,,transcriber',s ,,note ,italic text is denoted by underscores4 ,some minor changes to the text are noted at the end of the book4 ,,an ,,essay ,,on ,,combustion1 ,,with ,a ,,view ,,to ,a ,,new ,,art ,,of ,,dying ,,and ,,painting4 ,,wherein ,,the ,,phlogistic ,,and ,,antiphlogistic ,,hypotheses ,,are ,,proved ,,erroneous4 ,,by ,,mrs4 ,,fulhame4 ,,london3 ,,printed ,,for ,,the ,,author1 ,,by ,j4 ,,cooper1 ,,bow ,,street1 ,,covent ,,garden1 ,and ,sold by ,j4 ,,johnson1 ,no4 #gb1 ,st4 ,paul's ,church ,yard2 ,g4 ,g4 and ,j4 ,,robinson1 ,paternoster ,row2 and ,t4 ,,cadell1 ,jun4 and ,w4 ,,davies1 ,strand4 #agid4 ,,entered ,,at ,,stationers ,,hall4 ,,preface4 ,the possibility of making cloths of gold1 silver1 and other metals1 by chymical processes1 occurred to me in the year #aghj3 the project being mentioned to ,doctor ,fulhame1 and some friends1 was deemed improbable4 ,however1 after some time1 ,i had the satisfaction of realizing the idea1 in some degree1 by experiment4 ,animated by this small success1 ,i have1 from time to time1 ever since1 prosecuted the subject as far as pecuniary circumstances would permit4 ,i imagined in the beginning1 that a few experiments would determine the problem2 but experience soon convinced me1 that a very great number indeed were necessary1 before such an art could be brought to any tolerable degree of perfection4 ,a narration of the numerous experiments1 which ,i made with this view1 would far exceed the bounds1 ,i prescribe myself in this essay2 ,i shall therefore present the reader only with a few1 selecting such as ,i judge most interesting1 and best adapted to illustrate the subject4 ,though ,i was1 after some considerable time1 able to make small bits of cloth of gold1 and silver1 yet ,i did not think them worthy of public attention2 but by persevering1 ,i at length succeeded in making pieces of gold cloth1 as large as my finances would admit4 ,some time after this period1 ,i found the invention was applicable to painting1 and would also contribute to facilitate the study of geography3 for ,i have applied it to some maps1 the rivers of which ,i represented in silver1 and the cities in gold4 ,the rivers appearing1 as it were1 in silver streams1 have a most pleasing effect on the sight1 and relieve the eye of that painful search for the course1 and origin1 of rivers1 the minutest branches of which can be splendidly represented in this way4 ,notwithstanding this further success1 ,i was dubious about the propriety of publishing this ,essay2 ,i therefore shewed some specimens of these metallic stuffs to persons1 whom ,i thought qualified to judge of them3 some approved of them very much1 and were pleased to say1 that the invention would make an era in the arts2 others thought it a pretty conceit2 and others were of opinion1 that the stuffs had not that splendour1 or burnished appearance1 which could entitle them to public notice4 ,the latter opinion had much weight with me2 for it must be allowed1 that the specimens1 which ,i shewed them1 had not that lustre and polish1 necessary for shoulder-knots1 lace1 spangles1 gold muslins1 c42 that some of them had a reddish cast1 bordering on the colour of copper1 some a purple1 mixed with gold2 and that some of them were unequal in the die1 and seemed stained2 which imperfections were owing to a partial reduction of the metal in the fibres of the silk4 ,but all these imperfections1 except the want of that burnished lustre so necessary for gold lace1 spangles1 c4 ,i knew ,i could remedy2 and therefore the criticism1 as far as it relates to them1 had no great influence with me4 ,i am in possession of some pieces1 one of which is about a yard in length1 which have scarce any of these imperfections4 ,moreover1 that high polish of burnished gold1 so necessary in spangles1 lace1 c41 would1 in my opinion1 be a great imperfection in gold stuffs designed for whole suits2 as a person in such a habit1 would look like a gilded statue4 ,i saw a piece of gold stuff made for the late ,king of ,spain1 which was of a purple colour1 with gold wire shining through it1 though rather obscurely2 and it was much admired3 ,i was so struck with its beauty1 that ,i attempted to imitate it on a small bit of white silk2 and succeeded1 having produced a beautiful purple colour1 with gold beaming through it4 ,therefore1 the want of that burnished appearance is no objection to this art2 for the paler1 and cooler1 to a certain degree1 the colour of the gold is1 the more lovely do these metallic cloths appear4 ,i made small bits of gold tiffany1 which looked exceedingly beautiful2 the fineness of the thread contributing much to that effect2 and1 in my opinion1 such webs are inimitable by mechanical means4 ,beside1 though ,i am not able to make cloths like burnished gold1 others of greater means and abilities may2 for we cannot pretend to prescribe any limits to the perfection1 at which chymistry1 and the arts1 may arrive4 ,however1 ,i must acknowledge1 that this unfavourable judgement suspended my intention of publishing this little work1 until a celebrated philosopher happening1 some time in ,october #agic1 to see some of the same pieces1 and indeed1 some of the worst1 viewed the performance in a very different light4 ,this illustrious friend of science not only approved of the specimens shewn him1 but offered to have a memoir on the subject presented to the ,royal ,society3 but different incidents dissuaded me from that mode of publication1 and induced me to adopt the present4 ,i now no longer hesitated about the propriety of publishing2 for1 every thing considered1 ,i judged1 that though this art could never be established1 which is by no means my opinion1 yet the experiments themselves1 upon which ,i attempted to found it1 as they are new1 and seem to throw some light on the theory of combustion1 are not unworthy the attention of ,chymists4 ,those who viewed my performance with a favourable eye1 were of opinion1 that ,i should dedicate this ,essay to some patron of the arts2 or apply for his ,majesty's ,royal letters patent1 in order to reimburse the expence necessarily incurred in this investigation1 an expence so disproportionate to the fortune which supported it1 that nothing but a certain fatality1 and the hope of reward1 could induce me to persevere4 ,as to patrons1 ,i have heard of such beings on the record of fame2 but never saw one3 on the contrary1 it has been my lot to know of many1 whose malignant breath1 as far as its deadly influence can extend1 never ceases to blast the unsheltered blossoms of science4--,and as for a patent1 had ,i even the means1 ,i should perhaps never attempt it2 for if we may judge of the future by the past1 ,i can safely affirm1 that such an application would be vain4 ,thus circumstanced1 ,i publish this ,essay in its present imperfect state1 in order to prevent the furacious attempts of the prowling plagiary1 and the insidious pretender to chymistry1 from arrogating to themselves1 and assuming my invention1 in plundering silence3 for there are those1 who1 if they can not by chymical1 never fail by stratagem1 and mechanical means1 to deprive industry of the fruits1 and fame1 of her labours4 ,but the ,british empire should not forget1 that she owes her power and greatness to commerce2 that she is1 as it were1 the hive of the arts1 and should not1 by the sulphureous vapour of oppression1 and neglect1 compel her bees to swarm for protection to foreign climes1 but rather permit them to roam in their native soil1 and allow them1 in the winter of life1 to sip a little of the honey of their own industry4 ,the nation1 whose evil genius withholds this protection1 only sounds the trumpet of emigration2 and must erelong lament her cities deserted1 her fields brown with desolation1 and herself the easy prey1 and vile drudge of surrounding greatness4 ,i first imagined1 that the proper title of this performance1 should be1 an ,essay on the ,art of making ,cloths of ,gold1 ,silver1 and other ,metals1 by chymical processes2 but reflecting on the imperfect state of the art1 and that my experiments related not only to the reduction1 but also to the calcination of metals1 and other combustible bodies1 ,i determined to entitle it1 ,an ,essay on ,combustion1 with a view to a new ,art of ,dying and ,painting1 which includes every thing the experiments can extend to4 ,as to the style1 ,i have endeavoured to relate the experiments in a plain and simple manner1 aiming more at perspicuity1 than elegance4 ,i have adopted the ,french ,nomenclature1 as the terms of it are so framed1 as to prevent circumlocution1 assist the memory1 by pointing out the combination1 and state of the elements existing in each compound1 as far as they are known2 advantages to be found in no other ,nomenclature4 ,however1 the ,english reader must regret1 that the ,french chymists have not preferred the terms air1 and ammonia1 to the less harmonious sounds1 gas1 and ammoniac4 ,i took the liberty of writing the latter ammonia4 ,i have not related my experiments in the order1 in which they were made1 sensible that such a narration would be tedious1 and that a short extract from them would answer every purpose at present intended4 ,the experiments related ,i have endeavoured to arrange in such a manner1 as mutually to illustrate each other1 by contrasting the successful with those1 that failed1 thus pointing out a general principle1 which forms a chain through the whole1 connects all the experiments1 shows their points of coincidence1 and disagreement1 and by this means furnishes us with data1 by which1 ,i hope1 the art may be improved4 ,this arrangement also facilitates the perusal1 and relieves the mind of that fatiguing attention1 which must necessarily be given to an indigested mass of insulated experiments1 that have no clew to connect them1 but has1 on the other hand1 its disadvantages2 for it throws a sameness on the work1 incompatible with that variety which is often so agreeable4 ,my apparatus consisted chiefly of a few glass vessels for the solution of metals1 and the formation of such elastic fluids1 as ,i used4 ,the cheapest1 and the most simple of those described by ,dr4 ,priestley answered my purpose4 ,dr4 ,nooth's machine for combining carbonic acid with water1 is very convenient for making small experiments with some kinds of gas2 as the base of that machine serves to contain the materials1 from which the gas is obtained2 and the middle glass the cloth previously dipped in the metallic solution1 on which the experiment is to be made4 ,the cloth may be suspended in this part of the machine1 by means of a thread1 and a cork4 ,as this machine is useful only in experiments on a very small scale1 ,i sometimes used tall glass cylinders1 in which ,i suspended the subject of the experiment1 by means of a thread1 a cork1 and a bit of cement4 ,this cylinder ,i placed over a vessel containing the materials1 which produced the gas4 ,it is very convenient to have cylinders of different sizes1 proportioned to the scale1 on which the experiments are to be made4 ,but machinery for confining elastic fluids is not always necessary2 as most of the experiments may be performed in the open air4 ,it may appear presuming to some1 that ,i should engage in pursuits of this nature1 but averse from indolence1 and having much leisure1 my mind led me to this mode of amusement1 which ,i found entertaining1 and will1 ,i hope1 be thought inoffensive by the liberal1 and the learned4 ,but censure is perhaps inevitable2 for some are so ignorant1 that they grow sullen and silent1 and are chilled with horror at the sight of any thing1 that bears the semblance of learning1 in whatever shape it may appear2 and should the spectre appear in the shape of woman1 the pangs1 which they suffer1 are truly dismal4 ,there are others1 who suffer the same torture in a still higher degree2 but by virtue of an old inspiring tripod1 on which ignorance1 servility1 or chance1 has placed them1 assume a dictatorship in science1 and fancying their rights and prerogatives invaded1 swell with rage1 and are suddenly seized with a violent and irresistible desire of revenge1 manifesting itself by innuendos1 nods1 whispers1 sneers1 grins1 grimace1 satanic smiles1 and witticisms uttered sometimes in the acute1 and sometimes in the nasal obtuse twang1 with an affected hauteur1 and contempt of the spectre2 shrugs1 and a variety of other contortions1 attending4 ,sometimes the goblin1 which thus agitates them1 lurks latent1 and nothing is perceived but hollow murmurs1 portending storms3 sometimes the lurking fiend darts with sidelong fury at the devoted object1 which1 if unarmed1 falls a victim to the grisly monster4 ,but happily for human kind1 the magic tripod drags none into its dizzy vortex1 but those who are radically stupid1 and malicious1 who are the beasts of prey destined to hunt down unprotected genius1 to stain the page of biography1 or to rot unnoted in the grave of oblivion4 ,although the surge of deliberate malice be unavoidable1 its force is often spent in froth1 and bubbles2 for this little bark of mine has weathered out full many a storm1 and stemmed the boisterous tide2 and though the cargo be not rich1 the dangers1 which may hereafter be pourtrayed on votive tablet1 may serve as a beacon to future mariners4 ,but happen what may1 ,i hope ,i shall never experience such desertion of mind1 as not to hold the helm with becoming fortitude against the storm raised by ignorance1 petulant arrogance1 and privileged dulness4 ,however1 were ,i not