
+of that fluid.
+
+The same experiment succeeds on silk.
+
+
+EXP. 10. BISMUTH.
+
+A piece of silk, which was immersed in a solution of nitrate of
+Bismuth in distilled water, and dried in the air, suffered no visible
+alteration, on applying the solution of carbone.
+
+To a bit of calico, which was dipped in the solution of carbone, a few
+drops of the same solution of bismuth were applied; and immediately
+films of reduced bismuth were evident. The calico was immerged in
+water, and transferred a bright metallic film to its surface.
+
+This experiment succeeded also on silk.
+
+
+EXP. 11. ARSENIC.
+
+A bit of silk was immersed in a solution of muriate of arsenic in
+distilled water, and dried in the air, then a little of the solution of
+carbone was dropped on the silk; but no visible alteration took place.
+
+Another bit of silk was dipped in the solution of carbone, and when the
+alcohol evaporated, some drops of the same solution of arsenic were
+applied; and in a short time a few minute metallic films were visible
+on the silk, which, when transferred to water, were still more so.
+
+Tartarite of antimony, treated in the same manner, transferred a very
+delicate film, scarcely visible, to the surface of water.
+
+
+EXP. 12. IRON.
+
+A bit of calico, which was dipped in a largely diluted solution of
+sulphate of iron, and dried in the air, suffered no perceptible change,
+on applying the solution of carbone, except a slight tinge of brown.
+
+Another bit of calico was immersed in the same solution of iron, and
+placed on a bit of deal board, a few drops of the solution of carbone
+were then applied: the calico was kept constantly wet with water, and
+in about fifteen minutes films of reduced iron were visible: the calico
+was immersed in water, and left a bright metallic film on its surface.
+
+
+EXP. 13. ZINC.
+
+To a bit of silk, which was dipped in a largely diluted solution of
+muriate of zinc, and dried in the air, a few drops of the solution of
+carbone were applied; but scarce any alteration of colour, or other
+visible change, occurred.
+
+A piece of calico was immersed in the same solution of zinc, and placed
+on a bit of thin deal board, a few drops of the solution of carbone
+were then applied: the calico was kept constantly wet with water; and
+in about fifteen minutes films of reduced zinc were evident: the calico
+was immerged in water, and transferred a very bright metallic film of
+the colour of zinc to its surface.
+
+I also reduced muriate of cobalt in this manner.
+
+
+EXP. 14. MANGANESE.
+
+To a bit of silk, which was dipped in a diluted solution of nitrate of
+manganese, and dried in the air, some drops of the solution of carbone
+were applied; but nothing appeared, except a brown stain.
+
+Another bit of silk was immersed in the solution of carbone, when the
+alcohol evaporated, a few drops of the same solution of manganese were
+applied: a brown stain was soon produced; the silk was kept wet with
+water, and in about twenty minutes films of reduced manganese of a
+bluish white colour were evident on the silk.
+
+This experiment did not succeed with a strong solution of nitrate of
+manganese.
+
+The same experiment succeeds also on linen, and calico, both with
+nitrate, and sulphate of manganese; the reduction is attended with
+violet, and purple, colours, such as this metal imparts to glass,
+and other substances, in which it exists combined with different
+proportions of oxygen: this difference is the cause of the different
+colours, which solutions of manganese assume.
+
+The bright films of reduced manganese soon disappear, the cause of
+which has been explained in the first chapter of this essay: the
+explanation there offered is confirmed by the following facts.
+
+“Regulus of Manganese,” says Mr. Bergman, “when well fused generally
+persists in a dry place, but sometimes undergoes spontaneous
+calcination, and falls down in a brownish black powder.
+
+“Moisture, but particularly the access of aerial acid, assists this
+operation. A small piece, put into a dry bottle, well corked, remained
+perfect for the space of six months, but afterwards, exposed to the
+open air of a chamber for two days, contracted a browness on its
+surface, together with so much friability as to crumble between the
+fingers. The internal parts, however, retained an obscure metallic
+splendour, which disappeared in a few hours[18].”
+
+I shall now relate a few experiments made with ether, alcohol, and gum.
+
+
+EXP. 15. GOLD.
+
+I evaporated a solution of gold in nitro-muriatic acid to dryness,
+and dissolved the salt in pure alcohol: the solution was poured into
+a phial carefully dried in hot sand, and rinced with pure alcohol:
+the solution filled about ¾ of the phial, which was carefully corked,
+and though it was nine months exposed to the gray light, no films of
+reduced gold appeared.
+
+Part of the same solution was poured into a phial, and diluted with
+water; films of reduced gold soon appeared.
+
+
+EXP. 16. GOLD.
+
+A phial half filled with a solution of gold in sulphuric ether was
+exposed nine months to the gray light; but no films of reduced gold
+were produced.
+
+On a bit of silk, which was dipped in part of the same solution of
+gold, and exposed to the gray light, and kept wet with water, reduced
+gold appeared in the space of a few hours.
+
+
+EXP. 17. GOLD.
+
+I mixed an aqueous solution of gold with a solution of gum arabic in
+distilled water, in such proportion, as to prevent the solution from
+spreading in the silk.
+
+With this solution I drew several stripes on a piece of silk, and
+exposed it to the gray light of a chambre: in some time the gold was
+reduced attended with blue, and purple, colours.
+
+Similar stripes were drawn on another piece of silk, which, after the
+stripes became sufficiently dry, was placed over the vapour of hot
+water; and in about fifteen minutes the gold was reduced in a beautiful
+manner.
+
+This solution was applied to another bit of silk, which, after it
+became sufficiently dry, was placed between the leaves of a blank book,
+to exclude the action of light; the gold, after some time, was reduced.
+
+I found that small stripes, and spots, made with this solution, were
+reduced by breathing on them for some time.
+
+Sugar also, mixed with the solution of gold, promotes the reduction;
+but not so well as gum.
+
+A bit of silk was dipped in a solution of nitrate of silver in
+distilled water, and exposed, while wet, to the smoke of a common fire;
+in a short time reduced silver appeared.
+
+The following inferences are deducible from the experiments related in
+this chapter.
+
+1. Charcoal is capable of reducing the metals in the ordinary
+temperature of the atmosphere.
+
+2. Water is essential to the reduction of metals by charcoal: for these
+experiments prove, that the reduction cannot be effected without water.
+
+3. Charcoal does not reduce the metals by giving them phlogiston; nor
+by uniting with, and separating, their oxygen; for were either of these
+opinions true, metallic solutions in ether, and alcohol, should be as
+effectually reduced by charcoal, as metallic solutions in water are.
+
+4. Ether, and alcohol do not promote the reduction of metals without
+the aid of water: but when this is present in sufficient quantity, they
+effect the reduction, in the same manner, that charcoal, and other
+combustible bodies do.
+
+It is evident then that charcoal reduces the metals by decomposing
+water; which seems to be effected in the following manner.
+
+The carbone of the charcoal attracts the oxygen of the water, while the
+hydrogen of the latter unites, in its nascent state, with the oxygen of
+the metal, and reduces it.
+
+Hence it follows that the carbone is oxygenated by the oxygen of the
+water, and forms carbonic acid, while the metal is restored to its
+combustible state.
+
+This explanation is supported by the following fact: M. Gengembre
+has observed, that if charcoal be immersed in water, and kept at a
+temperature of 30 degrees of the thermometer of M. De Reaumur, the
+water is gradually decomposed, and inflammable gas is formed[19].
+
+That charcoal effects the reduction of metals, in high degrees of heat
+also, by decomposing water, is evident from the following observations.
+
+The great force with which charcoal attracts water is a fact
+sufficiently established; Dr. Priestley is so convinced of this, that
+he expresses himself in the following strong terms. “I did not know,
+nor could believe the powerful attraction, that charcoal, or iron,
+appear to have for water; when they are intensely heated, they will
+find, and attract it in the midst of the hottest fire through any pores
+in the retort[20].”
+
+Now since water is essential to the reduction of metals in low degrees
+of heat; and since that fluid is always present, when metals are
+reduced by charcoal in high degrees of heat; it is manifest, that
+charcoal acts in the same manner in both these temperatures; and since
+water is easily, and instantly, decomposed by charcoal at a red heat,
+as the Antiphlogistians themselves allow; it clearly follows that their
+theory of metallic reduction is erroneous: for since the water is
+instantly decomposed by the charcoal, it is a necessary consequence,
+that its carbone must unite with the oxygen of the water, while the
+hydrogen of the latter unites, in its nascent state, with the oxygen
+of the metal, and reduces it, forming a new quantity of water equal to
+that decomposed: this new quantity of water may be decomposed in its
+turn: so that a thimble full of water would be sufficient to reduce any
+quantity of metal; provided the water were prevented from escaping, and
+time enough allowed.
+
+Beside this source of water, the air of the atmosphere, which
+contributes to support the fire is an inexhaustible magazine of water:
+and the hotter the air is, the more water it holds in solution; as
+M. Le Roy has demonstrated[21]. Moreover all metallic oxids and ores
+contain a large proportion of water.
+
+From this view it appears, that the manner, in which charcoal, and
+other combustible bodies, effect the reduction of metals, is by
+assisting to decompose water, the hydrogen of which is therefore the
+only reducer of the metals.
+
+In order to point out the difference between this opinion, and that of
+the Antiphlogistians, I shall present the reader with M. Lavoisier’s
+idea of metallic reduction.
+
+“It can not be doubted,” says that celebrated chymist, “that charcoal
+at a red heat takes oxygen from all metallic substances: this is a fact
+against which no exception can be made: and it is the foundation of the
+whole theory of metallic reduction.”
+
+But the experiments in this essay demonstrate, that this assertion
+is erroneous in every instance of metallic reduction: for so far is
+it from being true, that charcoal takes oxygen from all metallic
+substances, that it never does so in one single instance; since its
+carbone always unites with the oxygen of the water, the hydrogen of
+which unites immediately to the oxygen of the metal, and reduces it.
+
+“But this action of charcoal on oxygen,” adds M. Lavoisier, “this
+property, which it possesses of taking it from metallic subsubstances,
+is not so strong in the cold, as at a red heat, since we are
+unacquainted with any metallic revivification effected by charcoal
+without heat[22].”
+
+It is evident that this mode of reasoning is no longer of any weight;
+since charcoal does reduce metals in the ordinary temperature of the
+atmosphere.
+
+The reason charcoal is more powerful in high degrees of heat, than
+other reducers of the metals, is its great fixity in the fire, and
+the immense force, with which it attracts, and imprisons water in its
+pores: thus preventing its escape till it be decomposed by an affinity,
+which is much more complex than has been hitherto imagined.
+
+Another reason of the superior power of charcoal in metallic reduction
+is, that it forms a volatile elastic fluid with the oxygen of the
+water, which flies off; and consequently does not react on the metal,
+or disturb, or impede, by its presence, the action of the reducing
+powers: advantages that phosphorus, or any other combustible substance,
+which forms a fixed acid, that reacts on the metal, can never possess.
+
+
+
+
+CHAPTER VIII.
+
+REDUCTION OF METALS
+
+BY
+
+_LIGHT_.
+
+
+The next substance, I shall treat of, is Light, which seems well
+adapted to illustrate the theory of metallic reduction; as in
+experiments made with this substance, water can be more effectually
+excluded, than in trials with any other reducer of the metals.
+
+Before any decisive experiments could be made on light, or indeed
+any other reducer of the metals, it is obvious that we should first
+ascertain the effects of water itself in the ordinary temperature of
+the atmosphere: to determine this point, the two following experiments
+were made.
+
+
+EXP. 1. GOLD.
+
+A piece of silk was immersed in an aqueous solution of nitro-muriate
+of gold, and suspended in a phial over water: the phial was corked,
+covered with black silk, and placed in a dark closet, to prevent the
+action of light. The experiment was continued from the 20th of July
+to the 20th of October, during which time the silk was frequently
+observed, and found to continue moist: but no alteration could be
+perceived, except that the yellow colour, which the solution of gold
+gave the silk, was changed to a light brown.
+
+The silk was now taken out of the phial, and a solution of phosphorus
+in ether applied to it: shortly after, a white metallic film appeared:
+the silk was then kept wet with water, and in some time, reduced gold
+of its proper colour appeared.
+
+
+EXP. 2. SILVER.
+
+A bit of silk, which was dipped in an aqueous solution of nitrate of
+silver, was suspended in a phial over water, and placed in a dark
+closet, from the 20th of July to the 20th of October, and examined from
+time to time; but no alteration could be observed; its white colour
+continued pure, and unchanged.
+
+The silk was now taken out of the phial, and the silver was immediately
+reduced by means of a solution of phosphorus in ether.
+
+Hence it appears, that water alone has not the power of reducing metals
+in the ordinary temperature of the atmosphere.
+
+
+EXP. 3. GOLD.
+
+On the 24th of July a piece of silk was immersed in a solution of
+nitro-muriate of gold in water, and dried by a gentle heat; it was
+then suspended in a window, exposed to the sunbeams, as much as
+possible: no change was perceived on it, till the 26th, when the margin
+of the silk began to assume a purple tinge, which increased gradually,
+and on the 29th exhibited a few obscure specks of reduced gold on the
+side of the silk opposed to the light.
+
+The purple tinge continued to increase, and the yellow, which the
+solution of gold gave the silk, decreased gradually, till on the 27th
+of August the colour was a mixture of purple, and light brown.
+
+The reduction of the gold seemed to keep pace with these changes of
+colour, and was very evident on some parts of the silk even in the gray
+light; but much more so in sunshine: these changes were observed till
+the 20th of October; the experiment was then discontinued; and scarce
+any reduced gold could be seen on the side of the silk not opposed to
+the light.
+
+That this slight reduction of the gold, and changes of colour in the
+silk, depended on water absorbed from the air of the chambre, will
+appear from the following experiments.
+
+
+EXP. 4. GOLD.
+
+A bit of silk, which was dipped in the solution of gold employed in
+the preceding experiment, was dried, and suspended in a crystal phial
+over dry carbonate of potash: the phial was then corked, and further
+secured from external humidity by covering the cork with wax: it was
+now placed in a dark closet 24 hours, that the carbonate of potash
+might have sufficient time to attract all the moisture, it could, from
+the air of the phial, before exposing it to the action of light.
+
+The phial was then placed in a window, exposed, as much as possible,
+to the solar light, from the 24th of July to the 20th of October, and
+carefully observed: the same side of the silk was always opposed to
+the light, and had the yellow tinge, which the solution of gold gave,
+altered to a brownish yellow: but the other side of the silk suffered
+no visible change whatever; nor could any purple tint, or the smallest
+vestige of reduced gold be perceived.
+
+Another bit of silk, which was immersed in the same solution of gold,
+and dried by a gentle heat, was suspended over some dry carbonate of
+potash, contained in a crystal phial covered with black silk, and
+placed in a dark closet, during the same space of time, underwent no
+visible change whatever.
+
+Both these bits of silk were now taken out of the phials, and the gold
+was instantly restored to its metallic splendour by means of water and
+a solution of phosphorus in ether: a proof that the nitro-muriate of
+gold, in these bits of silk, suffered no change, during that space of
+time.
+
+
+EXP. 5. GOLD.
+
+A piece of silk, which was dipped in the same solution of gold, and
+placed on a china plate exposed to the sunbeams, was kept moderately
+wet with water during the experiment: the first alteration observed
+was, that the yellow colour of the silk began to change to a faint
+green, succeeded by a purple tinge, which in about fifteen minutes
+exhibited some particles of reduced gold: soon after the threads of the
+silk, which acquired this purple tint, were gilded with gold; and, in
+about an hour, the whole of the silk was covered with a superb coat of
+reduced gold, exhibiting the texture of the silk in a beautiful manner.
+
+The purple tinge, which attended the reduction verged in some parts on
+red, and in others on blue.
+
+This experiment, which is very amusing, I have repeated times
+unnumbered: and when the sun is powerful, and the solution of gold
+properly prepared, and of due strength, the coat of reduced gold is so
+bright, and dazzling, as to distress the eye of the beholder.
+
+I find, that the best way of preparing a solution of gold for
+this purpose is to separate the oxid of gold from its solution in
+nitro-muriatic acid by means of good ether.
+
+The silk may be dipped in this solution, and when the ether
+evaporates, kept moderately wet with distilled water.
+
+It was with this solution in ether that I first reduced gold in the
+fibres of silk, and it was by means of the same, I discovered, that
+water was a necessary condition in these reductions by light.
+
+
+EXP. 6. GOLD.
+
+A bit of silk, which was dipped in a solution of nitro-muriate of gold
+in alcohol, and placed on a china saucer, exposed to the sunbeams, was
+kept wet with alcohol for the space of an hour; but no change even
+in the colour, which the solution of gold gave the silk, could be
+perceived.
+
+The alcohol diffused the solution of gold unequally through the silk:
+the rays of the sun being intercepted, suspended the experiment:
+there was no sunshine on the following day: on the third day the silk
+was again exposed to the sunbeams, and kept wet with alcohol, which
+extracted a yellow tincture; a proof that the gold in the silk suffered
+no degree of reduction: the sun shone pretty strong for an hour, or
+more; and, at length, a faint tinge of purple, followed by some reduced
+gold, appeared.
+
+The preceding experiments leave us no room to doubt, that the purple
+tinge and the small quantity of reduced gold, that appeared in this
+experiment, depended on water attracted from the air, or deposited in
+the silk by the alcohol during its evaporation.
+
+Mr. Scheele reduced a solution of nitro-muriate of gold in water by
+exposing it in a phial for a fortnight to the rays of the sun[23].
+
+Mr. Lewis also made many experiments on the staining of marble, and
+other substances with metallic solutions, and light[24].
+
+
+EXP. 7. SILVER.
+
+A piece of silk, which was immersed in a solution of nitrate of silver
+in water, was dried by a gentle heat, and exposed to the light of the
+sun as much as possible in the window of a chambre from the 20th of
+July to the 20th of October.
+
+In less than an hour the silk acquired a reddish brown colour: next day
+the colour became more intense, and gradually increased, till, on the
+third day, it bordered on black, which increased slowly: at length part
+of it became gray, and a few minute particles of reduced silver could
+be distinguished: the black tinge gradually disappeared, and the silk
+was of a reddish brown colour: the reduced silver had a gray cast.
+
+The following experiments demonstrate, that the changes of colour, and
+the few particles of semireduced silver depended on water attracted
+from the atmosphere.
+
+
+EXP. 8. SILVER.
+
+A bit of silk was immersed in part of the same solution of nitrate of
+silver in water, and dried in the dark: the silk retained its white
+colour: it was then suspended over dry carbonate of potash in a crystal
+phial, which was corked, and secured from the ingress of moisture by
+covering the cork with wax.
+
+The phial was left in a dark closet 24 hours, that the salt might
+imbibe as much moisture as possible from the silk, and air.
+
+The phial was then placed in a window, exposed, as much as possible, to
+the rays of the sun, from the 24th of July to the 20th of October: the
+silk scarcely suffered any visible change, except a very faint tinge of
+reddish brown; which was best seen by transmitted light; for the silk
+viewed by reflected light appeared nearly white: but that even this
+tinge, slight as it was, depended on a minute quantity of moisture,
+which the carbonate of potash was unable to extract, appears from the
+next experiment.
+
+
+EXP. 9. SILVER.
+
+A piece of silk was dipped in a solution of fused nitrate of silver in
+alcohol, and carefully dried: it was then suspended over a quantity of
+concentrated sulphuric acid in a crystal phial, which was coated with
+a double fold of black paper, and gum arabic, reaching somewhat above
+the level of the acid, to prevent the light from acting on it: the
+phial was corked, and to exclude moisture more effectually, the cork
+was covered with wax.
+
+The phial was now placed in a dark closet 24 hours, that the humidity
+of the enclosed silk and air might be attracted by the acid: it was
+then placed in a window, exposed as much as possible to the rays of
+the sun, from the 19th of July to the 26th of October: but the silk
+underwent no visible change whatever: its white colour remained pure,
+and unaltered.
+
+The silk, at the end of this period, was taken out of the phial, and
+wetted with water: a solution of phosphorus in ether was then applied
+to it; and instantly the metallic splendour of the silver appeared.
+
+Another bit of silk, which was immersed in a solution of nitrate
+of silver in water, and dried in the dark, was suspended over dry
+carbonate of potash in a phial, and placed in a dark closet about two
+months; the silk underwent no visible alteration whatever; its white
+colour remained pure.
+
+I was desirous of knowing, if the nitrate of silver in this bit of silk
+suffered any change, that might render it incapable of reduction: I
+therefore took it out of the phial, and divided it into two parts: one
+of these was wetted with water, and the silver was instantly reduced by
+a solution of phosphorus in ether. The other part, which was suspended
+in a window, exposed to the air of the chamber, and rays of the sun,
+soon acquired a reddish brown colour.
+
+Hence it is evident, that these changes of colour indicate partial
+reductions of the metal; and that they never happen without the
+presence of water.
+
+
+EXP. 10. SILVER.
+
+A bit of silk, which was dipped in a solution of nitrate of silver in
+water, was placed on a China saucer, exposed to the rays of the sun,
+and kept moderately wet with water: in a few minutes the white colour
+of the silk was changed to a reddish brown, which by degrees became
+darker; and, in about three or four hours, though the solar rays were
+often languid, and intercepted, acquired a blackish gray colour,
+most of the reddish brown having disappeared: next day there was no
+sunshine; but towards the evening particles of reduced silver were
+visible on the side of the silk opposed to the light.
+
+
+EXP. 11. SILVER.
+
+A bit of silk, which was immersed in a solution of nitrate of silver
+in alcohol, and exposed to the beams of the sun, as in the preceding
+experiment, was kept moderately wet with alcohol; but resisted the
+action of the light much longer than the preceding: however, in some
+time, specks, and lines, of a reddish brown, began to appear on some
+parts of the silk: next day, though there was no sunshine, the reddish
+brown colour increased a little: on the third day, it became more
+intense; but no black, or gray colour, or particle of reduced silver,
+could be observed.
+
+Whoever compares this with the preceding experiments, can have no
+doubt that the changes of colour, which appeared in this experiment,
+depended on water attracted from the air, or deposited in the silk by
+the alcohol during its evaporation.
+
+The experiments detailed in this Chapter, prove beyond the power of
+contradiction,
+
+1. That water is essential to the reduction of metals by light: for
+these experiments demonstrate, that the reduction can not take place
+without water, and that it is always in proportion to the quantity of
+that fluid present.
+
+2. That light does not reduce metals by giving them phlogiston, as
+Messrs. Macquer and Scheele supposed; for were this opinion true, light
+should reduce them without the aid of water, and as well with alcohol
+as with water.
+
+3. Light does not reduce metals by fusing and expelling their oxygen,
+as the antiphlogistians imagine; for were this its mode of agency, the
+reduction should happen without the assistance of water, and as well
+with alcohol as with water.
+
+4. Light is a combustible body; for it acts like hydrogen, phosphorus,
+sulphur, and charcoal, in the reduction of metals.
+
+Since water then is essential to the reduction of metals by light,
+and since light does not reduce metals by giving them phlogiston,
+nor by fusing, and expelling their oxygen, it follows, that the
+water is either decomposed, or that it unites with metallic earths,
+and constitutes their phlogiston, or that it unites with, and
+separates their oxygenous principle: but as the two last suppositions
+are inadmissible, it is obvious that light reduces the metals by
+decomposing water.
+
+After explaining the manner in which other combustible bodies reduce
+the metals by decomposing water; it will not be difficult to explain
+how light too produces the same effect.
+
+But in order to facilitate the explanation, it must be premised,
+
+1. That it is a law of attraction, that, when any body is deprived, to
+a certain degree, of another, for which it has a strong affinity, the
+attraction of the former for the latter is much increased.
+
+2. That light has a strong attraction for oxygen, or the base of vital
+air.
+
+3. That when oxygen is condensed, and fixed in any substance, it
+contains much less light, and caloric, than it does in the gazeous
+state.
+
+4. That the oxygenous principle exists in water in this condensed
+state, and consequently has a strong attraction for light.
+
+Therefore, when light reduces the metals, it attracts the oxygen of the
+water, while the hydrogen of the latter unites, in its nascent state,
+to the oxygen of the metal, and reduces it, forming at the same time a
+quantity of water equal to that decomposed.
+
+Hence it follows that the light is oxygenated, and changed into vital
+air, while the metal is restored to its combustible state.
+
+
+
+
+CHAPTER IX.
+
+REDUCTION OF METALS
+
+BY
+
+_ACIDS_.
+
+
+It is well known that solutions of gold throw up films of the reduced
+metal to the surface of the fluid, and sides of the phials that contain
+them.
+
+It has been shown, chap. 7th, that this effect depends on the presence
+of water, which is further illustrated by the following experiments.
+
+
+EXP. 1. SILVER.
+
+A dram of saturated solution of nitrate of silver in distilled
+water was mixed with half an ounce of vinegar, in a few minutes, a
+precipitate was formed: the whole was then poured on a filter, and
+washed with distilled water: the precipitate acquired a bluish gray
+metallic appearance: the liquor, which passed the filter, got a brown
+colour, and became blackish: next day bright films of reduced silver
+floated on the liquor; and in some months after, a considerable part
+of the inner surface of the phial was coated with reduced silver.
+Distilled vinegar did not produce this effect.
+
+
+EXP. 2. PLATINA.
+
+If a solution of the ore of platina in nitro-muriatic acid be
+evaporated to dryness; and the salt dissolved in water, films of a
+livid white metallic appearance are thrown up to the surface.
+
+
+EXP. 3. TIN.
+
+Some tin, which was dissolved in a china cup in muriatic acid, and
+evaporated to dryness, was dissolved in distilled water; immediately
+white metallic films appeared on the surface of the liquor; and after
+some hours, the whole surface of the solution was covered with a
+continuous metallic pellicle, which reflected all the colours of the
+rainbow, in a beautiful manner.
+
+
+EXP. 4. MERCURY.
+
+Mr. Bergman says, “calcined mercury is reduced by digestion in acid of
+salt; but the cause has not yet been sufficiently explored[25].”
+
+As this reduction of mercury by muriatic acid is doubted of by some; I
+made the following experiment.
+
+A quantity of precipitate _per se_ was put into a china cup, placed
+on hot sand, and some muriatic acid was poured on it: the oxid was
+gradually dissolved, and the digestion continued, till the acid was
+nearly evaporated: some distilled water was then poured on the salt,
+and minute films of a bright metallic appearance floated on the surface.
+
+A nitrate of mercury was evaporated to dryness; the salt acquired a
+slight tinge of yellow; the cup was removed from the hot sand, and
+some water poured on the salt: immediately bright films of reduced
+mercury appeared; and in about three or four hours the whole surface
+of the solution was covered with a metallic pellicle, parts of which
+had the colour and splendour of the metal; and other parts reflected a
+wonderful variety of the most beautiful colours.
+
+
+EXP. 5. ARSENIC.
+
+A quantity of white oxid of arsenic and muriatic acid was digested in
+the same manner in a china cup; a smart heat was continued, till most
+of the acid evaporated, and left behind a mass of the consistence of
+tar: the surface of which had a gray appearance; after it cooled, some
+distilled water was poured on, it diffused a disagreeable smell, and
+films of reduced arsenic were thrown up to the surface; these were for
+some time remarkably bright, but soon became of a dull gray colour,
+owing to the rapid tendency of this metal to spontaneous calcination.
+
+
+EXP. 6. MANGANESE.
+
+Some concentrated sulphuric acid was poured on a quantity of the black
+oxid of manganese in a china cup, placed on hot sand: an effervescence
+was visible, but no sulphurous acid gas was exhaled: the cup was
+removed from the sand, before any perceptible quantity of the acid
+evaporated: then some water was poured on the mixture: and instantly
+the surface of the fluid was covered with very brilliant metallic
+films: and, at the same time, the solution acquired a rose colour.
+
+Some of the same oxid of manganese was dissolved in nitric acid, in
+which a bit of sugar was put: the solution was poured into a china cup,
+placed on hot sand, and, as the evaporation proceeded, bright metallic
+films appeared on the surface.
+
+Mr. Bindheim of Moscow relates, that he reduced the aërated calx of
+manganese dissolved in nitrous acid: “the solution was placed upon an
+open fire in a glass retort[26].”
+
+Happening to pour out a very largely diluted solution of sulphate of
+iron, I was surprised to find the flags of the court in an hour or two
+after, covered with large films of a livid white metallic aspect:
+these films, after the water evaporated, remained on the flags several
+days.
+
+In consequence of this I poured a largely diluted solution of sulphate
+of iron into several shallow vessels, and always found the surface of
+the solution covered with abundance of bright metallic films.
+
+I also found that a largely diluted solution of muriate of zinc throws
+up bright metallic films to the surface.
+
+The reduction of metals by acids is a very convincing proof of the
+decomposition of water, and seems inexplicable on any other principle.
+
+The reduction and calcination of metals by heat and electricity are
+naturally explained on the same principle: Doctor Priestley informs us
+in his History of Electricity, Vol. I. p. 344, that S. Beccaria revived
+several of the metals by the electric shock. It is obvious that the
+electric fluid produces this effect in the same manner, that other
+combustible bodies do, viz. by decomposing water. When the red oxid
+of mercury is reduced in close vessels by heat; the latter attracts
+the oxygen of the water, contained both in the oxid, and in the air of
+the vessels, while the hydrogen of the water unites to the oxygen of
+the mercury, reduces it, and forms a quantity of water equal to that
+decomposed.
+
+It is found, that if light and caloric act both at the same time,
+the reduction is effected with more facility, than if either acted
+separately: in this case, the superior efficacy of the combined action
+of light, and caloric resembles that of other compound reducers of the
+metals; as that of sulphurated hydrogen gas, phosphorated hydrogen gas,
+alkaline sulphure, &c. which are more powerful than simple hydrogen
+gas, sulphur, or phosphorus.
+
+This superior efficacy of compound reducers, is similar to what happens
+with some other combinations of combustible bodies, as pyrites,
+pyrophori, a mixture of lead and tin, &c. which have a more powerful
+attraction for oxygen, than any of their ingredients, in a separate
+state.
+
+Other acids, as the gallic, the tartarous, the formic, &c. and also
+alkalis, as ammonia, and soda, have the power of reducing some of the
+metals, facts well known to chymists.
+
+
+
+
+CHAPTER X.
+
+OXYGENATION
+
+OF
+
+_COMBUSTIBLE BODIES_.
+
+
+It has been shown, in the preceding chapters, that water is essential
+to the reduction of metals; that it is always decomposed in that
+process; and that the reducing substances are oxygenated by the oxygen
+of the water, while the hydrogen of the latter reduces the metals.
+
+That water is also decomposed in every instance of oxygenation, and
+that the oxygen of water alone oxygenates combustible bodies, will
+appear from the following observations.
+
+
+AZOTE.
+
+The first case of oxygenation, we shall consider, is that of _azote_,
+in an experiment of Dr. Priestley, which has been urged by Mr. Kirwan
+with great success against the Antiphlogistians.
+
+“If the electric spark be taken in nitrous air, it will be reduced to
+⅓ of its bulk, and the residuum is mere phlogisticated air, and a
+little acid is deposited. Now the Antiphlogistians own that nitrous
+air contains both pure air and phlogisticated air; since, therefore,
+this pure air disappears, is it not evident that it was converted
+into water? and since the formation of water requires the presence of
+inflammable air, does it not follow that the nitrous air contained this
+also[27]?”
+
+To this objection M. Berthollet replies, that the diminution of the
+nitrous gas “is owing to the combination of the mercury with the
+oxygene, which existed in the gas[28].”
+
+But this answer is insufficient; as it does not account for the
+water, and acid, that appeared: and indeed, by this experiment,
+the Antiphlogistians are refuted on their own principles, and the
+decomposition of water is incontestably proved; for as nitrous acid
+could not be formed without more oxygen than what existed in the
+nitrous air, is it not evident, that this oxygen must be derived from
+the water contained in the nitrous air? It is obvious then, that the
+water of the gas was decomposed; which seems to have been effected in
+the following manner.
+
+The electric spark diminishes the attraction of the constituent
+principles of the water for each other; hence the azote of the gas
+unites with the oxygen of the water, while the hydrogen of the latter
+combines with the oxygen of the gas; and thus water and nitrous acid
+are formed.
+
+The formation of nitrous acid in Mr. Cavendish’s noted experiment,
+cannot be explained on any other principle than the decomposition of
+water: when the electric spark is taken in a mixture of azotic gas,
+and vital air; the water of these airs is decomposed: the electric
+flame lessens the force, with which the oxygen and hydrogen of the
+water adhere; hence the azote seizes the oxygen of the water, and forms
+nitrous acid, while the hydrogen of the water unites with the oxygen of
+the vital air, and forms a quantity of water equal to that decomposed.
+
+When nitrous, and vital air, are mixed; the whole mass “hisses, turns
+red, grows warm, and contracts in bulk,” the azote of the nitrous air
+attracts the oxygen of the water, and forms nitrous acid, while the
+hydrogen of the water unites in its nascent state with the oxygen of
+the vital air, and forms a quantity of water equal to that decomposed.
+
+Hence while the azote of the nitrous air is oxygenated; the caloric is
+restored to its combustible state.
+
+“But it is to be observed,” says M. Bergman, treating of this
+experiment, “that the decomposition of nitrous air is the effect of a
+double attraction; the phlogiston is attracted by the vital air, and
+the acid part by the water. Therefore, when the mixture is made in a
+phial immersed in mercury, the experiment fails[29].”
+
+
+HYDROGEN.
+
+The combustion of hydrogen gas with vital air is explicable only on the
+decomposition of the water contained in these airs: thus when flame,
+or a glowing body is applied to a mixture of them; the attraction of
+the principles of the water for each other is diminished; therefore
+the hydrogen of the inflammable air unites with the oxygen of the
+water, while the hydrogen of the latter seizes the oxygen of the
+vital air: thus the whole bulk of the airs, which are changed into
+water, disappears; and their light, and caloric, are restored to the
+combustible state.
+
+Hence it appears that water is not formed during the combustion of
+vital, and inflammable air, in the manner the Antiphlogistians suppose.
+
+Indeed it is obvious, that, if these airs contained no water, they
+could never be burned: for since they are already saturated with light,
+and caloric, they can have no attraction for any additional quantity
+of these fluids; and consequently can suffer no other change from
+the light, or caloric, of a glowing body, than a greater degree of
+expansion, and therefore could never unite.
+
+The same reasoning applies to the combustion of all elastic fluids.
+
+
+PHOSPHORUS.
+
+Vital air always contains a large proportion of water: when phosphorus
+is burned in this air, it attracts the oxygen of the water, and forms
+phosphoric acid, while the hydrogen of the water unites with the oxygen
+of the gas, and forms water, which unites with the acid.
+
+Hence the weight of the acid formed is equal to the weights of the
+oxygen gas, and phosphorus, consumed; and the light and caloric, which
+appear during the combustion, are restored to their combustible state.
+
+This explanation is confirmed by an observation of Mr. Bergman, who
+says,
+
+“In vital air, without the aid of external heat, phosphorus is consumed
+very slowly, and scarce at all, unless water be present[30].”
+
+Therefore the phosphorus does not unite to the oxygen of the vital air,
+as M. Lavoisier supposes, but to the oxygen of the water contained in
+the oxygen gas.
+
+
+SULPHUR.
+
+When sulphur is burned in vital air, it attracts the oxygen of the
+water, and forms sulphuric acid, while the hydrogen of the water
+attracts the oxygen of the gas, and forms a quantity of water equal to
+that decomposed: the light and caloric are at the same time restored to
+their combustible state.
+
+The sulphur then does not unite with the oxygen of the vital air,
+as the Antiphlogistians imagine, but with the oxygen of the water
+contained in that gas.
+
+
+CHARCOAL.
+
+In like manner during the combustion of charcoal in vital air, the
+carbone attracts the oxygen of the water, and forms carbonic acid,
+while the hydrogen of the water unites with the oxygen of the vital
+air, and forms a new quantity of water equal to that decomposed.
+
+Hence the carbone of the charcoal does not unite with the oxygen of the
+vital air, as M. Lavoisier supposes, but with the oxygen of the water
+contained in that gas.
+
+That water is decomposed in every instance of combustion, is further
+proved by attending to what passes during the burning of a common fire:
+the carbone of the fuel combines with the oxygen of the water, and
+forms carbonic acid, while the hydrogen of the water unites partly
+with the oxygen, and partly with the azote of the atmosphere, and forms
+water, and the ammonia, which abounds in soot.
+
+From these observations it is evident, that M. Lavoisier’s account of
+the formation of water, and acids, is erroneous, and inadequate to
+explain the phenomena.
+
+The different kinds of fermentation are so many instances of the
+decomposition of water: in every case of them, combustible bodies are
+oxygenated by the oxygen of the water, while others are restored by its
+hydrogen to their combustible state.
+
+Hence the azote, ammonia, and carbonic acid of fermentation, the
+inflammable air of marshes, mines, &c. the azotic, and hydrogen
+gas, ascending into the atmosphere, and there meeting the vital air
+discharged from the water of plants, &c. form new quantities of air,
+and water.
+
+When the azote is oxygenated, it unites with the oxygen of the water
+contained in the air, and forms atmospheric air, and sometimes perhaps
+nitrous acid, the hydrogen of the water combines, at the same time,
+with the oxygen of the vital air, and forms a quantity of water equal
+to that decomposed.
+
+But when the hydrogen is oxygenated, a quantity of water double that
+decomposed is regenerated; for the hydrogen of the gas unites with the
+oxygen of the water, while the hydrogen of the latter seizes the oxygen
+of the vital air: and thus a quantity of water double that decomposed
+is formed, and that part of it which the atmosphere cannot suspend
+descends in the form of rain.
+
+When these decompositions are rapid, the phenomena of thunder and
+lightning appear.
+
+This account of the renovation of our atmosphere explains why the
+phenomena of thunder and lightning appear sometimes with, and sometimes
+without rain, and also accounts for the production of the nitrous acid,
+which Mr. Margraaf discovered in the purest snow.
+
+The breathing of fishes is a striking proof of the decomposition of
+water in respiration.
+
+For this view of the formation of our atmosphere I am indebted to a
+friend well acquainted with the experiments related in this essay, and
+also for the application of the opinion which I venture to advance, to
+the respiration of animals.
+
+The phenomena of vegetation cannot be explained on any other principle,
+than the decomposition of water by heat, and light, which uniting to
+the oxygen of the water contained in vegetables change it into streams
+of vital air, that serve to renovate our atmosphere: the hydrogen of
+the water, at the same time, contributes to form the oil and other
+principles of plants, and when these are decomposed by the various
+processes of combustion, forms a quantity of water equal to that
+consumed in their formation.
+
+The changes, which nitric acid suffers by exposure to heat, or light,
+are explained with ease on this principle: the light unites with the
+oxygen of the water contained in the nitric acid, and forms vital air,
+while the hydrogen of the water combines with the oxygen of the acid,
+and forms a new quantity of water equal to that decomposed: thus the
+nitric is converted into the ruddy nitrous acid.
+
+
+METALS.
+
+According to the Antiphlogistians, “In every metallic solution by an
+acid, the metal, in order to become oxided, decomposes either the acid
+itself, or the water of solution, or it obtains from the atmosphere the
+requisite quantity of oxygene. In the second case, hydrogenous gas, in
+a state of greater or less purity is disengaged; and the acid remains
+entire without decomposition, which is proved by the quantity of alkali
+necessary to saturate it. In the first case, one of the principles of
+the acid, or the acid deprived of part of its oxygene, is disengaged,
+and fused in the caloric, which is separated at the same time; such are
+nitrous gas, and sulphurous acid gas. In the third case, neither the
+water nor the acid are changed; such is the solution of copper by the
+acetous acid.
+
+“The muriatic acid, and the vegetable acids, which are formed of
+radicals, or acidifiable principles, which have more affinity with
+oxygene, than the metals have, are not decomposed by these metals,
+and the oxygene is always afforded to these last by the water or
+atmosphere. Hence the solutions by these acids afford only hydrogenous
+gas, or do not effervese at all.