encouraged by the judgement of some friends1 and possessed of specimens1 to show the progress made in the art1 ,i should never perhaps venture to publish this ,essay2 as ,i am sensible1 it labours under many imperfections1 which inaccuracy of observation1 and the drapery of imagination1 must spread over the whole1 imperfections perhaps unavoidable in such a discussion4 ,finding1 the experiments could not be explained on any theory hitherto advanced1 ,i was led to form an opinion different from that of ,m4 ,lavoisier1 and other great names4 ,persuaded that we are not to be deterred from the investigation of truth by any authority however great1 and that every opinion must stand or fall by its own merits1 ,i venture with diffidence to offer mine to the world1 willing to relinquish it1 as soon as a more rational appears4 ,november #eth1 #agid4 ,,contents4 ,introduction #a ,chap4 ,i4 ,reduction of ,metals by ,hydrogen ,gas #ac ---- ,,ii4 ------------------- ,phosphorus #da ---- ,,iii4 ------------------- ,sulphur #fi ---- ,,iv4 ------------------- ,alkaline ,sulphure #hd ---- ,v4 ------------------- ,sulphurated ,hydrogen ,gas #ii ---- ,,vi4 ------------------- ,phosphorated ,hydrogen ,gas #aac ---- ,,vii4 ------------------- ,charcoal #abd ---- ,,viii4 ------------------- ,light #adb ---- ,,ix4 ------------------- ,acids #aee ---- ,x4 ,oxygenation of ,combustible ,bodies #afa -------------- ,azote ibid4 -------------- ,hydrogen #afd -------------- ,phosphorus #afe -------------- ,sulphur #aff -------------- ,charcoal ibid4 -------------- ,metals #afi -------------- ,light #afh1 #afi ---- ,,xi4 ,conclusion #agh ,nomenclature #aha ,,introduction4 ,though some of the phenomena of combustion were known from the earliest ages1 yet no rational attempt to explain them was made till about the middle of the #agth century4 ,before that period1 it was supposed by alchymists and physicians1 that sulphur was the inflammable principle1 on which all the phenomena of combustion depended4 ,but ,beecher perceiving1 that sulphur did not exist in several combustible bodies1 asserted it was not the principle of inflammability2 which1 he maintained1 was a different substance1 common to sulphur and other combustible bodies3 this principle he supposed to be of a dry nature1 and called it inflammable ,earth4 ,stahl refined this hypothesis by supposing the inflammable earth of ,beccher to be pure fire1 fixed in combustible bodies1 and constituting an essential part of them4 ,according to ,stahl1 a combustible body is a compound1 containing fixed fire1 or phlogiston2 and combustion is the disengagement of this phlogiston from a fixed to a free state1 attended sometimes with heat and light3 when these phenomena cease1 the body becomes incombustible2 if this calcined body be now heated with charcoal1 or any other inflammable substance1 capable of giving it phlogiston1 or fixed fire1 it returns again to the class of inflammable bodies4 ,this hypothesis is so simple and plausible1 that1 since the year #agcf1 it was received1 though differently modified1 all over ,europe4 ,the principal objections to it are1 that the existence of phlogiston cannot be demonstrated2 and that it does not explain1 why bodies become heavier after oxygenation1 and lighter after reduction4 ,m4 ,lavoisier discovering1 that the increase of weight1 which bodies acquire during combustion1 is equal to the weight of the combustible substance1 and that of the vital air employed1 denied the existence of phlogiston1 or fixed fire1 in combustible bodies2 though he grants the existence of combined caloric in them4 ,he seems then to allow the existence of phlogiston1 but to have changed its name to that of caloric1 and denied it the power of producing combustion4 ,however1 after discovering that the increase of weight1 which bodies acquire during combustion1 depended on the quantity of the air absorbed1 he was led to the following beautiful hypothesis1 equally simple as that of ,stahl2 and if ever any hypothesis deserved the name of theory1 surely it is that of ,m4 ,lavoisier4 ,according to ,m4 ,lavoisier1 8an inflammable body is nothing else but a body which has the property of decomposing vital air1 and taking the base from caloric and light2 that is to say1 the oxygene1 which was united to them2 and that a body ceases to be combustible when its affinity for the oxygene is satisfied1 or when it is saturated with that principle2 but that it becomes again combustible1 when the oxygene has been taken from it by another body1 which has a stronger affinity with that principle4 8,when this decomposition of the air is rapid1 and1 as it were1 instantaneous1 there is an appearance of flame1 heat1 and light2 when1 on the contrary1 the decomposition is very slow1 and quietly made1 the heat and light are scarcely perceptible#a40 ,thus all the phenomena of oxygenation1 which ,stahl ascribed to the disengagement of phlogiston1 ,m4 ,lavoisier ascribes to the union of oxygen with combustible bodies4 ,and1 on the other hand1 all the phenomena of reduction1 which ,stahl attributed to the union of phlogiston to calcined bodies1 ,m4 ,lavoisier attributes to the separation of oxygen from the same4 ,combustion1 then1 according to ,stahl1 is the transition of phlogiston from one body to another2 and1 according to ,m4 ,lavoisier1 'tis nothing but the transition of oxygen from one substance to another4 ,stahl supposed1 that the heat1 and light1 attending combustion proceed from the burning body2 but ,m4 ,lavoisier supposes1 that the heat1 and light1 proceed principally1 and almost entirely1 from the vital air4 ,however1 this opinion of ,m4 ,lavoisier is far from being established2 for ,doctor ,crawford has shown1 that inflammable air contains a much greater quantity of heat1 than vital air does4 ,it is evident1 then1 that the great advantage1 which ,m4 ,lavoisier's hypothesis has over that of ,stahl is1 that the former seems to account for the increase and decrease of weight1 which bodies suffer during calcination1 and reduction4 ,notwithstanding this brilliant discovery1 which seems to account1 with such ease1 for the increase of weight1 that bodies acquire during combustion1 ,m4 ,macquer was of opinion1 that ,m4 ,lavoisier's hypothesis was insufficient to explode that of ,stahl1 and endeavoured to remove the objection urged against the nonexistence of phlogiston1 by supposing it to be light2 and that in every case of combustion1 light1 and vital air1 mutually precipitate each other3 so that1 according to ,m4 ,macquer1 when a body is oxygenated1 vital air unites to it1 and disengages light2 and1 on the other hand1 when an oxygenated substance is reduced to its inflammable state1 light unites to it1 and disengages vital air4 ,m4 ,scheele also modified the hypothesis