+
+“There are some cases in which the water and the acid are at the same
+time decomposed by the metal, as in the solution of tin in the nitric
+acid, according to the observation of M. De Morveau.”
+
+“Tin is so greedy of oxygene, and requires so large a quantity for its
+saturation, that after having absorbed that of the nitric acid, and
+reduced it to the state of azote, it decomposes likewise the water,
+and disengages hydrogene. These two principles being separated from
+their first compounds, unite together, and immediately form ammoniac.
+Hence there is no disengagement of elastic fluid. In this case it
+appears, that the formation of ammoniac, in the solution of tin by the
+nitric acid, always takes place; for by throwing quicklime, or caustic
+fixed alkali, into this solution, there is always a disengagement of
+ammoniac[31].”
+
+It is evident, then, that this account of the oxygenation of metals,
+given by the Antiphlogistians, is equally complex, as their account
+of metallic reduction, and improbable; since every case, in which
+they deny the decomposition of water, and derive the oxygen from other
+sources, is easily, and naturally explained on that principle, as will
+appear from what follows.
+
+Thus when mercury, or silver, is dissolved in nitric acid; the metal
+attracts the oxygen of the water, while the hydrogen of the latter
+unites with, and separates, more or less of the oxygen of the acid,
+which is thus changed into nitrous air.
+
+The same thing happens during the solution of other metals in this
+acid; the only difference being the greater or less energy, and
+rapidity, with which they combine with the oxygen of the water.
+
+This decomposition of water is confirmed by the solution of tin in this
+acid; in which the Antiphlogistians allow the decomposition of the
+acid, and the water too; for ammonia is formed by part of the hydrogen
+of the water, and azote of the acid.
+
+In every case of metallic solution by sulphuric, and muriatic acids,
+whether concentrated, or diluted, water is decomposed: the metals
+attracting the oxygen of the water, while its hydrogen escapes in
+the form of inflammable air, or unites partly with the oxygen of the
+acid, and partly with caloric: hence the volatile sulphurous acid, and
+muriatic acid air, obtained, always contain some hydrogen gas, as
+appears from the following observation of M. Bergman.
+
+“By means of vitriolic acid, inflammable air is obtained from zinc,
+and iron, as also by means of marine acid; but, from the other metals
+dissolved in vitriolic acid, we obtain another species of air, called
+_vitriolic acid air_; and, by the marine acid, another similar to
+the former, called _muriatic air_, but both more or less mixed with
+_inflammable air_[32].”
+
+Again, when copper is dissolved in the acetous acid; the copper
+attracts the oxygen of the water, while the hydrogen of the latter
+unites with the oxygen of the atmosphere, and forms water: hence no
+effervescence appears.
+
+When alkalies dissolve metals, the latter are always oxygenated at the
+expence of the water, which holds the alkali in solution: thus when
+lead, and copper, are dissolved; the metals combine with the oxygen of
+the water, while its hydrogen unites to the oxygen of the atmosphere,
+and forms water: hence no hydrogen gas appears.
+
+The oxygenation of metals, and other substances by heat, and air, is
+easily explained on the same principle: the metals, &c. unite with the
+oxygen of the water contained in atmospheric air, while the hydrogen
+of the water combines with the oxygen of the air, and forms a quantity
+of water equal to that decomposed.
+
+This explanation is clearly proved by an experiment of Mr. Bergman on
+the regulus of manganese, which, if kept in a dry place, retains its
+metallic splendour; but, if exposed to moisture, is soon oxygenated,
+and loses its lustre[33].
+
+It is further confirmed by the authority of the distinguished Mr.
+Scheele, who says, that “the water contained in common atmospheric air
+is the chief cause of the ignition of pyrophorus,” which he proved by
+the following experiment.
+
+“I made a very dry air by putting some very small pieces of quicklime
+into a small matrass: then I put the neck of another matrass into
+that of the first, so that the air of both might communicate; and I
+luted the crevices with wax. Two days afterwards I separated the empty
+matrass, and poured half an ounce of pyrophorus from my phial into
+it, and immediately carefully shut the aperture up: but I did not
+observe, that it grew in the least warm: an hour after this, I put a
+sponge moistened in water into the matrass, and shut it up again: a few
+minutes after the pyrophorus began strongly to be heated, and some
+pieces kindled spontaneously[34].”
+
+Many other facts might be adduced to prove, that oxygenation cannot
+take place without water, as the combustion of mixtures of iron
+filings, sulphur and water, of alkaline sulphure and water, &c. in
+which the water is decomposed, and the combustible bodies oxygenated by
+its oxygen.
+
+It is evident then from the experiments and observations related in
+this essay, that water is essential to the oxygenation of combustible
+bodies; and that it is the only source of the oxygen that oxygenates
+them: it is also evident, that when one body is oxygenated, another,
+at least, is restored to the combustible state: hence it appears that
+the oxygenation of combustible bodies is never effected by a single
+affinity.
+
+The Antiphlogistians treating of the precipitation of metals by each
+other, say,
+
+“Since the metals cannot remain united to the acids, but in the state
+of oxides of a determinate degree, it is easily conceived, that by
+plunging into a metallic solution a metal which has a stronger affinity
+with oxygene than that which is dissolved, the former must deprive
+the latter of its oxygene, take its place in the acid, and cause the
+second to subside in a form more or less metallic, accordingly as it
+has deprived it of more or less oxygene. This is the reason of the
+precipitation of silver by copper, copper by iron[35],” &c.
+
+But this account of the precipitation of metals by one another cannot
+be admitted; for it has been proved in every instance of reduction
+related in this essay, that water is decomposed, and that its hydrogen
+is the only substance that restores bodies to their combustible state.
+
+There is no reason then to suppose that nature deviates, in this
+particular case, from that uniform simplicity, which she constantly
+observes in all her operations.
+
+Therefore it is obvious, that, when one metal precipitates another in
+a form more or less metallic; the precipitant unites with the oxygen
+of the water, while the hydrogen of the latter combines with, and
+separates, the oxygen of the precipitated metal, and thus reduces it.
+
+The experiments made with phosphorus and metallic solutions in ether,
+alcohol, and water, prove the truth of this explanation; and show that
+when one metal precipitates another in the metallic form, it acts like
+a stick of phosphorus, decomposing the water.
+
+This account of the reduction of one metal by another is supported by
+the opinion of Mr. Bergman, who says,
+
+“It is well known, that the calx of copper, dissolved in vitriolic
+acid, is precipitated in its metallic form on the addition of iron; and
+that by means of a double elective attraction; for the iron dissolving
+in the acid would form an inflammable air by its phlogiston, were not
+the copper present, which takes it up[36].”
+
+The same author remarks, that a small excess of acid is necessary, and
+that without it no precipitation begins.
+
+Now since water is decomposed by iron and sulphuric acid, it must be
+allowed, that, when iron is immersed in a solution of sulphate of
+copper, the water is decomposed by the iron and excess of acid, the
+iron attracting the oxygen of the water, while the hydrogen of the
+latter, unites to the oxygen of the copper, reduces it, and forms a
+quantity of water equal to that decomposed.
+
+The precipitation of silver in its metallic form by iron and other
+metals is to be explained in the same manner: and not by a single
+affinity, as the Antiphlogistians imagine.
+
+The reduction of gold, and some other metals, by solutions of sulphate
+of iron, and muriate of tin, is readily accounted for on the principles
+advanced here; for fresh made solutions of sulphate of iron, and
+muriate of tin, contain hydrogen, and have the power of decomposing
+water: the oxygen of which unites with the iron, and tin, while its
+hydrogen seizes the oxygen of the gold, &c. reduces it, and forms a
+quantity of water equal to that decomposed.
+
+The decomposition of water is further proved by the large dilution
+necessary to form the arbor Dianæ, the purple precipitate of Cassius,
+and other instances of the reduction of metals by one another.
+
+
+
+
+CHAPTER XI.
+
+_CONCLUSION._
+
+
+I shall conclude with a general view of the inferences, which I
+ventured to advance in this essay.
+
+1. Neither the Phlogistians, nor Antiphlogistians, account in a
+satisfactory manner for the increase of weight, which bodies acquire
+during combustion.
+
+2. Their account of the formation of water, acids, and oxids, is
+erroneous; for it has been shown that the oxygen of water alone
+oxygenates combustible bodies.
+
+3. Combustible bodies, as hydrogen, phosphorus, sulphur, charcoal,
+light, &c. are capable of reducing the metals in the ordinary
+temperature of the atmosphere; and indeed I might add, at a much lower
+temperature, as I frequently experienced.
+
+4. Combustible bodies do not reduce the metals by giving them
+phlogiston, as the Phlogistians suppose; nor by uniting with, and
+separating their oxygen, as the Antiphlogistians maintain.
+
+5. Water is essential both to the reduction and oxygenation of bodies,
+and is always decomposed in these operations.
+
+6. Water does not contribute to metallic reduction merely by
+dissolving and minutely dividing the particles of metallic salts, and
+thus removing the impediment opposed to chymical attraction by the
+attraction of cohesion: for were this the case, metallic solutions in
+ether and alcohol, in which that impediment is equally removed, should
+be as readily and effectually reduced, as metallic solutions in water
+are.
+
+This circumstance, in which all the experiments on metallic reduction
+detailed in this essay exactly coincide, merits particular attention,
+and shows that the manner, in which combustible bodies effect the
+reduction, is the same in them all.
+
+7. When one body is oxygenated, another, at least, is restored at
+the same time to its combustible state; and _v. v._ when one body is
+restored to its combustible state, another at least is at the same time
+oxygenated.
+
+8. Quantities of air, and water, equal to those decomposed in the
+different species of combustion, are constantly a forming.
+
+Thus nature, by maintaining this balance of power between combustible
+and oxygenated bodies, prevents the return of original chaos.
+
+Since then in every act of combustion, one body, at least, is
+oxygenated, and another restored, at the same time, to its combustible
+state, the phenomena of combustion may be referred to two heads, viz.
+
+_Oxygenation_, or the union of oxygen with combustible bodies, and
+
+_Reduction_, or the restoration of oxygenated bodies to their
+combustible state.
+
+And since in every instance of combustion water is decomposed, and one
+body oxygenated by the oxygen of the water, while another is restored
+to its combustible state by the hydrogen of the same fluid, it follows,
+
+1. That the hydrogen of water is the only substance, that restores
+bodies to their combustible state.
+
+2. That water is the only source of the oxygen, which oxygenates
+combustible bodies.
+
+3. That no case of combustion is effected by a single affinity.
+
+This view of combustion may serve to show how nature is always the
+same, and maintains her equilibrium by preserving the same quantities
+of air and water on the surface of our globe: for as fast as these are
+consumed in the various processes of combustion, equal quantities are
+formed, and rise regenerated like the Phenix from her ashes.
+
+
+
+
+        NOMENCLATURE _of the Chymical Terms used in this Essay_.
+
+
+       NEW NAMES.                      OLD NAMES.
+
+  Ammonia                           Caustic vol. alkali.
+
+  Acetite of lead                   Sugar of lead.
+
+  ---------- copper                 Verdirgris.
+
+  Azote                             Base of phlogisticated air.
+
+  Azotic gas                        Phlogisticated air.
+
+  Alkaline sulphure                 Liver of sulphur.
+
+  Alcohol                           Highly rectified spirit of wine.
+
+  Carbone                           Pure coal.
+
+  Carbonic acid                     Fixed air.
+
+  Caloric                           Heat.
+
+  Hydrogen                          Base of inflammable air.
+
+  Hydrogen gas                      Inflammable air.
+
+  Hydrure of sulphur                A compound of hydrogen and sulphur.
+
+  ---------- phosphorus             A compound of hydrogen and
+                                      phosphorus.
+
+  Muriate of tin                    Salt of Jupiter.
+
+  ---------- silver                 Luna cornea.
+
+  ---------- arsenic                Arsenic combined with muriatic acid.
+
+  ---------- zinc                   Marine salt of zinc.
+
+  ---------- cobalt                 Marine salt of cobalt.
+
+  Nitric acid                       Dephlogisticated nitrous acid.
+
+  Nitro-muriatic acid               Aqua regia.
+
+  Nitro-muriate of gold             A compound of gold and aqua regia.
+
+  ---------------- platina          A compound of platina and aqua
+                                      regia.
+
+  Nitrate of silver                 Lunar nitre, crystals of the moon.
+
+  ------- of mercury                Mercurial nitre.
+
+  ------- of bismuth                Nitre of bismuth.
+
+  ------- of manganese              Nitre of manganese.
+
+  Oxygen                            Base of vital air.
+
+  Oxygen gas                        Vital air.
+
+  Oxygenated muriate of mercury     Corrosive sublimate.
+
+  Prussiate of mercury              A compound of mercury and prussic
+                                     acid.
+
+  Phosphorated hydrogen gas         Phosphoric air.
+
+  Potash                            Caustic vegetable alkali.
+
+  Sulphuric ether                   Vitriolic ether.
+
+  Sulphureous acid gas              Vol. sulphureous acid.
+
+  Sulphurated hydrogen gas          Hepatic acid.
+
+  Sulphate of copper                Blue vitriol.
+
+  ----------- zinc                  White ditto.
+
+  ----------- iron                  Green ditto.
+
+  ----------- manganese             Vitriol of manganese.
+
+  Soda                              Caustic mineral alkali.
+
+  Tartarite of antimony             Emetic tartar.
+
+
+                                 FINIS.
+
+
+FOOTNOTES:
+
+[1] Essay on Phlogiston, by M. Kirwan, a new edition, p. 21, and 16.
+
+[2] Experiments on Air and Fire. Eng. trans. p. 174.
+
+[3] Essay on Phlogiston, a new edition, p. 38–166.
+
+[4] Essay on Phlogiston, p. 207.
+
+[5] Essay on Phlogiston, p. 205.
+
+[6] Essay on Phlogiston, p. 14.
+
+[7] Essay on Phlogiston, p. 13–15.
+
+[8] _Ibid._ p. 25. and Philo. Trans. Vol. 78. p. 314.
+
+[9] Scheele, p. 162, French translation.
+
+[10] Roz. Journ. Feb. 1782.
+
+[11] Elective Attractions, English Translation, p. 87.
+
+[12] M. Monnet Dissolution de Metaux, p. 159.
+
+[13] Phil. Trans. Vol. 73. An. 1783.
+
+[14] Essay on Phlogiston, a new Edit, by M. Kirwan, p. 46.
+
+[15] Priestley, Vol. VI. p. 150.
+
+[16] Chem. Essays, Vol. III. p. 219.
+
+[17] M. Kirwan, Phil. Trans. for 1786.
+
+[18] Chem. Essay. Vol. II. p. 206 and 207. Eng. Trans.
+
+[19] Essay on Phlogiston, new Ed. by M. Kirwan, p. 61.
+
+[20] Phil. Trans. 1785. Vol. LXXV. p. 289.
+
+[21] El. Nat. Hist. & Chem. Eng. Trans. in three volumes, p. 163. Vol.
+I.
+
+[22] Ess. on Phlog. a new Ed. by M. Kirwan, p. 60.
+
+[23] Experiments on Air and Fire, Eng. Trans. p. 82.
+
+[24] Commerce of the Arts.
+
+[25] Elec. Attrac. Eng. Tran. p. 223.
+
+[26] Crell’s Chem. Jour. Vol. II. p. 48. Eng. Trans.
+
+[27] Essay on Phlogiston, new Ed. p. 82.
+
+[28] Ibid. p. 122.
+
+[29] Elec. Attr. Eng. Trans. p. 211.
+
+[30] El. Att. Eng. Trans. p. 213.
+
+[31] Essay on Phlog. new Ed. by Mr. Kirwan, p. 233–235.
+
+[32] Chem. Ess. Vol. II. p. 358. Eng. Trans.
+
+[33] Chem Ess. Vol. II. p. 206–207. Eng. Trans.
+
+[34] Exper. on Air and Fire, Eng. Trans. p. 112, and 130.
+
+[35] Ess. on Phlog. new Ed. by Mr. Kirwan, p. 236, and 237.
+
+[36] Chem. Essays, Vol. II. p. 384, Eng. Trans.
+
+
+
+
+TRANSCRIBER’S NOTE
+
+
+  Obvious punctuation errors have been corrected after careful
+  comparison with other occurrences within the text.
+
+  Inconsistent hyphenations have been left as is.
+
+  The tables in this book are best viewed using a monospace font.
+
+  The original book used the character ſ (long-form s). This has been
+  changed to the modern s in this eBook.
+
+  Footnotes have been renumbered consecutively and moved to the end of
+  the text.
+
+  Except for those changes noted below, all misspellings in the text,
+  and inconsistent or archaic usage, have been retained.
+
+  Page 28. “hygrogen” replaced by “hydrogen”.
+  Page 39. Unclear image of potentially “horn” replaced by “both”.
+  Page 48. “theprecipitate” replaced by “the precipitate”.
+  Page 77. “evident manmer” replaced by “evident manner”.
+  Page 84. “CHAPTER III” replaced by “CHAPTER IV”.
+  Page 88. “immediaaely” replaced by “immediately”.
+  Page 106. “is influence” replaced by “its influence”.
+  Page 156. Added full stop after “Exp. 4. Mercury” for consistency.
+
+  Errata from the publisher has been applied as described below.
+
+  Page viii. “ere long” replaced by “erelong”.
+  Page 15. “particles of reduced gold were observed” replaced by
+    “I observed many particles of reduced gold”.
+  Page 17. Removed 3 duplicated lines of text.
+  Page 137. “or by uniting” replaced by “nor by uniting”.
+  Page 163. “and the caloric” replaced by “the caloric”.
+
+*** END OF THE PROJECT GUTENBERG EBOOK 77630 ***
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+      An essay on combustion, with a view to a new art of dying and painting | Project Gutenberg
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+<body>
+<div style='text-align:center'>*** START OF THE PROJECT GUTENBERG EBOOK 77630 ***</div>
+
+<div class="transnote">
+TRANSCRIBER’S NOTE
+
+<p>Some minor changes to the text are noted at the <a href="#transnote">end of the book</a>.
+</p>
+</div>
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<h1 class="center">
+<span class="fs70">AN</span><br>
+ESSAY<br>
+<span class="fs70">ON</span><br>
+<i>COMBUSTION</i>,<br>
+<span class="fs40">WITH A VIEW TO A</span><br>
+NEW ART<br>
+<span class="fs40">OF</span><br>
+DYING <span class="allsmcap fs90">AND</span> PAINTING.<br></h1>
+<p class="center fs80">
+WHEREIN</p>
+<p class="center fs90 p2">THE PHLOGISTIC AND ANTIPHLOGISTIC HYPOTHESES<br>
+ARE PROVED ERRONEOUS.</p>
+<br>
+<hr class="r33">
+<p class="center fs120">
+<span class="smcap">By Mrs.</span> FULHAME.</p>
+<hr class="r55">
+<p class="center p2">LONDON:</p>
+<p class="center">
+<span class="fs90">PRINTED FOR THE AUTHOR,<br>
+BY J. COOPER, BOW STREET, COVENT GARDEN,</span><br>
+And Sold by <span class="smcap">J. Johnson</span>, No. 72, St. Paul’s Church Yard;<br>
+G. G. and <span class="smcap">J. Robinson</span>, Paternoster Row; and<br>
+<span class="smcap">T. Cadell</span>, Jun. and <span class="smcap">W. Davies</span>, Strand.<br>
+</p>
+<hr class="r5">
+<p class="center">1794.</p>
+<p class="center p2">[ENTERED AT STATIONERS HALL.]</p>
+
+<p><span class="pagenum" id="Page_iii">[Pg iii]</span></p>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+  <h2 class="nobreak lsp2" id="PREFACE">
+    PREFACE.
+  </h2>
+</div>
+
+
+<p class="drop-cap">The possibility of making cloths of gold,
+silver, and other metals, by chymical processes,
+occurred to me in the year 1780: the
+project being mentioned to Doctor Fulhame,
+and some friends, was deemed improbable.
+However, after some time, I had the satisfaction
+of realizing the idea, in some degree,
+by experiment.</p>
+
+<p>Animated by this small success, I have,
+from time to time, ever since, prosecuted the
+subject as far as pecuniary circumstances
+would permit.</p>
+
+<p>I imagined in the beginning, that a few
+experiments would determine the problem;
+but experience soon convinced me, that a
+very great number indeed were necessary, before
+such an art could be brought to any tolerable
+degree of perfection.</p>
+
+<p>A narration of the numerous experiments,
+which I made with this view, would far exceed
+<span class="pagenum" id="Page_iv">[iv]</span>the bounds, I prescribe myself in this
+essay; I shall therefore present the reader only
+with a few, selecting such as I judge most interesting,
+and best adapted to illustrate the
+subject.</p>
+
+<p>Though I was, after some considerable
+time, able to make small bits of cloth of
+gold, and silver, yet I did not think them
+worthy of public attention; but by persevering,
+I at length succeeded in making pieces
+of gold cloth, as large as my finances would
+admit.</p>
+
+<p>Some time after this period, I found the
+invention was applicable to painting, and
+would also contribute to facilitate the study
+of geography: for I have applied it to some
+maps, the rivers of which I represented in
+silver, and the cities in gold. The rivers appearing,
+as it were, in silver streams, have a
+most pleasing effect on the sight, and relieve
+the eye of that painful search for the course,
+and origin, of rivers, the minutest branches of
+which can be splendidly represented in this
+way.</p>
+
+<p>Notwithstanding this further success, I was
+dubious about the propriety of publishing this
+Essay; I therefore shewed some specimens of
+these metallic stuffs to persons, whom I thought
+qualified to judge of them: some approved of
+them very much, and were pleased to say,
+that the invention would make an era in the
+arts; others thought it a pretty conceit; and
+others were of opinion, that the stuffs had
+<span class="pagenum" id="Page_v">[v]</span>not that splendour, or burnished appearance,
+which could entitle them to public notice.</p>
+
+<p>The latter opinion had much weight with
+me; for it must be allowed, that the specimens,
+which I shewed them, had not that
+lustre and polish, necessary for shoulder-knots,
+lace, spangles, gold muslins, <abbr title="et cetera">&amp;c.</abbr>; that some
+of them had a reddish cast, bordering on the
+colour of copper, some a purple, mixed with
+gold; and that some of them were unequal
+in the die, and seemed stained; which imperfections
+were owing to a partial reduction
+of the metal in the fibres of the silk.</p>
+
+<p>But all these imperfections, except the
+want of that burnished lustre so necessary for
+gold lace, spangles, <abbr title="et cetera">&amp;c.</abbr> I knew I could remedy;
+and therefore the criticism, as far as
+it relates to them, had no great influence with
+me.</p>
+
+<p>I am in possession of some pieces, one of
+which is about a yard in length, which have
+scarce any of these imperfections.</p>
+
+<p>Moreover, that high polish of burnished
+gold, so necessary in spangles, lace, <abbr title="et cetera">&amp;c.</abbr>,
+would, in my opinion, be a great imperfection
+in gold stuffs designed for whole suits; as
+a person in such a habit, would look like a
+gilded statue.</p>
+
+<p>I saw a piece of gold stuff made for the late
+King of Spain, which was of a purple colour,
+with gold wire shining through it, though
+rather obscurely; and it was much admired:
+I was so struck with its beauty, that I attempted
+<span class="pagenum" id="Page_vi">[vi]</span>to imitate it on a small bit of white
+silk; and succeeded, having produced a beautiful
+purple colour, with gold beaming through
+it.</p>
+
+<p>Therefore, the want of that burnished appearance
+is no objection to this art; for the
+paler, and cooler, to a certain degree, the colour
+of the gold is, the more lovely do these
+metallic cloths appear.</p>
+
+<p>I made small bits of gold tiffany, which
+looked exceedingly beautiful; the fineness of
+the thread contributing much to that effect;
+and, in my opinion, such webs are inimitable
+by mechanical means.</p>
+
+<p>Beside, though I am not able to make
+cloths like burnished gold, others of greater
+means and abilities may; for we cannot pretend
+to prescribe any limits to the perfection,
+at which chymistry, and the arts, may arrive.</p>
+
+<p>However, I must acknowledge, that this
+unfavourable judgement suspended my intention
+of publishing this little work, until a celebrated
+philosopher happening, some time in
+October 1793, to see some of the same pieces,
+and indeed, some of the worst, viewed the
+performance in a very different light.</p>
+
+<p>This illustrious friend of science not only
+approved of the specimens shewn him, but
+offered to have a memoir on the subject presented
+to the Royal Society: but different incidents
+dissuaded me from that mode of publication,
+and induced me to adopt the present.</p>
+
+<p><span class="pagenum" id="Page_vii">[vii]</span></p>
+
+<p>I now no longer hesitated about the propriety
+of publishing; for, every thing considered,
+I judged, that though this art could
+never be established, which is by no means
+my opinion, yet the experiments themselves,
+upon which I attempted to found it, as they
+are new, and seem to throw some light on
+the theory of combustion, are not unworthy
+the attention of Chymists.</p>
+
+<p>Those who viewed my performance with
+a favourable eye, were of opinion, that I
+should dedicate this Essay to some patron of
+the arts; or apply for his Majesty’s Royal
+letters patent, in order to reimburse the expence
+necessarily incurred in this investigation,
+an expence so disproportionate to the
+fortune which supported it, that nothing but
+a certain fatality, and the hope of reward,
+could induce me to persevere.</p>
+
+<p>As to patrons, I have heard of such beings
+on the record of fame; but never saw one:
+on the contrary, it has been my lot to know
+of many, whose malignant breath, as far as
+its deadly influence can extend, never ceases
+to blast the unsheltered blossoms of science.—And
+as for a patent, had I even the means, I
+should perhaps never attempt it; for if we
+may judge of the future by the past, I can
+safely affirm, that such an application would
+be vain.</p>
+
+<p>Thus circumstanced, I publish this Essay
+in its present imperfect state, in order to prevent
+the furacious attempts of the prowling
+<span class="pagenum" id="Page_viii">[viii]</span>plagiary, and the insidious pretender to chymistry,
+from arrogating to themselves, and
+assuming my invention, in plundering silence:
+for there are those, who, if they can not by
+chymical, never fail by stratagem, and mechanical
+means, to deprive industry of the
+fruits, and fame, of her labours.</p>
+
+<p>But the British empire should not forget,
+that she owes her power and greatness to commerce;
+that she is, as it were, the hive of the
+arts, and should not, by the sulphureous vapour
+of oppression, and neglect, compel her
+bees to swarm for protection to foreign climes,
+but rather permit them to roam in their native
+soil, and allow them, in the winter of
+life, to sip a little of the honey of their own
+industry.</p>
+
+<p>The nation, whose evil genius withholds
+this protection, only sounds the trumpet of
+emigration; and must <ins id="ER-1" class="corr" title="Transcriber's Note&mdash;original text: ere long">erelong</ins> lament her
+cities deserted, her fields brown with desolation,
+and herself the easy prey, and vile
+drudge of surrounding greatness.</p>
+
+<p>I first imagined, that the proper title of this
+performance, should be, an Essay on the Art
+of making Cloths of Gold, Silver, and other
+Metals, by chymical processes; but reflecting
+on the imperfect state of the art, and that
+my experiments related not only to the reduction,
+but also to the calcination of metals,
+and other combustible bodies, I determined
+to entitle it, An Essay on Combustion, with
+a view to a new Art of Dying and Painting,
+<span class="pagenum" id="Page_ix">[ix]</span>which includes every thing the experiments
+can extend to.</p>
+
+<p>As to the style, I have endeavoured to relate
+the experiments in a plain and simple
+manner, aiming more at perspicuity, than
+elegance.</p>
+
+<p>I have adopted the French Nomenclature,
+as the terms of it are so framed, as to prevent
+circumlocution, assist the memory, by pointing
+out the combination, and state of the
+elements existing in each compound, as far
+as they are known; advantages to be found
+in no other Nomenclature.</p>
+
+<p>However, the English reader must regret,
+that the French chymists have not preferred
+the terms <em>air</em>, and <em>ammonia</em>, to the less harmonious
+sounds, <em>gas</em>, and <em>ammoniac</em>. I took
+the liberty of writing the latter <em>ammonia</em>.</p>
+
+<p>I have not related my experiments in the
+order, in which they were made, sensible
+that such a narration would be tedious, and
+that a short extract from them would answer
+every purpose at present intended.</p>
+
+<p>The experiments related I have endeavoured
+to arrange in such a manner, as mutually
+to illustrate each other, by contrasting the
+successful with those, that failed, thus pointing
+out a general principle, which forms a
+chain through the whole, connects all the experiments,
+shows their points of coincidence,
+and disagreement, and by this means furnishes
+us with <em>data</em>, by which, I hope, the art may
+be improved.</p>
+
+<p><span class="pagenum" id="Page_x">[x]</span></p>
+
+<p>This arrangement also facilitates the perusal,
+and relieves the mind of that fatiguing attention,
+which must necessarily be given to
+an indigested mass of insulated experiments,
+that have no clew to connect them, but has,
+on the other hand, its disadvantages; for it
+throws a sameness on the work, incompatible
+with that variety which is often so agreeable.</p>
+
+<p>My apparatus consisted chiefly of a few
+glass vessels for the solution of metals, and
+the formation of such elastic fluids, as I used.
+The cheapest, and the most simple of those
+described by Dr. Priestley answered my purpose.</p>
+
+<p>Dr. Nooth’s machine for combining carbonic
+acid with water, is very convenient for
+making small experiments with some kinds of
+gas; as the base of that machine serves to
+contain the materials, from which the gas is
+obtained; and the middle glass the cloth previously
+dipped in the metallic solution, on
+which the experiment is to be made.</p>
+
+<p>The cloth may be suspended in this part of
+the machine, by means of a thread, and a
+cork.</p>
+
+<p>As this machine is useful only in experiments
+on a very small scale, I sometimes
+used tall glass cylinders, in which I suspended
+the subject of the experiment, by means of a
+thread, a cork, and a bit of cement.</p>
+
+<p>This cylinder I placed over a vessel containing
+the materials, which produced the gas.</p>
+
+<p><span class="pagenum" id="Page_xi">[xi]</span></p>
+
+<p>It is very convenient to have cylinders of
+different sizes, proportioned to the scale, on
+which the experiments are to be made.</p>
+
+<p>But machinery for confining elastic fluids
+is not always necessary; as most of the experiments
+may be performed in the open air.</p>
+
+<p>It may appear presuming to <em>some</em>, that I
+should engage in pursuits of this nature, but
+averse from indolence, and having much leisure,
+my mind led me to this mode of amusement,
+which I found entertaining, and will,
+I hope, be thought inoffensive by the liberal,
+and the learned. But censure is perhaps inevitable;
+for some are so ignorant, that they
+grow sullen and silent, and are chilled with
+horror at the sight of any thing, that bears the
+semblance of learning, in whatever shape it
+may appear; and should the <em>spectre</em> appear in
+the shape of <em>woman</em>, the pangs, which they
+suffer, are truly dismal.</p>
+
+<p>There are others, who suffer the same torture
+in a still higher degree; but by virtue of
+an <em>old inspiring tripod</em>, on which ignorance,
+servility, or chance, has placed them, assume a
+dictatorship in science, and fancying their
+rights and prerogatives invaded, swell with
+rage, and are suddenly seized with a violent
+and irresistible desire of revenge, manifesting
+itself by innuendos, nods, whispers, sneers,
+grins, grimace, satanic smiles, and witticisms
+uttered sometimes in the acute, and sometimes
+in the nasal obtuse twang, with an affected
+hauteur, and contempt of the <em>spectre</em>;
+<span class="pagenum" id="Page_xii">[xii]</span>shrugs, and a variety of other contortions,
+attending.</p>
+
+<p>Sometimes the goblin, which thus agitates
+them, lurks latent, and nothing is perceived
+but hollow murmurs, portending storms:
+sometimes the lurking fiend darts with sidelong
+fury at the devoted object, which, if unarmed,
+falls a victim to the grisly monster.</p>
+
+<p>But happily for human kind, the <em>magic
+tripod</em> drags none into its dizzy vortex, but
+those who are radically stupid, and malicious,
+who are the beasts of prey destined to hunt
+down unprotected genius, to stain the page
+of biography, or to rot unnoted in the grave
+of oblivion.</p>
+
+<p>Although the surge of deliberate malice be
+unavoidable, its force is often spent in froth,
+and bubbles; for this little bark of mine has
+weathered out full many a storm, and stemmed
+the boisterous tide; and though the cargo be
+not rich, the dangers, which may hereafter
+be pourtrayed on <em>votive tablet</em>, may serve as a
+beacon to future mariners.</p>
+
+<p>But happen what may, I hope I shall never
+experience such desertion of mind, as not to
+hold the helm with becoming fortitude against
+the storm raised by ignorance, petulant arrogance,
+and privileged dulness.</p>
+
+<p>However, were I not encouraged by the
+judgement of some friends, and possessed of
+specimens, to show the progress made in the
+art, I should never perhaps venture to publish
+this Essay; as I am sensible, it labours under
+<span class="pagenum" id="Page_xiii">[xiii]</span>many imperfections, which inaccuracy of observation,
+and the drapery of imagination,
+must spread over the whole, imperfections
+perhaps unavoidable in such a discussion.</p>
+
+<p>Finding, the experiments could not be explained
+on any theory hitherto advanced, I
+was led to form an opinion different from that
+of M. Lavoisier, and other great names.
+Persuaded that we are not to be deterred from
+the investigation of truth by any authority
+however great, and that every opinion must
+stand or fall by its own merits, I venture with
+diffidence to offer mine to the world, willing
+to relinquish it, as soon as a more rational
+appears.</p>
+
+<blockquote>
+<p>November 5th, 1794.</p>
+</blockquote>
+
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+
+<p><span class="pagenum"><a id="Page_xiv"></a><a id="Page_xv"></a>[xv]</span></p>
+
+
+  <h2 class="nobreak lsp2" id="CONTENTS">
+    CONTENTS.
+  </h2>
+</div>
+
+
+<table class="autotable">
+<tbody>
+<tr>
+<td colspan="3">Introduction</td>
+<td class="tdr"><a href="#INTRODUCTION">1</a></td>
+</tr>
+<tr>
+<td>Chap.</td>
+<td>I.</td>
+<td>Reduction of Metals by Hydrogen Gas</td>
+<td class="tdr"><a href="#CHAPTER_I">13</a></td>
+</tr>
+<tr>
+<td>——</td>
+<td>II.</td>
+<td>—————————— Phosphorus</td>
+<td class="tdr"><a href="#CHAPTER_II">41</a></td>
+</tr>
+<tr>
+<td>——</td>
+<td>III.</td>
+<td>——————————  Sulphur</td>
+<td class="tdr"><a href="#CHAPTER_III">69</a></td>
+</tr>
+<tr>
+<td>——</td>
+<td>IV.</td>
+<td>——————————  Alkaline Sulphure</td>
+<td class="tdr"><a href="#CHAPTER_IV">84</a></td>
+</tr>
+<tr>
+<td>——</td>
+<td>V.</td>
+<td>—————————— Sulphurated Hydrogen Gas</td>
+<td class="tdr"><a href="#CHAPTER_V">99</a></td>
+</tr>
+<tr>
+<td>——</td>
+<td>VI.</td>
+<td>—————————— Phosphorated Hydrogen Gas</td>
+<td class="tdr"><a href="#CHAPTER_VI">113</a></td>
+</tr>
+<tr>
+<td>——</td>
+<td>VII.</td>
+<td>—————————— Charcoal</td>
+<td class="tdr"><a href="#CHAPTER_VII">124</a></td>
+</tr>
+<tr>
+<td>——</td>
+<td>VIII.</td>
+<td>—————————— Light</td>
+<td class="tdr"><a href="#CHAPTER_VIII">142</a></td>
+</tr>
+<tr>
+<td>——</td>
+<td>IX.</td>
+<td>—————————— Acids</td>
+<td class="tdr"><a href="#CHAPTER_IX">155</a></td>
+</tr>
+<tr>
+<td>——</td>
+<td>X.</td>
+<td>Oxygenation of Combustible Bodies</td>
+<td class="tdr"><a href="#CHAPTER_X">161</a></td>
+</tr>
+<tr>
+<td></td>
+<td></td>
+<td>——————— Azote</td>
+<td class="tdr"><a href="#CHAPTER_X_AZOTE"><abbr title="ibidem">ibid</abbr></a>.</td>
+</tr>
+<tr>
+<td></td>
+<td></td>
+<td>——————— Hydrogen</td>
+<td class="tdr"><a href="#CHAPTER_X_HYDROGEN">164</a></td>
+</tr>
+<tr>
+<td></td>
+<td></td>
+<td>——————— Phosphorus</td>
+<td class="tdr"><a href="#CHAPTER_X_PHOSPHORUS">165</a></td>
+</tr>
+<tr>
+<td></td>
+<td></td>
+<td>——————— Sulphur</td>
+<td class="tdr"><a href="#CHAPTER_X_SULPHUR">166</a></td>
+</tr>
+<tr>
+<td></td>
+<td></td>
+<td>——————— Charcoal</td>
+<td class="tdr"><a href="#CHAPTER_X_CHARCOAL"><abbr title="ibidem">ibid</abbr></a>.</td>
+</tr>
+<tr>
+<td></td>
+<td></td>
+<td>——————— Metals</td>
+<td class="tdr"><a href="#CHAPTER_X_METALS">169</a></td>
+</tr>
+<tr>
+<td></td>
+<td></td>
+<td>——————— Light</td>
+<td class="tdr"><a href="#Page_168">168</a>, <a href="#Page_169">169</a></td>
+</tr>
+<tr>
+<td>——</td>
+<td>XI.</td>
+<td>Conclusion</td>
+<td class="tdr"><a href="#CHAPTER_XI">178</a></td>
+</tr>
+<tr>
+<td colspan="3">Nomenclature</td>
+<td class="tdr"><a href="#Nomenclature_of_the_Chymical_Terms">181</a></td>
+</tr>
+</tbody>
+</table>
+
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+
+<p><span class="pagenum"><a id="Page_xvi"></a><a id="Page_1"></a>[Pg 1]</span></p>
+
+
+  <h2 class="nobreak lsp2" id="INTRODUCTION">
+    INTRODUCTION.