of ,stahl1 by supposing that heat1 light1 and inflammable air1 were compounds of empyreal1 or vital air1 and phlogiston4 ,light1 he thought1 contained more phlogiston than heat did2 and inflammable air more than either3 he farther supposed1 that these compounds of vital air and phlogiston were convertible into one another1 by the addition1 or subtraction1 of phlogiston2 and that1 when a metal was reduced by them1 they were decomposed2 their phlogiston uniting to the substance reduced4 ,his idea of calcination is1 that metals either attract empyreal air by means of their phlogiston1 and thus form heat1 or that they communicate their phlogiston to the air1 and attract heat from the fire2 and that1 either way1 there is empyreal air in the calces1 which makes the overplus of their weight#b4 ,the last modification of ,stahl's hypothesis is that of ,m4 ,kirwan1 who supposes that inflammable air exists in a fixed1 or concrete1 state in all combustible bodies1 and is the true phlogiston of the antient chymists2 and1 as it can be exhibited in the form of air1 its existence is no longer doubtful4 ,m4 ,kirwan supposes1 that1 when combustible bodies are calcined1 or changed into acids1 they combine most commonly with fixed air1 formed during the operation1 by the union of their phlogiston to vital air2 and sometimes to other substances1 and water1 which is either absorbed in specie1 or formed by the union of their phlogiston to vital air1 during calcination4 ,he supposes1 that some of these are restored to their combustible state by the decomposition of their fixed air2 some partly by the decomposition of their fixed air1 and partly by its expulsion1 and that of the other foreign bodies1 they had absorbed2 and lastly1 that some recover their combustibility by the expulsion of water1 and others possibly by its decomposition in high degrees of heat4 ,in all these reductions he supposes a simultaneous reunion of these bodies to phlogiston1 or the inflammable principle#c4 ,though ,m4 ,kirwan's hypothesis seems to account for the increase of weight1 which bodies acquire during combustion1 yet he has not proved the existence of inflammable air1 in a concrete state1 in all combustible bodies2 nor has he shown1 that fixed air is a compound of inflammable1 and vital air2 neither has he proved1 that fixed air is the acidifying principle4 ,all these objections have been made1 with great justice1 to his hypothesis1 by the antiphlogistians2 who also object1 that ,m4 ,kirwan's account of calcination1 and reduction1 is complex1 and repugnant to the simplicity of nature2 8for10 says ,m4 ,de ,fourcroy1 8as the author had admitted three general species of calcination1 it was necessary1 that he should1 likewise1 admit three kinds of reduction#d40 ,this criticism is very just2 but it will appear1 that the antiphlogistic account of calcination1 and reduction1 is no less complex1 erroneous1 and repugnant to the simplicity of nature3 for when we consider the various sources1 whence they derive the oxygen1 which oxygenates bodies2 and the long list of metallic reducers1 which they suppose2 it must be allowed1 that if simplicity be a recommendation1 their hypothesis is destitute of that advantage4 ,thus1 according to ,m4 ,lavoisier1 the oxygen1 which oxygenates combustible bodies1 is sometimes derived from vital air2 sometimes from atmospheric air2 sometimes from acids2 sometimes from water2 and sometimes from metallic oxids1 c4 ,on the other hand1 the catalogue of substances1 which reduce bodies to their combustible state1 is no less numerous4 8,heat10 says ,m4 ,de ,fourcroy1 8separates oxygene from some2 one metal takes it from another2 hydrogene1 or inflammable gas1 takes it from most metals2 and carbone perhaps from all#e40 ,to this list1 may be added phosphorus1 sulphur1 and compounds of these with hydrogen2 also light1 and the electric fluid1 c41 as will appear in the sequel4 ,but1 ,i shall endeavour to show1 that the hydrogen of water is the only substance1 that restores oxygenated bodies to their combustible state2 and that water is the only source of the oxygen1 which oxygenates combustible bodies4 ,want of simplicity is not the only defect in ,mr4 ,lavoisier's hypothesis3 for he supposes1 that the increase of weight1 which bodies acquire during combustion1 depends on the absorption of the oxygenous principle alone4 ,thus1 when a bit of phosphorus1 sulphur1 or charcoal1 is burnt in vital air2 the increase of weight1 which these bodies acquire1 he attributes entirely to oxygen1 or the base of vital air4 ,these combustions he explains1 by supposing1 that the phosphorus1 sulphur1 and charcoal1 decompose oxygen gas1 by absorbing its base from caloric1 and light1 which are set free4 8,there is10 says ,m4 ,lavoisier1 8a total absorption of vital air1 or rather of the oxygene1 which forms its base in the combustion of phosphorus1 and the weight of the phosphoric acid obtained1 is found to be rigorously equal to the weight of the phosphorus1 added to that of the vital air employed in its combustion4 ,the same agreement of weights is observed in the combustion of inflammable gas and vital air1 in the combustion of charcoal#f01 c4 ,his idea of the calcination of metals is the same4 8,we do not10 says ,m4 ,lavoisier1 8affirm that vital air combines with metals to form metallic calces1 because this manner of enunciating would not be sufficiently accurate3 but we say1 when a metal is heated to a certain temperature1 and when its particles are separated from each other to a certain distance by heat1 and their attraction to each other is sufficiently diminished1 it becomes capable of decomposing vital air1 from which it seizes the base1 namely oxygene1 and sets the other principle1 namely caloric1 at liberty4 8,this explanation of what passes during the calcination is not an hypothesis1 but the result of facts4 ,it is upwards of twelve years1 since the proofs have been laid by one of us1 before the eyes of the academy1 and have been verified by a numerous commission4 ,it was then established1 that when the calcination of metals is effected beneath an inverted glass vessel1 or in closed vessels containing known quantities of air1 the air itself is decomposed1 and the weight of the metal becomes augmented by a quantity accurately equal to that of the air absorbed4 ,it has since been found1 that when the operation was performed in very pure vital air1 the whole might be absorbed40 8,no supposition enters into these explanations2 the whole is proved by weight and measure#g40 ,hence it is evident1 that ,m4 ,lavoisier confounds oxygen with oxygen gas2 and considers the latter as a compound of oxygen1 light1 and caloric4 ,but since the dryest oxygen gas contains a large proportion of water1 as ,dr4 ,priestley