+  </h2>
+</div>
+
+
+<p class="drop-cap">Though some of the phenomena of
+combustion were known from the earliest
+ages, yet no rational attempt to explain them
+was made till about the middle of the 17th
+century.</p>
+
+<p>Before that period, it was supposed by
+alchymists and physicians, that sulphur was
+the inflammable principle, on which all the
+phenomena of combustion depended.</p>
+
+<p>But Beecher perceiving, that sulphur did
+not exist in several combustible bodies, asserted
+it was not the principle of inflammability;
+which, he maintained, was a different
+substance, common to sulphur and other
+combustible bodies: this principle he supposed
+to be of a dry nature, and called it inflammable
+Earth.</p>
+
+<p>Stahl refined this hypothesis by supposing
+the inflammable earth of Beccher to be pure
+fire, fixed in combustible bodies, and constituting
+an essential part of them.</p>
+
+<p><span class="pagenum" id="Page_2">[2]</span></p>
+
+<p>According to Stahl, a combustible body is
+a compound, containing fixed fire, or <em>phlogiston</em>;
+and combustion is the disengagement
+of this phlogiston from a fixed to a free
+state, attended sometimes with heat and
+light: when these phenomena cease, the
+body becomes incombustible; if this calcined
+body be now heated with charcoal, or any
+other inflammable substance, capable of giving
+it phlogiston, or fixed fire, it returns
+again to the class of inflammable bodies.</p>
+
+<p>This hypothesis is so simple and plausible,
+that, since the year 1736, it was received,
+though differently modified, all over Europe.</p>
+
+<p>The principal objections to it are, that the
+existence of phlogiston cannot be demonstrated;
+and that it does not explain, why
+bodies become heavier after oxygenation,
+and lighter after reduction.</p>
+
+<p>M. Lavoisier discovering, that the increase
+of weight, which bodies acquire during combustion,
+is equal to the weight of the combustible
+substance, and that of the vital air
+employed, denied the existence of phlogiston,
+or fixed fire, in combustible bodies; though
+he grants the existence of combined <em>caloric</em>
+in them. He seems then to allow the existence
+of phlogiston, but to have changed its
+name to that of <em>caloric</em>, and denied it the
+power of producing combustion.</p>
+
+<p>However, after discovering that the increase
+of weight, which bodies acquire during
+combustion, depended on the quantity
+<span class="pagenum" id="Page_3">[3]</span>of the air absorbed, he was led to the following
+beautiful hypothesis, equally simple as
+that of Stahl; and if ever any hypothesis
+deserved the name of theory, surely it is that
+of M. Lavoisier.</p>
+
+<p>According to M. Lavoisier, “an inflammable
+body is nothing else but a body
+which has the property of decomposing
+vital air, and taking the base from caloric
+and light; that is to say, the oxygene,
+which was united to them; and that a
+body ceases to be combustible when its
+affinity for the oxygene is satisfied, or when
+it is saturated with that principle; but
+that it becomes again combustible, when
+the oxygene has been taken from it by
+another body, which has a stronger affinity
+with that principle.</p>
+
+<p>“When this decomposition of the air is
+rapid, and, as it were, instantaneous, there
+is an appearance of flame, heat, and light;
+when, on the contrary, the decomposition
+is very slow, and quietly made, the heat
+and light are scarcely perceptible&#x2060;<a id="FNanchor_1_1" href="#Footnote_1_1" class="fnanchor">[1]</a>.”</p>
+
+<p>Thus all the phenomena of oxygenation,
+which Stahl ascribed to the disengagement of
+phlogiston, M. Lavoisier ascribes to the union
+of oxygen with combustible bodies.</p>
+
+<p>And, on the other hand, all the phenomena
+of reduction, which Stahl attributed
+<span class="pagenum" id="Page_4">[4]</span>to the union of phlogiston to calcined bodies,
+M. Lavoisier attributes to the separation of
+oxygen from the same. Combustion, then,
+according to Stahl, is the transition of phlogiston
+from one body to another; and, according
+to M. Lavoisier, ’tis nothing but the
+transition of oxygen from one substance to
+another.</p>
+
+<p>Stahl supposed, that the heat, and light,
+attending combustion proceed from the
+burning body; but M. Lavoisier supposes,
+that the heat, and light, proceed principally,
+and almost entirely, from the vital air.</p>
+
+<p>However, this opinion of M. Lavoisier is
+far from being established; for Doctor Crawford
+has shown, that inflammable air contains
+a much greater quantity of heat, than vital
+air does.</p>
+
+<p>It is evident, then, that the great advantage,
+which M. Lavoisier’s hypothesis has over
+that of Stahl is, that the former seems to
+account for the increase and decrease of
+weight, which bodies suffer during calcination,
+and reduction.</p>
+
+<p>Notwithstanding this brilliant discovery,
+which seems to account, with such ease,
+for the increase of weight, that bodies acquire
+during combustion, M. Macquer
+was of opinion, that M. Lavoisier’s hypothesis
+was insufficient to explode that of
+Stahl, and endeavoured to remove the objection
+urged against the nonexistence of phlogiston,
+by supposing it to be light; and that
+in every case of combustion, light, and vital
+<span class="pagenum" id="Page_5">[5]</span>air, mutually precipitate each other: so that,
+according to M. Macquer, when a body is
+oxygenated, vital air unites to it, and disengages
+light; and, on the other hand, when
+an oxygenated substance is reduced to its inflammable
+state, light unites to it, and disengages
+vital air.</p>
+
+<p>M. Scheele also modified the hypothesis of
+Stahl, by supposing that heat, light, and inflammable
+air, were compounds of empyreal,
+or vital air, and phlogiston. Light, he
+thought, contained more phlogiston than
+heat did; and inflammable air more than
+either: he farther supposed, that these compounds
+of vital air and phlogiston were convertible
+into one another, by the addition, or
+subtraction, of phlogiston; and that, when a
+metal was reduced by them, they were decomposed;
+their phlogiston uniting to the
+substance reduced.</p>
+
+<p>His idea of calcination is, that metals either
+attract empyreal air by means of their phlogiston,
+and thus form heat, or that they
+communicate their phlogiston to the air, and
+attract heat from the fire; and that, either
+way, there is empyreal air in the calces,
+which makes the overplus of their weight&#x2060;<a id="FNanchor_2_2" href="#Footnote_2_2" class="fnanchor">[2]</a>.</p>
+
+<p>The last modification of Stahl’s hypothesis
+is that of M. Kirwan, who supposes that inflammable
+air exists in a fixed, or concrete,
+state in all combustible bodies, and is the
+<span class="pagenum" id="Page_6">[6]</span>true phlogiston of the antient chymists; and,
+as it can be exhibited in the form of air, its
+existence is no longer doubtful.</p>
+
+<p>M. Kirwan supposes, that, when combustible
+bodies are calcined, or changed into
+acids, they combine most commonly with
+fixed air, formed during the operation, by
+the union of their phlogiston to vital air;
+and sometimes to other substances, and water,
+which is either absorbed <i lang="la">in specie</i>, or
+formed by the union of their phlogiston to
+vital air, during calcination.</p>
+
+<p>He supposes, that some of these are restored
+to their combustible state by the decomposition
+of their fixed air; some partly by the
+decomposition of their fixed air, and partly
+by its expulsion, and that of the other foreign
+bodies, they had absorbed; and lastly, that
+some recover their combustibility by the expulsion
+of water, and others possibly by its
+decomposition in high degrees of heat. In
+all these reductions he supposes a simultaneous
+reunion of these bodies to phlogiston,
+or the inflammable principle&#x2060;<a id="FNanchor_3_3" href="#Footnote_3_3" class="fnanchor">[3]</a>.</p>
+
+<p>Though M. Kirwan’s hypothesis seems to
+account for the increase of weight, which
+bodies acquire during combustion, yet he has
+not proved the existence of inflammable air,
+in a concrete state, in all combustible bodies;
+nor has he shown, that fixed air is a compound
+of inflammable, and vital air; neither
+<span class="pagenum" id="Page_7">[7]</span>has he proved, that fixed air is the acidifying
+principle.</p>
+
+<p>All these objections have been made, with
+great justice, to his hypothesis, by the antiphlogistians;
+who also object, that M. Kirwan’s
+account of calcination, and reduction,
+is complex, and repugnant to the simplicity of
+nature; “for,” says M. De Fourcroy, “as
+the author had admitted three general species
+of calcination, it was necessary, that
+he should, likewise, admit three kinds of
+reduction&#x2060;<a id="FNanchor_4_4" href="#Footnote_4_4" class="fnanchor">[4]</a>.”</p>
+
+<p>This criticism is very just; but it will appear,
+that the antiphlogistic account of calcination,
+and reduction, is no less complex,
+erroneous, and repugnant to the simplicity
+of nature: for when we consider the various
+sources, whence they derive the oxygen,
+which oxygenates bodies; and the long list
+of metallic reducers, which they suppose;
+it must be allowed, that if simplicity be a recommendation,
+their hypothesis is destitute
+of that advantage.</p>
+
+<p>Thus, according to M. Lavoisier, the oxygen,
+which oxygenates combustible bodies,
+is sometimes derived from vital air; sometimes
+from atmospheric air; sometimes from
+acids; sometimes from water; and sometimes
+from metallic oxids, <abbr title="et cetera">&amp;c.</abbr></p>
+
+<p>On the other hand, the catalogue of substances,
+<span class="pagenum" id="Page_8">[8]</span>which reduce bodies to their combustible
+state, is no less numerous.</p>
+
+<p>“Heat,” says M. De Fourcroy, “separates
+oxygene from some; one metal takes it
+from another; hydrogene, or inflammable
+gas, takes it from most metals; and
+carbone perhaps from all&#x2060;<a id="FNanchor_5_5" href="#Footnote_5_5" class="fnanchor">[5]</a>.”</p>
+
+<p>To this list, may be added phosphorus,
+sulphur, and compounds of these with hydrogen;
+also light, and the electric fluid,
+<abbr title="et cetera">&amp;c.</abbr>, as will appear in the sequel.</p>
+
+<p>But, I shall endeavour to show, that the
+hydrogen of water is the only substance,
+that restores oxygenated bodies to their combustible
+state; and that water is the only
+source of the oxygen, which oxygenates combustible
+bodies.</p>
+
+<p>Want of simplicity is not the only defect
+in Mr. Lavoisier’s hypothesis: for he supposes,
+that the increase of weight, which bodies
+acquire during combustion, depends on
+the absorption of the oxygenous principle
+alone.</p>
+
+<p>Thus, when a bit of phosphorus, sulphur,
+or charcoal, is burnt in vital air; the increase
+of weight, which these bodies acquire, he attributes
+entirely to oxygen, or the base of
+vital air.</p>
+
+<p>These combustions he explains, by supposing,
+that the phosphorus, sulphur, and charcoal,
+decompose oxygen gas, by absorbing
+<span class="pagenum" id="Page_9">[9]</span>its base from caloric, and light, which are
+set free.</p>
+
+<p>“There is,” says M. Lavoisier, “a total
+absorption of vital air, or rather of the
+oxygene, which forms its base in the combustion
+of phosphorus, and the weight of
+the phosphoric acid obtained, is found to
+be rigorously equal to the weight of the
+phosphorus, added to that of the vital air
+employed in its combustion. The same
+agreement of weights is observed in the
+combustion of inflammable gas and vital
+air, in the combustion of charcoal&#x2060;<a id="FNanchor_6_6" href="#Footnote_6_6" class="fnanchor">[6]</a>”, <abbr title="et cetera">&amp;c.</abbr></p>
+
+<p>His idea of the calcination of metals is the
+same.</p>
+
+<p>“We do not,” says M. Lavoisier, “affirm
+that vital air combines with metals to
+form metallic calces, because this manner
+of enunciating would not be sufficiently
+accurate: but we say, when a metal
+is heated to a certain temperature, and
+when its particles are separated from each
+other to a certain distance by heat, and
+their attraction to each other is sufficiently
+diminished, it becomes capable of decomposing
+vital air, from which it seizes the
+base, namely oxygene, and sets the other
+principle, namely caloric, at liberty.</p>
+
+<p>“This explanation of what passes during
+the calcination is not an hypothesis, but
+the result of facts. It is upwards of twelve
+<span class="pagenum" id="Page_10">[10]</span>years, since the proofs have been laid by
+one of us, before the eyes of the academy,
+and have been verified by a numerous
+commission. It was then established, that
+when the calcination of metals is effected
+beneath an inverted glass vessel, or in
+closed vessels containing known quantities
+of air, the air itself is decomposed, and
+the weight of the metal becomes augmented
+by a quantity accurately equal to that
+of the air absorbed. It has since been found,
+that when the operation was performed in
+very pure vital air, the whole might be
+absorbed.”</p>
+
+<p>“No supposition enters into these explanations;
+the whole is proved by weight
+and measure&#x2060;<a id="FNanchor_7_7" href="#Footnote_7_7" class="fnanchor">[7]</a>.”</p>
+
+<p>Hence it is evident, that M. Lavoisier confounds
+oxygen with oxygen gas; and considers
+the latter as a compound of oxygen,
+light, and caloric.</p>
+
+<p>But since the dryest oxygen gas contains a
+large proportion of water, as Dr. Priestley
+and M. Kirwan have shown&#x2060;<a id="FNanchor_8_8" href="#Footnote_8_8" class="fnanchor">[8]</a>; and since the
+whole of the gas, except the caloric, and
+light, is absorbed, it necessarily follows, that
+the increase of weight, which bodies acquire
+during combustion, depends not only on the
+oxygen, but also on the water, contained in
+vital air.</p>
+
+<p><span class="pagenum" id="Page_11">[11]</span></p>
+
+<p>Therefore oxids are compounds of combustible
+bodies united to oxygen, and water.</p>
+
+<p>Another great objection to M. Lavoisier’s
+hypothesis, is, that he supposes both oxygenation,
+and reduction, effected by a single
+affinity.</p>
+
+<p>Thus, according to him, when iron reduces
+a sulphate of copper, the iron does nothing
+more, than separate the oxygen from the copper,
+by its superior attraction for that principle.</p>
+
+<p>From this view of combustion, grounded
+on the most accurate experiments in chymistry,
+it is manifest, that the antiphlogistic
+hypothesis does not account fully for the increase
+of weight, which bodies acquire during
+combustion; and consequently, that it
+cannot be admitted as a just theory.</p>
+
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+
+<p><span class="pagenum"><a id="Page_12"></a><a id="Page_13"></a>[13]</span></p>
+
+
+  <h2 class="nobreak" style="line-height: 2" id="CHAPTER_I">
+    CHAPTER I.
+    <br>
+    <span class="smcap">REDUCTION of METALS</span>
+    <br>
+    <span class="fs60">BY</span>
+    <br>
+    HYDROGEN GAS.
+  </h2>
+</div>
+
+
+<p class="drop-cap">As Hydrogen, or the base of inflammable
+air, seems to act an important part in the
+following experiments, and is, according to
+some chymists, pure phlogiston itself; I have
+therefore assigned the first chapter in this
+essay to hydrogen gas, this being the most
+simple form, in which hydrogen has hitherto
+been obtained.</p>
+
+<p>But I had not the means of procuring this
+gas free of carbone, and other impurities,
+that it dissolves and elevates during its formation;
+or of excluding atmospheric air,
+which circumstances, I am sensible, must,
+in some measure, influence the result; as it
+cannot be supposed, that these extraneous
+bodies would remain inactive during the process
+of reduction. However, as such exactness
+<span class="pagenum" id="Page_14">[14]</span>is not in the power of every experimenter,
+I was under a necessity of using hydrogen
+gas, with the disadvantages here mentioned.</p>
+
+<p>Though most of the experiments in this
+essay were made on a variety of white and
+coloured silks, I shall relate only those made
+on the former, as it exhibits the changes
+produced more distinctly, and contains less
+foreign matter to modify the result of experiment;
+and, for brevity’s sake, I shall use
+the term <em>silk</em>, by which <em>white silk</em> is always
+designed.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 1. Gold.</span></h3>
+
+<p>I poured a quantity of sulphuric ether on a
+solution of gold in nitro-muriatic acid, and,
+by this means, obtained a solution of gold in
+ether, which I separated from the acid.</p>
+
+<p>In this ethereal solution of gold, I dipped
+a piece of silk, after it was taken out, and
+the ether evaporated, it was suspended in a
+tall glass cylinder, placed over a vessel, containing
+a mixture of diluted sulphuric acid,
+and iron filings.</p>
+
+<p>The silk thus exposed to a rapid current
+of hydrogen gas acquired, after some time,
+a purple colour, and a large spangle of gold,
+of an irregular figure, appeared on the upper
+end of the silk, and looked very brilliant.</p>
+
+<p>The silk was kept exposed to the gas about
+four months, and frequently observed, but no
+<span class="pagenum" id="Page_15">[15]</span>other remarkable change was perceived, except
+that the purple colour became more intense:
+the experiment was now discontinued; and
+on taking out the silk, and examining it in
+the light of the sun, <ins id="ER-2" class="corr" title="Transcriber's Note&mdash;original text: particles of reduced gold were observed">I observed many particles
+of reduced gold</ins>; but they were very small,
+and by no means so brilliant, as that, which
+first appeared.</p>
+
+<p>During the experiment, fresh quantities of
+materials for supplying hydrogen gas were
+occasionally added.</p>
+
+<p>From the brilliant spangle of reduced gold
+observed in this experiment, I concluded,
+that there was a sufficient quantity of the
+metal in the fibres of the silk, could it be
+reduced.</p>
+
+<p>This spot of reduced gold was very permanent,
+and adhered firmly to the silk.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 2. Gold.</span></h3>
+
+<p>In order to determine, whether a solution
+of gold in ether, or one in water, were best
+adapted to the object of these experiments;
+I evaporated to dryness a solution of gold in
+nitro-muriatic acid, and dissolved the salt in
+distilled water: in this solution, I immersed
+a piece of silk, which, after it was dried in
+the air, was suspended in a glass cylinder,
+like the former piece, and exposed to the
+action of hydrogen gas about two months.</p>
+
+<p>The silk after some time assumed a purple
+colour, and five or six specks of reduced gold,
+<span class="pagenum" id="Page_16">[16]</span>of the size of pin heads, and one much larger,
+were observed. Examining the silk in the
+sun-beams, I perceived the whole of it spangled
+with minute particles of reduced gold.</p>
+
+<p>After many experiments with these two
+solutions of gold, I was led to conclude, that
+the solution in water answered best.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 3. Silver.</span></h3>
+
+<p>Having dissolved some pure silver in diluted
+nitric acid, and evaporated some of the
+water by a gentle heat, I placed it in the
+dark to crystallize. The crystals were separated
+from the solution, and dissolved in
+distilled water; to one measure of this solution,
+which was saturated with the nitrate of
+silver, ten or twelve measures of distilled
+water were added.</p>
+
+<p>In this diluted solution, a piece of silk was
+dipped; after it was taken out, it was dried
+at the fire: the silk dried in this manner,
+retained its white colour; whereas, were it
+dried gradually in the air; and especially,
+were the light considerable, its white colour
+would be changed to a reddish brown, more
+or less intense, according to the quantity of
+light present.</p>
+
+<p>Some kinds of silk, on being immersed in
+<ins id="ER-3" class="corr" title="Transcriber's Note&mdash;Removed duplicated text per errata.">a solution of nitrate of silver, have some of
+their threads immediately coloured brown:
+but I often got white silk, which would retain</ins>
+<span class="pagenum" id="Page_17">[17]</span>its pure white colour, if dried at the
+fire, or in the dark.</p>
+
+<p>The piece of silk dried, as above, was suspended
+in the middle glass of Dr. Nooth’s
+machine; and into the lower glass were introduced
+a diluted solution of sulphuric acid,
+and some small iron nails.</p>
+
+<p>The machine was now placed in a dark
+closet, to exclude the action of light; after
+some time, the silk, thus exposed to hydrogen
+gas, put on a light brown colour, which
+gradually became deeper, until it was changed
+to a disagreeable black, with some mixture
+of brown: then very small particles of reduced
+silver began to appear, which increased
+by degrees, in number, and brightness.</p>
+
+<p>The experiment was continued four
+months; after which time, the silk was
+taken out of the machine: it had a gray metallic
+appearance, intermixed with a considerable
+tinge of brown.</p>
+
+<p>This experiment was repeated on another
+piece of silk, every circumstance being the
+same, except that a quantity of water was
+put in the middle glass of the machine, over
+which the silk was suspended; the intention
+of interposing the water in this experiment
+was to purify the gas.</p>
+
+<p>The appearances were much the same, as
+in the last experiment; except that the silk
+<span class="pagenum" id="Page_18">[18]</span>became black sooner; and that some spangles
+of the silver were larger, and better reduced.</p>
+
+<p>The specks of reduced silver were permanent,
+and adhered firmly to the silk.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 4. Lead.</span></h3>
+
+<p>In a solution of acetite of lead in distilled
+water I dipped a piece of silk, and dried it
+in the air; it was then suspended over a quantity
+of water in Dr. Nooth’s machine, and
+exposed to hydrogen gas about three months.</p>
+
+<p>The appearances were much the same as
+in the last experiment, except that the silk
+was not so black: the particles of reduced
+lead resembled silver.</p>
+
+<p>Similar experiments were made in this machine
+on bits of silk imbued with a solution
+of nitro-muriate of gold in water; but the
+appearances being much the same as those
+mentioned in the first and second experiments,
+it is unnecessary to repeat them here.</p>
+
+<p>It is much easier to imagine, than express
+my anxiety, to discover the cause of the brilliant
+specks of reduced gold and silver, with
+which the pieces of silk in these experiments
+were sometimes spangled; concluding, that
+were the cause ascertained, it would be a considerable
+step towards accomplishing the object
+in view.</p>
+
+<p>But many and diversified were the experiments
+I made before the circumstance, on
+which these spangles depended, was perceived.</p>
+
+<p><span class="pagenum" id="Page_19">[19]</span></p>
+
+<p>At length, I found it depended on the presence
+of moisture; and that the spangles of
+reduced metal were owing to small drops of
+water carried up by the elastic fluid, and deposited
+on the silk.</p>
+
+<p>The experiments, which led to this conclusion,
+shall be related in their proper places.
+I shall now proceed to recite the remainder
+of the experiments in this essay, conformable
+to the plan laid down in the preface, premising
+an occurrence observed in the course
+of them.</p>
+
+<p>I sometimes found, that the production of
+hydrogen gas from a mixture of acid, water,
+and iron nails, would unexpectedly stop,
+which induced me to add more acid; this not
+succeeding, I added more water; but still no
+gas was formed: the proportions of acid and
+water were varied without effect. Thinking
+the mixture of acid and water unfit for the
+purpose, I poured it off, and repeatedly
+washed and agitated the nails with more water,
+which was also poured off; but happening
+inadvertently to add some of the mixture
+of acid and water, which I had before
+poured off as unfit for use, I was surprised
+to find the gas produced with great rapidity.</p>
+
+<p>Reflecting on the cause of this odd circumstance,
+I concluded that it depended on
+a crust of superoxygenated iron, formed on
+the surface of the nails, which defended
+them from the action of the water and acid,
+and that this crust was removed by the agitation
+<span class="pagenum" id="Page_20">[20]</span>and washing, which enabled the diluted
+acid to act again on the iron.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 5. Gold.</span></h3>
+
+<p>I immersed a bit of silk in a solution of
+nitro-muriate of gold in distilled water, and
+dried it in the air; it was then placed over a
+cylindrical glass vessel, containing a mixture
+of diluted sulphuric acid and iron nails, for
+about half an hour; but no reduction of the
+metal could be observed.</p>
+
+<p>I dipped another bit of silk in the same
+solution of gold, and exposed it, while wet,
+to the same current of hydrogen gas, and
+instantly signs of reduction appeared; for the
+yellow colour, which the solution imparts to
+silk, began to change to a green, and very
+soon a film of reduced gold glittered on the
+surface opposed to the gas: shortly after, a
+beautiful blue spot, fringed with orange and
+purple, was formed on the middle of the
+silk. During the experiment, which lasted
+about half an hour, the silk was kept constantly
+wet with distilled water.</p>
+
+<p>When experiments are made with this preparation
+of gold, it is necessary to evaporate
+the solution to dryness, before the salt be dissolved
+in the water; as an excess of acid prevents
+the reduction in a great measure. Solutions
+of gold in these experiments do not
+admit of being so largely diluted, as solutions
+of silver, and other metals do.</p>
+
+<p><span class="pagenum" id="Page_21">[21]</span></p>
+
+
+<h3 class="center"><span class="smcap">Exp. 6. Silver.</span></h3>
+
+<p>I immersed a piece of silk in a solution of
+nitrate of silver, and dried it in a dark place;
+it was then exposed to a current of hydrogen
+gas about twenty minutes; but no reduced silver
+appeared, the only change observable was
+a brown stain.</p>
+
+<p>I immersed another bit of the same silk in
+the same solution of silver, and having exposed
+it, while wet, to a stream of hydrogen
+gas, I soon observed evident signs of reduction;
+the white colour of the silk was
+changed to a brown, which became gradually
+more intense; and the surface of the
+silk, opposed to the gas, was coated with
+reduced silver: various colours, as blue,
+purple, red, orange, and yellow, attended
+the reduction. These colours often change,
+and are succeeded by others in the progress
+of the reduction. The threads of the silk
+look like silver wire, tarnished in some parts,
+but of great lustre in others.</p>
+
+<p>The silk was kept wet with distilled water
+during the experiment. When the silk happened
+to be too much wetted, the under surface
+opposed to the gas was often covered
+with scales of a dull blue colour: these, after
+the silk dries, may be brushed off, and another
+coat of reduced silver, which adheres
+firmly, but has no considerable brightness,
+is left behind.</p>
+
+<p><span class="pagenum" id="Page_22">[22]</span></p>
+
+<p>These experiments on the reduction of
+gold, and silver, were often repeated with
+nearly the same result.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 7. Silver.</span></h3>
+
+<p>Thinking some other preparation of silver
+might answer better than a nitrate, I precipitated
+some of the latter with a solution of
+muriate of soda, and poured the whole on a
+filter; the precipitate was well washed with
+distilled water, and dissolved in ammonia.
+In this solution I immersed a piece of silk,
+and dried it in the air; and having exposed
+it to the action of hydrogen gas, I could perceive
+no signs of reduction, except a faint
+brown colour.</p>
+
+<p>I dipped another bit of silk in the same
+solution of silver, and in order to determine
+if water had the power of promoting the
+reduction of the silver in this preparation, as
+it had in the former experiments, I exposed
+the silk, while wet, to the same current of
+hydrogen gas; and in a few seconds the metallic
+lustre was evident on the surface opposed
+to the current. After some little time,
+a blue speck and a faint trace of yellow appeared,
+but soon vanished.</p>
+
+<p>This preparation of silver does not stain
+white silk so much as a nitrate does; the reduced
+silver was indeed very brilliant, but
+soon grew dull, and disappeared; a brown
+stain only remaining; so that it seems rather
+<span class="pagenum" id="Page_23">[23]</span>inferior to nitrate of silver, which also, after
+reduction, tarnishes, grows dull, and often
+disappears; but sometimes part of it remains
+permanently reduced.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 8. Platina.</span></h3>
+
+<p>With much difficulty I procured a small
+quantity of the ore of platina, and dissolved
+it in nitro-muriatic acid. The solution was
+evaporated to dryness, and the salt was then
+dissolved in distilled water.</p>
+
+<p>A bit of silk was dipped in part of this
+solution, and dried in the air; it was then
+exposed to a brisk current of hydrogen gas
+about twenty minutes, but no signs of reduction
+appeared.</p>
+
+<p>Another bit of silk was immersed in the
+solution of platina, and exposed, while wet,
+to the same current of hydrogen gas; in five
+or six minutes the platina was reduced, exhibiting
+a livid white metallic appearance on
+the surface of the silk opposed to the current.
+No colours attended the reduction. This solution
+imparts a yellowish brown colour to
+silk.</p>
+
+<p>After some time, the whole of the metallic
+lustre disappeared, in proportion as the
+silk became dry.</p>
+
+<p>The solution of platina requires more
+time, and a stronger current of hydrogen
+gas for its reduction, than solutions of silver
+and gold do.</p>
+
+<p><span class="pagenum" id="Page_24">[24]</span></p>
+
+
+<h3 class="center"><span class="smcap">Exp. 9. Mercury.</span></h3>
+
+<p>I immersed a bit of silk in a solution of
+oxygenated muriate of mercury in distilled
+water, and dried it in the air: it was then
+exposed to a stream of hydrogen gas; but
+underwent no visible change.</p>
+
+<p>I dipped another bit of silk in the same
+solution of mercury, and exposed it, while
+wet, to the same current of gas; the metal
+was soon reduced in a beautiful manner, and
+resembled silver.</p>
+
+<p>The reduction began suddenly, with scarce
+any appearance of previous stain; some very
+faint, but at the same time transparent colours
+attended it: the most remarkable of
+these were a light orange, with a fringe of
+blue, and a yellow verging on a faint green.
+These colours soon disappeared.</p>
+
+<p>After the silk was turned, I observed, that
+its texture was, in some parts, concealed by
+a thin film, which, as the reduction proceeded,
+was perceived to dart along the
+threads of the silk, gilding them in a beautiful
+manner, and exhibiting the texture very
+distinctly.</p>
+
+<p>After some time, the mercury seemed to
+disappear, so as to render it doubtful whether
+any of it remained in the silk; but shaking
+it in the sunbeams, I perceived bright atoms
+fly off; and rubbing the silk on a bit of blue
+paper, I observed shining metallic particles,
+<span class="pagenum" id="Page_25">[25]</span>which seemed to have lost their affinity of
+aggregation, for they did not unite.</p>
+
+<p>One remarkable difference between this
+preparation of mercury and nitrate of silver,
+is, that no black or brown stain preceded,
+attended, or followed, the reduction of the
+mercury.</p>
+
+<p>Mr. Scheele reduced a prussiate of mercury,
+dissolved in water, by adding iron filings and
+a small quantity of sulphuric acid to the
+solution&#x2060;<a id="FNanchor_9_9" href="#Footnote_9_9" class="fnanchor">[9]</a>.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 10. Copper.</span></h3>
+
+<p>A piece of silk was immersed in a solution
+of sulphate of copper, then taken out, and
+dried, and exposed for a considerable time to
+a brisk current of hydrogen gas; but no
+signs of reduction could be perceived.</p>
+
+<p>Another bit of silk was dipped in the same
+solution of copper, and exposed, while wet,
+to the same rapid current of hydrogen gas;
+the appearances were the following.</p>
+
+<p>After a minute, or two, the silk assumed
+a faint brown colour, and, on the surface opposed
+to the gas, a white metallic pellicle appeared,
+which vanished in proportion as the
+silk became dry: wetting the silk again, I
+perceived a similar pellicle appear, which
+also vanished, as soon as the silk dried. If
+the silk be kept constantly wet, the brown
+<span class="pagenum" id="Page_26">[26]</span>colour becomes much more intense, attended
+with a very slight tinge of red. The margins
+of the silk projecting beyond the verge
+of the glass cylinder, and therefore not exposed
+to the current of the gas, retained the
+blue colour, which the solution imparts.</p>
+
+<p>In some of these white metallic pellicles
+there appeared a faint brown inclining to yellow,
+which reflected the light, though obscurely.</p>
+
+<p>After the silk dried, nothing remained, but
+a brown stain.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 11. Lead.</span></h3>
+
+<p>A piece of silk was immersed in a solution
+of acetite of lead in distilled water; it was
+then dried, and exposed for some time to a
+stream of hydrogen gas; but underwent no
+perceptible change.</p>
+
+<p>Another bit of silk was dipped in the same
+solution of lead, and exposed, while wet, to
+the same current of hydrogen gas; in a second,
+or two, the surface of the silk, opposed
+to the current, was coated with reduced
+lead, which looked like silver.</p>
+
+<p>The reduction was accompanied with a
+brown stain, but by no means so intense as
+that, which attends the reduction of nitrate
+of silver.</p>
+
+<p>The other side of the silk was opposed to
+the current of hydrogen gas, and soon acquired
+a metallic coat of the same brilliant
+<span class="pagenum" id="Page_27">[27]</span>appearance, exhibiting the texture of the
+silk, in a very striking manner.</p>
+
+<p>It is remarkable, that lead exhibits no colour,
+but a light brown, during its reduction;
+whereas gold, silver, and mercury, display
+a great variety of colours, especially the two
+former.</p>
+
+<p>After some time the lead reduced in this
+manner loses its metallic splendour considerably;
+and that in proportion as the silk
+dries.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 12. Tin.</span></h3>
+
+<p>I dissolved some crystals of muriate of tin
+in distilled water; dipped a bit of silk in
+the solution; and dried it in the air: it was
+then exposed to a stream of hydrogen gas a
+considerable time; but no change, or appearance
+of reduction, could be observed.</p>
+
+<p>Another bit of silk was immersed in the
+same solution of tin, and exposed, while wet,
+to the same current of gas; after some little
+time, the reduction commenced, attended
+with a great variety of beautiful colours; as
+red, yellow, orange, green, and blue, variously
+intermixed.</p>
+
+<p>The reduced tin disappears along with these
+colours, as the silk dries; nothing remaining
+but a feuille-morte colour.</p>
+
+<p>The same solution of tin was also reduced
+by hydrogen gas, obtained from tin, and the
+muriatic acid.</p>
+
+<p><span class="pagenum" id="Page_28">[28]</span></p>
+
+<p>These experiments do not succeed well
+with muriate of tin containing an excess of
+acid.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 13. Arsenic.</span></h3>
+
+<p>A muriate of arsenic, which was prepared
+by digesting white oxid of arsenic in muriatic
+acid, and continuing the heat, till most
+of the acid evaporated, and left behind a soft
+mass of the consistence of tar, was dissolved
+in distilled water.</p>
+
+<p>In this solution a bit of silk was immersed,
+and dried in the air: it was exposed to a brisk
+stream of hydrogen gas, obtained from zinc,
+and muriatic acid; but no reduction took
+place.</p>
+
+<p>Another bit of silk was dipped in the same
+solution, and exposed, while wet, to the
+same current of hydrogen gas; and instantly,
+the surface of the silk, opposed to the gas,
+was covered with a bright coat of reduced
+arsenic, accompanied with a yellow stain.
+In a short time the metallic lustre vanished;
+and nothing remained but the yellow stain.</p>
+
+<p>M. Pelletier restored the acid of arsenic to
+its metallic state, by passing <ins id="TN-1" class="corr" title="Transcriber's Note&mdash;original text: hygrogen">hydrogen</ins> gas
+through a solution of that acid, in twice its
+weight of water&#x2060;<a id="FNanchor_10_10" href="#Footnote_10_10" class="fnanchor">[10]</a>.</p>
+
+<p><span class="pagenum" id="Page_29">[29]</span></p>
+
+
+<h3 class="center"><span class="smcap">Exp. 14. Bismuth.</span></h3>
+
+<p>A bit of silk, which was immersed in a
+solution of nitrate of bismuth in distilled
+water, and exposed dry to hydrogen gas, obtained
+from zinc, and muriatic acid, underwent
+no visible change.</p>
+
+<p>Another bit of silk was dipped in the same
+solution of bismuth, and placed over a languid
+stream of hydrogen gas; the bismuth
+was soon restored to its metallic form, on the
+surface of the silk opposed to the elastic fluid.
+The reduction was attended with a reddish
+brown stain, intermixed with a tinge of
+violet.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 15. Antimony.</span></h3>
+
+<p>A bit of silk was immersed in a solution of
+tartarite of antimony in distilled water; and
+dried in the air. It was then exposed to hydrogen
+gas, obtained from zinc, and muriatic
+acid; but suffered no visible alteration.</p>
+
+<p>Another bit of silk, which was dipped in
+the same solution of antimony, was exposed
+wet to a weak stream of the gas; and, in a
+short time, the metallic lustre appeared, accompanied
+by a light yellow colour.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 16. Iron.</span></h3>
+
+<p>A bit of silk, which was immersed in a
+largely diluted solution of sulphate of iron,
+and dried in the air, was exposed to a strong
+<span class="pagenum" id="Page_30">[30]</span>current of hydrogen gas, obtained from iron
+nails, and diluted sulphuric acid; but no visible
+change was produced on the silk.</p>
+
+<p>Another bit of silk was dipped in the same
+solution of iron, and placed wet over the
+same stream of hydrogen gas; but no reduced
+iron could be perceived. The silk was
+then immersed in a glass of clear water, and
+transferred a very minute metallic film to
+the surface of that fluid.</p>
+
+<p>This experiment was repeated with a rapid
+current of hydrogen gas, obtained from
+zinc, and muriatic acid; and, in about a minute,
+small films of reduced iron were visible
+on the surface of the silk, opposed to
+the gas.</p>
+
+<p>The silk was then immerged in water,
+and transferred to its surface a large metallic
+pellicle; parts of which were very brilliant;
+but other parts were dull, and much more
+imperfectly reduced.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 17. Zinc.</span></h3>
+
+<p>A bit of silk, which was dipped in a muriate
+of zinc, largely diluted with water, and
+dried in the air, was exposed to a rapid current
+of hydrogen gas, obtained from zinc,
+and muriatic acid; but suffered no visible
+alteration.</p>
+
+<p>Another piece of silk was immersed in the
+same solution of zinc, and exposed, while
+<span class="pagenum" id="Page_31">[31]</span>wet, to the same rapid current of hydrogen
+gas: in about half a minute, the metal was
+reduced in a very evident manner, on part
+of the silk. The silk was then dipped in
+a glass of clear water, and transferred a bright
+metallic film to its surface.</p>
+
+<p>As these reductions of iron, and zinc, by
+hydrogen, are contrary to M. Lavoisier’s
+table of the affinities of the oxygenous principle;
+I began to suspect, that the films,
+which were so evident, both on the silk, and
+the water, might be abraded, or torn from
+the zinc, by the muriatic acid; and elevated,
+and deposited on the silk by the gas.</p>
+
+<p>In order to remove this doubt, I dipped a
+bit of the same silk in distilled water; and
+exposed it, while wet, to the same current of
+hydrogen gas, but nothing metallic could be
+seen on the silk; nor did it when immersed
+in water transfer a film, or the smallest appearance
+of a metal, to the surface of that
+fluid: and, therefore, there can be no doubt
+of the reality of these reductions.</p>
+
+<p>Dr. Priestley restored iron, and lead, to
+their metallic state, by heating their oxids
+with a burning glass in hydrogen gas.</p>
+
+<p>These experiments point out an error in
+M. Bergman’s table of elective attractions in
+the humid way; for he assigned the last place
+in that table to phlogiston, which he considered
+as the base of inflammable air; because
+he was unacquainted with any metallic reductions
+<span class="pagenum" id="Page_32">[32]</span>effected by hydrogen in the humid
+way&#x2060;<a id="FNanchor_11_11" href="#Footnote_11_11" class="fnanchor">[11]</a>.</p>
+
+<p>Having found, that water promoted, and
+accelerated, these reductions in a very remarkable
+manner; I was curious to know,
+if alcohol, and ether, would produce the
+same effect. With this view, I evaporated a
+solution of gold in nitro-muriatic acid to
+dryness; when the vessel cooled, some alcohol
+was poured on to dissolve the salt;
+and immediately the vessel containing the
+salt, became so hot, that it could be scarcely
+endured by the hand; and diffused a fragrant
+smell, like that of ether, which, no doubt,
+was a species of that fluid.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 18. Gold.</span></h3>
+
+<p>In this solution of gold in alcohol, a bit of
+silk was dipped, and exposed to a stream of
+hydrogen gas, obtained from diluted sulphuric
+acid, and iron nails; and kept wet with
+alcohol: in about two minutes, the silk began
+to assume a brown colour, and white
+metallic films appeared on some parts of the
+surface opposed to the gas; some of these
+disappeared in a short time; and were succeeded
+by a few very small spangles of the
+proper colour of gold. These also soon vanished;
+and nothing remained but a disgreeable
+<span class="pagenum" id="Page_33">[33]</span>brown stain, intermixed with specks of
+a dull blue.</p>
+
+<p>I sometimes found, on repeating this experiment,
+that no yellow films or spangles
+appeared; and am persuaded, that their appearance,
+and that of the white pellicles also,
+depends on the presence of water, contained
+in the alcohol, or the gas, and deposited on
+the silk.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 19. Gold.</span></h3>
+
+<p>A bit of silk was immersed in a solution of
+gold in ether, and exposed to a stream of hydrogen
+gas, and kept wet with ether. The
+silk underwent no alteration for a few minutes;
+at length, it began to assume a faint
+brown colour, but no white, or yellow films
+appeared.</p>
+
+<p>If this experiment be continued till the
+silks collects a sufficient quantity of water
+from the gas, some films will appear.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 20. Silver.</span></h3>
+
+<p>I procured some nitrate of silver, which
+had been fused in order to expell as much of
+its water as possible; and dissolved it in alcohol.
+I immersed a bit of silk in this solution,
+and exposed it to a stream of hydrogen
+gas, and kept it wet with alcohol: in a few
+seconds, the silk assumed a brown colour,
+which gradually became more intense: but
+no reduced silver appeared for several minutes;
+<span class="pagenum" id="Page_34">[34]</span>at length, a few metallic films appeared
+on part of the surface opposed to the
+gas.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 21. Mercury.</span></h3>
+
+<p>A bit of silk was dipped in a solution of
+oxygenated muriate of mercury, and dried;
+it was then exposed to hydrogen gas about
+ten or fifteen minutes, and kept constantly
+wet with alcohol. The silk, during the first
+minutes, suffered no perceptible alteration:
+at length, a few small films were visible on
+the side of the silk opposed to the current.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 22. Lead.</span></h3>
+
+<p>A bit of silk, which was immersed in a solution
+of acetite of lead, and dried, was exposed
+about fifteen minutes to a stream of the
+gas; and kept constantly wet with alcohol;
+but suffered no visible change; except that
+a very minute film was reduced on one of its
+margins, which did not project beyond the
+verge of the glass vessel on which it was
+placed.</p>
+
+<p>When we compare these experiments with
+those, in which water was used, to wet the
+silk, ’tis evident, that alcohol, and ether,
+do not promote the reduction of metals, as
+water does; and that the few films, which
+appear, when the silk is kept wet with ether
+or alcohol, depend entirely on water collected
+from the gas, or deposited by them on
+the silk during their evaporation.</p>
+
+<p><span class="pagenum" id="Page_35">[35]</span></p>
+
+<p>In order to compare the effects of hydrogen
+gas, obtained from water, iron nails,
+and muriatic acid, with that, procured from
+the same materials, by means of the sulphuric;
+I made some experiments on gold, silver,
+mercury, and lead, in the same manner,
+as the preceding; and the principal difference
+was, that the colours produced in all the
+pieces of silk, except that, which was dipped
+in acetite of lead, were much brighter, and
+more beautiful, than any produced, when
+the sulphuric acid was used.</p>
+
+<p>The reduction of the lead was accompanied
+with its usual brown colour.</p>
+
+<p>On the upper surface of a bit of silk, which
+was dipped in a solution of gold, a green
+colour instantly appeared; and soon changed
+to a deep olive, in proportion as the reduction
+advanced: now examining the under surface,
+I saw it coated with a bright film of reduced
+gold, in the middle of which a blue spangle,
+mixed with purple, soon began to appear: I
+then moistened the upper surface of the silk
+with water; and in a few seconds, it also
+was coated with reduced gold.</p>
+
+<p>The blue on the other side of the silk became
+much more intense: the piece was
+now turned; and on each colour I let fall a
+drop of water: the drop on the blue had a
+blue film, the drop on the purple, had a
+purple film, and the drop on the yellow, a
+film of reduced gold.</p>
+
+<p>After some time, these drops of water evaporated,
+<span class="pagenum" id="Page_36">[36]</span>and the films came again in contact
+with the silk: some parts of which were
+left bare, as generally happens, when too
+much water is applied.</p>
+
+<p>On the under surface of a bit of silk,
+which was immersed in a solution of nitrate
+of silver in water, a coat of reduced metal
+was formed, with various colours, as green,
+blue, orange, and yellow, the beauty and
+brightness of which were remarkable.</p>
+
+<p>In some time a muriate of silver is formed
+in the fibres of the silk, which on exposure
+to light becomes of a bluish black colour:
+but the whole of the silver does not undergo
+this change; for part of it remains in its
+metallic state. The colours remain a considerable
+time, if the silk be removed from the
+gas before this muriate is formed.</p>
+
+<p>Hence it appears, that hydrogen gas should
+not be prepared with an acid, which forms
+an insoluble compound with the metal to be
+reduced.</p>
+
+<p>I also found, that hydrogen gas produces
+different effects not only according to the
+difference of the acid, but also according to
+the difference of the metal employed to obtain
+it: for this gas procured from zinc or
+tin, and muriatic acid, did not restore gold
+to its proper metallic lustre; but formed on
+the silk, a white metalline coat like silver.</p>
+
+<p>The experiments related in this chapter
+indicate the following conclusions.</p>
+
+<ol>
+<li>Hydrogen is capable of reducing the
+<span class="pagenum" id="Page_37">[37]</span>metals in the ordinary temperature of the
+atmosphere.</li>
+
+<li>Water promotes, and accelerates, these
+reductions, in a very remarkable manner.</li>
+
+<li>Ether, and alcohol, do not promote
+these reductions, without the aid of water.</li>
+
+<li>A variety of colours accompanies these
+reductions, similar to what appears, during
+the calcination of metals by heat and air;
+and depends on the same cause: <abbr title="videlicet">viz.</abbr> the
+quantity of oxygen combined with the metal.
+
+<p class="noindent" style="margin-bottom: 0">These colours have not been observed hitherto;
+nor indeed could they; as the metals
+were reduced in close vessels, and in high
+degrees of heat.</p></li>
+
+<li>These reductions often disappear.</li>
+</ol>
+
+<p>This is commonly owing to an imperfect,
+and partial reduction of the metal: for the
+acid, and water, remaining in that part of
+the metallic solution, not reduced, recalcines
+these delicate films: sometimes the disappearance
+of the metallic lustre depends on
+the nature of the metal itself: thus arsenic,
+lead, silver, <abbr title="et cetera">&amp;c.</abbr>, suffer some degree of calcination
+by water and atmospheric air.</p>
+
+<p>Messrs. Bergman and Keir relate instances,
+in which silver after being precipitated in
+its metallic state, was recalcined, and disappeared.</p>
+
+<p>I first imagined, that water promoted these
+reductions by minutely dividing the particles
+of the metallic salt, and by condensing the
+gas, and bringing its hydrogen, and the metallic
+<span class="pagenum" id="Page_38">[38]</span>oxid, within the sphere of attraction;
+the hydrogen either uniting to the metallic
+earth and reducing it, as the Phlogistians
+suppose; or uniting with, and separating the
+oxygen of the metal, and thus restoring it to
+the metallic form, as the Antiphlogistians
+maintain.</p>
+
+<p>But it is evident from the experiments related,
+that water does not promote these reductions
+solely, by minutely dividing the
+particles of the metallic salt: for were this
+the case; ether, and alcohol, should promote
+the reduction of the metallic salts, which
+they dissolve, since they divide their particles,
+as minutely as water can.</p>
+
+<p>Since then metallic solutions in ether, and
+alcohol, cannot be reduced by hydrogen gas;
+it follows that the above supposition concerning
+the mode of agency of water does not account
+for the reduction of metals in this way.</p>
+
+<p>And indeed were it true that hydrogen condensed
+by water reduced metals in the manner
+above mentioned, it would follow, that
+the reduction was effected by a single affinity,
+which cannot be admitted; 1st. because the
+existence of a single affinity in such cases has
+not been proved; 2dly, because a double affinity
+always takes place in preference to a
+single affinity, which is demonstrated by the
+following facts, transcribed from the works
+of Mr. Kirwan.</p>
+
+<p>“If a solution of silver in the nitrous acid
+be thrown into a mixed solution of fixed
+<span class="pagenum" id="Page_39">[39]</span>alkali and common salt, the silver will be
+precipitated by the marine acid of the
+common salt, and not by the free alkali,
+contained in the liquor: for a luna cornea
+is found&#x2060;<a id="FNanchor_12_12" href="#Footnote_12_12" class="fnanchor">[12]</a>.”</p>
+
+<p>“I repeated the experiment with a solution
+of lead, and also of mercury in the
+nitrous acid, and the result was similar:
+<ins id="TN-2" class="corr" title="Transcriber's Note&mdash;unclear text was potentially horn.">both</ins> lead and marine salt of mercury were
+formed&#x2060;<a id="FNanchor_13_13" href="#Footnote_13_13" class="fnanchor">[13]</a>.”</p>
+
+<p>In these experiments of Messrs. Monnet
+and Kirwan, ’tis evident that a double affinity
+takes place in preference to a single one: for
+the nitrous acid of these different nitrates
+unites with the alkali of the common salt,
+while the muriatic acid of the latter seizes
+the silver, mercury, and lead, of the nitrates,
+and forms muriates of silver, mercury, and
+lead: the free alkali remaining passive in the
+mixture.</p>
+
+<p>M. Lavoisier says, “There exists only in
+nature, as far as we can observe them,
+cases of double affinity, often triple, and
+others perhaps still more complicated&#x2060;<a id="FNanchor_14_14" href="#Footnote_14_14" class="fnanchor">[14]</a>.”</p>
+
+<p>Now as water does not promote these reductions
+merely by dissolving, and minutely
+dividing, the particles of the metallic salts,
+and condensing the hydrogen gas; and since
+a double affinity takes place in preference to
+<span class="pagenum" id="Page_40">[40]</span>a single affinity; it is obvious that the water
+must be decomposed in these reductions in the
+following manner.</p>
+
+<p>The hydrogen of the gas unites to the oxygen
+of the water, while the hydrogen of the
+latter unites in its nascent state to the oxygen
+of the metal, reduces it, and forms water.</p>
+
+<p>Thus what could never be effected by a
+single, is readily performed by a double
+affinity.</p>
+
+<p>Hence it follows, that the hydrogen of the
+gas is oxygenated by the oxygen of the water,
+while the metal is, at the same time,
+restored to its combustible state. It also follows,
+that the quantity of water formed is
+double that decomposed.</p>
+
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+
+<p><span class="pagenum" id="Page_41">[41]</span></p>
+
+
+  <h2 class="nobreak" style="line-height: 2em" id="CHAPTER_II">
+    CHAPTER II.
+    <br>
+    <i>Reduction of Metals by Phosphorus.</i>
+  </h2>
+</div>
+
+
+<p class="drop-cap">The next substance, of whose effects in
+reducing metals in the fibres of silk, I shall
+treat, is Phosphorus, one of the most inflammable
+substances, we are acquainted with.</p>
+
+<p>I was for some time at a loss, how to apply
+it to this purpose; but learning from a
+note of Mr. Lewis, that it is soluble in
+ether; I dissolved a small quantity of it in
+that fluid, which can be easily effected, if
+the ether be good. The solution is considerably
+promoted by a gentle heat, as that
+of the hand, and may be made in a small
+phial, which should be nearly filled with the
+ether, and accurately corked: a common
+cork is preferable, for this purpose, to a glass
+stopper; and a single grain of phosphorus is
+sufficient for a great number of experiments.</p>
+
+<p>I sometimes applied a much greater degree
+of heat than the above, by placing the phial
+in hot sand, pressing on the cork at the
+same time with my finger, to prevent its
+being forced out by the expansion of the
+ether, part of which is converted into an
+elastic fluid, and holds some phosphorus in
+solution: the ether soon begins to boil; the
+<span class="pagenum" id="Page_42">[42]</span>phosphorus melts; and a strong solution is
+obtained in a few minutes by shaking the
+phial. If the solution be removed to a cool
+place it frequently deposits crystals.</p>
+
+<p>This manner of preparing the solution is
+attended with some danger; for should the
+phial burst, or the cork be extruded, the
+contents will be thrown out with considerable
+force, and that part of the phosphorus not
+dissolved by the ether burn with great violence.</p>
+
+<p>The only objection to this preparation of
+phosphorus is the ether, which must necessarily
+modify the result, and prevent that
+simplicity so desirable in experiment.</p>
+
+<p>But, after some observation, it was perceived,
+that the ether flies off, and leaves the
+phosphorus pure, and minutely divided in
+the fibres of the silk: the ether, from its
+great volatility, first evaporates, and, at the
+same time, produces a very considerable degree
+of cold, which effectually prevents the
+evaporation, and combustion, of the phosphorus.</p>
+
+<p>After the ether evaporates; the cold ceases,
+and the combustion of the phosphorus commences,
+attended with white fumes, which
+continue till the whole is consumed, if no
+other power intervene.</p>
+
+<p>Hence it is evident, that this preparation
+of phosphorus has a simplicity, and elegance,
+not always to be obtained.</p>
+
+<p>It has also another great advantage in experiments
+<span class="pagenum" id="Page_43">[43]</span>of this kind; for it does not
+change, in the smallest degree, the white
+colour of silk, during its slow combustion,
+which is not attended with heat sufficient to
+affect the most delicate colour. This property
+of not affecting the colour of the silk
+renders observation, and experiment, more
+accurate; as whatever change supervenes,
+must depend either on the metallic solution
+itself, or on the action of the phosphorus on
+the same. But this advantage is confined to
+a certain range of the thermometer; for if
+the heat be increased to about 86° of Fahrenheit,
+and the silk be dry, the phosphorus
+is apt to set fire to it.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 1. Gold.</span></h3>
+
+<p>I immersed a bit of silk in a solution of
+gold in ether, and after the ether evaporated,
+dropped on it some of the solution of phosphorus,
+which diffused itself through the
+silk, like a drop of oil, and formed a circumscribed
+spot, whose limits, as the ether evaporated,
+assumed a brown colour, which soon
+diffused itself equally over every part, to
+which the solution of phosphorus was applied;
+but the parts of the silk, to which
+the latter did not reach, retained the yellow
+colour, which the solution of gold gave
+them.</p>
+
+<p>The silk viewed by transmitted light presented
+the same colours, except that the limits
+<span class="pagenum" id="Page_44">[44]</span>of the brown appeared more intense,
+and seemed to border on a faint purple.</p>
+
+<p>Examining the silk next day, I found, that
+the whole of the brown stain acquired a faint
+shade of purple, which was most evident on
+the margins of the stain.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 2. Gold.</span></h3>
+
+<p>I dipped a bit of silk in the solution of gold
+in ether, and after it was well dried, half of
+it was wetted with distilled water; the other
+half remaining dry: the solution of phosphorus
+was applied to both the moist and dry
+parts of the silk: instantly the part wetted
+with the water began to acquire a purple colour;
+and, soon after, the metallic splendour
+of the gold appeared; but that part, which
+was kept dry, acquired only a brown stain,
+similar to that described in the preceding experiment.</p>
+
+<p>I repeated these experiments many times,
+and always found, that the gold was reduced
+only in proportion to the water applied.</p>
+
+<p>Finding water promoted the reduction of
+gold by phosphorus, I began to form various
+conjectures about its mode of action: I first
+supposed, it acted by holding the particles of
+the salt minutely divided, thus diminishing
+their attraction of cohesion, and consequently
+increasing their chymical attraction.</p>
+
+<p>The truth of this supposition might, I
+thought, be decided by using ether, and alcohol,
+<span class="pagenum" id="Page_45">[45]</span>instead of water, to wet the silk,
+avoiding aqueous moisture, as much as possible;
+accordingly, I made the following experiments,
+which were frequently repeated
+with nearly the same result.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 3. Gold.</span></h3>
+
+<p>A piece of silk was immersed in the solution
+of phosphorus; as soon as the ether evaporated,
+and the phosphorus began to fume,
+an ethereal solution of gold was dropped on
+the silk, which immediately got a brown
+colour; the piece was kept constantly wet
+with ether; in some time a purple tinge appeared
+on parts of the silk; and, shortly after,
+small films of reduced gold appeared: the
+silk was now remarkably wet, and seemed
+to have a great power of collecting water;
+this, I supposed, was partly attracted from
+the air by the salt, and phosphorous acid
+formed during the combustion, which has a
+powerful attraction for water; and partly deposited
+in the silk by the ether during its
+evaporation.</p>
+
+<p>In order to determine if the ether during its
+evaporation deposited water in the silk, I kept
+a bit of silk wet with ether for a few minutes,
+and found, that, after the evaporation ceased,
+the silk was moist: but this humidity was
+not so great, as that observed in the silk, to
+which the ethereal solutions of phosphorus,
+and gold, were applied.</p>
+
+<p><span class="pagenum" id="Page_46">[46]</span></p>
+
+<p>Another bit of silk was dipped in the
+ethereal solution of gold, and after the ether
+evaporated, the solution of phosphorus was
+applied: a brown colour was produced; the
+silk was kept wet with ether, and, in a short
+time, a purple tinge appeared on parts of it;
+but chiefly at the margin of the stain, which
+gradually diffused itself over the whole.</p>
+
+<p>The only difference between this and the
+preceding experiment on gold is the order, in
+which the solution of gold, and phosphorus,
+were applied to the silk; but there is a considerable
+difference in the result; for in this
+the brown and purple colours were formed
+much more slowly, and no particles of reduced
+gold appeared till after a much longer
+time.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 4. Gold.</span></h3>
+
+<p>A piece of silk was immersed in the solution
+of phosphorus, and when the white
+fumes began to rise, a solution of gold in alcohol
+was applied to the silk, which was
+kept wet with alcohol; a brown tinge, which
+soon changed to a purple, appeared on different
+parts; and, in a little time after, a
+very small film of reduced gold was visible on
+a part of the margin.</p>
+
+<p>In another experiment, conducted in the
+same manner, the reduction was more evident.</p>
+
+<p>The solution of gold used in this experiment
+<span class="pagenum" id="Page_47">[47]</span>was very rich; and had a great attraction
+for water; for bits of silk tinged
+with it, could not be dried without difficulty;
+and after they were removed to a cool place,
+they very soon became moist again. This is
+more or less the case with solutions of gold
+in general.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 5. Gold.</span></h3>
+
+<p>A bit of silk was dipped in a solution of
+gold in alcohol, and dried; then some of the
+solution of phosphorus was poured on the
+silk; a brown, and then a purple colour, appeared;
+and in some parts a small portion of
+the gold was reduced: the reduction was
+very obscure; but became gradually more
+evident, in proportion as it attracted water
+from the air. The silk was occasionally wetted
+with alcohol.</p>
+
+<p>This experiment was repeated, with this
+difference, that the silk was not kept wet
+with alcohol; and no reduced gold could be
+perceived.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 6. Gold.</span></h3>
+
+<p>In order to exclude water more effectually,
+a small phial was carefully dried by placing
+it in hot sand, and then corked, to prevent
+the access of moisture from the air; when
+the phial cooled, it was nearly filled with
+ether, and a small bit of phosphorus dropped
+into it; it was then corked, and replaced
+<span class="pagenum" id="Page_48">[48]</span>on the hot sand; the phosphorus soon melted,
+and a strong solution was obtained by
+shaking the phial.</p>
+
+<p>Into this solution a small bit of silk, which
+was dipped in a rich solution of gold, and
+carefully dried, was introduced: the silk immediately
+got a brown tinge; but not a particle
+of reduced gold could be perceived.
+The solution in a short time became turbid,
+and deposited a brown powder. The colour
+of <ins id="TN-3" class="corr" title="Transcriber's Note&mdash;original text: theprecipitate">the precipitate</ins> was exactly the same, as that
+which the silk acquired. The experiment
+was continued about three months, and carefully
+observed; but no other change could be
+perceived: at the end of this time the silk
+was taken out of the phial; and the solution
+of phosphorus was found capable of reducing
+gold and silver by the aid of water.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 7. Gold.</span></h3>
+
+<p>In order to contrast the effects of water
+with those of ether, and alcohol, more fully,
+a piece of silk was immersed in a solution of
+nitro-muriate of gold in water, and dried in
+the air about twelve hours; during which
+time the yellow tinge, the solution of gold
+gave the silk, remained unchanged: the solution
+of phosphorus was then applied; a
+brown stain appeared; the ether soon evaporated;
+the phosphorus began to fume; and
+the silk acquired a purple colour; but not a
+particle of reduced gold could be perceived.
+<span class="pagenum" id="Page_49">[49]</span>The purple tinge in this bit of silk was
+much more intense, and more equal, than
+in the pieces, in which ether and alcohol were
+used.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 8. Gold.</span></h3>
+
+<p>I dipped a piece of silk in the solution of
+phosphorus, when the ether evaporated,
+and the phosphorus began to fume, a solution
+of gold in water was applied; instantly
+the silk was covered with a splendid coat of
+reduced gold.</p>
+
+<p>Nothing can be more striking than this
+experiment, which was repeated times without
+number, or demonstrates the necessity of
+water in these reductions in a more convincing
+manner.</p>
+
+<p>This piece, viewed by transmitted light,
+had a purple colour with a considerable tinge
+of blue; and the margin of the reduced gold
+was fringed with purple.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 9. Gold.</span></h3>
+
+<p>Thinking that phosphorus applied in the
+form of vapour through the medium of water
+might be more effectual than a solution of
+it in ether, I immersed a small bit of silk in
+an aqueous solution of gold, and suffered it
+to dry a little; it was then suspended in a
+phial over a little water, into which a small
+bit of phosphorus was previously introduced:
+the phial was then corked, and placed on hot
+<span class="pagenum" id="Page_50">[50]</span>sand: the phosphorus began to melt, and
+ascend in white vapours, which, as soon as
+they reached the lower end of the silk, gave
+it a brown tinge, succeeded by a purple; and
+the gold began to assume its metallic splendour:
+in a short time these appearances were
+evident over the whole silk.</p>
+
+<p>The following propositions are deducible
+from these experiments.</p>
+
+<ol>
+<li>Water does not promote the reduction
+of gold merely by dissolving, and minutely
+dividing, the particles of the salt, and thus
+diminishing their attraction of cohesion, and
+consequently increasing their chymical attraction,
+as I first supposed; for were this
+the case, ether and alcohol, which equally
+dissolve, and divide, the salt, should produce
+the same effect.</li>
+
+<li>Ether and alcohol do not promote these
+reductions without the aid of water; for it
+is evident from the experiments related, that
+the few particles of reduced gold, which appear,
+when they are employed, depend entirely
+on the quantity of water, which they
+leave in the silk during their evaporation, and
+that attracted from the air by the solution of
+gold, and by the phosphorus during its combustion,
+both of which have a strong attraction
+for water.</li>
+
+<li>Phosphorus does not reduce gold by
+giving the metallic earth phlogiston, as the
+Phlogistians suppose; for were this opinion
+true, a solution of gold in ether, or alcohol,
+<span class="pagenum" id="Page_51">[51]</span>should be reduced by the phosphorus as effectually
+as a solution of gold in water is.</li>
+
+<li>Phosphorus does not reduce gold, by
+combining with, and separating, the oxygen
+of the gold, as the Antiphlogistians assert;
+for were this the case, the particles of the
+phosphorus so attenuated by the ether, should
+reduce a solution of gold in ether, or alcohol,
+as well as a solution of gold in water, since
+the impediment opposed by the attraction of
+cohesion is equally removed in both cases.</li>
+</ol>
+
+<p>I shall conclude these remarks on the reduction
+of gold with the following experiment,
+which often amused me.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 10. Gold.</span></h3>
+
+<p>A small bit of silk was immersed in a
+solution of gold in ether, and dried; then
+the solution of phosphorus was applied, which
+changed the yellow colour of the silk to a
+brown: when the phosphorus began to fume,
+I placed the silk on the palm of my hand,
+and breathed on it a considerable time; a
+purple tinge gradually succeeded the brown,
+and, in some little time after, the metallic
+lustre of the gold began to appear.</p>
+
+<p>The same experiment succeeds with a solution
+of gold in alcohol.</p>
+
+<p>Another bit of silk, treated in the same
+manner, was placed over the vapour of
+warm water for some time; the same appearances
+<span class="pagenum" id="Page_52">[52]</span>took place, and particles of reduced
+gold were evident in the silk.</p>
+
+<p>If the water, whence the vapour arises,
+be too hot; the heat retards, and sometimes
+prevents, the reduction, by volatilizing the
+phosphorus.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 11. Silver.</span></h3>
+
+<p>I dipped a bit of silk in a solution of fused
+nitrate of silver in alcohol, and dried it in the
+air: then some of the solution of phosphorus
+was applied, which produced a brown
+stain, whose margin, after a few minutes
+exposure to the air, acquired a livid white
+appearance, caused by a partial and imperfect
+reduction of the silver.</p>
+
+<p>This, however, would not be taken by a
+person unacquainted with experiments of this
+kind for reduced silver.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 12. Silver.</span></h3>
+
+<p>A bit of silk was immersed in the solution
+of phosphorus; as soon as the ether evaporated,
+and the phosphorus began to fume;
+a few drops of the solution of silver in alcohol
+were applied: immediately a black
+stain, intermixed with some brown, appeared:
+and, after some time, obscure films
+of reduced silver presented themselves; these
+appeared on different parts of the stain; but
+were so minute as to be scarce visible. The
+only difference between this and the preceding
+<span class="pagenum" id="Page_53">[53]</span>experiment is the order, in which,
+the solutions were applied; but even this
+modifies the result in some measure.</p>
+
+<p>That these imperfect reductions depended
+on water, deposited in the silk, by the alcohol
+during its evaporation, or attracted from
+the air by the phosphorus during its combustion,
+will appear from the following experiment.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 13. Silver.</span></h3>
+
+<p>A small phial was well dried in hot sand,
+then corked, and removed to a cool place;
+after the phial cooled, it was nearly filled
+with ether, and a small bit of phosphorus,
+which was repeatedly washed in alcohol to
+free it from any aqueous moisture, that might
+adhere to it, was introduced; the phial was
+then corked, and placed in hot sand; when
+the phosphorus melted, I shook the phial,
+and obtained a strong solution.</p>
+
+<p>Into this solution a small bit of silk, which
+was dipped in a solution of silver in alcohol,
+and dried, was introduced: the phial was
+corked; the silk instantly assumed a brown
+colour; but not a particle of reduced silver
+could be seen, though the experiment was
+continued about three months; nor did the
+solution of phosphorus become turbid, or deposit
+any precipitate, as happened in similar
+experiments on gold.</p>
+
+<p>At the end of this period the silk was
+<span class="pagenum" id="Page_54">[54]</span>taken out of the phial, wetted with water,
+and suspended in a window; and, after a
+considerable time, reduced silver was manifest
+on different parts of the silk.</p>
+
+<p>With the solution of phosphorus, in which
+the silk stood during that time, I reduced
+gold, and silver, with the assistance of water.</p>
+
+<p>In order to compare the effects of water
+with those of ether and alcohol, I made the
+following experiments.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 14. Silver.</span></h3>
+
+<p>I dipped a bit of silk in a solution of nitrate
+of silver in water, and dried it at the
+fire: the silk thus dried retained its white
+colour: the solution of phosphorus was then
+applied, and immediately produced a brown
+colour, which soon, in proportion as the
+phosphorus fumed, acquired a deeper tinge,
+verging on black; and slight signs of reduction
+appeared after a little time on the margin
+of the stain.</p>
+
+<p>Another bit of silk, treated in the same
+manner, but dried much better, exhibited
+still fainter signs of reduction: for the
+brown stain did not appear on this piece as
+soon as on the former, nor was it so intense;
+however, after some minutes exposure to the
+air, the stain became deeper, and its margin
+acquired a livid white appearance, owing to a
+partial reduction of the silver.</p>
+
+<p><span class="pagenum" id="Page_55">[55]</span></p>
+
+<p>It has been often remarked, that the reduction
+commences first on the margin of the
+stain, which the solution of phosphorus, and
+that of the metal, produce in the silk: I was
+a long time at a loss to account for this appearance;
+but the cause was accidentally discovered;
+for happening to spill a few drops
+of the solution of phosphorus on a table, I
+observed, that, as they evaporated, watery
+circles were formed round the spaces, on
+which the drops fell; and, that all the parts
+within the circles were dry.</p>
+
+<p>This explains why the reduction begins on
+the margin of the stain.</p>
+
+<p>I observed the same of alcohol; for if it
+be dropped on a level surface, it leaves a watery
+ring behind, though not near so soon,
+as a solution of phosphorus in ether does:
+this is the reason why alcohol seems to promote
+the reduction of some metals; I say
+seems; for it does not promote it, but in
+proportion to the quantity of water it contains,
+or attracts from the air, and deposits in
+the silk during its evaporation.</p>
+
+<p>How essential water is to the reduction of
+metals will appear from the following experiment.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 15. Silver.</span></h3>
+
+<p>I immersed a piece of silk in the solution
+of phosphorus, and after the ether evaporated,
+and the phosphorus began to fume,
+<span class="pagenum" id="Page_56">[56]</span>a solution of nitrate of silver in water was
+applied; instantly the silver was restored to
+its metallic splendour.</p>
+
+<p>This experiment is very amusing, and well
+calculated to strike the beholder with surprise.</p>
+
+<p>The reduction is sometimes attended with
+spangles of a beautiful blue, which appear
+chiefly where the solution of silver is most
+abundant.</p>
+
+<p>The solution of silver is commodiously applied
+by a camel hair pencil.</p>
+
+<p>I also tried the effects of the vapour of
+phosphorus on bits of silk dipped in a solution
+of nitrate of silver in water, and exposed to
+the vapour, in the same manner as in experiment
+the 9th; and the silver was always
+reduced: but a solution of phosphorus in
+ether seems preferable to the vapour.</p>
+
+<p>A small glass tube, resembling a thermometer,
+with its bulb terminating in a smaller
+and nearly capillary tube, I found useful, and
+economic, especially in experiments on gold:
+by immersing the smaller end in the metallic
+solution, and inspiring through the tube at
+the same time, the bulb may be filled: by
+this means a single drop, or more, if necessary,
+may be applied to the silk; and, thus,
+a great number of experiments can be made
+on a single grain, or a much less quantity,
+of gold, or any other metal.</p>
+
+<p>This little instrument may be used also to
+apply the solution of phosphorus to the silk;
+<span class="pagenum" id="Page_57">[57]</span>and it was by using it for this purpose, I discovered,
+that phosphorus has not the power
+of reducing silver without the aid of water;
+for blowing the solution of phosphorus from
+the tube on bits of silk, which had been dipped
+in a solution of silver, and dried, I was
+surprised to find films of reduced silver frequently
+appear; whereas none appeared, when
+I applied the solution of phosphorus in a different
+manner: this unexpected event often
+occurred, before I learned the cause; at length
+I suspected, it might depend on the moisture
+of the breath; and I was soon convinced by
+moistening the silk with water, that the suspicion
+was well founded.</p>
+
+<p>It is evident from these experiments on silver,
+that water is essential to the reduction of
+this metal by phosphorus; and that ether,
+and alcohol, do not promote it.</p>
+
+<p>It is also evident, that these experiments,
+and those, made on the reduction of gold,
+mutually illustrate each other; and confirm
+the conclusions drawn from them.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 16. Platina.</span></h3>
+
+<p>I immersed a bit of silk in a solution of
+nitro-muriate of platina in distilled water, and
+dried it in the air; the solution of phosphorus
+was then applied to the silk; but no appearance
+of reduction could be perceived.</p>
+
+<p>Another bit of silk was dipped in the solution
+of phosphorus; when the ether evaporated,
+<span class="pagenum" id="Page_58">[58]</span>and the phosphorus began to fume,
+the solution of platina was applied to the silk;
+and, in some time, delicate films of reduced
+platina were visible where the water was most
+abundant. These films of platina commonly
+disappear; and nothing remains but a brown
+tinge, which, however, is more intense, than
+what the solution of platina alone gives the
+silk.</p>
+
+<p>To succeed in this experiment, the silk
+should be replete with phosphorus; which is
+easily done by applying the solution twice or
+thrice, and waiting after each application,
+till the fumes begin to appear. It is also necessary
+to keep the silk constantly wet with
+water. Sometimes it requires from ten to
+twenty minutes to reduce platina in this
+manner.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 17. Mercury.</span></h3>
+
+<p>I dipped a bit of silk in a solution of oxygenated
+muriate of mercury, and dried it in
+the air; then the solution of phosphorus was
+applied; when the ether evaporated, and the
+phosphorus began to fume, a yellow stain
+commenced on the margin, and gradually
+appeared over the whole.</p>
+
+<p>To compare the effects of different degrees
+of moisture, I immersed a bit of silk in the
+same solution of mercury, and dried it carefully
+at the fire; the solution of phosphorus
+was then applied; the silk began to fume;
+<span class="pagenum" id="Page_59">[59]</span>but no change, except a very slight ring of a
+yellow hue, appeared. The rest of the silk
+retained its white colour.</p>
+
+<p>Another bit of silk was immersed in the
+solution of phosphorus, when the ether evaporated,
+and the phosphorus began to fume,
+the same solution of mercury in distilled water
+was applied; and, in a few seconds, a
+bright film of reduced mercury was visible
+on the margin of the part, to which the
+metallic solution was applied, and after some
+time appeared on the whole. The reduction
+was attended with the colours of the rainbow.</p>
+
+<p>After a little time, these colours vanish,
+and the metallic film becomes much more
+obscure, according as the silk dries, and is
+succeeded by a yellow stain.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 18. Mercury.</span></h3>
+
+<p>A bit of silk was dipped in a solution of
+nitrate of mercury in distilled water, and
+dried at the fire; then the solution of phosphorus
+was applied; and, when it began to
+fume, a brown stain commenced at the margin,
+which soon diffused itself over the whole,
+and gradually acquired a faint tinge of black.</p>
+
+<p>Another piece of silk, treated in the same
+manner, but dried in the air, exhibited the
+same appearances; except that the brown
+tinge verged more on black.</p>
+
+<p>Another bit of silk was immersed in the
+<span class="pagenum" id="Page_60">[60]</span>solution of phosphorus, and when it began
+to fume, the solution of nitrate of mercury
+was applied; a brown colour instantly appeared,
+accompanied with a film of reduced
+mercury, which was most evident where the
+metallic solution was most abundant. This
+film soon disappeared, and was succeeded by
+a black stain, in which, however, reduced
+mercury was visible. No colours but black,
+and brown, appeared in this experiment.</p>
+
+<p>It appears from these experiments on mercury,
+that the reduction kept pace with the
+quantity of water present.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 19. Copper.</span></h3>
+
+<p>A piece of silk was immersed in a solution
+of sulphate of copper, and dried in the air:
+then a strong solution of phosphorus was applied;
+the silk acquired a brown colour; but
+no other visible alteration occurred.</p>
+
+<p>Another piece of silk was dipped in the
+same solution of copper, and dried at the fire
+much better than the preceding; the solution
+of phosphorus was applied; when the ether
+evaporated, and the phosphorus began to
+fume, a brown tinge commenced on the margin
+of the silk, and gradually diffused itself
+over the whole; but the stain was by no
+means so intense as that produced in the preceding
+piece: so that there can be no doubt
+that the difference was owing to the different
+degrees of moisture in the silk.</p>
+
+<p><span class="pagenum" id="Page_61">[61]</span></p>
+
+<p>After this piece remained in the air for
+some time, the brown tinge became more
+intense, a proof that it attracted water from
+the air. This difference in the appearances
+of pieces dried in the air, and at the fire, I
+frequently remarked.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 20. Copper.</span></h3>
+
+<p>A strong solution of phosphorus was applied
+to a piece of silk, when the ether evaporated,
+and the phosphorus began to fume,
+a solution of sulphate of copper was applied;
+a brown stain was instantly produced, and
+its margins were soon covered with a <em>white</em>
+metallic film, parts of which, after some
+time, verged on the colour of copper, intermixed
+with purple, green, and blue. If
+the solution of phosphorus be weak, which
+is always the case, when the ether is bad,
+nothing appears on the silk but the brown
+stain, and the <em>white</em> metallic film. As the
+silk dries most of these appearances vanish;
+but some of the blue tinge survives; and the
+silk looks very unseemly.</p>
+
+<p>A bit of silk was immersed in the same
+solution of copper, and exposed to the vapour
+of phosphorus, as in experiment the 9th;
+but no change was produced on the silk, except
+a few brown spots, though the heat was
+such that the vapour filled the phial, and circulated
+through it: the vapour corroded a
+brass pin, which was used to suspend the silk
+<span class="pagenum" id="Page_62">[62]</span>in the phial. This induced me to try its effects
+on copper, which was corroded by it
+in a remarkable manner, and changed into a
+black substance resembling a mixture of charcoal
+and oil. It appears then that phosphorus
+is ill adapted to the reduction of this metal.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 21. Tin.</span></h3>
+
+<p>A bit of silk was immersed in a solution
+of muriate of tin in distilled water, and dried
+in the air; the solution of phosphorus was
+then applied to the silk, and though it fumed
+considerably, no change whatever could be
+perceived in the colour of the silk; nor was
+there the smallest appearance of reduction.</p>
+
+<p>I poured some of the solution of phosphorus
+on a bit of silk, and when it began to
+fume, the solution of tin was applied: after
+a few seconds, white metallic films appeared,
+first on the margin, and were gradually diffused
+over that part of the silk, to which the
+muriate of tin was applied: a yellow colour
+intermixed with red sometimes attends the
+reduction. After some little time these films
+of reduced tin vanish, and scarcely leave a
+stain behind.</p>
+
+<p>I did not succeed in reducing acetite of lead,
+muriate of arsenic, or sulphates of iron, and
+zinc, in this way.</p>
+
+<p>These experiments on tin shew that water
+is essential to its reduction by phosphorus, and
+<span class="pagenum" id="Page_63">[63]</span>give additional force to the preceding conclusions.</p>
+
+<p>M. Sage discovered that gold, silver, <abbr title="et cetera">&amp;c.</abbr>
+are precipitated from their solutions in the
+metallic form, by pieces of phosphorus, which
+are covered at the same time with bright coats
+of gold, silver, <abbr title="et cetera">&amp;c.</abbr></p>
+
+<p>To determine if water were essential to
+these reductions performed by M. Sage, I
+made the following experiments.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 22. Gold.</span></h3>
+
+<p>Some solution of phosphorus in ether was
+poured into a china cup, and a few drops of
+the ethereal solution of gold were added;
+instantly a brown powder was precipitated
+similar to what appeared in experiment the
+6th, but no gold in its metallic form could be
+perceived.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 23. Gold.</span></h3>
+
+<p>A solution of nitro-muriate of gold in water
+was poured into a china cup, containing a
+solution of phosphorus in ether; instantly
+the gold began to assume its metallic splendour,
+attended with a variety of colours, as
+purple, blue, and red, the beauty of which
+cannot be described: the quantity of the
+blue was gradually diminished, and what remained,
+was dispersed over the surface in
+small films, intermixed with spangles of reduced
+gold. Most of the blue films were of
+<span class="pagenum" id="Page_64">[64]</span>a circular figure; some had a central speck
+of ruby red, and were fringed with purple;
+some had a round central speck of a darker
+blue than the surrounding parts: and some
+were of an irregular figure, fringed with
+purple, or ruby red. I often observed these
+blue films assume the real colour of gold
+without suffering any intermediate change of
+colour; and, I think, I observed the same of
+one of the largest specks of ruby red, that
+appeared in this experiment. All these colours
+disappeared, when the reduction was
+completed.</p>
+
+<p>The variety of colours, which those films
+assume, depends on the different degrees of
+reduction; that is to say, on the quantity of
+oxygen combined with the metal: in proportion
+as the metal is deprived of the oxygen,
+it assumes various colours, which often
+succeed each other in a regular order, showing
+the different stages of the reduction:
+thus when gold is reduced; the first perceptible
+change is a green, which soon becomes
+olive; this is succeeded by blue, and purple;
+and sometimes by a ruby red: the purple
+tinge is a mixture of blue, and red.</p>
+
+<p>The various colours, which metals, and
+their calces, communicate to glass, and other
+substances, are explicable on these principles:
+and the difficulty of obtaining a ruby-coloured
+glass by gold is readily understood from
+the facility, with which that metal parts with
+oxygen.</p>
+
+<p><span class="pagenum" id="Page_65">[65]</span></p>
+
+
+<h3 class="center"><span class="smcap">Exp. 24. Gold.</span></h3>
+
+<p>A thread was passed by means of a needle
+through a small bit of phosphorus, which was
+freed from any moisture, that might adhere
+to it, by immersing it for some time in alcohol;
+it was then suspended by means of
+the thread in a solution of gold in ether, contained
+in a phial, which was carefully dried
+in hot sand: in a few minutes, the solution
+became turbid, an effervescence commenced,
+and a brown precipitate was formed: according
+as the precipitate fell, the solution
+became clear, lost its yellow colour; and the
+whole of the gold seemed to have been precipitated:
+but not a particle of reduced gold
+could be seen.</p>
+
+<p>Another bit of phosphorus was suspended
+in the same manner in a solution of nitro-muriate
+of gold in water; and in a few minutes
+got a splendid coat of reduced gold.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 25. Silver.</span></h3>
+
+<p>A few drops of a solution of fused nitrate
+of silver in alcohol were poured into a china
+cup containing a solution of phosphorus in
+ether: instantly a black precipitate, with a
+tinge of brown, was formed; but no silver
+in its metallic state could be perceived.</p>
+
+<p>After some time the precipitate attracted
+moisture from the air; and some films of reduced
+silver appeared.</p>
+
+<p><span class="pagenum" id="Page_66">[66]</span></p>
+
+<p>The same experiment was made in a phial,
+which was corked, to exclude the moisture
+of the air; and nothing, but the black precipitate,
+appeared.</p>
+
+<p>Some of the same solution of silver was diluted
+with water, and dropped on a solution
+of phosphorus in ether; and instantly films
+of reduced silver floated on the surface.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 26. Silver.</span></h3>
+
+<p>A bit of phosphorus was suspended by a
+thread in some of the same solution of silver
+in alcohol, contained in a phial carefully
+dried: a black precipitate with a tinge of
+brown soon appeared; but no silver in its
+metallic state could be observed; part of the
+precipitate adhered to the phosphorus, and
+part fell to the bottom of the phial.</p>
+
+<p>In another experiment made in a phial not
+sufficiently dried, a few small films of reduced
+silver were observed on the sides of
+the phial; but not a particle of silver in its
+metallic form could be seen on the phosphorus.</p>
+
+<p>Another bit of phosphorus was suspended
+in a diluted solution of nitrate of silver in
+water: and in some hours, the phosphorus
+was covered with reduced silver.</p>
+
+<p>The case of silver, which covered the
+phosphorus, prevented its spontaneous combustion
+in the air; the same was observed
+of the bit of phosphorus coated with gold.</p>
+
+<p><span class="pagenum" id="Page_67">[67]</span></p>
+
+<p>Hence it appears, that M. Sage’s success
+in reducing metals by phosphorus depended
+on the water of the metallic solution.</p>
+
+<p>These experiments were often repeated
+with nearly the same result; but some variety
+often occurs, depending on various circumstances;
+as the strength of the metallic
+solution, and that of the phosphorus; the
+quantity of water present, and the purity of
+the materials employed.</p>
+
+<p>It is difficult to obtain ether, or alcohol,
+with the least possible quantity of water;
+and equally difficult to expel all moisture
+from the surface of glass; for this reason,
+the bits of phosphorus in the experiments
+made with alcohol and ether were suspended
+by threads, so as not to touch the sides of
+the glass.</p>
+
+<p>I shall conclude this chapter with a general
+view of the inferences, which seem naturally
+to flow from these experiments with
+phosphorus.</p>
+
+<ol>
+<li>Water is essential to the reduction of
+metals by phosphorus; for these experiments
+show that the reduction is effected only in
+proportion to the quantity of water present.</li>
+
+<li>Phosphorus does not reduce the metals
+by giving them phlogiston.</li>
+
+<li>Phosphorus does not reduce the metals
+by uniting with, and separating, their oxygen.</li>
+</ol>
+
+<p>How then is the reduction effected? are we
+not to conclude, that it is effected by the decomposition
+<span class="pagenum" id="Page_68">[68]</span>of the water, in the following
+manner?</p>
+
+<p>The phosphorus attracts the oxygen of the
+water, while the hydrogen of the latter
+unites, in its nascent state, with the oxygen
+of the metal, and effects the reduction.</p>
+
+<p>Hence it follows, that the phosphorus is
+oxygenated by the oxygen of the water,
+while the metal is restored to its combustible
+state.</p>
+
+<p>Thus what could never be effected by a
+single, is readily performed by a double affinity;
+which always takes place in preference
+to a single affinity, as the experiments of
+Messrs. Monnet, and Kirwan, mentioned in
+the preceding chapter, show.</p>
+
+<p>It is well known, that phosphorus kept in
+water acquires an oxygenated crust, which
+could not happen without a decomposition of
+the water: this fact serves to confirm the explanation
+here offered.</p>
+
+<p>And indeed the decomposition of water in
+these experiments must be granted, or it must
+be supposed, that water itself reduces the
+metals, by uniting with their earths, and
+constituting their phlogiston; or by uniting
+with, and separating, their oxygen; suppositions
+repugnant to our present knowledge
+of chymistry.</p>
+
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+
+<p><span class="pagenum" id="Page_69">[69]</span></p>
+
+
+  <h2 class="nobreak" style="line-height: 2em" id="CHAPTER_III">
+    CHAPTER III.