and ,m4 ,kirwan have shown#h2 and since the whole of the gas1 except the caloric1 and light1 is absorbed1 it necessarily follows1 that the increase of weight1 which bodies acquire during combustion1 depends not only on the oxygen1 but also on the water1 contained in vital air4 ,therefore oxids are compounds of combustible bodies united to oxygen1 and water4 ,another great objection to ,m4 ,lavoisier's hypothesis1 is1 that he supposes both oxygenation1 and reduction1 effected by a single affinity4 ,thus1 according to him1 when iron reduces a sulphate of copper1 the iron does nothing more1 than separate the oxygen from the copper1 by its superior attraction for that principle4 ,from this view of combustion1 grounded on the most accurate experiments in chymistry1 it is manifest1 that the antiphlogistic hypothesis does not account fully for the increase of weight1 which bodies acquire during combustion2 and consequently1 that it cannot be admitted as a just theory4 ,,chapter ,i4 ,,reduction ,,of ,,metals ,,by ,,hydrogen ,,gas4 ,as ,hydrogen1 or the base of inflammable air1 seems to act an important part in the following experiments1 and is1 according to some chymists1 pure phlogiston itself2 ,i have therefore assigned the first chapter in this essay to hydrogen gas1 this being the most simple form1 in which hydrogen has hitherto been obtained4 ,but ,i had not the means of procuring this gas free of carbone1 and other impurities1 that it dissolves and elevates during its formation2 or of excluding atmospheric air1 which circumstances1 ,i am sensible1 must1 in some measure1 influence the result2 as it cannot be supposed1 that these extraneous bodies would remain inactive during the process of reduction4 ,however1 as such exactness is not in the power of every experimenter1 ,i was under a necessity of using hydrogen gas1 with the disadvantages here mentioned4 ,though most of the experiments in this essay were made on a variety of white and coloured silks1 ,i shall relate only those made on the former1 as it exhibits the changes produced more distinctly1 and contains less foreign matter to modify the result of experiment2 and1 for brevity's sake1 ,i shall use the term silk1 by which white silk is always designed4 ,,exp4 #a4 ,,gold4 ,i poured a quantity of sulphuric ether on a solution of gold in nitro-muriatic acid1 and1 by this means1 obtained a solution of gold in ether1 which ,i separated from the acid4 ,in this ethereal solution of gold1 ,i dipped a piece of silk1 after it was taken out1 and the ether evaporated1 it was suspended in a tall glass cylinder1 placed over a vessel1 containing a mixture of diluted sulphuric acid1 and iron filings4 ,the silk thus exposed to a rapid current of hydrogen gas acquired1 after some time1 a purple colour1 and a large spangle of gold1 of an irregular figure1 appeared on the upper end of the silk1 and looked very brilliant4 ,the silk was kept exposed to the gas about four months1 and frequently observed1 but no other remarkable change was perceived1 except that the purple colour became more intense3 the experiment was now discontinued2 and on taking out the silk1 and examining it in the light of the sun1 ,i observed many particles of reduced gold2 but they were very small1 and by no means so brilliant1 as that1 which first appeared4 ,during the experiment1 fresh quantities of materials for supplying hydrogen gas were occasionally added4 ,from the brilliant spangle of reduced gold observed in this experiment1 ,i concluded1 that there was a sufficient quantity of the metal in the fibres of the silk1 could it be reduced4 ,this spot of reduced gold was very permanent1 and adhered firmly to the silk4 ,,exp4 #b4 ,,gold4 ,in order to determine1 whether a solution of gold in ether1 or one in water1 were best adapted to the object of these experiments2 ,i evaporated to dryness a solution of gold in nitro-muriatic acid1 and dissolved the salt in distilled water3 in this solution1 ,i immersed a piece of silk1 which1 after it was dried in the air1 was suspended in a glass cylinder1 like the former piece1 and exposed to the action of hydrogen gas about two months4 ,the silk after some time assumed a purple colour1 and five or six specks of reduced gold1 of the size of pin heads1 and one much larger1 were observed4 ,examining the silk in the sun-beams1 ,i perceived the whole of it spangled with minute particles of reduced gold4 ,after many experiments with these two solutions of gold1 ,i was led to conclude1 that the solution in water answered best4 ,,exp4 #c4 ,,silver4 ,having dissolved some pure silver in diluted nitric acid1 and evaporated some of the water by a gentle heat1 ,i placed it in the dark to crystallize4 ,the crystals were separated from the solution1 and dissolved in distilled water2 to one measure of this solution1 which was saturated with the nitrate of silver1 ten or twelve measures of distilled water were added4 ,in this diluted solution1 a piece of silk was dipped2 after it was taken out1 it was dried at the fire3 the silk dried in this manner1 retained its white colour2 whereas1 were it dried gradually in the air2 and especially1 were the light considerable1 its white colour would be changed to a reddish brown1 more or less intense1 according to the quantity of light present4 ,some kinds of silk1 on being immersed in a solution of nitrate of silver1 have some of their threads immediately coloured brown3 but ,i often got white silk1 which would retain its pure white colour1 if dried at the fire1 or in the dark4 ,the piece of silk dried1 as above1 was suspended in the middle glass of ,dr4 ,nooth's machine2 and into the lower glass were introduced a diluted solution of sulphuric acid1 and some small iron nails4 ,the machine was now placed in a dark closet1 to exclude the action of light2 after some time1 the silk1 thus exposed to hydrogen gas1 put on a light brown colour1 which gradually became deeper1 until it was changed to a disagreeable black1 with some mixture of brown3 then very small particles of reduced silver began to appear1 which increased by degrees1 in number1 and brightness4 ,the experiment was continued four months2 after which time1 the silk was taken out of the machine3 it had a gray metallic appearance1 intermixed with a considerable tinge of brown4 ,this experiment was repeated on another piece of silk1 every circumstance being the same1 except that a quantity of water was put in the middle glass of the machine1 over which the silk was suspended2 the intention of interposing the water in this experiment was to purify the gas4 ,the appearances were much the same1 as in the last experiment2 except that the silk became black sooner2 and that some spangles of the silver were larger1 and better reduced4 ,the specks of