+    <br>
+    <i>Reduction of Metals by Sulphur.</i>
+  </h2>
+</div>
+
+
+<p class="drop-cap">Though Sulphur, as far as my reading
+extends, has seldom been considered as a reducer
+of the metals, yet as it holds a distinguished
+rank among combustible bodies, analogy
+led me to examine its powers in reducing
+and fixing the metals in the fibres of silk.</p>
+
+<p>The vapour of sulphur appeared to be the
+most simple form, in which it could be applied
+to this purpose; and may be obtained
+by placing a phial containing flowers of sulphur
+in hot sand: as the sulphur melts, it
+assumes the form of vapour, which soon fills
+the phial, expels the atmospheric air, and
+bears a considerable heat, before it inflames;
+a bit of silk, prepared for the experiment,
+may be held over the vapour, as it issues
+from the phial, or immersed in it. The
+neck of the phial should be of a convenient
+size for this purpose.</p>
+
+<p>But these experiments are more conveniently
+made by means of a sulphurous
+match, and a glass funnel, in which the silk
+imbued with the metallic solution may be
+suspended by a thread passed through it, and
+<span class="pagenum" id="Page_70">[70]</span>made fast with a cork, which also serves to
+confine the vapour.</p>
+
+<p>The glass is then placed on a table, and
+by moving it a little beyond the verge of the
+same, a lighted match is readily introduced,
+which, as soon as the glass is filled with vapour,
+may be withdrawn; the vapour is confined
+by making the glass glide back on the
+table; and thus the phenomena of the experiment
+can be easily observed.</p>
+
+<p>Though the vapour obtained in this manner
+be chiefly sulphurous acid gas; yet its effects
+are not less interesting on that account.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 1. Gold.</span></h3>
+
+<p>A bit of silk was dipped in a solution of
+gold in ether, and dried: it was then suspended
+in the glass funnel, and exposed for
+some time to the vapour obtained from a
+burning match: but no change could be perceived,
+except that the silk became a little
+brown.</p>
+
+<p>Another bit of silk, prepared in the same
+manner, was immersed in the vapour of sulphur,
+formed in a phial placed in hot sand,
+with the same result.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 2. Gold.</span></h3>
+
+<p>A piece of silk was immersed in a solution
+of nitro-muriate of gold in water, suspended
+in the glass funnel, and exposed, while wet,
+to vapour of sulphur, formed by a burning
+<span class="pagenum" id="Page_71">[71]</span>match; no sooner did the vapour touch the
+silk, than the reduction commenced; and in
+a few seconds the whole piece was covered
+with a splendid coat of reduced gold, permanent,
+and retentive of its lustre; but had
+a few specks of a dull violet hue.</p>
+
+<p>The silk viewed by transmitted light appeared
+of a beautiful blue colour; and being
+removed from the vapour, and suspended in
+the air, began in about ten minutes to exhale
+a vapour, which continued about two hours,
+and smelled acid, and pungent.</p>
+
+<p>Another bit of silk, dipped in the same solution
+of gold, and dried, was wetted with alcohol,
+and exposed to the same vapour: the
+silk acquired a brownish hue; and a small
+white metallic film appeared on its lower end,
+where the alcohol most abounded: the silk
+was then wetted with water, and replaced in
+the vapour; instantly a lively purple with a
+bright pellicle of reduced gold appeared.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 3. Silver.</span></h3>
+
+<p>A piece of silk was immersed in a solution
+of nitrate of silver in water, and suspended
+in the air of a dark closet to dry; the silk
+retained its white colour, though it remained
+in the air twenty-four hours; it was then
+exposed fourteen hours to the vapour obtained
+from a burning match; but suffered no
+change, except that it acquired a brown
+tinge: it was now wetted with alcohol, and
+<span class="pagenum" id="Page_72">[72]</span>replaced in the vapour for some time; no
+signs of reduction appearing, it was wetted
+again with the alcohol, and exposed to the
+vapour; but still no signs of reduction could
+be perceived: I then wetted the silk with distilled
+water, replaced it in the sulphureous
+vapour; and in about a minute reduced silver
+appeared.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 4. Silver.</span></h3>
+
+<p>I dipped a bit of silk in a solution of nitrate
+of silver in distilled water, and exposed it,
+while wet, to the vapour of sulphur, as in
+the preceding experiment; in a few seconds
+the silver appeared in its metallic form, attended
+with a variety of lively colours: the
+most remarkable of these were a pleasant
+blue, orange, purple, and yellow, which
+soon disappeared: the reduced silver also disappeared
+in a great measure, some faint traces
+only remaining. The silk was removed from
+the vapour into the air, but exhaled no vapour,
+as happened in experiment the second.</p>
+
+<p>A small bit of sulphur was suspended in a
+phial containing a solution of nitrate of silver
+in water; and after some weeks the sulphur
+was coated with reduced silver of no great
+lustre.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 5. Platina.</span></h3>
+
+<p>A bit of silk was immersed in a solution
+of nitro-muriate of the ore of platina in distilled
+<span class="pagenum" id="Page_73">[73]</span>water, and dried in the air; it was then
+suspended in the glass funnel, and exposed to
+the vapour of a burning match: but no signs
+of reduction could be observed: the silk retained
+the colour, the solution gave it.</p>
+
+<p>Another bit of silk was dipped in the same
+solution of platina, and exposed, while wet,
+to the sulphureous vapour; in a few seconds
+the reduction was very evident. The silk was
+immerged in a glass of clear water, and
+transferred bright films of reduced platina to
+the surface of that fluid; most of them were
+of the same colour as the spangles in the ore
+of platina; and some were distinguished by
+lively blue and purple colours.</p>
+
+<p>Another bit of silk, dipped in the same
+solution of platina, was immersed, while
+wet, in the vapour of sulphur, formed in a
+phial placed in hot sand; the reduction soon
+commenced, and was much more perfect,
+and permanent, than in pieces exposed to the
+vapour obtained from ignited matches.</p>
+
+<p>It is remarkable that sulphur reduced this
+metal much better, than phosphorus or hydrogen
+gas did: but the reduced platina disappears
+after some time, and leaves nothing
+behind but a brown stain.</p>
+
+<p>If the films be transferred from the silk to
+water, they may be preserved in their metallic
+form.</p>
+
+<p><span class="pagenum" id="Page_74">[74]</span></p>
+
+
+<h3 class="center"><span class="smcap">Exp. 6. Mercury.</span></h3>
+
+<p>A bit of silk was immersed in a solution of
+nitrate of mercury in distilled water, and
+dried; parts of the silk immediately acquired
+a slate colour: the silk was then exposed to
+the vapour of sulphur, obtained from a burning
+match; but it suffered no change, except
+that the colour became a little more intense.</p>
+
+<p>Another bit of silk was dipped in the same
+solution of mercury, and exposed, while wet,
+to the same vapour: the reduction instantly
+commenced in a very evident manner, accompanied
+with several colours, as blue, purple,
+and yellow.</p>
+
+<p>The silk was removed from the vapour,
+and soon lost most of its lustre, which was
+succeeded by a slate colour, through which
+some particles of reduced mercury were observed
+to shine.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 7. Mercury.</span></h3>
+
+<p>A bit of silk was immersed in a solution
+of oxygenated muriate of mercury in water,
+and dried in the air: it was then exposed to
+the sulphureous vapour obtained from a burning
+match; but the silk underwent no visible
+change. This solution of mercury does not
+change the white colour of silk, as that of
+nitrate does.</p>
+
+<p>Another bit of silk was dipped in the same
+<span class="pagenum" id="Page_75">[75]</span>solution of oxygenated muriate of mercury,
+and exposed, while wet, to the vapour; in
+a few seconds reduced mercury appeared, unattended
+by any colour, except a slight tinge
+of citron yellow on part of the silk. After
+some time the whole of the reduced mercury
+vanished.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 8. Copper.</span></h3>
+
+<p>A piece of silk was immersed in a solution
+of sulphate of copper, and dried; it was then
+suspended in the glass funnel, and exposed to
+the vapour obtained from a burning match;
+but the silk suffered no change, retaining the
+colour, which the solution gave it.</p>
+
+<p>Another bit of silk was dipped in the same
+solution of copper, and exposed, while wet,
+to the vapour of an ignited match; in a short
+time a white metallic film appeared, accompanied
+with a brown tinge; the silk becoming
+dry, was wetted with water, and exposed
+to a brisk vapour from another match: the
+film became more evident, and parts of it
+verged on yellow, bordering on a copper colour.
+After some time this white metallic
+film disappears, and nothing remains but a
+light brown stain.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 9. Lead.</span></h3>
+
+<p>A bit of silk was immersed in a solution of
+acetite of lead in distilled water, and dried in
+the air: it was then exposed to the sulphureous
+<span class="pagenum" id="Page_76">[76]</span>vapour of a burning match; but underwent
+no visible change whatever.</p>
+
+<p>Another bit of silk was dipped in the same
+solution of lead, and exposed, while wet, to
+the vapour; reduced lead soon appeared all
+over the silk; but after some time this reduced
+lead disappears, unless it be transferred
+to the surface of water.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 10. Tin.</span></h3>
+
+<p>A bit of silk was immersed in a solution
+of muriate of tin in distilled water, and dried
+in the air: it was then exposed to the vapour
+obtained from a burning match, which soon
+filled the glass; but produced no visible
+change on the silk.</p>
+
+<p>Another bit of silk was dipped in the same
+solution of tin, and exposed, while wet, to
+the sulphureous vapour; and in a few seconds
+reduced tin appeared all over the silk;
+but the tin soon disappears, if not transferred
+to water.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 11. Arsenic.</span></h3>
+
+<p>A bit of silk was immersed in a solution of
+muriate of arsenic in distilled water, and
+dried in the air; it was then exposed to the
+vapour of sulphur, obtained from a burning
+match; but the silk suffered no apparent alteration.</p>
+
+<p>Another bit of silk was dipped in the same
+solution of arsenic, and exposed, while wet,
+<span class="pagenum" id="Page_77">[77]</span>to the vapour: in a few seconds the arsenic
+was reduced, but not in a very <ins id="TN-4" class="corr" title="Transcriber's Note&mdash;original text: evident manmer">evident manner</ins>;
+the silk was immerged in water, and
+several bright films of reduced arsenic floated
+on the surface of that fluid.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 12. Bismuth.</span></h3>
+
+<p>A bit of silk was immersed in a solution of
+nitrate of bismuth in distilled water, and
+dried in the air; it was then exposed to the
+vapour of sulphur obtained from a burning
+match; but no signs of reduction appeared.</p>
+
+<p>Another bit of silk was dipped in the same
+solution of bismuth, and exposed, while wet,
+to the sulphureous vapour; the bismuth was
+soon reduced, accompanied with a brown
+stain: but the metallic lustre soon disappeared.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 13. Antimony.</span></h3>
+
+<p>A piece of silk was immersed in a solution
+of tartarite of antimony in water, and dried;
+it was then exposed to the vapour of a burning
+match; but no change could be observed;
+nor did the silk immerged in water deposit
+any films on its surface.</p>
+
+<p>Another piece of silk was dipped in the
+same solution of antimony, and exposed,
+while wet, to the vapour: the silk, in a few
+seconds, acquired a yellow colour, and a
+bright bluish film of reduced antimony appeared
+on the lower end of the silk, where
+the water was most abundant: the silk was
+<span class="pagenum" id="Page_78">[78]</span>then immerged in a glass of water, and transferred
+a large pellicle of reduced antimony to
+the surface of that fluid.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 14. Iron.</span></h3>
+
+<p>A bit of silk was immersed in a largely
+diluted solution of sulphate of iron in distilled
+water, and dried in the air; it was then
+exposed to the vapour of sulphur obtained
+from a burning match; after some time the
+colour of the silk became a little brown; but
+no reduced iron could be seen; nor did the
+silk immerged in a glass of clear water transfer
+any thing metallic to its surface.</p>
+
+<p>Another bit of silk was dipped in the same
+solution of iron, and exposed, while wet, to
+the sulphureous vapour; in a short time the
+silk was withdrawn, and a minute shining
+film, of a livid white colour, was visible on
+its lower margin, where the water most
+abounded: the silk was then immerged in a
+glass of water, and transferred a large film of
+reduced iron to its surface.</p>
+
+<p>This experiment succeeded also with the
+vapour of sulphur formed in a phial placed
+on hot sand. The films of reduced iron were
+seldom visible on the silk; but were soon
+rendered visible, by transferring them to
+water.</p>
+
+<p><span class="pagenum" id="Page_79">[79]</span></p>
+
+
+<h3 class="center"><span class="smcap">Exp. 15. Zinc.</span></h3>
+
+<p>A piece of silk was dipped in a diluted solution
+of sulphate of zinc, and dried; it was
+then exposed to the vapour obtained from a
+burning match; no change whatever could
+be perceived: the silk was immerged in a
+glass of water, but deposited no film on its
+surface.</p>
+
+<p>Another piece of silk was dipped in the
+same solution of zinc, and immersed while
+wet in the vapour of sulphur formed in a
+phial placed on hot sand; in about half a
+minute the silk was withdrawn from the vapour,
+and some parts of it had a shining livid
+appearance, which I took for reduced zinc:
+in order to determine if the reduction were
+real, the silk was immerged in a glass of
+clear water, and transferred to its surface a
+bright film of reduced zinc.</p>
+
+<p>If the silk be kept too long in the vapour,
+some sulphur will be condensed on its surface,
+and give it a yellow colour: if it be then
+dipped in a glass of water, it will deposit
+both the sulphur, and the metallic films on
+its surface; but the appearance of the sulphur
+is so different from that of the reduced
+metal, that they are easily distinguished.</p>
+
+<p>Another bit of silk was immersed in a
+largely diluted solution of muriate of zinc,
+and exposed, while wet, to the vapour obtained
+from a burning match: the silk being
+<span class="pagenum" id="Page_80">[80]</span>withdrawn exhibited a few minute shining
+films on its lower end, and on immersion in
+water, left bright films of reduced zinc floating
+on the surface of that fluid.</p>
+
+<p>Very often these films cannot be seen, until
+they are transferred to water, which I
+found a very useful test in doubtful cases:
+they are better seen in the gray light than in
+sunshine.</p>
+
+<p>These experiments on the reduction of metals
+by sulphur were often repeated with
+nearly the same result: but some variety occurs
+depending on the quantity of water present,
+the strength of the metallic solution,
+and sulphureous vapour, and also on the time
+the silk is exposed to the vapour.</p>
+
+<p>When the experiments are made in a phial
+placed in hot sand, part of the metallic solution
+frequently drops from the silk, and
+falling on the bottom, or sides of the phial,
+is reduced, covering these parts with a metallic
+crust; on which the sulphur soon reacts,
+and changes the greater part into a sulphure.
+The phial commonly cracks.</p>
+
+<p>The following conclusions are deducible
+from the experiments related in this chapter.</p>
+
+<ol>
+<li>Water is essential to the reduction of
+metals by sulphur; for this effect is always
+in proportion to the quantity of water present.</li>
+
+<li>Alcohol does not promote these reductions
+without the aid of water.</li>
+
+<li>Sulphur does not reduce the metals by
+<span class="pagenum" id="Page_81">[81]</span>giving them phlogiston; nor by uniting with
+and separating their oxygen; for were either
+of these opinions just, the sulphur, so minutely
+divided by heat, should reduce metallic
+solutions in alcohol as effectually as it does
+metallic solutions in water.</li>
+</ol>
+
+<p>When we compare these reductions by
+sulphur, with those effected by phosphorus,
+and consider that water is essential to both;
+we must conclude, that the reduction is effected
+in the same manner, <abbr title="videlicet">viz.</abbr> by the decomposition
+of water; which may be thus
+explained.</p>
+
+<p>The sulphur attracts the oxygen of the
+water, while the hydrogen of the latter unites,
+in its nascent state, to the oxygen of the metal,
+and restores it to the metallic form.</p>
+
+<p>Hence it follows, that the sulphur is oxygenated
+by the oxygen of the water, while
+the metal is restored to its combustible state.</p>
+
+<p>It also follows, that a quantity of water
+equal to that consumed is formed by the hydrogen
+of the water, and the oxygen of the
+metal.</p>
+
+<p>This explanation is supported by a fine experiment
+of Dr. Priestley, who obtained inflammable
+air by passing the vapour of water
+through sulphur heated in an earthen tube&#x2060;<a id="FNanchor_15_15" href="#Footnote_15_15" class="fnanchor">[15]</a>;
+and farther confirmed by the experience of
+some judicious makers of oil of vitriol, who
+<span class="pagenum" id="Page_82">[82]</span>always sprinkle the sulphur with a certain
+proportion of water, before they inflame it.</p>
+
+<p>The decomposition of water in these reductions
+must be granted, or it must be supposed,
+that a single takes place in preference
+to a double affinity; which cannot be admitted.</p>
+
+<p>These experiments point out several errors
+in M. Lavoisier’s Table of the Affinities of
+the Oxygenous Principle; for he has placed
+sulphur at a much greater distance from that
+principle than any of the metals treated of in
+this chapter, except gold; and even in this
+instance his table is erroneous, unless it be
+proved, that sulphur reduces metals by directly
+uniting with, and separating their oxygen;
+a supposition which implies, that the
+reduction is effected by a single affinity; and
+therefore inadmissible.</p>
+
+<p>I shall close this chapter with a short extract
+from the chemical essays of Bishop
+Watson; as it seems to have some relation
+to the experiments related here.</p>
+
+<p>His lordship says, that his experiments on
+“the Derbyshire lead ore instruct us to believe,
+that the lead in this kind of ore is
+in its metallic state; as the ore was changed
+into lead without the addition of any
+substance containing the inflammable principle&#x2060;<a id="FNanchor_16_16" href="#Footnote_16_16" class="fnanchor">[16]</a>.”</p>
+
+<p>But the reduction of lead by sulphur and
+<span class="pagenum" id="Page_83">[83]</span>water, related in this chapter, points out an
+evident source of the inflammable principle;
+for the ore itself must contain some water, a
+constituent part of which is hydrogen, or the
+base of inflammable air: beside his lordship
+thinks, no appearance of lead would have
+taken place, had there been no communication
+with the external air: but as air always
+holds water in solution, an ample source of
+the inflammable principle is evident.</p>
+
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+
+<p><span class="pagenum" id="Page_84">[84]</span></p>
+
+
+  <h2 class="nobreak" style="line-height: 2em" id="CHAPTER_IV">
+    <ins id="TN-5" class="corr" title="Transcriber's Note&mdash;original text: CHAPTER III.">CHAPTER IV.</ins>
+    <br>
+    <i>Reduction of Metals by Alkaline Sulphure.</i>
+  </h2>
+</div>
+
+
+<p class="drop-cap">The Sulphure, I made use of, was prepared
+by fusing equal parts of carbonate of
+potash, and flowers of sulphur, till the effervescence
+ceased.</p>
+
+<p>M. Gengembre has made a very important
+observation on alkaline sulphure, prepared in
+this way, which is, that this substance has
+no smell, and that it exhales no gas, while it
+continues dry; but that, when it is dissolved
+in water, or attracts humidity from the air,
+it diffuses an offensive smell.</p>
+
+<p>From this circumstance M. Gengembre
+inferred, that the disengagement of this gas
+depended on the decomposition of water; for
+he discovered both by analysis, and synthesis,
+that this air consists of hydrogen, one of the
+principles of water, combined with sulphur,
+and caloric.</p>
+
+<p>There can then be no doubt, but alkaline
+sulphure has the power of decomposing water;
+and may therefore be happily employed
+to illustrate the mode of action of sulphur,
+and other combustible substances, treated of
+in this essay.</p>
+
+<p><span class="pagenum" id="Page_85">[85]</span></p>
+
+<p>When dilated acids are poured on solid alkaline
+sulphure, the decomposition of the
+water is promoted, and accelerated, sulphurated
+hydrogen gas being formed in great
+abundance.</p>
+
+<p>I made two solutions of this alkaline sulphure,
+one in water, and the other in alcohol.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 1. Gold.</span></h3>
+
+<p>A bit of silk was immersed in the solution
+of sulphure in alcohol, and then a solution of
+gold in ether was applied: a brown matter
+was formed in the silk; but no reduced gold
+could be perceived.</p>
+
+<p>Another bit of silk was dipped in the same
+solution of sulphure in alcohol, and a solution
+of nitro-muriate of gold in water was applied;
+a white metallic film was slowly formed;
+but no other signs of reduction were
+visible.</p>
+
+<p>This experiment was repeated on another
+bit of silk, with this difference, that the solutions
+of the gold, and sulphure, were both
+in water; and the white metallic film was
+instantly formed, accompanied by a considerable
+precipitate of a brown matter.</p>
+
+<p>It is obvious then, that water accelerates,
+and is necessary to the appearance of this
+film: for when both solutions were in water,
+it appeared much sooner.</p>
+
+<p><span class="pagenum" id="Page_86">[86]</span></p>
+
+
+<h3 class="center"><span class="smcap">Exp. 2. Gold.</span></h3>
+
+<p>A piece of silk was immersed in an aqueous
+solution of gold, in which the acid predominated,
+then a few drops of the aqueous solution
+of sulphure were applied: a white pellicle,
+which looked like silver, was immediately
+formed, and the silk got a deep brown
+colour.</p>
+
+<p>To another piece of silk, dipped in the
+same solution of gold, the solution of sulphure
+in alcohol was applied, a white metallic
+film appeared; but not so evident, or so
+soon, as in the preceding experiment, wherein
+the solution of sulphure in water was
+used: beside the film produced by the aqueous
+solution of sulphure was more permanent,
+and the stain, which the silk acquired, was
+more intense, than those produced by the
+solution of sulphure in alcohol.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 3. Silver.</span></h3>
+
+<p>I immersed a piece of silk in a solution
+of the sulphure in alcohol, and after most of
+the spirit evaporated, a solution of nitrate of
+silver in alcohol was applied: nothing appeared
+on the silk, but a brown stain. The nitrate
+of silver, used in this experiment, was
+fused, to expel as much water as possible.</p>
+
+<p>Another piece of silk was dipped in the
+same solution of sulphure; when most of
+the alcohol evaporated, a solution of crystallized
+<span class="pagenum" id="Page_87">[87]</span>nitrate of silver in water was applied to
+the silk; and instantly the metallic lustre of
+the silver appeared, attended with a brown
+stain.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 4. Silver.</span></h3>
+
+<p>A piece of silk was dipped in the solution
+of alkaline sulphure in water, and an aqueous
+solution of crystallized nitrate of silver was
+applied; the silver was immediately reduced
+in greater quantity than in the preceding experiment,
+in which the alkaline sulphure employed
+was dissolved in alcohol. The stain
+produced in the silk was also more intense.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 5. Silver.</span></h3>
+
+<p>A bit of silk was immersed in a solution
+of the sulphure in water, and then a solution
+of nitrate of silver in alcohol was applied:
+but nothing appeared on the silk, except a
+brown stain. The nitrate of silver, used in
+this experiment, was fused, which deprived
+it of a great part of its acid. That this was
+the circumstance, which prevented the reduction
+of the silver, appears from the following
+experiment.</p>
+
+<p>A bit of silk was immersed in the same
+solution of silver in alcohol, then some diluted
+nitric acid was applied, lastly the
+aqueous solution of sulphure was dropped on
+the silk: and instantly the silver was restored
+to its metallic splendour. It is evident then,
+<span class="pagenum" id="Page_88">[88]</span>that acids contribute to the reduction of silver
+by alkaline sulphure, which they effect by
+promoting the decomposition of water.</p>
+
+<p>In some time the reduced silver disappears
+for the most part: and indeed the white metallic
+films, which were produced in the experiments
+on gold, totally disappeared.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 6. Platina.</span></h3>
+
+<p>A bit of silk was immersed in a solution of
+nitro-muriate of the ore of platina in distilled
+water, and dried; then the solution of sulphure
+in alcohol was dropped on the silk:
+nothing appeared but a brown stain.</p>
+
+<p>Another bit of silk was dipped in the
+aqueous solution of sulphure, and a little of
+the solution of platina applied; in a short
+time, a film of reduced platina appeared.</p>
+
+<p>To another bit of silk, which was dipped
+in the solution of platina, a few drops of distilled
+vinegar were applied, and then the solution
+of sulphure in water was added; a
+brown stain was <ins id="TN-6" class="corr" title="Transcriber's Note&mdash;original text: immediaaely">immediately</ins> produced, and
+more platina reduced than in the preceding
+experiment.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 7. Mercury.</span></h3>
+
+<p>To a bit of silk, which was immersed in a
+solution of oxygenated muriate of mercury
+in water, and dried in the air; some of the
+solution of sulphure in alcohol was applied;
+<span class="pagenum" id="Page_89">[89]</span>but no change, except a light yellowish
+brown, was produced.</p>
+
+<p>After the silk was some time exposed to the
+air, some very faint shades of black were visible
+on parts of it.</p>
+
+<p>To a piece of silk, which was immersed
+in the solution of sulphure in water, some
+of the same solution of mercury was applied;
+immediately the metal was restored to its metallic
+lustre, in a very striking manner; and
+it was remarkable, that the precipitate on the
+silk was very small.</p>
+
+<p>This experiment was repeated with this
+difference, that the silk was first wetted with
+distilled vinegar: and more of the mercury
+was reduced, than in the preceding experiment,
+attended with an olive precipitate,
+which gradually turned blackish: the quantity
+of precipitated matter in this was much
+greater than in the former experiment; but
+the reduced metal was not so bright.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 8. Mercury.</span></h3>
+
+<p>A bit of silk, which was dipped in a solution
+of nitrate of mercury, and dried in the
+air, had no change produced on it by a solution
+of sulphure in alcohol, except a stain
+compounded of the slate colour, which the
+nitrate imparts, and the yellow of the sulphure.</p>
+
+<p>To another bit of silk, which was immersed
+in the aqueous solution of sulphure,
+<span class="pagenum" id="Page_90">[90]</span>some of the same solution of mercury was
+applied: the metal was immediately reduced;
+and a very black stain attended the reduction.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 9. Copper.</span></h3>
+
+<p>A piece of silk was dipped in a solution of
+sulphate of copper, and dried in the air; a
+solution of the sulphure in alcohol was applied
+to it; but no change, except a brown
+stain, was produced.</p>
+
+<p>To another bit of silk, immersed in the
+aqueous solution of sulphure, some of the
+same solution of copper was applied: a white
+metallic film was slowly formed, attended
+with a brown colour.</p>
+
+<p>On another bit of silk, which was dipped
+in the same solution of copper, and placed
+on a saucer, some distilled vinegar was dropped,
+and then a few drops of the aqueous solution
+of sulphure were added: immediately
+a white metallic film appeared in greater
+quantity than in the preceding experiment.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 10. Lead.</span></h3>
+
+<p>A piece of silk was immersed in a solution
+of acetite of lead in distilled water, and dried
+in the air; then the solution of sulphure in
+alcohol was applied: but nothing appeared
+on the silk, except a brown stain.</p>
+
+<p>A bit of the same silk was dipped in the
+same solution of lead, then the solution of
+sulphure in water was applied: the lead was
+<span class="pagenum" id="Page_91">[91]</span>soon reduced to its metallic state: a brown
+stain, and precipitate of the same colour, attending
+the reduction.</p>
+
+<p>The same experiment was repeated with
+this difference, that the silk was first wetted
+with distilled vinegar, and instantly the lead
+was reduced of greater lustre, and in greater
+quantity, than in the preceding experiment.</p>
+
+<p>This experiment was tried on a bit of
+white calico, dipped in distilled vinegar, and
+placed on the palm of my hand; and instantly
+the metallic lustre of the lead, which
+was reduced in great quantity, appeared in a
+very remarkable manner, attended with a
+brown stain.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 11. Tin.</span></h3>
+
+<p>To a bit of silk dipped in a solution of muriate
+of tin in distilled water, and dried in the
+air, the solution of sulphure in alcohol was
+applied: nothing appeared but a brown stain.</p>
+
+<p>Another bit of silk was immersed in the
+solution of sulphure in water, then the same
+solution of muriate of tin was applied; in a
+short time some reduced tin appeared on the
+silk. Vinegar promoted the reduction of this
+metal also, in a remarkable manner.</p>
+
+
+<h3><span class="smcap">Exp. 12. Arsenic.</span></h3>
+
+<p>A bit of silk was immersed in a solution
+of muriate of arsenic in distilled water, and
+dried in the air: the solution of sulphure in
+<span class="pagenum" id="Page_92">[92]</span>alcohol was then applied: the silk first looked
+yellow, in a short time the yellow colour
+almost entirely disappeared, leaving behind a
+whitish precipitate; but no other change was
+produced.</p>
+
+<p>Another bit of silk was dipped in the solution
+of sulphure in water; then some of
+the same solution of arsenic was applied; a
+yellow precipitate was formed; and shortly
+after, this precipitate was surrounded by a
+violet margin; but no other change could be
+observed.</p>
+
+<p>I immersed another bit of the same silk in
+the same solution of arsenic, some distilled
+vinegar was then dropped on it; and lastly
+the aqueous solution of sulphure was applied:
+after some time, a few minute films of
+reduced arsenic bright as silver were visible.</p>
+
+<p>Some attention is necessary to discover the
+reduced arsenic, as the particles reduced are
+few, and minute; and sometimes none can
+be seen.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 13. Bismuth.</span></h3>
+
+<p>To a bit of silk, which was dipped in a
+solution of nitrate of Bismuth in distilled
+water, and dried in the air, the solution of
+sulphure in alcohol was applied: the silk appeared
+first yellow, then brown; but no farther
+change could be observed.</p>
+
+<p>Another bit of silk was immersed in the
+solution of sulphure in water; some of the
+<span class="pagenum" id="Page_93">[93]</span>same solution of bismuth was then applied to
+it; the metal was immediately reduced; and
+a brown precipitate was formed. Vinegar
+seems neither to promote, nor retard the reduction.</p>
+
+<p>Two bits of white calico were dipped in
+the same solution of bismuth; to one of these
+placed on a saucer some distilled vinegar was
+added; then a single drop of the solution of
+sulphure in water was applied; and the whole
+of the calico, except that part on which the
+drop fell, was covered with reduced bismuth,
+which looked exceedingly bright: the same
+appearance was observed on the other bit, to
+which no vinegar was added.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 14. Antimony.</span></h3>
+
+<p>To a bit of silk, which was dipped in a
+solution of tartarite of antimony in distilled
+water, and dried in the air, the solution of
+sulphure in alcohol was applied; the silk
+got a yellow colour, whose margins, some
+time after, acquired an orange hue; but no
+other change was perceived.</p>
+
+<p>Another bit of the same silk was immersed
+in the aqueous solution of sulphure, the same
+solution of antimony was then applied: part
+of the metal was reduced, though in small
+quantity, attended with an orange precipitate.</p>
+
+<p>The acids of vinegar, and tartar, seemed
+to impede the reduction; the muriatic acid
+<span class="pagenum" id="Page_94">[94]</span>also seemed to have the same effect, though
+not in so great a degree as the two former.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 15. Cobalt.</span></h3>
+
+<p>To a bit of silk, which was dipped in a
+solution of nitrate of cobalt, and dried in the
+air, the solution of sulphure in alcohol was
+applied; the silk soon became brown; but
+no farther change could be perceived.</p>
+
+<p>To another bit of silk, which was immersed
+in the solution of sulphure in water,
+a few drops of the same solution of cobalt
+were applied: the silk immediately acquired
+a dark colour, and, in a little time, some of
+the metal was reduced, attended with a dull
+blue precipitate, which changed to a blackish
+brown.</p>
+
+<p>Muriate of cobalt was reduced in the same
+manner: vinegar promoted the reduction of
+both these preparations of cobalt.</p>
+
+<h3 class="center"><span class="smcap">Exp. 16. Iron.</span></h3>
+
+<p>To a piece of silk, which was immersed in
+a solution of sulphate of iron largely diluted,
+and dried in the air, the solution of sulphure
+in alcohol was applied: the silk soon became
+black; but no other change could be perceived.</p>
+
+<p>Another bit of silk was dipped in the solution
+of sulphure in water, some of the same
+solution of iron was then applied: the silk
+instantly assumed a black colour; but no reduced
+<span class="pagenum" id="Page_95">[95]</span>iron appearing, it was immerged in a
+glass of water, and transferred a bright film
+of reduced iron to the surface of that fluid.</p>
+
+<p>Sometimes part of the film has not the
+metallic lustre, which is very evident in other
+parts of it; so that the parts completely reduced
+can be easily distinguished from the
+dull and imperfectly reduced black oxid of
+iron, intermixed with these bright films.</p>
+
+<p>The same experiments were repeated on
+bits of calico with the same result: the calico
+from its spongy texture is better suited to
+produce strong films than silk is.</p>
+
+<p>Vinegar did not promote the reduction of
+iron in these experiments.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 17. Zinc.</span></h3>
+
+<p>To a bit of silk, which was immersed in a
+largely diluted solution of muriate of zinc,
+and dried in the air, some of the solution of
+sulphure in alcohol was applied; nothing appeared
+on the silk, but the yellow colour,
+which the solution of sulphure imparts.</p>
+
+<p>Another bit of silk was dipped in the solution
+of sulphure in water, and some of the
+same solution of zinc was applied: the yellow
+colour, which the solution of sulphure
+gave the silk, soon became white; but no
+reduced zinc could be seen. The silk was
+then immerged in a glass of clear water, and
+transferred a bright film of reduced zinc to
+its surface.</p>
+
+<p><span class="pagenum" id="Page_96">[96]</span></p>
+
+<p>In another experiment, made with white
+calico, the pellicle transferred to the surface
+of water was brighter; and more zinc was
+reduced, than in the preceding experiment.</p>
+
+<p>Sulphate of zinc also was reduced both on
+silk, and calico, with this difference that
+black, and olive, precipitates, attended the reduction.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 18. Manganese.</span></h3>
+
+<p>I dipped a bit of silk in a diluted solution
+of nitrate of manganese, and dried it in the
+air; the solution of sulphure in alcohol was
+then applied: the silk acquired a yellow colour,
+which soon disappeared; but no other
+change could be observed.</p>
+
+<p>To another bit of silk, which was immersed
+in the solution of sulphure in water, a drop
+of the same solution of manganese was applied:
+instantly a pearl-white precipitate was
+formed, the margin of which soon acquired
+a bright film of reduced manganese. Under
+this film a violet tinge was evident.</p>
+
+<p>The nitrate of manganese used in this experiment
+was very acid.</p>
+
+<p>A solution of alkaline sulphure in water
+after a certain length of time loses the power
+of reducing the metals, in which respect it
+resembles an old solution of sulphate of iron.</p>
+
+<p>Having procured a more neutral solution
+of nitrate of manganese, I immersed a bit of
+silk in the solution of sulphure in alcohol,
+<span class="pagenum" id="Page_97">[97]</span>when most of the spirit evaporated; a single
+drop of this solution of manganese was applied;
+instantly a bright film of reduced
+manganese appeared, attended with a violet
+tinge, and a brown precipitate. After some
+time the violet tinge disappears.</p>
+
+<p>On another bit of silk immersed in the
+same solution of sulphure in alcohol, a drop
+of a solution of sulphate of manganese in distilled
+water was applied: instantly films of
+reduced manganese bright as silver appeared,
+accompanied with a faint violet tinge, and a
+pearl-white precipitate. These films soon disappear.</p>
+
+<p>A solution of alkaline sulphure in alcohol
+does not by age lose its power of reducing the
+metals, as that in water does; I kept the
+former solution more than two years, and
+found it, at the end of that time, as capable
+of reducing the metals, as when it was made.</p>
+
+<p>It is manifest from the experiments related
+in this chapter,</p>
+
+<ol>
+<li>That water is essential to the reduction
+of metals by alkaline sulphure.</li>
+
+<li>That alcohol does not promote these reductions,
+without the aid of water.</li>
+
+<li>That alkaline sulphure does not reduce
+the metals by giving them phlogiston; nor
+by uniting with, and separating, their oxygen;
+for were either of these opinions true, a solution
+of alkaline sulphure in alcohol should reduce
+them as effectually, as a solution of the
+same in water does.