reduced silver were permanent1 and adhered firmly to the silk4 ,,exp4 #d4 ,,lead4 ,in a solution of acetite of lead in distilled water ,i dipped a piece of silk1 and dried it in the air2 it was then suspended over a quantity of water in ,dr4 ,nooth's machine1 and exposed to hydrogen gas about three months4 ,the appearances were much the same as in the last experiment1 except that the silk was not so black3 the particles of reduced lead resembled silver4 ,similar experiments were made in this machine on bits of silk imbued with a solution of nitro-muriate of gold in water2 but the appearances being much the same as those mentioned in the first and second experiments1 it is unnecessary to repeat them here4 ,it is much easier to imagine1 than express my anxiety1 to discover the cause of the brilliant specks of reduced gold and silver1 with which the pieces of silk in these experiments were sometimes spangled2 concluding1 that were the cause ascertained1 it would be a considerable step towards accomplishing the object in view4 ,but many and diversified were the experiments ,i made before the circumstance1 on which these spangles depended1 was perceived4 ,at length1 ,i found it depended on the presence of moisture2 and that the spangles of reduced metal were owing to small drops of water carried up by the elastic fluid1 and deposited on the silk4 ,the experiments1 which led to this conclusion1 shall be related in their proper places4 ,i shall now proceed to recite the remainder of the experiments in this essay1 conformable to the plan laid down in the preface1 premising an occurrence observed in the course of them4 ,i sometimes found1 that the production of hydrogen gas from a mixture of acid1 water1 and iron nails1 would unexpectedly stop1 which induced me to add more acid2 this not succeeding1 ,i added more water2 but still no gas was formed3 the proportions of acid and water were varied without effect4 ,thinking the mixture of acid and water unfit for the purpose1 ,i poured it off1 and repeatedly washed and agitated the nails with more water1 which was also poured off2 but happening inadvertently to add some of the mixture of acid and water1 which ,i had before poured off as unfit for use1 ,i was surprised to find the gas produced with great rapidity4 ,reflecting on the cause of this odd circumstance1 ,i concluded that it depended on a crust of superoxygenated iron1 formed on the surface of the nails1 which defended them from the action of the water and acid1 and that this crust was removed by the agitation and washing1 which enabled the diluted acid to act again on the iron4 ,,exp4 #e4 ,,gold4 ,i immersed a bit of silk in a solution of nitro-muriate of gold in distilled water1 and dried it in the air2 it was then placed over a cylindrical glass vessel1 containing a mixture of diluted sulphuric acid and iron nails1 for about half an hour2 but no reduction of the metal could be observed4 ,i dipped another bit of silk in the same solution of gold1 and exposed it1 while wet1 to the same current of hydrogen gas1 and instantly signs of reduction appeared2 for the yellow colour1 which the solution imparts to silk1 began to change to a green1 and very soon a film of reduced gold glittered on the surface opposed to the gas3 shortly after1 a beautiful blue spot1 fringed with orange and purple1 was formed on the middle of the silk4 ,during the experiment1 which lasted about half an hour1 the silk was kept constantly wet with distilled water4 ,when experiments are made with this preparation of gold1 it is necessary to evaporate the solution to dryness1 before the salt be dissolved in the water2 as an excess of acid prevents the reduction in a great measure4 ,solutions of gold in these experiments do not admit of being so largely diluted1 as solutions of silver1 and other metals do4 ,,exp4 #f4 ,,silver4 ,i immersed a piece of silk in a solution of nitrate of silver1 and dried it in a dark place2 it was then exposed to a current of hydrogen gas about twenty minutes2 but no reduced silver appeared1 the only change observable was a brown stain4 ,i immersed another bit of the same silk in the same solution of silver1 and having exposed it1 while wet1 to a stream of hydrogen gas1 ,i soon observed evident signs of reduction2 the white colour of the silk was changed to a brown1 which became gradually more intense2 and the surface of the silk1 opposed to the gas1 was coated with reduced silver3 various colours1 as blue1 purple1 red1 orange1 and yellow1 attended the reduction4 ,these colours often change1 and are succeeded by others in the progress of the reduction4 ,the threads of the silk look like silver wire1 tarnished in some parts1 but of great lustre in others4 ,the silk was kept wet with distilled water during the experiment4 ,when the silk happened to be too much wetted1 the under surface opposed to the gas was often covered with scales of a dull blue colour3 these1 after the silk dries1 may be brushed off1 and another coat of reduced silver1 which adheres firmly1 but has no considerable brightness1 is left behind4 ,these experiments on the reduction of gold1 and silver1 were often repeated with nearly the same result4 ,,exp4 #g4 ,,silver4 ,thinking some other preparation of silver might answer better than a nitrate1 ,i precipitated some of the latter with a solution of muriate of soda1 and poured the whole on a filter2 the precipitate was well washed with distilled water1 and dissolved in ammonia4 ,in this solution ,i immersed a piece of silk1 and dried it in the air2 and having exposed it to the action of hydrogen gas1 ,i could perceive no signs of reduction1 except a faint brown colour4 ,i dipped another bit of silk in the same solution of silver1 and in order to determine if water had the power of promoting the reduction of the silver in this preparation1 as it had in the former experiments1 ,i exposed the silk1 while wet1 to the same current of hydrogen gas2 and in a few seconds the metallic lustre was evident on the surface opposed to the current4 ,after some little time1 a blue speck and a faint trace of yellow appeared1 but soon vanished4 ,this preparation of silver does not stain white silk so much as a nitrate does2 the reduced silver was indeed very brilliant1 but soon grew dull1 and disappeared2 a brown stain only remaining2 so that it seems rather inferior to nitrate of silver1 which also1 after reduction1 tarnishes1 grows dull1 and often disappears2 but sometimes part of it remains permanently reduced4 ,,exp4 #h4 ,,platina4 ,with much difficulty ,i procured a small quantity of the ore of platina1 and dissolved it in nitro-muriatic acid4 ,the solution was evaporated to dryness1 and the salt was then dissolved in distilled water4 ,a bit of silk was dipped in part of this