+<span class="pagenum" id="Page_98">[98]</span>
+</li>
+
+<li>That acids contribute to these reductions
+by promoting the decomposition of
+water.</li>
+</ol>
+
+<p>Now since M. Gengembre has demonstrated,
+that water is decomposed by alkaline sulphure;
+who can doubt, that it is decomposed
+in these reductions?</p>
+
+<p>The manner, in which metals are reduced
+by this substance, seems to be the following.</p>
+
+<p>An hydrure of sulphur, that is, a combination
+of hydrogen, and sulphur, is formed:
+this hydrure of sulphur attracts the oxygen
+of the water, while the hydrogen of the latter
+unites, in its nascent state, with the oxygen
+of the metal, and reduces it.</p>
+
+<p>The experiments in this chapter leave us
+no room to doubt of the decomposition of
+water in metallic reductions by alkaline sulphure,
+and serve to illustrate, and confirm,
+the manner, in which sulphur, phosphorus,
+and other combustible bodies, effect the reduction
+of metals.</p>
+
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+
+<p><span class="pagenum" id="Page_99">[99]</span></p>
+
+
+  <h2 class="nobreak" style="line-height: 2em" id="CHAPTER_V">
+    CHAPTER V.
+    <br>
+    <span class="smcap">REDUCTION of METALS</span>
+    <br>
+    <span class="fs60">BY</span>
+    <br>
+    <i>SULPHURATED HYDROGEN GAS</i>.
+  </h2>
+</div>
+
+
+<p class="drop-cap">Having treated of the effects of hydrogen
+gas, and sulphur, separately, I shall next
+treat of their effects, when combined in the
+form of sulphurated hydrogen gas.</p>
+
+<p>I obtained this elastic fluid by pouring
+water, acidulated with sulphuric acid, on alkaline
+sulphure, prepared in the manner
+mentioned in the preceding chapter; but had
+it been prepared with a caustic alkali, it is
+probable, the gas would be more powerful.
+The sulphure of the shops is generally unfit
+for these experiments.</p>
+
+<p>It is necessary in experiments with sulphurated
+hydrogen gas, hydrogen gas, <abbr title="et cetera">&amp;c.</abbr>
+to have some mode of conveying them into
+a chimney; as they are offensive, and unwholesome.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 1. Gold</span></h3>
+
+<p>A piece of silk, which was immersed in a
+solution of nitro-muriate of gold in water,
+and dried in the air, was exposed to sulphurated
+hydrogen gas: the silk got a slight
+<span class="pagenum" id="Page_100">[100]</span>tinge of brown; but no other change occurred:
+it was then wetted with alcohol, and
+after some time, the brown became more intense;
+and white films appeared on some
+parts of the silk, owing to moisture collected
+from the gas, which is always replete with
+water.</p>
+
+<p>Another bit of silk was dipped in the same
+solution of gold, and exposed, while wet, to
+the gas: the yellow colour, which the solution
+of gold gave the silk, was immediately
+changed to a brown; and a white metallic
+pellicle appeared, and covered the whole surface
+of the silk opposed to the gas; but no
+purple, or other colours, that usually attend
+the reduction of this metal by other agents,
+could be perceived. This pellicle did not
+entirely disappear, as the silk became dry;
+though it lost most of its lustre, and looked
+more like silver, or some other white metal
+imperfectly reduced, than gold.</p>
+
+<p>This elastic fluid, and alkaline sulphure,
+have an effect on the reduction of gold, very
+different from that of the vapour of sulphur,
+obtained from a burning match, which further
+appears from the following experiment,
+made with sulphurated hydrogen gas, that
+happened to be mixed with some sulphurous
+acid gas.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 2. Gold.</span></h3>
+
+<p>A piece of silk, which was dipped in a
+solution of gold in ether, and dried in the
+<span class="pagenum" id="Page_101">[101]</span>air, was exposed to a current of sulphurated
+hydrogen gas, containing some sulphurous
+acid gas; but no signs of reduction could be
+perceived: the silk was then wetted with alcohol;
+still no visible change was produced,
+except a brown stain, where the alcohol most
+abounded: this stain, after some minutes exposure
+to atmospheric air, was covered with
+a white metallic film, which soon disappeared:
+after some minutes, the silk was
+wetted with water, and exposed again to the
+gas; a white metallic film immediately appeared,
+and the brown stain began to change
+slowly to a purple; the silk was soon covered
+with various colours, as blue, red, and
+orange; and some spots of reduced gold of
+its own proper colour appeared: after some
+time the white film, and all the colours, except
+the purple, disappeared: some specks of
+the perfectly reduced gold were permanent.</p>
+
+<p>Another bit of silk, which was immersed
+in an aqueous solution of gold, and exposed
+to the same mixed gas, exhibited nearly the
+same appearances.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 3. Gold.</span></h3>
+
+<p>Having found that sulphurated hydrogen
+gas had a powerful effect in reducing other
+metals, I was desirous of trying its effects on
+a larger scale, thinking it might be attended
+with more success: I therefore immersed a
+quarter of a yard of silk in an aqueous solution
+<span class="pagenum" id="Page_102">[102]</span>of gold, and exposed it, while wet, to
+this gas in close vessels: the silk was soon
+covered with a white metallic pellicle, which
+disappeared in a short time: the experiment
+was continued about twelve hours, and, on
+withdrawing the silk from the gas, I could
+not perceive the smallest vestige of reduced
+metal, or purple, or other colours, that constantly
+attend the reduction of gold.</p>
+
+<p>The silk had a dull brown hue verging on
+a slate colour.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 4. Silver.</span></h3>
+
+<p>A piece of silk, which was immersed in a
+solution of nitrate of silver in water, and
+dried in the air, was exposed to a current of
+sulphurated hydrogen gas; but no change
+could be perceived for some time; at length,
+when the silk collected moisture from the gas,
+some particles of reduced silver were visible,
+accompanied by a brown stain.</p>
+
+<p>Another piece of silk was dipped in the
+same solution of nitrate of silver, and exposed,
+while wet, to the gas: the silver was
+instantly reduced all over the side of the silk
+opposed to the current: a great variety of
+beautiful colours, as red, orange, yellow,
+green, and blue, attended the reduction:
+most of these disappeared; but part of the
+silver remained permanently reduced.</p>
+
+<p>I found, that, if the silk be immersed in
+a solution of silver in alcohol, and dried, and
+<span class="pagenum" id="Page_103">[103]</span>then moistened with water, and exposed,
+while wet, to the gas, none of these colours
+appear.</p>
+
+<p>This experiment was repeated on a quarter
+of a yard of silk in close vessels, and immediately
+both sides of the silk were covered
+with reduced silver, attended with the same
+beautiful colours: the silk was left exposed to
+the gas seven or eight hours; and being then
+examined, no reduced silver could be seen:
+nothing remained, but a strange medley of
+colours, chiefly blue, green, purple, and
+orange, unequally mixed, some prevailing
+more than others in certain parts of the silk:
+however the die is by no means disagreeable.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 5. Silver.</span></h3>
+
+<p>A piece of silk, which was immersed in a
+solution of fused nitrate of silver in alcohol,
+and dried in the air, was exposed to a current
+of the gas; but no change could be perceived
+for some time: it was then wetted with alcohol,
+still no alteration could be observed,
+till the silk attracted moisture from the gas,
+when small particles of reduced silver began
+to appear, attended with a brown stain.</p>
+
+<p>If the silk immersed in the solution of silver
+in alcohol, and exposed while wet to the
+gas, be kept constantly wet with alcohol,
+these appearances take place sooner.</p>
+
+<p>A piece of silk, which was dipped in a solution
+of muriate of silver in ammonia, and
+<span class="pagenum" id="Page_104">[104]</span>exposed, while wet, to the gas, had in a
+short time its surface covered with reduced
+silver: but another piece of silk dipped in the
+same solution of silver, and dried, underwent
+no such change.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 6. Platina.</span></h3>
+
+<p>A bit of silk, which was dipped in a solution
+of nitro-muriate of the ore of platina
+in distilled water, and dried in the air, was
+exposed to a current of sulphurated hydrogen
+gas; but underwent no perceptible change.</p>
+
+<p>Another bit of silk was immersed in the
+same solution of platina, and exposed, while
+wet, to the gas; the whole surface of the
+silk, opposed to the current, was instantly
+covered with reduced platina, which soon
+lost its lustre; nothing remaining but a brown
+colour, with some faint vestiges of the reduced
+metal.</p>
+
+<p>This experiment was repeated on a bit of
+linen with the same result.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 7. Mercury.</span></h3>
+
+<p>A bit of silk, which was dipped in a solution
+of oxygenated muriate of mercury in
+distilled water, and dried in the air, was exposed
+to a current of the gas; the only visible
+change produced was a slight shade of yellow
+on part of the silk.</p>
+
+<p>Another bit of silk was immersed in the
+same solution of mercury, and exposed, while
+<span class="pagenum" id="Page_105">[105]</span>wet, to the gas: the mercury was immediately
+reduced; but soon lost its lustre: the
+gas reacting changed most of it to a substance
+of a dull white colour.</p>
+
+<p>The same experiments were made with nitrate
+of mercury, with the same result.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 8. Copper.</span></h3>
+
+<p>A bit of silk was immersed in a solution of
+sulphate of copper in distilled water, and suspended
+in the air to dry; it was then exposed
+to a current of the gas: the silk assumed a
+brown colour; but no other change appeared.</p>
+
+<p>Another bit of silk was dipped in the same
+solution of copper, and exposed, while wet,
+to the gas: a white metallic film, attended
+with a brown stain, immediately appeared:
+some parts had a yellow film approaching to
+the colour of copper: these films all disappeared,
+leaving behind a brown stain: the
+parts, which were covered with the yellow
+film, resembling copper, exhibited, after some
+time, a dull bluish disagreeable matter.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 9. Lead.</span></h3>
+
+<p>Having dipped a piece of silk in a solution
+of acetite of lead in distilled water, and
+dried it in the air, I exposed it to a stream of
+the gas: the silk became a little brown; but
+no other change could be observed.</p>
+
+<p>Another bit of silk was immersed in the
+same solution of lead, and exposed while wet
+<span class="pagenum" id="Page_106">[106]</span>to the gas; no sooner did it touch the silk,
+than a brown tinge diffused itself, like a passing
+shadow, over the whole surface of the
+silk, accompanied with a bright coat of reduced
+lead, which resembled silver.</p>
+
+<p>The brown tinge, which the silk acquires,
+resembles what happens when white paper
+is slightly singed by holding it near a burning
+body.</p>
+
+<p>This experiment was repeated on a quarter
+of a yard of silk in close vessels; and the
+silk was immediately covered with a coat of
+reduced lead, which had the brilliance of silver,
+and was attended with a brown tinge:
+the experiment was continued several hours,
+after which the silk was examined, and found
+to have lost all the argentine lustre, which
+was succeeded by a sparkling gray die: a
+sulphure of lead, or galena, being formed
+in the fibres of the silk. The same experiment
+was repeated on two other pieces of silk
+with the same result.</p>
+
+<p>This elastic fluid is so powerful a reducer
+of the metals, that if chambers, painted with
+white lead, have any considerable degree of
+moisture, and are exposed to <ins id="TN-7" class="corr" title="Transcriber's Note&mdash;original text: is influence">its influence</ins>,
+the lead on the surface of the walls is reduced,
+and that chiefly where the humidity
+is most abundant: this effect, I observed, was
+produced, even at the distance of three chambers
+from the place, where the gas was
+formed: and the lead was reduced most evidently
+<span class="pagenum" id="Page_107">[107]</span>behind the window-shutters where the
+moisture of the wall was most considerable.</p>
+
+<p>It is a common experiment with chymists,
+in order to show the effects of this gas, to
+draw characters with a solution of sugar of
+lead on paper, which they place over a glass
+of water, containing some alkaline sulphure:
+in some time the characters drawn on the
+paper acquire a brown, or black colour, and
+become visible; which amuses the spectators.</p>
+
+<p>But it is surprising, that the metal has
+never been reduced in this experiment even
+by chance; and not less so, why <em>lead</em> should
+be singled out for this trial of skill, in preference
+to other metals, which are equally affected
+by this gas.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 10. Tin.</span></h3>
+
+<p>A piece of silk was dipped in a solution of
+muriate of tin in distilled water, and dried
+in the air; the silk, on exposure to a current
+of the gas, scarce underwent any change,
+except a few brown specks dispersed over its
+surface.</p>
+
+<p>Another bit of silk was immersed in the
+same solution of tin, and exposed, while
+wet, to the gas, which no sooner touched
+the silk, than the surface opposed to the current
+was covered with reduced tin of great
+brightness: in some time various colours, as
+blue, orange, and a faint purple, appeared,
+<span class="pagenum" id="Page_108">[108]</span>and became more evident, as the reduction
+proceeded.</p>
+
+<p>The gas does not react on this metal so
+much as on mercury, and some other metals:
+part of the reduced tin remained permanent;
+but most of it disappeared, and left behind a
+disagreeable brown stain.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 11. Arsenic.</span></h3>
+
+<p>A bit of silk was immersed in a solution
+of muriate of arsenic in distilled water, and
+dried in the air; it was then exposed to a
+stream of sulphurated hydrogen gas; but no
+change could be observed, except a faint
+tinge of citron yellow, which appeared on
+some parts of the silk.</p>
+
+<p>Another bit of silk was dipped in the
+same solution of arsenic, and exposed, while
+wet, to the gas: the arsenic was instantly
+reduced all over the surface, opposed to the
+gas, attended with a citron yellow colour.</p>
+
+<p>The gas soon reacted on the reduced arsenic;
+and nothing remained but the yellow
+stain.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 12. Bismuth.</span></h3>
+
+<p>I dissolved some bismuth in nitric acid,
+and evaporated the solution to dryness; the
+salt was then dissolved in distilled water, and
+the solution deposited a copious white precipitate,
+but retained a quantity of the metal
+sufficient for these experiments.</p>
+
+<p><span class="pagenum" id="Page_109">[109]</span></p>
+
+<p>In this solution of bismuth a piece of silk
+was immersed, and dried in the air; it was
+then exposed to a stream of the gas: and the
+only visible effect produced was a very faint
+tinge of brown.</p>
+
+<p>Another bit of silk was dipped in the same
+solution of bismuth, and exposed wet to the
+gas: the silk was instantly covered with a
+bright pellicle of reduced bismuth, which
+soon lost most of its metallic lustre, being
+changed by the reaction of the gas to a sulphure.</p>
+
+<p>Mr. Kirwan in his experiments on hepatic
+air, found, that nitrous solution of bismuth,
+by mixture with a solution of hepatic air in
+water, changes to a reddish brown, and even
+assumes a metallic appearance.</p>
+
+<p>He also found that nitrates of silver, lead,
+and acetite of lead, were precipitated black.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 13. Antimony.</span></h3>
+
+<p>A piece of silk, which was immersed in
+a solution of tartarite of antimony in distilled
+water, and dried in the air, was exposed to
+a stream of the gas; but suffered no visible
+change, except that a few specks of yellow,
+and orange appeared.</p>
+
+<p>A bit of silk was dipped in the same solution
+of antimony, and exposed, while wet,
+to the gas; the antimony was immediately
+reduced to its metallic form, attended with
+a deep orange colour: in some time, most of
+<span class="pagenum" id="Page_110">[110]</span>the metallic lustre disappeared, a few specks
+only remaining permanent.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 14. Iron.</span></h3>
+
+<p>A piece of silk was immersed in a diluted
+solution of sulphate of iron in distilled water,
+and dried; it was then exposed to a current
+of the gas; but underwent no visible
+change.</p>
+
+<p>Another bit of silk was dipped in the
+same solution of iron, and exposed, while
+wet, to the gas: the silk soon began to acquire
+a dark colour, which gradually increased,
+and, at length, became black, attended
+with an obscure metallic film. The
+silk was immersed in water, and deposited
+a bright metallic film on the surface of that
+fluid.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 15. Zinc.</span></h3>
+
+<p>A bit of silk, which was immersed in a
+diluted solution of sulphate of zinc in distilled
+water, and dried in the air, was exposed
+to a current of the gas; but underwent no
+visible change.</p>
+
+<p>Another bit of silk was dipped in the same
+solution of zinc, and exposed, while wet, to
+the gas; but no change in the colour of the
+silk, or sign of reduction could be perceived:
+the silk was then immerged in a glass of clear
+water, and transferred to its surface a bright
+metallic film of the colour of zinc.</p>
+
+<p><span class="pagenum" id="Page_111">[111]</span></p>
+
+<p>When a languid stream of gas was employed
+in these experiments, the films transferred
+to water were scarce visible.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 16. Zinc.</span></h3>
+
+<p>A piece of silk, which was immersed in a
+largely diluted solution of muriate of zinc,
+and dried in the air, was exposed to a brisk
+current of sulphurated hydrogen gas; but
+underwent no visible alteration.</p>
+
+<p>Another bit of silk was dipped in the same
+solution of zinc, and exposed, while wet,
+to the same brisk current of gas; instantly
+the surface of the silk, opposed to the gas,
+was covered with a bright coat of reduced
+zinc, attended with faint orange, and purple
+colours.</p>
+
+<p>Though the reduced zinc was quite evident;
+yet I had the curiosity to examine its
+appearance on the surface of water; I therefore
+immersed the silk in a glass of that
+fluid, and a bright metallic pellicle, which
+retained the texture of the silk, as wax retains
+the impression of a seal, was transferred
+to its surface.</p>
+
+<p>Another bit of silk, dipped in the same
+solution of zinc, and exposed for a longer
+time to the gas, lost its metallic lustre, the
+zinc being changed to a sulphure by the reaction
+of the gas.</p>
+
+<p>These experiments on sulphate, and muriate
+of zinc, show, that the acid, in which
+<span class="pagenum" id="Page_112">[112]</span>the metal is dissolved, influences the reduction
+in a remarkable manner.</p>
+
+<p>It is evident from the experiments related
+in this chapter,</p>
+
+<ol>
+<li>That water is essential to the reduction
+of metals by sulphurated hydrogen gas.</li>
+
+<li>That alcohol does not promote these
+reductions, without the aid of water.</li>
+
+<li>That sulphurated hydrogen gas does not
+reduce the metals by giving them phlogiston;
+nor by uniting with, and separating, their
+oxygen: for were either of these opinions
+well founded; metallic solutions in alcohol
+should be as effectually reduced by this gas,
+as metallic solutions in water are.</li>
+</ol>
+
+<p>When we consider, that alkaline sulphure
+reduces the metals by decomposing water;
+we have every reason to conclude, that sulphurated
+hydrogen gas reduces them in the
+same manner; since the same circumstances
+are necessary to both: the hydrure of sulphur,
+which constitutes the base of this gas,
+attracts the oxygen of the water, while the
+hydrogen of the latter unites, in its nascent
+state, with the oxygen of the metal, and reduces
+it.</p>
+
+<p>Hence it follows, that the hydrure of sulphur
+is oxygenated by the oxygen of the water,
+while the metal is restored to its combustible
+state.</p>
+
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+
+<p><span class="pagenum" id="Page_113">[113]</span></p>
+
+
+  <h2 class="nobreak" style="line-height: 2em;" id="CHAPTER_VI">
+    CHAPTER VI.
+    <br>
+    <span class="smcap">REDUCTION of METALS</span>
+    <br>
+    <span class="fs60">BY</span>
+    <br>
+    <i>PHOSPHORATED HYDROGEN GAS</i>.
+  </h2>
+</div>
+
+
+<p class="drop-cap">The effects of hydrogen gas and phosphorus
+on the reduction of metals in the
+fibres of silk have been treated of separately
+in the two first chapters; in this, I shall
+briefly treat of their effects, when combined
+in the form of phosphorated hydrogen gas,
+which from its high degree of inflammability
+seemed well adapted to this purpose.</p>
+
+<p>The spontaneous inflammation of this kind
+of air was known to M. Gengembre in 1783;
+and his experiments were published in Rosier’s
+journal for October 1785.</p>
+
+<p>Mr. Kirwan also, without any knowledge
+of M. Gengembre’s experiments, discovered
+the same air, which he calls phosphoric air,
+and published his experiments in the 76th
+volume of the Philosophical Transactions for
+1786.</p>
+
+<p>This elastic fluid may be obtained by digesting
+a solution of potash in water with
+about half its weight of phosphorus in a heat
+sufficient to melt the latter; and may be received
+in glass vessels over mercury.</p>
+
+<p>But finding it inconvenient to introduce
+<span class="pagenum" id="Page_114">[114]</span>pieces of silk prepared for these experiments
+over mercury in close vessels, I exposed them
+to the gas, as it issued from the neck of the
+phial in which it was prepared.</p>
+
+<p>Part of this elastic fluid is spontaneously
+inflammable; but the other has not that property,
+which M. Gengembre imputes to the
+presence of carbonic acid; for the sake of
+brevity, I shall design the latter by the term
+<em>gas</em>, or <em>phosphorated hydrogen gas</em>; and the
+former by the epithets <em>spontaneously inflammable</em>,
+or <em>detonating</em> gas, which, I found, does
+not burn or scorch silk wetted with metallic
+solutions.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 1. Gold.</span></h3>
+
+<p>A piece of silk, which was immersed in a
+solution of nitro-muriate of gold in distilled
+water, and suspended in the air twelve hours
+to dry, was divided into three parts.</p>
+
+<p>One of these was exposed to a stream of
+phosphorated hydrogen gas: the silk became
+brown, and its margins, which happened to
+touch the sides of the phial, acquired a violet
+tinge: but no reduction took place.</p>
+
+<p>Another of these parts was wetted with
+alcohol, and exposed to the gas; but no signs
+of reduction could be perceived.</p>
+
+<p>The remaining part was wetted with water,
+and was no sooner exposed to the gas, than
+the reduction commenced over the whole silk,
+which was soon covered with a bright coat of
+reduced gold.</p>
+
+<p><span class="pagenum" id="Page_115">[115]</span></p>
+
+
+<h3 class="center"><span class="smcap">Exp. 2. Silver.</span></h3>
+
+<p>A piece of silk was dipped in a solution of
+fused nitrate of silver in alcohol, and dried
+in the air: it was then divided into three
+parts.</p>
+
+<p>One of these, in order to dissipate moisture
+more effectually, was dried still better by
+a gentle heat, and exposed to the gas; the
+silk acquired a brownish dark colour: but
+no other alteration could be perceived.</p>
+
+<p>Another of these parts, which was also
+better dried by a gentle heat, was wetted with
+alcohol, and exposed to the gas: the silk acquired
+a dark brown colour; but no other
+change could be observed.</p>
+
+<p>The remaining part was wetted with water,
+and exposed to the gas: the reduction
+commenced immediately, and in a short time
+the silk was covered with reduced silver.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 3. Platina.</span></h3>
+
+<p>A piece of silk was immersed in a solution
+of nitro-muriate of the ore of platina in distilled
+water, and dried in the air; it was then
+divided into three parts.</p>
+
+<p>One of these parts was exposed to the gas;
+but suffered no visible change.</p>
+
+<p>Another of them was wetted with alcohol,
+and exposed to the gas; but underwent no
+perceptible change.</p>
+
+<p>The remaining part was wetted with water,
+<span class="pagenum" id="Page_116">[116]</span>and exposed to the gas: in about three
+or four minutes, a bright metallic film, of
+great lustre, appeared on the side of the silk,
+opposed to the gas.</p>
+
+<p>Another bit of silk, which was dipped in
+the same solution of platina, and exposed,
+while wet, to the spontaneously inflammable
+gas, was immediately covered with reduced
+platina, which being transferred to the surface
+of water looked bright as silver, and retained
+the impression of the silk.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 4. Mercury.</span></h3>
+
+<p>A bit of silk, which was immersed in a solution
+of nitrate of mercury in distilled water,
+and dried in the air, was exposed to the
+gas; but underwent no visible change.</p>
+
+<p>Another bit of silk was dipped in the same
+solution of mercury, and dried: it was then
+wetted with alcohol, and exposed to the gas;
+but no sign of reduction appeared.</p>
+
+<p>Another bit of silk was immersed in the
+same solution of mercury, and exposed to the
+gas; the metal was instantly reduced all over
+the silk; a great variety of beautiful colours
+attending.</p>
+
+<p>A piece of silk was dipped in a solution of
+oxygenated muriate of mercury in distilled
+water, and dried in the air: it was then divided
+into two parts.</p>
+
+<p>One of these was exposed to the gas: no
+change appearing, it was wetted with alcohol,
+<span class="pagenum" id="Page_117">[117]</span>and exposed again to the gas; but still
+no alteration could be perceived.</p>
+
+<p>The remaining part was wetted with water,
+and was no sooner exposed to the gas,
+than the mercury was reduced over the whole
+silk. No colours attended the reduction.</p>
+
+<p>Mr. Kirwan introduced some precipitate
+per se to a small portion of phosphoric air:
+the precipitate soon grew black; and a white
+smoke appeared; in two days the precipitate
+remained solid; yet acquired a pale white
+colour, like that of steel: the air lost its
+spontaneous inflammability&#x2060;<a id="FNanchor_17_17" href="#Footnote_17_17" class="fnanchor">[17]</a>.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 5. Copper.</span></h3>
+
+<p>A piece of silk, which was immersed in a
+solution of sulphate of copper in distilled
+water, and dried in the air, was divided into
+two parts.</p>
+
+<p>One of these was exposed to the gas; but
+no visible change occurred.</p>
+
+<p>The remaining part was wetted with water,
+and exposed to the gas: in a few minutes
+a brownish matter appeared in the silk; but
+nothing metallic could be seen: the silk was
+then dipped in a glass of clear water, and
+transferred a small white metallic pellicle to
+its surface.</p>
+
+<p>In another experiment, made with the
+spontaneously inflammable gas, a white metallic
+<span class="pagenum" id="Page_118">[118]</span>pellicle was immediately formed, attended
+with a brown stain; this pellicle resembled
+silver, or a white metal: but the
+gas soon reacted on it, and formed a disagreeable
+brown matter in the fibres of the
+silk.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 6. Lead.</span></h3>
+
+<p>A bit of silk, which was dipped in a solution
+of acetite of lead in distilled water, and
+dried in the air, was exposed to the gas; but
+suffered no visible change.</p>
+
+<p>Another bit of silk was immersed in the
+same solution of lead, and exposed, while
+wet, to the gas; but nothing metallic could
+be seen: the silk, however, on immersion in
+water, transferred a few minute bright films
+to the surface of that fluid.</p>
+
+<p>In another experiment, made with the detonating
+gas, the reduced films were more
+evident.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 7. Tin.</span></h3>
+
+<p>A bit of silk, which was dipped in a solution
+of muriate of tin in distilled water,
+and dried in the air, was exposed to the action
+of the gas, without suffering any visible alteration.</p>
+
+<p>Another piece of silk was immersed in the
+same solution of tin, and exposed, while wet,
+to the gas; but no signs of reduction could
+be perceived: the silk was then immersed in
+<span class="pagenum" id="Page_119">[119]</span>water, and transferred a delicate metallic film
+to its surface.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 8. Arsenic.</span></h3>
+
+<p>A bit of silk, which was immersed in a solution
+of muriate of arsenic in distilled water,
+and dried in the air, was exposed to the gas;
+but no change could be perceived.</p>
+
+<p>Another bit of silk, immersed in the same
+solution of arsenic, and exposed, while wet,
+to the gas, acquired in a few minutes a brown
+stain; but nothing metallic could be seen on
+the silk; which, however, on being dipped
+in water, transferred a very minute film of
+reduced arsenic to its surface.</p>
+
+<p>In another experiment, made with the detonating
+gas, the films of reduced arsenic
+were much more evident, of greater brilliance,
+and attended with a brown stain
+produced in the fibres of the silk.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 9. Bismuth.</span></h3>
+
+<p>A piece of silk, which was dipped in a solution
+of nitrate of bismuth in distilled water,
+and dried in the air, was exposed to the gas;
+but no alteration could be observed.</p>
+
+<p>Another bit of silk was immersed in the
+same solution of bismuth, and exposed, while
+wet, to the gas: the silk in two or three minutes
+got a brown stain, which gradually became
+more intense; and a very delicate metallic
+film appeared: the silk was then immerged
+<span class="pagenum" id="Page_120">[120]</span>in water, and transferred a bright
+film of reduced bismuth to the surface of that
+fluid: the film retained the impression of the
+silk.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 10. Antimony.</span></h3>
+
+<p>A bit of silk, immersed in a solution of
+tartarite of antimony in distilled water, and
+dried in the air, was exposed to the gas; but
+suffered no apparent change.</p>
+
+<p>Another piece of silk was dipped in the
+same solution of antimony, and exposed,
+while wet, to the gas; but no signs of reduction
+appeared: the silk was then immerged
+in water, to the surface of which, it
+transferred one small spangle.</p>
+
+<p>This experiment was repeated with the
+detonating gas, which with difficulty produced
+some sparkling films: the silk was immersed
+in water, and transferred the films to
+its surface.</p>
+
+<p>A white matter was visible in the fibres of
+the silk.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 11. Cobalt.</span></h3>
+
+<p>A piece of silk, immersed in a solution
+of muriate of cobalt, and dried in the air,
+was exposed to the gas; but suffered no visible
+alteration.</p>
+
+<p>Another bit of silk was dipped in the same
+solution of cobalt, and exposed, while wet,
+to the gas: but no sign of reduction appeared;
+<span class="pagenum" id="Page_121">[121]</span>nor did the silk transfer a film to
+water.</p>
+
+<p>Another bit of silk was immersed in a solution
+of nitrate of cobalt, and exposed, while
+wet, to the detonating gas: no signs of reduction
+were visible for some time; but at
+length a few small spangles of the metal
+appeared on the silk, and were very brilliant,
+and when transferred to water, were still
+more so: a white matter could be seen in the
+fibres of the silk.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 12. Iron.</span></h3>
+
+<p>A bit of silk was immersed in a largely
+diluted solution of sulphate of iron in distilled
+water, and dried: it was then exposed
+to the action of the gas; but no alteration
+could be perceived.</p>
+
+<p>Another bit of silk was dipped in the same
+solution of iron, and exposed, while wet, to
+the gas: in a few minutes some parts of the
+silk acquired a light brown colour; but no
+reduced iron could be seen on the silk, which
+however transferred a very minute, and delicate
+film to water.</p>
+
+<p>This experiment was repeated with a
+strong detonating gas, and a very brilliant
+metallic film about four lines in diameter
+was reduced on the silk accompanied with a
+brown stain: but nothing like the black oxid
+of iron appeared.</p>
+
+<p><span class="pagenum" id="Page_122">[122]</span></p>
+
+
+<h3 class="center"><span class="smcap">Exp. 13. Zinc.</span></h3>
+
+<p>A bit of silk, which was immersed in a
+largely diluted solution of muriate of zinc,
+was exposed dry to the gas; but underwent
+no visible alteration.</p>
+
+<p>Another piece of silk was dipped in the
+same solution of zinc, and exposed wet to
+the gas; no signs of reduction appearing,
+the silk was immerged in water, and left a
+very minute metallic film on its surface,
+which could with difficulty be seen.</p>
+
+<p>The experiment was repeated with the detonating
+gas, and a very bright metallic film
+of zinc, four or five lines in diameter, was
+reduced on the silk.</p>
+
+<p>This experiment succeeded also with a
+largely diluted solution of sulphate of zinc.</p>
+
+<p>The silk, viewed by transmitted light, exhibited
+a brown stain beneath these films of
+iron and zinc.</p>
+
+<p>The experiments detailed in this chapter
+show,</p>
+
+<ol>
+<li>That water is essential to the reduction
+of metals by phosphorated hydrogen gas.</li>
+
+<li>That alcohol does not promote these
+reductions, without the aid of water.</li>
+
+<li>That this elastic fluid does not reduce
+metals by giving them phlogiston; nor by
+combining with, and separating, their oxygen;
+for were either of these suppositions
+true, it should reduce them as well with alcohol,
+as with water.</li>
+</ol>
+
+<p><span class="pagenum" id="Page_123">[123]</span></p>
+
+<p>After explaining the manner, in which sulphurated
+hydrogen gas reduces the metals;
+the mode of agency of phosphorated hydrogen
+gas is sufficiently obvious.</p>
+
+<p>The gas attracts the oxygen of the water,
+while the hydrogen of the latter unites, in
+its nascent state, with the oxygen of the metal,
+and reduces it.</p>
+
+<p>Hence it follows, that the hydrure of
+phosphorus, which constitutes the base of
+this gas, is oxygenated by the oxygen of the
+water, while the metal is, at the same time,
+restored to its combustible state.</p>
+
+<p>By hydrure of phosphorus is meant, a
+combination of hydrogen and phosphorus,
+containing less caloric, than is necessary to
+the gazeous state.</p>
+
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+
+<p><span class="pagenum" id="Page_124">[124]</span></p>
+
+
+  <h2 class="nobreak" style="line-height: 2em;" id="CHAPTER_VII">
+    CHAPTER VII.
+    <br>
+    <span class="smcap">REDUCTION of METALS</span>
+    <br>
+    <span class="fs60">BY</span>
+    <br>
+    <i>CHARCOAL</i>.
+  </h2>
+</div>
+
+
+<p class="drop-cap">Finding several combustible bodies, as
+hydrogen, phosphorus, sulphur, and combinations
+of these, capable of reducing the
+metals in the ordinary temperature of the
+atmosphere; I was desirous of knowing, if
+Charcoal also possessed that power.</p>
+
+<p>Charcoal may be applied with this view in
+several forms. M. Rouelle has observed that
+caustic fixed alkali dissolves a considerable
+quantity of this substance.</p>
+
+<p>Charcoal also exists in a very attenuated
+state in ether, alcohol, gum, <abbr title="et cetera">&amp;c.</abbr></p>
+
+<p>I have examined some of its effects on the
+reduction of metals, in these different forms,
+in which it probably exists combined with
+hydrogen, and also some of its effects in the
+solid form.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 1. Gold.</span></h3>
+
+<p>A small bit of well burned charcoal was
+suspended by a thread in a phial containing a
+diluted solution of nitro-muriate of gold in
+<span class="pagenum" id="Page_125">[125]</span>distilled water: some air bubbles soon appeared
+on the charcoal: and in about two hours
+reduced gold was evident on its lower surface,
+and increased gradually, till the charcoal was
+nearly coated with gold of its proper colour.</p>
+
+<p>This experiment was repeated with a richer
+solution of gold; the reduction did not
+commence near so soon, nor was the quantity
+reduced so great, or brilliant, as in the
+preceding experiment.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 2. Gold.</span></h3>
+
+<p>A small bit of charcoal was suspended in a
+solution of gold in ether: an effervescence
+immediately commenced, and continued for a
+considerable time: but the solution suffered
+no change of colour; nor was there a particle
+of the gold reduced.</p>
+
+<p>I should not be surprised, if the gold were
+reduced in this experiment, as charcoal contains
+a large quantity of water, which it
+powerfully attracts from the surrounding air:
+however not a vestige of reduced gold could
+be perceived.</p>
+
+<p>Bits of charcoal were suspended in the
+same manner in most of the metallic solutions
+treated of in this essay: no change was perceived
+on those immersed in solutions of arsenic,
+manganese, and fused nitrate of silver
+in water: but a bit immersed in a solution of
+the same nitrate in alcohol, had parts of it
+covered with bright sparkling particles, which
+<span class="pagenum" id="Page_126">[126]</span>seemed to vegetate from the charcoal, and
+were evidently reduced silver: for they were
+not soluble in water, on the surface of which
+the bit of charcoal deposited some small spangles
+of great lustre. The bits immersed in
+solutions of sulphate of iron and zinc exhibited
+some very faint signs of reduction.</p>
+
+<p>But these experiments were not repeated,
+nor sufficiently varied, to enable us to form
+a just opinion of the power of charcoal in
+reducing metals in this way.</p>
+
+<p>A small quantity of charcoal, reduced to
+fine powder, was digested several days in a
+strong solution of caustic potash in alcohol;
+the phial was frequently shaken to promote
+the solution.</p>
+
+<p>Some of the clear solution, which was of
+a reddish colour, was poured into a phial for
+use.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 3. Gold.</span></h3>
+
+<p>A few drops of this solution of charcoal,
+or carbone, were applied to a bit of silk;
+after the alcohol evaporated, a solution of gold
+in ether was dropped on, and immediately
+produced a brown, which, in about half an
+hour, was changed to a purple hue, owing
+to water attracted from the air; but no other
+sign of reduction appeared.</p>
+
+<p>Another bit of silk was immersed in the
+solution of carbone, and when the alcohol
+evaporated, a few drops of an aqueous solution
+<span class="pagenum" id="Page_127">[127]</span>of gold were applied; a brown stain was
+instantly formed; the silk was kept wet
+with water; the stain gradually assumed a
+purple tinge, and, in about five minutes,
+some reduced gold of its proper splendour,
+and colour, appeared: and in some time after
+every part of the silk, to which the solutions
+of carbone and gold were applied, was coated
+with reduced gold, which remained permanent.
+During the experiment, it is necessary
+to keep the silk constantly wet with
+water.</p>
+
+<p>If the solution of gold be applied before
+the alcohol evaporates, a black precipitate is
+formed, along with the brown stain. In an
+experiment made in this manner, a metallic
+film, whitish, and obscure, appeared in the
+beginning; but soon vanished: and in some
+time after the gold was reduced of its proper
+colour; and a speck of ruby red appeared on
+the margin.</p>
+
+<p>The silk viewed by transmitted light presented
+various colours, as purple, blue, and
+some green.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 4. Silver.</span></h3>
+
+<p>A few drops of the solution of carbone
+were applied to a bit of silk; when the alcohol
+evaporated, a solution of fused nitrate of
+silver in alcohol was applied: a light brown
+stain was immediately produced in the silk;
+but no reduced silver could be seen.</p>
+
+<p><span class="pagenum" id="Page_128">[128]</span></p>
+
+<p>The solution of carbone was applied to another
+bit of silk, and when the alcohol evaporated,
+an aqueous solution of fused nitrate
+of silver was dropped on: a brown stain was
+instantly formed, and, in about ten minutes,
+minute films of reduced silver were visible.</p>
+
+<p>The silk was kept wet with water during
+the experiment; and the brown stain was
+gradually changed to black. In some little
+time the metallic films disappeared.</p>
+
+<p>If the solution of silver be applied to the
+silk, before the alcohol evaporates, black and
+brown precipitates are immediately formed;
+and commonly no reduced silver can be seen;
+but sometimes very minute films appear.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 5. Platina.</span></h3>
+
+<p>To a bit of silk, which was immersed in
+a solution of nitro-muriate of platina in distilled
+water, and dried in the air, a few drops
+of the solution of carbone were applied; but
+no visible change was produced.</p>
+
+<p>Another bit of silk was dipped in the solution
+of carbone, and when the alcohol evaporated,
+a few drops of the solution of platina
+were applied: a yellow precipitate was
+immediately formed, and, in about ten minutes
+delicate films of reduced platina were
+visible: these metallic films soon vanished;
+and nothing but a yellow stain and the precipitate
+remained.</p>
+
+<p>A bit of calico, on which this experiment
+<span class="pagenum" id="Page_129">[129]</span>was repeated, transferred a bright film of reduced
+platina to the surface of water.</p>
+
+<p>During the experiments, the silk and calico
+were kept wet with water.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 6. Mercury.</span></h3>
+
+<p>On a bit of silk, which was immersed in a
+solution of oxygenated muriate of mercury
+in distilled water, and dried in the air, a little
+of the solution of carbone was dropped; but
+the silk underwent no visible change.</p>
+
+<p>Another bit of silk was dipped in the solution
+of carbone, and, when the alcohol evaporated,
+a little of the same solution of mercury
+was applied; a yellow precipitate was
+immediately formed; and soon after small
+films of reduced mercury appeared on the
+margin of the stain.</p>
+
+<p>This experiment was repeated with a solution
+of nitrate of mercury, and the reduction
+of the metal was very evident on the margin
+of the stain, which was black: the precipitate
+on the bit of silk was of the colour
+of sulphur.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 7. Copper.</span></h3>
+
+<p>To a bit of calico, which was immersed in
+a solution of acetite of copper in distilled water,
+and dried in the air, a few drops of the
+solution of carbone were applied; but no visible
+change was produced.</p>
+
+<p>On another bit of calico, which was dipped
+<span class="pagenum" id="Page_130">[130]</span>in the same solution of copper, some of
+the solution of carbone was dropped: the calico
+acquired a slight tinge of brown; it was
+kept wet with water; and, in about twenty
+minutes, several white metallic films were
+evident.</p>
+
+<p>A bit of silk, on which this experiment
+was made, acquired a beautiful red colour,
+similar to the ruby red, with which copper
+tinges glass, and depending on the same cause,
+<abbr title="videlicet">viz.</abbr> the quantity of oxygen combined with
+the metal.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 8. Lead.</span></h3>
+
+<p>A bit of white calico was immersed in a
+solution of acetite of lead in distilled water,
+and dried in the air: then a few drops of the
+solution of carbone were applied; but no visible
+alteration took place.</p>
+
+<p>On another bit of the same calico, which
+was dipped in the solution of carbone, a little
+of the same solution of lead was dropped;
+and in a few seconds films of reduced lead,
+bright as silver, appeared: the calico was
+then immerged in water, and transferred a
+continuous pellicle of reduced lead to its surface.</p>
+
+<p>This experiment was often repeated both
+on silk, and calico: sometimes the lead is reduced
+in an instant; but at other times five
+or six seconds elapse, before any reduced lead
+becomes visible.</p>
+
+<p><span class="pagenum" id="Page_131">[131]</span></p>
+
+<p>I also found, that a solution of potash in
+alcohol reduces lead; but not so soon, or effectually,
+or in such quantity, as the former
+solution does; but it is evident, that these solutions
+differ only in the quantity of carbone,
+which they contain.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 9. Tin.</span></h3>
+
+<p>To a bit of calico, which was immersed
+in a solution of muriate of tin in distilled
+water, and dried in the air, some of the solution
+of carbone was applied: but no signs of
+reduction appeared, nor was the colour of the
+calico much altered.</p>
+
+<p>On another bit of calico, which was dipped
+in the solution of carbone, some of the
+same solution of tin was dropped: a white
+precipitate was instantly formed, attended
+with bright films of reduced tin: the calico
+was immerged in water; and left a bright
+metallic film on the surface of that fluid.</p>
+
+<p>The same experiment succeeds on silk.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 10. Bismuth.</span></h3>
+
+<p>A piece of silk, which was immersed in a
+solution of nitrate of Bismuth in distilled
+water, and dried in the air, suffered no visible
+alteration, on applying the solution of
+carbone.</p>
+
+<p>To a bit of calico, which was dipped in
+the solution of carbone, a few drops of the
+same solution of bismuth were applied; and
+<span class="pagenum" id="Page_132">[132]</span>immediately films of reduced bismuth were
+evident. The calico was immerged in water,
+and transferred a bright metallic film to its
+surface.</p>
+
+<p>This experiment succeeded also on silk.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 11. Arsenic.</span></h3>
+
+<p>A bit of silk was immersed in a solution
+of muriate of arsenic in distilled water, and
+dried in the air, then a little of the solution
+of carbone was dropped on the silk; but no
+visible alteration took place.</p>
+
+<p>Another bit of silk was dipped in the solution
+of carbone, and when the alcohol evaporated,
+some drops of the same solution of
+arsenic were applied; and in a short time a
+few minute metallic films were visible on the
+silk, which, when transferred to water, were
+still more so.</p>
+
+<p>Tartarite of antimony, treated in the same
+manner, transferred a very delicate film,
+scarcely visible, to the surface of water.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 12. Iron.</span></h3>
+
+<p>A bit of calico, which was dipped in a
+largely diluted solution of sulphate of iron,
+and dried in the air, suffered no perceptible
+change, on applying the solution of carbone,
+except a slight tinge of brown.</p>
+
+<p>Another bit of calico was immersed in the
+same solution of iron, and placed on a bit of
+deal board, a few drops of the solution of
+<span class="pagenum" id="Page_133">[133]</span>carbone were then applied: the calico was
+kept constantly wet with water, and in about
+fifteen minutes films of reduced iron were
+visible: the calico was immersed in water,
+and left a bright metallic film on its surface.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 13. Zinc.</span></h3>
+
+<p>To a bit of silk, which was dipped in a
+largely diluted solution of muriate of zinc,
+and dried in the air, a few drops of the solution
+of carbone were applied; but scarce
+any alteration of colour, or other visible
+change, occurred.</p>
+
+<p>A piece of calico was immersed in the
+same solution of zinc, and placed on a bit of
+thin deal board, a few drops of the solution
+of carbone were then applied: the calico was
+kept constantly wet with water; and in about
+fifteen minutes films of reduced zinc were
+evident: the calico was immerged in water,
+and transferred a very bright metallic film of
+the colour of zinc to its surface.</p>
+
+<p>I also reduced muriate of cobalt in this
+manner.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 14. Manganese.</span></h3>
+
+<p>To a bit of silk, which was dipped in a
+diluted solution of nitrate of manganese, and
+dried in the air, some drops of the solution
+of carbone were applied; but nothing appeared,
+except a brown stain.</p>
+
+<p>Another bit of silk was immersed in the
+<span class="pagenum" id="Page_134">[134]</span>solution of carbone, when the alcohol evaporated,
+a few drops of the same solution of
+manganese were applied: a brown stain was
+soon produced; the silk was kept wet with
+water, and in about twenty minutes films of
+reduced manganese of a bluish white colour
+were evident on the silk.</p>
+
+<p>This experiment did not succeed with a
+strong solution of nitrate of manganese.</p>
+
+<p>The same experiment succeeds also on
+linen, and calico, both with nitrate, and sulphate
+of manganese; the reduction is attended
+with violet, and purple, colours, such as
+this metal imparts to glass, and other substances,
+in which it exists combined with
+different proportions of oxygen: this difference
+is the cause of the different colours,
+which solutions of manganese assume.</p>
+
+<p>The bright films of reduced manganese
+soon disappear, the cause of which has been
+explained in the first chapter of this essay:
+the explanation there offered is confirmed by
+the following facts.</p>
+
+<p>“Regulus of Manganese,” says Mr. Bergman,
+“when well fused generally persists in
+a dry place, but sometimes undergoes
+spontaneous calcination, and falls down in
+a brownish black powder.</p>
+
+<p>“Moisture, but particularly the access of
+aerial acid, assists this operation. A small
+piece, put into a dry bottle, well corked,
+remained perfect for the space of six
+months, but afterwards, exposed to the
+<span class="pagenum" id="Page_135">[135]</span>open air of a chamber for two days, contracted
+a browness on its surface, together
+with so much friability as to crumble between
+the fingers. The internal parts,
+however, retained an obscure metallic
+splendour, which disappeared in a few
+hours&#x2060;<a id="FNanchor_18_18" href="#Footnote_18_18" class="fnanchor">[18]</a>.”</p>
+
+<p>I shall now relate a few experiments made
+with ether, alcohol, and gum.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 15. Gold.</span></h3>
+
+<p>I evaporated a solution of gold in nitro-muriatic
+acid to dryness, and dissolved the
+salt in pure alcohol: the solution was poured
+into a phial carefully dried in hot sand, and
+rinced with pure alcohol: the solution filled
+about ¾ of the phial, which was carefully
+corked, and though it was nine months exposed
+to the gray light, no films of reduced
+gold appeared.</p>
+
+<p>Part of the same solution was poured into
+a phial, and diluted with water; films of reduced
+gold soon appeared.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 16. Gold.</span></h3>
+
+<p>A phial half filled with a solution of gold
+in sulphuric ether was exposed nine months
+to the gray light; but no films of reduced
+gold were produced.</p>
+
+<p><span class="pagenum" id="Page_136">[136]</span></p>
+
+<p>On a bit of silk, which was dipped in part
+of the same solution of gold, and exposed to
+the gray light, and kept wet with water, reduced
+gold appeared in the space of a few
+hours.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 17. Gold.</span></h3>
+
+<p>I mixed an aqueous solution of gold with a
+solution of gum arabic in distilled water, in
+such proportion, as to prevent the solution
+from spreading in the silk.</p>
+
+<p>With this solution I drew several stripes
+on a piece of silk, and exposed it to the gray
+light of a chambre: in some time the gold
+was reduced attended with blue, and purple,
+colours.</p>
+
+<p>Similar stripes were drawn on another piece
+of silk, which, after the stripes became sufficiently
+dry, was placed over the vapour of
+hot water; and in about fifteen minutes the
+gold was reduced in a beautiful manner.</p>
+
+<p>This solution was applied to another bit of
+silk, which, after it became sufficiently dry,
+was placed between the leaves of a blank
+book, to exclude the action of light; the
+gold, after some time, was reduced.</p>
+
+<p>I found that small stripes, and spots, made
+with this solution, were reduced by breathing
+on them for some time.</p>
+
+<p>Sugar also, mixed with the solution of gold,
+promotes the reduction; but not so well as
+gum.</p>
+
+<p><span class="pagenum" id="Page_137">[137]</span></p>
+
+<p>A bit of silk was dipped in a solution of
+nitrate of silver in distilled water, and exposed,
+while wet, to the smoke of a common fire;
+in a short time reduced silver appeared.</p>
+
+<p>The following inferences are deducible
+from the experiments related in this chapter.</p>
+
+<ol>
+<li>Charcoal is capable of reducing the metals
+in the ordinary temperature of the atmosphere.</li>
+
+<li>Water is essential to the reduction of
+metals by charcoal: for these experiments
+prove, that the reduction cannot be effected
+without water.</li>
+
+<li>Charcoal does not reduce the metals by
+giving them phlogiston; <ins id="ER-4" class="corr" title="Transcriber's Note&mdash;original text: or by uniting">nor by uniting</ins> with,
+and separating, their oxygen; for were either
+of these opinions true, metallic solutions in
+ether, and alcohol, should be as effectually
+reduced by charcoal, as metallic solutions in
+water are.</li>
+
+<li>Ether, and alcohol do not promote the
+reduction of metals without the aid of water:
+but when this is present in sufficient
+quantity, they effect the reduction, in the
+same manner, that charcoal, and other combustible
+bodies do.</li>
+</ol>
+
+<p>It is evident then that charcoal reduces the
+metals by decomposing water; which seems
+to be effected in the following manner.</p>
+
+<p>The carbone of the charcoal attracts the
+oxygen of the water, while the hydrogen of
+the latter unites, in its nascent state, with
+the oxygen of the metal, and reduces it.</p>
+
+<p><span class="pagenum" id="Page_138">[138]</span></p>
+
+<p>Hence it follows that the carbone is oxygenated
+by the oxygen of the water, and forms
+carbonic acid, while the metal is restored to
+its combustible state.</p>
+
+<p>This explanation is supported by the following
+fact: M. Gengembre has observed,
+that if charcoal be immersed in water, and
+kept at a temperature of 30 degrees of the
+thermometer of M. De Reaumur, the water
+is gradually decomposed, and inflammable
+gas is formed&#x2060;<a id="FNanchor_19_19" href="#Footnote_19_19" class="fnanchor">[19]</a>.</p>
+
+<p>That charcoal effects the reduction of metals,
+in high degrees of heat also, by decomposing
+water, is evident from the following
+observations.</p>
+
+<p>The great force with which charcoal attracts
+water is a fact sufficiently established;
+Dr. Priestley is so convinced of this, that he
+expresses himself in the following strong
+terms. “I did not know, nor could believe
+the powerful attraction, that charcoal, or
+iron, appear to have for water; when they
+are intensely heated, they will find, and
+attract it in the midst of the hottest fire
+through any pores in the retort&#x2060;<a id="FNanchor_20_20" href="#Footnote_20_20" class="fnanchor">[20]</a>.”</p>
+
+<p>Now since water is essential to the reduction
+of metals in low degrees of heat; and
+since that fluid is always present, when metals
+are reduced by charcoal in high degrees
+of heat; it is manifest, that charcoal acts in
+<span class="pagenum" id="Page_139">[139]</span>the same manner in both these temperatures;
+and since water is easily, and instantly, decomposed
+by charcoal at a red heat, as the
+Antiphlogistians themselves allow; it clearly
+follows that their theory of metallic reduction
+is erroneous: for since the water is instantly
+decomposed by the charcoal, it is a
+necessary consequence, that its carbone must
+unite with the oxygen of the water, while
+the hydrogen of the latter unites, in its nascent
+state, with the oxygen of the metal, and
+reduces it, forming a new quantity of water
+equal to that decomposed: this new quantity
+of water may be decomposed in its turn: so
+that a thimble full of water would be sufficient
+to reduce any quantity of metal; provided
+the water were prevented from escaping,
+and time enough allowed.</p>
+
+<p>Beside this source of water, the air of the
+atmosphere, which contributes to support the
+fire is an inexhaustible magazine of water:
+and the hotter the air is, the more water it
+holds in solution; as M. Le Roy has demonstrated&#x2060;<a id="FNanchor_21_21" href="#Footnote_21_21" class="fnanchor">[21]</a>.
+Moreover all metallic oxids and
+ores contain a large proportion of water.</p>
+
+<p>From this view it appears, that the manner,
+in which charcoal, and other combustible
+bodies, effect the reduction of metals, is by
+assisting to decompose water, the hydrogen
+<span class="pagenum" id="Page_140">[140]</span>of which is therefore the only reducer of the
+metals.</p>
+
+<p>In order to point out the difference between
+this opinion, and that of the Antiphlogistians,
+I shall present the reader with M. Lavoisier’s
+idea of metallic reduction.</p>
+
+<p>“It can not be doubted,” says that celebrated
+chymist, “that charcoal at a red heat
+takes oxygen from all metallic substances:
+this is a fact against which no exception
+can be made: and it is the foundation of
+the whole theory of metallic reduction.”</p>
+
+<p>But the experiments in this essay demonstrate,
+that this assertion is erroneous in every
+instance of metallic reduction: for so far is
+it from being true, that charcoal takes oxygen
+from all metallic substances, that it never
+does so in one single instance; since its carbone
+always unites with the oxygen of the
+water, the hydrogen of which unites immediately
+to the oxygen of the metal, and reduces
+it.</p>
+
+<p>“But this action of charcoal on oxygen,”
+adds M. Lavoisier, “this property, which it
+possesses of taking it from metallic subsubstances,
+is not so strong in the cold, as
+at a red heat, since we are unacquainted
+with any metallic revivification effected by
+charcoal without heat&#x2060;<a id="FNanchor_22_22" href="#Footnote_22_22" class="fnanchor">[22]</a>.”</p>
+
+<p>It is evident that this mode of reasoning is
+no longer of any weight; since charcoal does
+<span class="pagenum" id="Page_141">[141]</span>reduce metals in the ordinary temperature of
+the atmosphere.</p>
+
+<p>The reason charcoal is more powerful in
+high degrees of heat, than other reducers of
+the metals, is its great fixity in the fire, and
+the immense force, with which it attracts,
+and imprisons water in its pores: thus preventing
+its escape till it be decomposed by
+an affinity, which is much more complex than
+has been hitherto imagined.</p>
+
+<p>Another reason of the superior power of
+charcoal in metallic reduction is, that it forms
+a volatile elastic fluid with the oxygen of the
+water, which flies off; and consequently does
+not react on the metal, or disturb, or impede,
+by its presence, the action of the reducing
+powers: advantages that phosphorus, or any
+other combustible substance, which forms a
+fixed acid, that reacts on the metal, can never
+possess.</p>
+
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+
+<p><span class="pagenum" id="Page_142">[142]</span></p>
+
+
+  <h2 class="nobreak" style="line-height: 2em;" id="CHAPTER_VIII">
+    CHAPTER VIII.
+    <br>
+    <span class="smcap">REDUCTION of METALS</span>
+    <br>
+    <span class="fs60">BY</span>
+    <br>
+    <i>LIGHT</i>.
+  </h2>
+</div>
+
+
+<p class="drop-cap">The next substance, I shall treat of, is
+Light, which seems well adapted to illustrate
+the theory of metallic reduction; as in experiments
+made with this substance, water
+can be more effectually excluded, than in
+trials with any other reducer of the metals.</p>
+
+<p>Before any decisive experiments could be
+made on light, or indeed any other reducer
+of the metals, it is obvious that we should
+first ascertain the effects of water itself in the
+ordinary temperature of the atmosphere: to
+determine this point, the two following experiments
+were made.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 1. Gold.</span></h3>
+
+<p>A piece of silk was immersed in an aqueous
+solution of nitro-muriate of gold, and suspended
+in a phial over water: the phial was
+corked, covered with black silk, and placed
+in a dark closet, to prevent the action of
+light. The experiment was continued from
+the 20th of July to the 20th of October,
+<span class="pagenum" id="Page_143">[143]</span>during which time the silk was frequently
+observed, and found to continue moist: but
+no alteration could be perceived, except that
+the yellow colour, which the solution of gold
+gave the silk, was changed to a light brown.</p>
+
+<p>The silk was now taken out of the phial,
+and a solution of phosphorus in ether applied
+to it: shortly after, a white metallic film appeared:
+the silk was then kept wet with
+water, and in some time, reduced gold of its
+proper colour appeared.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 2. Silver.</span></h3>
+
+<p>A bit of silk, which was dipped in an
+aqueous solution of nitrate of silver, was suspended
+in a phial over water, and placed in
+a dark closet, from the 20th of July to the
+20th of October, and examined from time
+to time; but no alteration could be observed;
+its white colour continued pure, and unchanged.</p>
+
+<p>The silk was now taken out of the phial,
+and the silver was immediately reduced by
+means of a solution of phosphorus in ether.</p>
+
+<p>Hence it appears, that water alone has not
+the power of reducing metals in the ordinary
+temperature of the atmosphere.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 3. Gold.</span></h3>
+
+<p>On the 24th of July a piece of silk was
+immersed in a solution of nitro-muriate of
+gold in water, and dried by a gentle heat; it
+<span class="pagenum" id="Page_144">[144]</span>was then suspended in a window, exposed to
+the sunbeams, as much as possible: no change
+was perceived on it, till the 26th, when the
+margin of the silk began to assume a purple
+tinge, which increased gradually, and on the
+29th exhibited a few obscure specks of reduced
+gold on the side of the silk opposed to the
+light.</p>
+
+<p>The purple tinge continued to increase,
+and the yellow, which the solution of gold
+gave the silk, decreased gradually, till on the
+27th of August the colour was a mixture of
+purple, and light brown.</p>
+
+<p>The reduction of the gold seemed to keep
+pace with these changes of colour, and was
+very evident on some parts of the silk even
+in the gray light; but much more so in sunshine:
+these changes were observed till the
+20th of October; the experiment was then
+discontinued; and scarce any reduced gold
+could be seen on the side of the silk not opposed
+to the light.</p>
+
+<p>That this slight reduction of the gold, and
+changes of colour in the silk, depended on
+water absorbed from the air of the chambre,
+will appear from the following experiments.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 4. Gold.</span></h3>
+
+<p>A bit of silk, which was dipped in the
+solution of gold employed in the preceding
+experiment, was dried, and suspended in a
+crystal phial over dry carbonate of potash:
+<span class="pagenum" id="Page_145">[145]</span>the phial was then corked, and further secured
+from external humidity by covering the
+cork with wax: it was now placed in a dark
+closet 24 hours, that the carbonate of potash
+might have sufficient time to attract all the
+moisture, it could, from the air of the phial,
+before exposing it to the action of light.</p>
+
+<p>The phial was then placed in a window,
+exposed, as much as possible, to the solar
+light, from the 24th of July to the 20th of
+October, and carefully observed: the same
+side of the silk was always opposed to the
+light, and had the yellow tinge, which the
+solution of gold gave, altered to a brownish
+yellow: but the other side of the silk suffered
+no visible change whatever; nor could any
+purple tint, or the smallest vestige of reduced
+gold be perceived.</p>
+
+<p>Another bit of silk, which was immersed
+in the same solution of gold, and dried by a
+gentle heat, was suspended over some dry
+carbonate of potash, contained in a crystal
+phial covered with black silk, and placed in a
+dark closet, during the same space of time,
+underwent no visible change whatever.</p>
+
+<p>Both these bits of silk were now taken out
+of the phials, and the gold was instantly restored
+to its metallic splendour by means of
+water and a solution of phosphorus in ether:
+a proof that the nitro-muriate of gold, in
+these bits of silk, suffered no change, during
+that space of time.</p>
+
+<p><span class="pagenum" id="Page_146">[146]</span></p>
+
+
+<h3 class="center"><span class="smcap">Exp. 5. Gold.</span></h3>
+
+<p>A piece of silk, which was dipped in the
+same solution of gold, and placed on a china
+plate exposed to the sunbeams, was kept moderately
+wet with water during the experiment:
+the first alteration observed was,
+that the yellow colour of the silk began to
+change to a faint green, succeeded by a purple
+tinge, which in about fifteen minutes exhibited
+some particles of reduced gold: soon
+after the threads of the silk, which acquired
+this purple tint, were gilded with gold; and,
+in about an hour, the whole of the silk was
+covered with a superb coat of reduced gold,
+exhibiting the texture of the silk in a beautiful
+manner.</p>
+
+<p>The purple tinge, which attended the reduction
+verged in some parts on red, and in
+others on blue.</p>
+
+<p>This experiment, which is very amusing,
+I have repeated times unnumbered: and
+when the sun is powerful, and the solution of
+gold properly prepared, and of due strength,
+the coat of reduced gold is so bright, and
+dazzling, as to distress the eye of the beholder.</p>
+
+<p>I find, that the best way of preparing a
+solution of gold for this purpose is to separate
+the oxid of gold from its solution in nitro-muriatic
+acid by means of good ether.</p>
+
+<p>The silk may be dipped in this solution,
+<span class="pagenum" id="Page_147">[147]</span>and when the ether evaporates, kept moderately
+wet with distilled water.</p>
+
+<p>It was with this solution in ether that I
+first reduced gold in the fibres of silk, and it
+was by means of the same, I discovered, that
+water was a necessary condition in these reductions
+by light.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 6. Gold.</span></h3>
+
+<p>A bit of silk, which was dipped in a solution
+of nitro-muriate of gold in alcohol, and
+placed on a china saucer, exposed to the sunbeams,
+was kept wet with alcohol for the
+space of an hour; but no change even in the
+colour, which the solution of gold gave the
+silk, could be perceived.</p>
+
+<p>The alcohol diffused the solution of gold
+unequally through the silk: the rays of the
+sun being intercepted, suspended the experiment:
+there was no sunshine on the following
+day: on the third day the silk was
+again exposed to the sunbeams, and kept wet
+with alcohol, which extracted a yellow tincture;
+a proof that the gold in the silk suffered
+no degree of reduction: the sun shone
+pretty strong for an hour, or more; and, at
+length, a faint tinge of purple, followed by
+some reduced gold, appeared.</p>
+
+<p>The preceding experiments leave us no
+room to doubt, that the purple tinge and the
+small quantity of reduced gold, that appeared
+in this experiment, depended on water attracted
+<span class="pagenum" id="Page_148">[148]</span>from the air, or deposited in the silk
+by the alcohol during its evaporation.</p>
+
+<p>Mr. Scheele reduced a solution of nitro-muriate
+of gold in water by exposing it in a
+phial for a fortnight to the rays of the sun&#x2060;<a id="FNanchor_23_23" href="#Footnote_23_23" class="fnanchor">[23]</a>.</p>
+
+<p>Mr. Lewis also made many experiments
+on the staining of marble, and other substances
+with metallic solutions, and light&#x2060;<a id="FNanchor_24_24" href="#Footnote_24_24" class="fnanchor">[24]</a>.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 7. Silver.</span></h3>
+
+<p>A piece of silk, which was immersed in a
+solution of nitrate of silver in water, was
+dried by a gentle heat, and exposed to the
+light of the sun as much as possible in the
+window of a chambre from the 20th of July
+to the 20th of October.</p>
+
+<p>In less than an hour the silk acquired a
+reddish brown colour: next day the colour
+became more intense, and gradually increased,
+till, on the third day, it bordered on black,
+which increased slowly: at length part of it
+became gray, and a few minute particles of
+reduced silver could be distinguished: the
+black tinge gradually disappeared, and the
+silk was of a reddish brown colour: the reduced
+silver had a gray cast.</p>
+
+<p>The following experiments demonstrate,
+that the changes of colour, and the few particles
+of semireduced silver depended on water
+attracted from the atmosphere.</p>
+
+<p><span class="pagenum" id="Page_149">[149]</span></p>
+
+
+<h3 class="center"><span class="smcap">Exp. 8. Silver.</span></h3>
+
+<p>A bit of silk was immersed in part of the
+same solution of nitrate of silver in water,
+and dried in the dark: the silk retained its
+white colour: it was then suspended over dry
+carbonate of potash in a crystal phial, which
+was corked, and secured from the ingress of
+moisture by covering the cork with wax.</p>
+
+<p>The phial was left in a dark closet 24 hours,
+that the salt might imbibe as much moisture
+as possible from the silk, and air.</p>
+
+<p>The phial was then placed in a window,
+exposed, as much as possible, to the rays of
+the sun, from the 24th of July to the 20th
+of October: the silk scarcely suffered any visible
+change, except a very faint tinge of reddish
+brown; which was best seen by transmitted
+light; for the silk viewed by reflected light
+appeared nearly white: but that even this
+tinge, slight as it was, depended on a minute
+quantity of moisture, which the carbonate of
+potash was unable to extract, appears from
+the next experiment.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 9. Silver.</span></h3>
+
+<p>A piece of silk was dipped in a solution of
+fused nitrate of silver in alcohol, and carefully
+dried: it was then suspended over a
+quantity of concentrated sulphuric acid in a
+crystal phial, which was coated with a double
+fold of black paper, and gum arabic, reaching
+<span class="pagenum" id="Page_150">[150]</span>somewhat above the level of the acid, to
+prevent the light from acting on it: the phial
+was corked, and to exclude moisture more
+effectually, the cork was covered with wax.</p>
+
+<p>The phial was now placed in a dark closet
+24 hours, that the humidity of the enclosed
+silk and air might be attracted by the acid: it
+was then placed in a window, exposed as
+much as possible to the rays of the sun, from
+the 19th of July to the 26th of October: but
+the silk underwent no visible change whatever:
+its white colour remained pure, and
+unaltered.</p>
+
+<p>The silk, at the end of this period, was
+taken out of the phial, and wetted with water:
+a solution of phosphorus in ether was
+then applied to it; and instantly the metallic
+splendour of the silver appeared.</p>
+
+<p>Another bit of silk, which was immersed
+in a solution of nitrate of silver in water, and
+dried in the dark, was suspended over dry
+carbonate of potash in a phial, and placed in a
+dark closet about two months; the silk underwent
+no visible alteration whatever; its
+white colour remained pure.</p>
+
+<p>I was desirous of knowing, if the nitrate of
+silver in this bit of silk suffered any change,
+that might render it incapable of reduction:
+I therefore took it out of the phial, and divided
+it into two parts: one of these was
+wetted with water, and the silver was instantly
+reduced by a solution of phosphorus
+in ether. The other part, which was suspended
+<span class="pagenum" id="Page_151">[151]</span>in a window, exposed to the air of the
+chamber, and rays of the sun, soon acquired
+a reddish brown colour.</p>
+
+<p>Hence it is evident, that these changes of
+colour indicate partial reductions of the metal;
+and that they never happen without the
+presence of water.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 10. Silver.</span></h3>
+
+<p>A bit of silk, which was dipped in a solution
+of nitrate of silver in water, was placed
+on a China saucer, exposed to the rays of the
+sun, and kept moderately wet with water:
+in a few minutes the white colour of the silk
+was changed to a reddish brown, which by
+degrees became darker; and, in about three
+or four hours, though the solar rays were
+often languid, and intercepted, acquired a
+blackish gray colour, most of the reddish
+brown having disappeared: next day there
+was no sunshine; but towards the evening
+particles of reduced silver were visible on the
+side of the silk opposed to the light.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 11. Silver.</span></h3>
+
+<p>A bit of silk, which was immersed in a solution
+of nitrate of silver in alcohol, and exposed
+to the beams of the sun, as in the preceding
+experiment, was kept moderately wet
+with alcohol; but resisted the action of the
+light much longer than the preceding: however,
+in some time, specks, and lines, of a
+<span class="pagenum" id="Page_152">[152]</span>reddish brown, began to appear on some parts
+of the silk: next day, though there was no
+sunshine, the reddish brown colour increased
+a little: on the third day, it became more intense;
+but no black, or gray colour, or particle
+of reduced silver, could be observed.</p>
+
+<p>Whoever compares this with the preceding
+experiments, can have no doubt that the
+changes of colour, which appeared in this
+experiment, depended on water attracted from
+the air, or deposited in the silk by the alcohol
+during its evaporation.</p>
+
+<p>The experiments detailed in this Chapter,
+prove beyond the power of contradiction,</p>
+
+<ol>
+<li>That water is essential to the reduction
+of metals by light: for these experiments demonstrate,
+that the reduction can not take
+place without water, and that it is always in
+proportion to the quantity of that fluid present.</li>
+
+<li>That light does not reduce metals by
+giving them phlogiston, as Messrs. Macquer
+and Scheele supposed; for were this opinion
+true, light should reduce them without the
+aid of water, and as well with alcohol as with
+water.</li>
+
+<li>Light does not reduce metals by fusing
+and expelling their oxygen, as the antiphlogistians
+imagine; for were this its mode of
+agency, the reduction should happen without
+the assistance of water, and as well with alcohol
+as with water.</li>
+
+<li>Light is a combustible body; for it acts
+<span class="pagenum" id="Page_153">[153]</span>like hydrogen, phosphorus, sulphur, and charcoal,
+in the reduction of metals.</li>
+</ol>
+
+<p>Since water then is essential to the reduction
+of metals by light, and since light does
+not reduce metals by giving them phlogiston,
+nor by fusing, and expelling their oxygen, it
+follows, that the water is either decomposed,
+or that it unites with metallic earths, and
+constitutes their phlogiston, or that it unites
+with, and separates their oxygenous principle:
+but as the two last suppositions are inadmissible,
+it is obvious that light reduces the metals
+by decomposing water.</p>
+
+<p>After explaining the manner in which other
+combustible bodies reduce the metals by decomposing
+water; it will not be difficult to
+explain how light too produces the same effect.</p>
+
+<p>But in order to facilitate the explanation,
+it must be premised,</p>
+
+<ol>
+<li>That it is a law of attraction, that, when
+any body is deprived, to a certain degree, of
+another, for which it has a strong affinity,
+the attraction of the former for the latter is
+much increased.</li>
+
+<li>That light has a strong attraction for
+oxygen, or the base of vital air.</li>
+
+<li>That when oxygen is condensed, and
+fixed in any substance, it contains much less
+light, and caloric, than it does in the gazeous
+state.</li>
+
+<li>That the oxygenous principle exists in
+<span class="pagenum" id="Page_154">[154]</span>water in this condensed state, and consequently
+has a strong attraction for light.</li>
+</ol>
+
+<p>Therefore, when light reduces the metals,
+it attracts the oxygen of the water, while the
+hydrogen of the latter unites, in its nascent
+state, to the oxygen of the metal, and reduces
+it, forming at the same time a quantity
+of water equal to that decomposed.</p>
+
+<p>Hence it follows that the light is oxygenated,
+and changed into vital air, while the
+metal is restored to its combustible state.</p>
+
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+
+<p><span class="pagenum" id="Page_155">[155]</span></p>
+
+
+  <h2 class="nobreak" style="line-height: 2em;" id="CHAPTER_IX">
+    CHAPTER IX.
+    <br>
+    <span class="smcap">REDUCTION of METALS</span>
+    <br>
+    <span class="fs60">BY</span>
+    <br>
+    <i>ACIDS</i>.
+  </h2>
+</div>
+
+
+<p class="drop-cap">It is well known that solutions of gold
+throw up films of the reduced metal to the
+surface of the fluid, and sides of the phials
+that contain them.</p>
+
+<p>It has been shown, chap. 7th, that this
+effect depends on the presence of water, which
+is further illustrated by the following experiments.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 1. Silver.</span></h3>
+
+<p>A dram of saturated solution of nitrate of
+silver in distilled water was mixed with half
+an ounce of vinegar, in a few minutes, a precipitate
+was formed: the whole was then
+poured on a filter, and washed with distilled
+water: the precipitate acquired a bluish gray
+metallic appearance: the liquor, which passed
+the filter, got a brown colour, and became
+blackish: next day bright films of reduced
+silver floated on the liquor; and in some
+months after, a considerable part of the inner
+surface of the phial was coated with reduced
+<span class="pagenum" id="Page_156">[156]</span>silver. Distilled vinegar did not produce this
+effect.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 2. Platina.</span></h3>
+
+<p>If a solution of the ore of platina in nitro-muriatic
+acid be evaporated to dryness; and
+the salt dissolved in water, films of a livid
+white metallic appearance are thrown up to
+the surface.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 3. Tin.</span></h3>
+
+<p>Some tin, which was dissolved in a china
+cup in muriatic acid, and evaporated to dryness,
+was dissolved in distilled water; immediately
+white metallic films appeared on the
+surface of the liquor; and after some hours,
+the whole surface of the solution was covered
+with a continuous metallic pellicle, which
+reflected all the colours of the rainbow, in a
+beautiful manner.</p>
+
+
+<h3 class="center"><span class="smcap"><ins id="TN-8" class="corr" title="Transcriber's Note&mdash;Added full stop.">Exp. 4. Mercury.</ins></span></h3>
+
+<p>Mr. Bergman says, “calcined mercury is
+reduced by digestion in acid of salt; but
+the cause has not yet been sufficiently explored&#x2060;<a id="FNanchor_25_25" href="#Footnote_25_25" class="fnanchor">[25]</a>.”</p>
+
+<p>As this reduction of mercury by muriatic
+acid is doubted of by some; I made the following
+experiment.</p>
+
+<p><span class="pagenum" id="Page_157">[157]</span></p>
+
+<p>A quantity of precipitate <i lang="la">per se</i> was put
+into a china cup, placed on hot sand, and some
+muriatic acid was poured on it: the oxid was
+gradually dissolved, and the digestion continued,
+till the acid was nearly evaporated:
+some distilled water was then poured on the
+salt, and minute films of a bright metallic
+appearance floated on the surface.</p>
+
+<p>A nitrate of mercury was evaporated to
+dryness; the salt acquired a slight tinge of
+yellow; the cup was removed from the hot
+sand, and some water poured on the salt: immediately
+bright films of reduced mercury
+appeared; and in about three or four hours
+the whole surface of the solution was covered
+with a metallic pellicle, parts of which had
+the colour and splendour of the metal; and
+other parts reflected a wonderful variety of
+the most beautiful colours.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 5. Arsenic.</span></h3>
+
+<p>A quantity of white oxid of arsenic and
+muriatic acid was digested in the same manner
+in a china cup; a smart heat was continued,
+till most of the acid evaporated, and
+left behind a mass of the consistence of tar:
+the surface of which had a gray appearance;
+after it cooled, some distilled water was poured
+on, it diffused a disagreeable smell, and
+films of reduced arsenic were thrown up to
+the surface; these were for some time remarkably
+bright, but soon became of a dull
+<span class="pagenum" id="Page_158">[158]</span>gray colour, owing to the rapid tendency of
+this metal to spontaneous calcination.</p>
+
+
+<h3 class="center"><span class="smcap">Exp. 6. Manganese.</span></h3>
+
+<p>Some concentrated sulphuric acid was poured
+on a quantity of the black oxid of manganese
+in a china cup, placed on hot sand: an
+effervescence was visible, but no sulphurous
+acid gas was exhaled: the cup was removed
+from the sand, before any perceptible quantity
+of the acid evaporated: then some water
+was poured on the mixture: and instantly
+the surface of the fluid was covered with
+very brilliant metallic films: and, at the same
+time, the solution acquired a rose colour.</p>
+
+<p>Some of the same oxid of manganese was
+dissolved in nitric acid, in which a bit of
+sugar was put: the solution was poured into
+a china cup, placed on hot sand, and, as the
+evaporation proceeded, bright metallic films
+appeared on the surface.</p>
+
+<p>Mr. Bindheim of Moscow relates, that he
+reduced the aërated calx of manganese dissolved
+in nitrous acid: “the solution was
+placed upon an open fire in a glass retort&#x2060;<a id="FNanchor_26_26" href="#Footnote_26_26" class="fnanchor">[26]</a>.”</p>
+
+<p>Happening to pour out a very largely diluted
+solution of sulphate of iron, I was surprised
+to find the flags of the court in an
+hour or two after, covered with large films
+<span class="pagenum" id="Page_159">[159]</span>of a livid white metallic aspect: these films,
+after the water evaporated, remained on the
+flags several days.</p>
+
+<p>In consequence of this I poured a largely
+diluted solution of sulphate of iron into several
+shallow vessels, and always found the
+surface of the solution covered with abundance
+of bright metallic films.</p>
+
+<p>I also found that a largely diluted solution
+of muriate of zinc throws up bright metallic
+films to the surface.</p>
+
+<p>The reduction of metals by acids is a very
+convincing proof of the decomposition of
+water, and seems inexplicable on any other
+principle.</p>
+
+<p>The reduction and calcination of metals by
+heat and electricity are naturally explained on
+the same principle: Doctor Priestley informs
+us in his History of Electricity, Vol. I. p. 344,
+that S. Beccaria revived several of the metals
+by the electric shock. It is obvious that the
+electric fluid produces this effect in the same
+manner, that other combustible bodies do,
+<abbr title="videlicet">viz.</abbr> by decomposing water. When the red
+oxid of mercury is reduced in close vessels
+by heat; the latter attracts the oxygen of the
+water, contained both in the oxid, and in the
+air of the vessels, while the hydrogen of the
+water unites to the oxygen of the mercury,
+reduces it, and forms a quantity of water
+equal to that decomposed.</p>
+
+<p>It is found, that if light and caloric act
+both at the same time, the reduction is effected
+<span class="pagenum" id="Page_160">[160]</span>with more facility, than if either acted separately:
+in this case, the superior efficacy of
+the combined action of light, and caloric resembles
+that of other compound reducers of
+the metals; as that of sulphurated hydrogen
+gas, phosphorated hydrogen gas, alkaline
+sulphure, <abbr title="et cetera">&amp;c.</abbr> which are more powerful than
+simple hydrogen gas, sulphur, or phosphorus.</p>
+
+<p>This superior efficacy of compound reducers,
+is similar to what happens with some
+other combinations of combustible bodies, as
+pyrites, pyrophori, a mixture of lead and tin,
+<abbr title="et cetera">&amp;c.</abbr> which have a more powerful attraction
+for oxygen, than any of their ingredients, in
+a separate state.</p>
+
+<p>Other acids, as the gallic, the tartarous,
+the formic, <abbr title="et cetera">&amp;c.</abbr> and also alkalis, as ammonia,
+and soda, have the power of reducing some
+of the metals, facts well known to chymists.</p>
+
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+
+<p><span class="pagenum" id="Page_161">[161]</span></p>
+
+
+  <h2 class="nobreak" style="line-height: 2em;" id="CHAPTER_X">
+    CHAPTER X.
+    <br>
+    OXYGENATION
+    <br>
+    <span class="fs60">OF</span>
+    <br>
+    <i>COMBUSTIBLE BODIES</i>.