solution1 and dried in the air2 it was then exposed to a brisk current of hydrogen gas about twenty minutes1 but no signs of reduction appeared4 ,another bit of silk was immersed in the solution of platina1 and exposed1 while wet1 to the same current of hydrogen gas2 in five or six minutes the platina was reduced1 exhibiting a livid white metallic appearance on the surface of the silk opposed to the current4 ,no colours attended the reduction4 ,this solution imparts a yellowish brown colour to silk4 ,after some time1 the whole of the metallic lustre disappeared1 in proportion as the silk became dry4 ,the solution of platina requires more time1 and a stronger current of hydrogen gas for its reduction1 than solutions of silver and gold do4 ,,exp4 #i4 ,,mercury4 ,i immersed a bit of silk in a solution of oxygenated muriate of mercury in distilled water1 and dried it in the air3 it was then exposed to a stream of hydrogen gas2 but underwent no visible change4 ,i dipped another bit of silk in the same solution of mercury1 and exposed it1 while wet1 to the same current of gas2 the metal was soon reduced in a beautiful manner1 and resembled silver4 ,the reduction began suddenly1 with scarce any appearance of previous stain2 some very faint1 but at the same time transparent colours attended it3 the most remarkable of these were a light orange1 with a fringe of blue1 and a yellow verging on a faint green4 ,these colours soon disappeared4 ,after the silk was turned1 ,i observed1 that its texture was1 in some parts1 concealed by a thin film1 which1 as the reduction proceeded1 was perceived to dart along the threads of the silk1 gilding them in a beautiful manner1 and exhibiting the texture very distinctly4 ,after some time1 the mercury seemed to disappear1 so as to render it doubtful whether any of it remained in the silk2 but shaking it in the sunbeams1 ,i perceived bright atoms fly off2 and rubbing the silk on a bit of blue paper1 ,i observed shining metallic particles1 which seemed to have lost their affinity of aggregation1 for they did not unite4 ,one remarkable difference between this preparation of mercury and nitrate of silver1 is1 that no black or brown stain preceded1 attended1 or followed1 the reduction of the mercury4 ,mr4 ,scheele reduced a prussiate of mercury1 dissolved in water1 by adding iron filings and a small quantity of sulphuric acid to the solution#i4 ,,exp4 #aj4 ,,copper4 ,a piece of silk was immersed in a solution of sulphate of copper1 then taken out1 and dried1 and exposed for a considerable time to a brisk current of hydrogen gas2 but no signs of reduction could be perceived4 ,another bit of silk was dipped in the same solution of copper1 and exposed1 while wet1 to the same rapid current of hydrogen gas2 the appearances were the following4 ,after a minute1 or two1 the silk assumed a faint brown colour1 and1 on the surface opposed to the gas1 a white metallic pellicle appeared1 which vanished in proportion as the silk became dry3 wetting the silk again1 ,i perceived a similar pellicle appear1 which also vanished1 as soon as the silk dried4 ,if the silk be kept constantly wet1 the brown colour becomes much more intense1 attended with a very slight tinge of red4 ,the margins of the silk projecting beyond the verge of the glass cylinder1 and therefore not exposed to the current of the gas1 retained the blue colour1 which the solution imparts4 ,in some of these white metallic pellicles there appeared a faint brown inclining to yellow1 which reflected the light1 though obscurely4 ,after the silk dried1 nothing remained1 but a brown stain4 ,,exp4 #aa4 ,,lead4 ,a piece of silk was immersed in a solution of acetite of lead in distilled water2 it was then dried1 and exposed for some time to a stream of hydrogen gas2 but underwent no perceptible change4 ,another bit of silk was dipped in the same solution of lead1 and exposed1 while wet1 to the same current of hydrogen gas2 in a second1 or two1 the surface of the silk1 opposed to the current1 was coated with reduced lead1 which looked like silver4 ,the reduction was accompanied with a brown stain1 but by no means so intense as that1 which attends the reduction of nitrate of silver4 ,the other side of the silk was opposed to the current of hydrogen gas1 and soon acquired a metallic coat of the same brilliant appearance1 exhibiting the texture of the silk1 in a very striking manner4 ,it is remarkable1 that lead exhibits no colour1 but a light brown1 during its reduction2 whereas gold1 silver1 and mercury1 display a great variety of colours1 especially the two former4 ,after some time the lead reduced in this manner loses its metallic splendour considerably2 and that in proportion as the silk dries4 ,,exp4 #ab4 ,,tin4 ,i dissolved some crystals of muriate of tin in distilled water2 dipped a bit of silk in the solution2 and dried it in the air3 it was then exposed to a stream of hydrogen gas a considerable time2 but no change1 or appearance of reduction1 could be observed4 ,another bit of silk was immersed in the same solution of tin1 and exposed1 while wet1 to the same current of gas2 after some little time1 the reduction commenced1 attended with a great variety of beautiful colours2 as red1 yellow1 orange1 green1 and blue1 variously intermixed4 ,the reduced tin disappears along with these colours1 as the silk dries2 nothing remaining but a feuille-morte colour4 ,the same solution of tin was also reduced by hydrogen gas1 obtained from tin1 and the muriatic acid4 ,these experiments do not succeed well with muriate of tin containing an excess of acid4 ,,exp4 #ac4 ,,arsenic4 ,a muriate of arsenic1 which was prepared by digesting white oxid of arsenic in muriatic acid1 and continuing the heat1 till most of the acid evaporated1 and left behind a soft mass of the consistence of tar1 was dissolved in distilled water4 ,in this solution a bit of silk was immersed1 and dried in the air3 it was exposed to a brisk stream of hydrogen gas1 obtained from zinc1 and muriatic acid2 but no reduction took place4 ,another bit of silk was dipped in the same solution1 and exposed1 while wet1 to the same current of hydrogen gas2 and instantly1 the surface of the silk1 opposed to the gas1 was covered with a bright coat of reduced arsenic1 accompanied with a yellow stain4 ,in a short time the metallic lustre vanished2 and nothing remained but the yellow stain4 ,m4 ,pelletier restored the acid of arsenic to its metallic state1 by passing hydrogen gas through a solution of that acid1 in twice its weight of water#aj4 ,,exp4 #ad4 ,,bismuth4 ,a bit of silk1 which was immersed in a solution of nitrate of bismuth in distilled water1 and exposed dry to hydrogen gas1 obtained from zinc1 and muriatic acid1 underwent no visible change4 ,another bit