+  </h2>
+</div>
+
+
+<p class="drop-cap">It has been shown, in the preceding chapters,
+that water is essential to the reduction
+of metals; that it is always decomposed in
+that process; and that the reducing substances
+are oxygenated by the oxygen of the water,
+while the hydrogen of the latter reduces the
+metals.</p>
+
+<p>That water is also decomposed in every instance
+of oxygenation, and that the oxygen
+of water alone oxygenates combustible bodies,
+will appear from the following observations.</p>
+
+
+<h3 id="CHAPTER_X_AZOTE" class="center"><span class="smcap">Azote.</span></h3>
+
+<p>The first case of oxygenation, we shall
+consider, is that of <em>azote</em>, in an experiment
+of Dr. Priestley, which has been urged by
+Mr. Kirwan with great success against the
+Antiphlogistians.</p>
+
+<p>“If the electric spark be taken in nitrous
+air, it will be reduced to ⅓ of its bulk,
+and the residuum is mere phlogisticated
+<span class="pagenum" id="Page_162">[162]</span>air, and a little acid is deposited. Now
+the Antiphlogistians own that nitrous air
+contains both pure air and phlogisticated
+air; since, therefore, this pure air disappears,
+is it not evident that it was converted
+into water? and since the formation
+of water requires the presence of inflammable
+air, does it not follow that the nitrous
+air contained this also&#x2060;<a id="FNanchor_27_27" href="#Footnote_27_27" class="fnanchor">[27]</a>?”</p>
+
+<p>To this objection M. Berthollet replies,
+that the diminution of the nitrous gas “is
+owing to the combination of the mercury
+with the oxygene, which existed in the
+gas&#x2060;<a id="FNanchor_28_28" href="#Footnote_28_28" class="fnanchor">[28]</a>.”</p>
+
+<p>But this answer is insufficient; as it does
+not account for the water, and acid, that appeared:
+and indeed, by this experiment, the
+Antiphlogistians are refuted on their own
+principles, and the decomposition of water is
+incontestably proved; for as nitrous acid
+could not be formed without more oxygen
+than what existed in the nitrous air, is it not
+evident, that this oxygen must be derived
+from the water contained in the nitrous air?
+It is obvious then, that the water of the gas
+was decomposed; which seems to have been
+effected in the following manner.</p>
+
+<p>The electric spark diminishes the attraction
+of the constituent principles of the water for
+each other; hence the azote of the gas unites
+<span class="pagenum" id="Page_163">[163]</span>with the oxygen of the water, while the hydrogen
+of the latter combines with the oxygen
+of the gas; and thus water and nitrous
+acid are formed.</p>
+
+<p>The formation of nitrous acid in Mr. Cavendish’s
+noted experiment, cannot be explained
+on any other principle than the decomposition
+of water: when the electric
+spark is taken in a mixture of azotic gas, and
+vital air; the water of these airs is decomposed:
+the electric flame lessens the force,
+with which the oxygen and hydrogen of the
+water adhere; hence the azote seizes the oxygen
+of the water, and forms nitrous acid,
+while the hydrogen of the water unites with
+the oxygen of the vital air, and forms a quantity
+of water equal to that decomposed.</p>
+
+<p>When nitrous, and vital air, are mixed;
+the whole mass “hisses, turns red, grows
+warm, and contracts in bulk,” the azote of
+the nitrous air attracts the oxygen of the
+water, and forms nitrous acid, while the hydrogen
+of the water unites in its nascent
+state with the oxygen of the vital air, and
+forms a quantity of water equal to that decomposed.</p>
+
+<p>Hence while the azote of the nitrous air is
+oxygenated; <ins id="ER-5" class="corr" title="Transcriber's Note&mdash;original text: and the caloric">the caloric</ins> is restored to its
+combustible state.</p>
+
+<p>“But it is to be observed,” says M. Bergman,
+treating of this experiment, “that the
+decomposition of nitrous air is the effect
+of a double attraction; the phlogiston is
+<span class="pagenum" id="Page_164">[164]</span>attracted by the vital air, and the acid part
+by the water. Therefore, when the mixture
+is made in a phial immersed in mercury,
+the experiment fails&#x2060;<a id="FNanchor_29_29" href="#Footnote_29_29" class="fnanchor">[29]</a>.”</p>
+
+
+<h3  id="CHAPTER_X_HYDROGEN" class="center"><span class="smcap">Hydrogen.</span></h3>
+
+<p>The combustion of hydrogen gas with vital
+air is explicable only on the decomposition of
+the water contained in these airs: thus when
+flame, or a glowing body is applied to a mixture
+of them; the attraction of the principles
+of the water for each other is diminished;
+therefore the hydrogen of the inflammable
+air unites with the oxygen of the water,
+while the hydrogen of the latter seizes the
+oxygen of the vital air: thus the whole bulk
+of the airs, which are changed into water,
+disappears; and their light, and caloric, are
+restored to the combustible state.</p>
+
+<p>Hence it appears that water is not formed
+during the combustion of vital, and inflammable
+air, in the manner the Antiphlogistians
+suppose.</p>
+
+<p>Indeed it is obvious, that, if these airs contained
+no water, they could never be burned:
+for since they are already saturated with light,
+and caloric, they can have no attraction for
+any additional quantity of these fluids; and
+consequently can suffer no other change from
+the light, or caloric, of a glowing body, than
+<span class="pagenum" id="Page_165">[165]</span>a greater degree of expansion, and therefore
+could never unite.</p>
+
+<p>The same reasoning applies to the combustion
+of all elastic fluids.</p>
+
+
+<h3  id="CHAPTER_X_PHOSPHORUS" class="center"><span class="smcap">Phosphorus.</span></h3>
+
+<p>Vital air always contains a large proportion
+of water: when phosphorus is burned in this
+air, it attracts the oxygen of the water, and
+forms phosphoric acid, while the hydrogen
+of the water unites with the oxygen of the
+gas, and forms water, which unites with the
+acid.</p>
+
+<p>Hence the weight of the acid formed is
+equal to the weights of the oxygen gas, and
+phosphorus, consumed; and the light and caloric,
+which appear during the combustion,
+are restored to their combustible state.</p>
+
+<p>This explanation is confirmed by an observation
+of Mr. Bergman, who says,</p>
+
+<p>“In vital air, without the aid of external
+heat, phosphorus is consumed very slowly,
+and scarce at all, unless water be present&#x2060;<a id="FNanchor_30_30" href="#Footnote_30_30" class="fnanchor">[30]</a>.”</p>
+
+<p>Therefore the phosphorus does not unite
+to the oxygen of the vital air, as M. Lavoisier
+supposes, but to the oxygen of the water
+contained in the oxygen gas.</p>
+
+<p><span class="pagenum" id="Page_166">[166]</span></p>
+
+
+<h3  id="CHAPTER_X_SULPHUR" class="center"><span class="smcap">Sulphur.</span></h3>
+
+<p>When sulphur is burned in vital air, it
+attracts the oxygen of the water, and forms
+sulphuric acid, while the hydrogen of the
+water attracts the oxygen of the gas, and
+forms a quantity of water equal to that decomposed:
+the light and caloric are at the
+same time restored to their combustible state.</p>
+
+<p>The sulphur then does not unite with the
+oxygen of the vital air, as the Antiphlogistians
+imagine, but with the oxygen of the
+water contained in that gas.</p>
+
+
+<h3  id="CHAPTER_X_CHARCOAL" class="center"><span class="smcap">Charcoal.</span></h3>
+
+<p>In like manner during the combustion of
+charcoal in vital air, the carbone attracts the
+oxygen of the water, and forms carbonic
+acid, while the hydrogen of the water unites
+with the oxygen of the vital air, and forms
+a new quantity of water equal to that decomposed.</p>
+
+<p>Hence the carbone of the charcoal does
+not unite with the oxygen of the vital air,
+as M. Lavoisier supposes, but with the oxygen
+of the water contained in that gas.</p>
+
+<p>That water is decomposed in every instance
+of combustion, is further proved by
+attending to what passes during the burning
+of a common fire: the carbone of the fuel
+combines with the oxygen of the water, and
+forms carbonic acid, while the hydrogen of
+<span class="pagenum" id="Page_167">[167]</span>the water unites partly with the oxygen, and
+partly with the azote of the atmosphere, and
+forms water, and the ammonia, which
+abounds in soot.</p>
+
+<p>From these observations it is evident, that
+M. Lavoisier’s account of the formation of
+water, and acids, is erroneous, and inadequate
+to explain the phenomena.</p>
+
+<p>The different kinds of fermentation are so
+many instances of the decomposition of water:
+in every case of them, combustible bodies
+are oxygenated by the oxygen of the
+water, while others are restored by its hydrogen
+to their combustible state.</p>
+
+<p>Hence the azote, ammonia, and carbonic
+acid of fermentation, the inflammable air of
+marshes, mines, <abbr title="et cetera">&amp;c.</abbr> the azotic, and hydrogen
+gas, ascending into the atmosphere, and
+there meeting the vital air discharged from
+the water of plants, <abbr title="et cetera">&amp;c.</abbr> form new quantities
+of air, and water.</p>
+
+<p>When the azote is oxygenated, it unites
+with the oxygen of the water contained in
+the air, and forms atmospheric air, and sometimes
+perhaps nitrous acid, the hydrogen of
+the water combines, at the same time, with
+the oxygen of the vital air, and forms a quantity
+of water equal to that decomposed.</p>
+
+<p>But when the hydrogen is oxygenated, a
+quantity of water double that decomposed is
+regenerated; for the hydrogen of the gas
+unites with the oxygen of the water, while
+the hydrogen of the latter seizes the oxygen
+<span class="pagenum" id="Page_168">[168]</span>of the vital air: and thus a quantity of water
+double that decomposed is formed, and that
+part of it which the atmosphere cannot suspend
+descends in the form of rain.</p>
+
+<p>When these decompositions are rapid, the
+phenomena of thunder and lightning appear.</p>
+
+<p>This account of the renovation of our atmosphere
+explains why the phenomena of
+thunder and lightning appear sometimes with,
+and sometimes without rain, and also accounts
+for the production of the nitrous acid, which
+Mr. Margraaf discovered in the purest snow.</p>
+
+<p>The breathing of fishes is a striking proof
+of the decomposition of water in respiration.</p>
+
+<p>For this view of the formation of our atmosphere
+I am indebted to a friend well acquainted
+with the experiments related in this
+essay, and also for the application of the opinion
+which I venture to advance, to the respiration
+of animals.</p>
+
+<p>The phenomena of vegetation cannot be
+explained on any other principle, than the
+decomposition of water by heat, and light,
+which uniting to the oxygen of the water
+contained in vegetables change it into streams
+of vital air, that serve to renovate our atmosphere:
+the hydrogen of the water, at the
+same time, contributes to form the oil and
+other principles of plants, and when these are
+decomposed by the various processes of combustion,
+forms a quantity of water equal to
+that consumed in their formation.</p>
+
+<p>The changes, which nitric acid suffers by
+<span class="pagenum" id="Page_169">[169]</span>exposure to heat, or light, are explained with
+ease on this principle: the light unites with
+the oxygen of the water contained in the nitric
+acid, and forms vital air, while the hydrogen
+of the water combines with the oxygen
+of the acid, and forms a new quantity of
+water equal to that decomposed: thus the
+nitric is converted into the ruddy nitrous acid.</p>
+
+
+<h3  id="CHAPTER_X_METALS" class="center"><span class="smcap">Metals</span>.</h3>
+
+<p>According to the Antiphlogistians, “In
+every metallic solution by an acid, the
+metal, in order to become oxided, decomposes
+either the acid itself, or the water of
+solution, or it obtains from the atmosphere
+the requisite quantity of oxygene. In the
+second case, hydrogenous gas, in a state
+of greater or less purity is disengaged; and
+the acid remains entire without decomposition,
+which is proved by the quantity of
+alkali necessary to saturate it. In the first
+case, one of the principles of the acid, or
+the acid deprived of part of its oxygene,
+is disengaged, and fused in the caloric,
+which is separated at the same time; such
+are nitrous gas, and sulphurous acid gas.
+In the third case, neither the water nor
+the acid are changed; such is the solution
+of copper by the acetous acid.</p>
+
+<p>“The muriatic acid, and the vegetable
+acids, which are formed of radicals, or
+acidifiable principles, which have more
+<span class="pagenum" id="Page_170">[170]</span>affinity with oxygene, than the metals
+have, are not decomposed by these metals,
+and the oxygene is always afforded to these
+last by the water or atmosphere. Hence
+the solutions by these acids afford only hydrogenous
+gas, or do not effervese at all.</p>
+
+<p>“There are some cases in which the water
+and the acid are at the same time decomposed
+by the metal, as in the solution
+of tin in the nitric acid, according to the
+observation of M. De Morveau.”</p>
+
+<p>“Tin is so greedy of oxygene, and requires
+so large a quantity for its saturation, that
+after having absorbed that of the nitric
+acid, and reduced it to the state of azote,
+it decomposes likewise the water, and disengages
+hydrogene. These two principles
+being separated from their first compounds,
+unite together, and immediately form ammoniac.
+Hence there is no disengagement
+of elastic fluid. In this case it appears,
+that the formation of ammoniac, in the
+solution of tin by the nitric acid, always
+takes place; for by throwing quicklime,
+or caustic fixed alkali, into this solution,
+there is always a disengagement of ammoniac&#x2060;<a id="FNanchor_31_31" href="#Footnote_31_31" class="fnanchor">[31]</a>.”</p>
+
+<p>It is evident, then, that this account of the
+oxygenation of metals, given by the Antiphlogistians,
+is equally complex, as their account
+<span class="pagenum" id="Page_171">[171]</span>of metallic reduction, and improbable;
+since every case, in which they deny the decomposition
+of water, and derive the oxygen
+from other sources, is easily, and naturally
+explained on that principle, as will appear
+from what follows.</p>
+
+<p>Thus when mercury, or silver, is dissolved
+in nitric acid; the metal attracts the oxygen
+of the water, while the hydrogen of the latter
+unites with, and separates, more or less
+of the oxygen of the acid, which is thus
+changed into nitrous air.</p>
+
+<p>The same thing happens during the solution
+of other metals in this acid; the only
+difference being the greater or less energy,
+and rapidity, with which they combine with
+the oxygen of the water.</p>
+
+<p>This decomposition of water is confirmed
+by the solution of tin in this acid; in which
+the Antiphlogistians allow the decomposition
+of the acid, and the water too; for ammonia
+is formed by part of the hydrogen of the
+water, and azote of the acid.</p>
+
+<p>In every case of metallic solution by sulphuric,
+and muriatic acids, whether concentrated,
+or diluted, water is decomposed: the
+metals attracting the oxygen of the water,
+while its hydrogen escapes in the form of inflammable
+air, or unites partly with the oxygen
+of the acid, and partly with caloric:
+hence the volatile sulphurous acid, and muriatic
+acid air, obtained, always contain some
+<span class="pagenum" id="Page_172">[172]</span>hydrogen gas, as appears from the following
+observation of M. Bergman.</p>
+
+<p>“By means of vitriolic acid, inflammable
+air is obtained from zinc, and iron, as also
+by means of marine acid; but, from the
+other metals dissolved in vitriolic acid, we
+obtain another species of air, called <em>vitriolic
+acid air</em>; and, by the marine acid, another
+similar to the former, called <em>muriatic
+air</em>, but both more or less mixed with <em>inflammable
+air</em>&#x2060;<a id="FNanchor_32_32" href="#Footnote_32_32" class="fnanchor">[32]</a>.”</p>
+
+<p>Again, when copper is dissolved in the
+acetous acid; the copper attracts the oxygen
+of the water, while the hydrogen of the latter
+unites with the oxygen of the atmosphere,
+and forms water: hence no effervescence appears.</p>
+
+<p>When alkalies dissolve metals, the latter
+are always oxygenated at the expence of the
+water, which holds the alkali in solution:
+thus when lead, and copper, are dissolved;
+the metals combine with the oxygen of the
+water, while its hydrogen unites to the oxygen
+of the atmosphere, and forms water:
+hence no hydrogen gas appears.</p>
+
+<p>The oxygenation of metals, and other substances
+by heat, and air, is easily explained
+on the same principle: the metals, <abbr title="et cetera">&amp;c.</abbr> unite
+with the oxygen of the water contained in
+<span class="pagenum" id="Page_173">[173]</span>atmospheric air, while the hydrogen of the
+water combines with the oxygen of the air,
+and forms a quantity of water equal to that
+decomposed.</p>
+
+<p>This explanation is clearly proved by an
+experiment of Mr. Bergman on the regulus
+of manganese, which, if kept in a dry place,
+retains its metallic splendour; but, if exposed
+to moisture, is soon oxygenated, and loses its
+lustre&#x2060;<a id="FNanchor_33_33" href="#Footnote_33_33" class="fnanchor">[33]</a>.</p>
+
+<p>It is further confirmed by the authority of
+the distinguished Mr. Scheele, who says, that
+“the water contained in common atmospheric
+air is the chief cause of the ignition of
+pyrophorus,” which he proved by the following
+experiment.</p>
+
+<p>“I made a very dry air by putting some
+very small pieces of quicklime into a small
+matrass: then I put the neck of another
+matrass into that of the first, so that the
+air of both might communicate; and I
+luted the crevices with wax. Two days
+afterwards I separated the empty matrass,
+and poured half an ounce of pyrophorus
+from my phial into it, and immediately
+carefully shut the aperture up: but I did
+not observe, that it grew in the least warm:
+an hour after this, I put a sponge moistened
+in water into the matrass, and shut it up
+again: a few minutes after the pyrophorus
+<span class="pagenum" id="Page_174">[174]</span>began strongly to be heated, and some
+pieces kindled spontaneously&#x2060;<a id="FNanchor_34_34" href="#Footnote_34_34" class="fnanchor">[34]</a>.”</p>
+
+<p>Many other facts might be adduced to
+prove, that oxygenation cannot take place
+without water, as the combustion of mixtures
+of iron filings, sulphur and water, of
+alkaline sulphure and water, <abbr title="et cetera">&amp;c.</abbr> in which
+the water is decomposed, and the combustible
+bodies oxygenated by its oxygen.</p>
+
+<p>It is evident then from the experiments
+and observations related in this essay, that
+water is essential to the oxygenation of combustible
+bodies; and that it is the only source
+of the oxygen that oxygenates them: it is
+also evident, that when one body is oxygenated,
+another, at least, is restored to the
+combustible state: hence it appears that the
+oxygenation of combustible bodies is never
+effected by a single affinity.</p>
+
+<p>The Antiphlogistians treating of the precipitation
+of metals by each other, say,</p>
+
+<p>“Since the metals cannot remain united
+to the acids, but in the state of oxides of
+a determinate degree, it is easily conceived,
+that by plunging into a metallic solution a
+metal which has a stronger affinity with
+oxygene than that which is dissolved, the
+former must deprive the latter of its oxygene,
+take its place in the acid, and cause
+the second to subside in a form more or
+less metallic, accordingly as it has deprived
+<span class="pagenum" id="Page_175">[175]</span>it of more or less oxygene. This is the
+reason of the precipitation of silver by copper,
+copper by iron&#x2060;<a id="FNanchor_35_35" href="#Footnote_35_35" class="fnanchor">[35]</a>,” <abbr title="et cetera">&amp;c.</abbr></p>
+
+<p>But this account of the precipitation of
+metals by one another cannot be admitted;
+for it has been proved in every instance of reduction
+related in this essay, that water is
+decomposed, and that its hydrogen is the only
+substance that restores bodies to their combustible
+state.</p>
+
+<p>There is no reason then to suppose that
+nature deviates, in this particular case, from
+that uniform simplicity, which she constantly
+observes in all her operations.</p>
+
+<p>Therefore it is obvious, that, when one
+metal precipitates another in a form more or
+less metallic; the precipitant unites with the
+oxygen of the water, while the hydrogen of
+the latter combines with, and separates, the
+oxygen of the precipitated metal, and thus
+reduces it.</p>
+
+<p>The experiments made with phosphorus
+and metallic solutions in ether, alcohol, and
+water, prove the truth of this explanation;
+and show that when one metal precipitates
+another in the metallic form, it acts like a
+stick of phosphorus, decomposing the water.</p>
+
+<p>This account of the reduction of one metal
+by another is supported by the opinion of
+Mr. Bergman, who says,</p>
+
+<p><span class="pagenum" id="Page_176">[176]</span></p>
+
+<p>“It is well known, that the calx of copper,
+dissolved in vitriolic acid, is precipitated
+in its metallic form on the addition
+of iron; and that by means of a double
+elective attraction; for the iron dissolving
+in the acid would form an inflammable air
+by its phlogiston, were not the copper
+present, which takes it up&#x2060;<a id="FNanchor_36_36" href="#Footnote_36_36" class="fnanchor">[36]</a>.”</p>
+
+<p>The same author remarks, that a small excess
+of acid is necessary, and that without it
+no precipitation begins.</p>
+
+<p>Now since water is decomposed by iron
+and sulphuric acid, it must be allowed,
+that, when iron is immersed in a solution of
+sulphate of copper, the water is decomposed
+by the iron and excess of acid, the iron attracting
+the oxygen of the water, while the
+hydrogen of the latter, unites to the oxygen
+of the copper, reduces it, and forms a quantity
+of water equal to that decomposed.</p>
+
+<p>The precipitation of silver in its metallic
+form by iron and other metals is to be explained
+in the same manner: and not by a
+single affinity, as the Antiphlogistians imagine.</p>
+
+<p>The reduction of gold, and some other metals,
+by solutions of sulphate of iron, and
+muriate of tin, is readily accounted for on the
+principles advanced here; for fresh made solutions
+of sulphate of iron, and muriate of
+tin, contain hydrogen, and have the power
+<span class="pagenum" id="Page_177">[177]</span>of decomposing water: the oxygen of which
+unites with the iron, and tin, while its hydrogen
+seizes the oxygen of the gold, <abbr title="et cetera">&amp;c.</abbr>
+reduces it, and forms a quantity of water
+equal to that decomposed.</p>
+
+<p>The decomposition of water is further
+proved by the large dilution necessary to form
+the arbor Dianæ, the purple precipitate of
+Cassius, and other instances of the reduction
+of metals by one another.</p>
+
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+
+<p><span class="pagenum" id="Page_178">[178]</span></p>
+
+
+  <h2 class="nobreak" style="line-height: 2em;" id="CHAPTER_XI">
+    CHAPTER XI.
+    <br>
+    <i>CONCLUSION.</i>
+  </h2>
+</div>
+
+
+<p class="drop-cap">I shall conclude with a general view of
+the inferences, which I ventured to advance
+in this essay.</p>
+
+<ol>
+<li>Neither the Phlogistians, nor Antiphlogistians,
+account in a satisfactory manner
+for the increase of weight, which bodies
+acquire during combustion.</li>
+
+<li>Their account of the formation of water,
+acids, and oxids, is erroneous; for it has
+been shown that the oxygen of water alone
+oxygenates combustible bodies.</li>
+
+<li>Combustible bodies, as hydrogen, phosphorus,
+sulphur, charcoal, light, <abbr title="et cetera">&amp;c.</abbr> are capable
+of reducing the metals in the ordinary
+temperature of the atmosphere; and indeed
+I might add, at a much lower temperature,
+as I frequently experienced.</li>
+
+<li>Combustible bodies do not reduce the
+metals by giving them phlogiston, as the
+Phlogistians suppose; nor by uniting with,
+and separating their oxygen, as the Antiphlogistians
+maintain.</li>
+
+<li>Water is essential both to the reduction
+and oxygenation of bodies, and is always decomposed
+in these operations.
+<span class="pagenum" id="Page_179">[179]</span>
+</li>
+
+<li>Water does not contribute to metallic
+reduction merely by dissolving and minutely
+dividing the particles of metallic salts, and
+thus removing the impediment opposed to
+chymical attraction by the attraction of cohesion:
+for were this the case, metallic solutions
+in ether and alcohol, in which that
+impediment is equally removed, should be as
+readily and effectually reduced, as metallic
+solutions in water are.
+
+<p class="noindent" style="margin-bottom: 0">This circumstance, in which all the experiments
+on metallic reduction detailed in this
+essay exactly coincide, merits particular attention,
+and shows that the manner, in which
+combustible bodies effect the reduction, is the
+same in them all.</p></li>
+
+<li>When one body is oxygenated, another,
+at least, is restored at the same time to its
+combustible state; and <i lang="la"><abbr title="vice versa">v. v.</abbr></i> when one body
+is restored to its combustible state, another at
+least is at the same time oxygenated.</li>
+
+<li>Quantities of air, and water, equal to
+those decomposed in the different species of
+combustion, are constantly a forming.</li>
+</ol>
+
+<p>Thus nature, by maintaining this balance
+of power between combustible and oxygenated
+bodies, prevents the return of original
+chaos.</p>
+
+<p>Since then in every act of combustion, one
+body, at least, is oxygenated, and another
+restored, at the same time, to its combustible
+state, the phenomena of combustion may be
+referred to two heads, <abbr title="videlicet">viz.</abbr></p>
+
+<p><span class="pagenum" id="Page_180">[180]</span></p>
+
+<p><em>Oxygenation</em>, or the union of oxygen with
+combustible bodies, and</p>
+
+<p><em>Reduction</em>, or the restoration of oxygenated
+bodies to their combustible state.</p>
+
+<p>And since in every instance of combustion
+water is decomposed, and one body oxygenated
+by the oxygen of the water, while another
+is restored to its combustible state by
+the hydrogen of the same fluid, it follows,</p>
+
+<ol>
+<li>That the hydrogen of water is the only
+substance, that restores bodies to their combustible
+state.</li>
+
+<li>That water is the only source of the
+oxygen, which oxygenates combustible bodies.</li>
+
+<li>That no case of combustion is effected
+by a single affinity.</li>
+</ol>
+
+<p>This view of combustion may serve to
+show how nature is always the same, and
+maintains her equilibrium by preserving the
+same quantities of air and water on the surface
+of our globe: for as fast as these are
+consumed in the various processes of combustion,
+equal quantities are formed, and
+rise regenerated like the Phenix from her
+ashes.</p>
+
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+
+<p><span class="pagenum" id="Page_181">[181]</span></p>
+
+
+  <h2 class="nobreak" style="line-height: 2em;" id="Nomenclature_of_the_Chymical_Terms">
+    <span class="smcap">Nomenclature</span> <i>of the Chymical Terms
+    used in this Essay</i>.
+  </h2>
+</div>
+
+<table class="autotable">
+<thead>
+<tr>
+<td class="tdc">NEW NAMES.</td>
+<td class="tdc">OLD NAMES.</td>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>Ammonia</td>
+<td>Caustic vol. alkali.</td>
+</tr>
+<tr>
+<td>Acetite of lead</td>
+<td>Sugar of lead.</td>
+</tr>
+<tr>
+<td>———— copper</td>
+<td>Verdirgris.</td>
+</tr>
+<tr>
+<td>Azote</td>
+<td>Base of phlogisticated air.</td>
+</tr>
+<tr>
+<td>Azotic gas</td>
+<td>Phlogisticated air.</td>
+</tr>
+<tr>
+<td>Alkaline sulphure</td>
+<td>Liver of sulphur.</td>
+</tr>
+<tr>
+<td>Alcohol</td>
+<td>Highly rectified spirit of wine.</td>
+</tr>
+<tr>
+<td>Carbone</td>
+<td>Pure coal.</td>
+</tr>
+<tr>
+<td>Carbonic acid</td>
+<td>Fixed air.</td>
+</tr>
+<tr>
+<td>Caloric</td>
+<td>Heat.</td>
+</tr>
+<tr>
+<td>Hydrogen</td>
+<td>Base of inflammable air.</td>
+</tr>
+<tr>
+<td>Hydrogen gas</td>
+<td>Inflammable air.</td>
+</tr>
+<tr>
+<td>Hydrure of sulphur</td>
+<td>A compound of hydrogen and sulphur.</td>
+</tr>
+<tr>
+<td>———— phosphorus</td>
+<td>A compound of hydrogen and phosphorus.</td>
+</tr>
+<tr>
+<td>Muriate of tin</td>
+<td>Salt of Jupiter.</td>
+</tr>
+<tr>
+<td>———— silver</td>
+<td>Luna cornea.</td>
+</tr>
+<tr>
+<td>———— arsenic</td>
+<td>Arsenic combined with muriatic acid.</td>
+</tr>
+<tr>
+<td>———— zinc</td>
+<td>Marine salt of zinc.</td>
+</tr>
+<tr>
+<td>———— cobalt</td>
+<td>Marine salt of cobalt.</td>
+</tr>
+<tr>
+<td>Nitric acid</td>
+<td>Dephlogisticated nitrous acid.</td>
+</tr>
+<tr>
+<td>Nitro-muriatic acid</td>
+<td>Aqua regia.</td>
+</tr>
+<tr>
+<td>Nitro-muriate of gold</td>
+<td>A compound of gold and aqua regia.</td>
+</tr>
+<tr>
+<td>—————— platina</td>
+<td>A compound of platina and aqua regia.</td>
+</tr>
+<tr>
+<td>
+<span class="pagenum" id="Page_182">[182]</span>
+Nitrate of silver</td>
+<td>Lunar nitre, crystals of the moon.</td>
+</tr>
+<tr>
+<td>——— of mercury</td>
+<td>Mercurial nitre.</td>
+</tr>
+<tr>
+<td>——— of bismuth</td>
+<td>Nitre of bismuth.</td>
+</tr>
+<tr>
+<td>——— of manganese</td>
+<td>Nitre of manganese.</td>
+</tr>
+<tr>
+<td>Oxygen</td>
+<td>Base of vital air.</td>
+</tr>
+<tr>
+<td>Oxygen gas</td>
+<td>Vital air.</td>
+</tr>
+<tr>
+<td>Oxygenated muriate of mercury</td>
+<td>Corrosive sublimate.</td>
+</tr>
+<tr>
+<td>Prussiate of mercury</td>
+<td>A compound of mercury and prussic acid.</td>
+</tr>
+<tr>
+<td>Phosphorated hydrogen gas</td>
+<td>Phosphoric air.</td>
+</tr>
+<tr>
+<td>Potash</td>
+<td>Caustic vegetable alkali.</td>
+</tr>
+<tr>
+<td>Sulphuric ether</td>
+<td>Vitriolic ether.</td>
+</tr>
+<tr>
+<td>Sulphureous acid gas</td>
+<td>Vol. sulphureous acid.</td>
+</tr>
+<tr>
+<td>Sulphurated hydrogen gas</td>
+<td>Hepatic acid.</td>
+</tr>
+<tr>
+<td>Sulphate of copper</td>
+<td>Blue vitriol.</td>
+</tr>
+<tr>
+<td>———— zinc</td>
+<td>White ditto.</td>
+</tr>
+<tr>
+<td>———— iron</td>
+<td>Green ditto.</td>
+</tr>
+<tr>
+<td>———— manganese</td>
+<td>Vitriol of manganese.</td>
+</tr>
+<tr>
+<td>Soda</td>
+<td>Caustic mineral alkali.</td>
+</tr>
+<tr>
+<td>Tartarite of antimony</td>
+<td>Emetic tartar.</td>
+</tr>
+</tbody>
+</table>
+
+<p class="center p4">FINIS.</p>
+
+<div class="footnotes">
+<h2>FOOTNOTES:</h2>
+
+<div class="footnote"><p><a id="Footnote_1_1" href="#FNanchor_1_1" class="label">[1]</a> Essay on Phlogiston, by M. Kirwan, a new edition,
+p. 21, and 16.</p></div>
+
+<div class="footnote"><p><a id="Footnote_2_2" href="#FNanchor_2_2" class="label">[2]</a> Experiments on Air and Fire. Eng. trans. p. 174.</p></div>
+
+<div class="footnote"><p><a id="Footnote_3_3" href="#FNanchor_3_3" class="label">[3]</a> Essay on Phlogiston, a new edition, p. 38–166.</p></div>
+
+<div class="footnote"><p><a id="Footnote_4_4" href="#FNanchor_4_4" class="label">[4]</a> Essay on Phlogiston, p. 207.</p></div>
+
+<div class="footnote"><p><a id="Footnote_5_5" href="#FNanchor_5_5" class="label">[5]</a> Essay on Phlogiston, p. 205.</p></div>
+
+<div class="footnote"><p><a id="Footnote_6_6" href="#FNanchor_6_6" class="label">[6]</a> Essay on Phlogiston, p. 14.</p></div>
+
+<div class="footnote"><p><a id="Footnote_7_7" href="#FNanchor_7_7" class="label">[7]</a> Essay on Phlogiston, p. 13–15.</p></div>
+
+<div class="footnote"><p><a id="Footnote_8_8" href="#FNanchor_8_8" class="label">[8]</a> <i lang="la"><abbr title="ibidem">Ibid</abbr>.</i> p. 25. and Philo. Trans. Vol. 78. p. 314.</p></div>
+
+<div class="footnote"><p><a id="Footnote_9_9" href="#FNanchor_9_9" class="label">[9]</a> Scheele, p. 162, French translation.</p></div>
+
+<div class="footnote"><p><a id="Footnote_10_10" href="#FNanchor_10_10" class="label">[10]</a> Roz. Journ. Feb. 1782.</p></div>
+
+<div class="footnote"><p><a id="Footnote_11_11" href="#FNanchor_11_11" class="label">[11]</a> Elective Attractions, English Translation, p. 87.</p></div>
+
+<div class="footnote"><p><a id="Footnote_12_12" href="#FNanchor_12_12" class="label">[12]</a> M. Monnet Dissolution de Metaux, p. 159.</p></div>
+
+<div class="footnote"><p><a id="Footnote_13_13" href="#FNanchor_13_13" class="label">[13]</a> Phil. Trans. Vol. 73. An. 1783.</p></div>
+
+<div class="footnote"><p><a id="Footnote_14_14" href="#FNanchor_14_14" class="label">[14]</a> Essay on Phlogiston, a new Edit, by M. Kirwan,
+p. 46.</p></div>
+
+<div class="footnote"><p><a id="Footnote_15_15" href="#FNanchor_15_15" class="label">[15]</a> Priestley, Vol. VI. p. 150.</p></div>
+
+<div class="footnote"><p><a id="Footnote_16_16" href="#FNanchor_16_16" class="label">[16]</a> Chem. Essays, Vol. III. p. 219.</p></div>
+
+<div class="footnote"><p><a id="Footnote_17_17" href="#FNanchor_17_17" class="label">[17]</a> M. Kirwan, Phil. Trans. for 1786.</p></div>
+
+<div class="footnote"><p><a id="Footnote_18_18" href="#FNanchor_18_18" class="label">[18]</a> Chem. Essay. Vol. II. p. 206 and 207. Eng. Trans.</p></div>
+
+<div class="footnote"><p><a id="Footnote_19_19" href="#FNanchor_19_19" class="label">[19]</a> Essay on Phlogiston, new Ed. by M. Kirwan, p. 61.</p></div>
+
+<div class="footnote"><p><a id="Footnote_20_20" href="#FNanchor_20_20" class="label">[20]</a> Phil. Trans. 1785. Vol. LXXV. p. 289.</p></div>
+
+<div class="footnote"><p><a id="Footnote_21_21" href="#FNanchor_21_21" class="label">[21]</a> El. Nat. Hist. &amp; Chem. Eng. Trans. in three volumes,
+p. 163. Vol. I.</p></div>
+
+<div class="footnote"><p><a id="Footnote_22_22" href="#FNanchor_22_22" class="label">[22]</a> Ess. on Phlog. a new Ed. by M. Kirwan, p. 60.</p></div>
+
+<div class="footnote"><p><a id="Footnote_23_23" href="#FNanchor_23_23" class="label">[23]</a> Experiments on Air and Fire, Eng. Trans. p. 82.</p></div>
+
+<div class="footnote"><p><a id="Footnote_24_24" href="#FNanchor_24_24" class="label">[24]</a> Commerce of the Arts.</p></div>
+
+<div class="footnote"><p><a id="Footnote_25_25" href="#FNanchor_25_25" class="label">[25]</a> Elec. Attrac. Eng. Tran. p. 223.</p></div>
+
+<div class="footnote"><p><a id="Footnote_26_26" href="#FNanchor_26_26" class="label">[26]</a> Crell’s Chem. Jour. Vol. II. p. 48. Eng. Trans.</p></div>
+
+<div class="footnote"><p><a id="Footnote_27_27" href="#FNanchor_27_27" class="label">[27]</a> Essay on Phlogiston, new Ed. p. 82.</p></div>
+
+<div class="footnote"><p><a id="Footnote_28_28" href="#FNanchor_28_28" class="label">[28]</a> <abbr title="ibidem">Ibid</abbr>. p. 122.</p></div>
+
+<div class="footnote"><p><a id="Footnote_29_29" href="#FNanchor_29_29" class="label">[29]</a> Elec. Attr. Eng. Trans. p. 211.</p></div>
+
+<div class="footnote"><p><a id="Footnote_30_30" href="#FNanchor_30_30" class="label">[30]</a> El. Att. Eng. Trans. p. 213.</p></div>
+
+<div class="footnote"><p><a id="Footnote_31_31" href="#FNanchor_31_31" class="label">[31]</a> Essay on Phlog. new Ed. by Mr. Kirwan, p. 233–235.</p></div>
+
+<div class="footnote"><p><a id="Footnote_32_32" href="#FNanchor_32_32" class="label">[32]</a> Chem. Ess. Vol. II. p. 358. Eng. Trans.</p></div>
+
+<div class="footnote"><p><a id="Footnote_33_33" href="#FNanchor_33_33" class="label">[33]</a> Chem Ess. Vol. II. p. 206–207. Eng. Trans.</p></div>
+
+<div class="footnote"><p><a id="Footnote_34_34" href="#FNanchor_34_34" class="label">[34]</a> Exper. on Air and Fire, Eng. Trans. p. 112, and 130.</p></div>
+
+<div class="footnote"><p><a id="Footnote_35_35" href="#FNanchor_35_35" class="label">[35]</a> Ess. on Phlog. new Ed. by Mr. Kirwan, p. 236, and
+237.</p></div>
+
+<div class="footnote"><p><a id="Footnote_36_36" href="#FNanchor_36_36" class="label">[36]</a> Chem. Essays, Vol. II. p. 384, Eng. Trans.</p></div>
+</div>
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<div class="transnote" id="transnote">
+<h2>TRANSCRIBER’S NOTE</h2>
+  <p>
+  Obvious punctuation errors have been corrected after careful
+  comparison with other occurrences within the text.</p>
+  <p>
+  Inconsistent hyphenations have been left as is.</p>
+  <p>
+  The original book used the character ſ (long-form s). This has been
+  changed to the modern s in this eBook.</p>
+  <p>
+  Footnotes have been renumbered consecutively and moved to the end of
+  the text.</p>
+  <p class='tn-hang'>
+  Except for those changes noted below, all misspellings in the text,
+  and inconsistent or archaic usage, have been retained.</p>
+  <ul>
+  <li>Page <a href="#TN-1">28</a>. “hygrogen” <i>replaced by</i> “hydrogen”.</li>
+  <li>Page <a href="#TN-2">39</a>. Unclear image of potentially “horn” <i>replaced by</i> “both”.</li>
+  <li>Page <a href="#TN-3">48</a>. “theprecipitate” <i>replaced by</i> “the precipitate”.</li>
+  <li>Page <a href="#TN-4">77</a>. “evident manmer” <i>replaced by</i> “evident manner”.</li>
+  <li>Page <a href="#TN-5">84</a>. “CHAPTER III” <i>replaced by</i> “CHAPTER IV”.</li>
+  <li>Page <a href="#TN-6">88</a>. “immediaaely” <i>replaced by</i> “immediately”.</li>
+  <li>Page <a href="#TN-7">106</a>. “is influence” <i>replaced by</i> “its influence”.</li>
+  <li>Page <a href="#TN-8">156</a>. Added full stop after “Exp. 4. Mercury” for consistency.</li>
+  </ul>
+<p class='tn-hang'>
+  Errata from the publisher has been applied as described below.</p>
+  <ul>
+  <li>Page <a href="#ER-1">viii</a>. “ere long” <i>replaced by</i> “erelong”.</li>
+  <li>Page <a href="#ER-2">15</a>. “particles of reduced gold were observed” <i>replaced by</i> “I observed many particles of reduced gold”.</li>
+  <li>Page <a href="#ER-3">17</a>. Removed 3 duplicated lines of text.</li>
+  <li>Page <a href="#ER-4">137</a>. “or by uniting” <i>replaced by</i> “nor by uniting”.</li>
+  <li>Page <a href="#ER-5">163</a>. “and the caloric” <i>replaced by</i> “the caloric”.</li>
+</ul>
+</div>
+</div>
+<div style='text-align:center'>*** END OF THE PROJECT GUTENBERG EBOOK 77630 ***</div>
+</body>
+</html>
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+Project Gutenberg (https://www.gutenberg.org) public repository for eBook #77630
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