of silk was dipped in the same solution of bismuth1 and placed over a languid stream of hydrogen gas2 the bismuth was soon restored to its metallic form1 on the surface of the silk opposed to the elastic fluid4 ,the reduction was attended with a reddish brown stain1 intermixed with a tinge of violet4 ,,exp4 #ae4 ,,antimony4 ,a bit of silk was immersed in a solution of tartarite of antimony in distilled water2 and dried in the air4 ,it was then exposed to hydrogen gas1 obtained from zinc1 and muriatic acid2 but suffered no visible alteration4 ,another bit of silk1 which was dipped in the same solution of antimony1 was exposed wet to a weak stream of the gas2 and1 in a short time1 the metallic lustre appeared1 accompanied by a light yellow colour4 ,,exp4 #af4 ,,iron4 ,a bit of silk1 which was immersed in a largely diluted solution of sulphate of iron1 and dried in the air1 was exposed to a strong current of hydrogen gas1 obtained from iron nails1 and diluted sulphuric acid2 but no visible change was produced on the silk4 ,another bit of silk was dipped in the same solution of iron1 and placed wet over the same stream of hydrogen gas2 but no reduced iron could be perceived4 ,the silk was then immersed in a glass of clear water1 and transferred a very minute metallic film to the surface of that fluid4 ,this experiment was repeated with a rapid current of hydrogen gas1 obtained from zinc1 and muriatic acid2 and1 in about a minute1 small films of reduced iron were visible on the surface of the silk1 opposed to the gas4 ,the silk was then immerged in water1 and transferred to its surface a large metallic pellicle2 parts of which were very brilliant2 but other parts were dull1 and much more imperfectly reduced4 ,,exp4 #ag4 ,,zinc4 ,a bit of silk1 which was dipped in a muriate of zinc1 largely diluted with water1 and dried in the air1 was exposed to a rapid current of hydrogen gas1 obtained from zinc1 and muriatic acid2 but suffered no visible alteration4 ,another piece of silk was immersed in the same solution of zinc1 and exposed1 while wet1 to the same rapid current of hydrogen gas3 in about half a minute1 the metal was reduced in a very evident manner1 on part of the silk4 ,the silk was then dipped in a glass of clear water1 and transferred a bright metallic film to its surface4 ,as these reductions of iron1 and zinc1 by hydrogen1 are contrary to ,m4 ,lavoisier's table of the affinities of the oxygenous principle2 ,i began to suspect1 that the films1 which were so evident1 both on the silk1 and the water1 might be abraded1 or torn from the zinc1 by the muriatic acid2 and elevated1 and deposited on the silk by the gas4 ,in order to remove this doubt1 ,i dipped a bit of the same silk in distilled water2 and exposed it1 while wet1 to the same current of hydrogen gas1 but nothing metallic could be seen on the silk2 nor did it when immersed in water transfer a film1 or the smallest appearance of a metal1 to the surface of that fluid3 and1 therefore1 there can be no doubt of the reality of these reductions4 ,dr4 ,priestley restored iron1 and lead1 to their metallic state1 by heating their oxids with a burning glass in hydrogen gas4 ,these experiments point out an error in ,m4 ,bergman's table of elective attractions in the humid way2 for he assigned the last place in that table to phlogiston1 which he considered as the base of inflammable air2 because he was unacquainted with any metallic reductions effected by hydrogen in the humid way#aa4 ,having found1 that water promoted1 and accelerated1 these reductions in a very remarkable manner2 ,i was curious to know1 if alcohol1 and ether1 would produce the same effect4 ,with this view1 ,i evaporated a solution of gold in nitro-muriatic acid to dryness2 when the vessel cooled1 some alcohol was poured on to dissolve the salt2 and immediately the vessel containing the salt1 became so hot1 that it could be scarcely endured by the hand2 and diffused a fragrant smell1 like that of ether1 which1 no doubt1 was a species of that fluid4 ,,exp4 #ah4 ,,gold4 ,in this solution of gold in alcohol1 a bit of silk was dipped1 and exposed to a stream of hydrogen gas1 obtained from diluted sulphuric acid1 and iron nails2 and kept wet with alcohol3 in about two minutes1 the silk began to assume a brown colour1 and white metallic films appeared on some parts of the surface opposed to the gas2 some of these disappeared in a short time2 and were succeeded by a few very small spangles of the proper colour of gold4 ,these also soon vanished2 and nothing remained but a disgreeable brown stain1 intermixed with specks of a dull blue4 ,i sometimes found1 on repeating this experiment1 that no yellow films or spangles appeared2 and am persuaded1 that their appearance1 and that of the white pellicles also1 depends on the presence of water1 contained in the alcohol1 or the gas1 and deposited on the silk4 ,,exp4 #ai4 ,,gold4 ,a bit of silk was immersed in a solution of gold in ether1 and exposed to a stream of hydrogen gas1 and kept wet with ether4 ,the silk underwent no alteration for a few minutes2 at length1 it began to assume a faint brown colour1 but no white1 or yellow films appeared4 ,if this experiment be continued till the silks collects a sufficient quantity of water from the gas1 some films will appear4 ,,exp4 #bj4 ,,silver4 ,i procured some nitrate of silver1 which had been fused in order to expell as much of its water as possible2 and dissolved it in alcohol4 ,i immersed a bit of silk in this solution1 and exposed it to a stream of hydrogen gas1 and kept it wet with alcohol3 in a few seconds1 the silk assumed a brown colour1 which gradually became more intense3 but no reduced silver appeared for several minutes2 at length1 a few metallic films appeared on part of the surface opposed to the gas4 ,,exp4 #ba4 ,,mercury4 ,a bit of silk was dipped in a solution of oxygenated muriate of mercury1 and dried2 it was then exposed to hydrogen gas about ten or fifteen minutes1 and kept constantly wet with alcohol4 ,the silk1 during the first minutes1 suffered no perceptible alteration3 at length1 a few small films were visible on the side of the silk opposed to the current4 ,,exp4 #bb4 ,,lead4 ,a bit of silk1 which was immersed in a solution of acetite of lead1 and dried1 was exposed about fifteen minutes to a stream of the gas2 and kept constantly wet with alcohol2 but suffered no visible change2 except that a very minute film was reduced on one of its margins1 which did not project beyond the verge of the glass vessel on which it was placed4 ,when we compare these experiments with those1 in which water was used1 to wet the silk1 'tis evident1 that alcohol1 and ether1 do not promote the reduction of metals1 as water does2 and that the few films1 which appear1 when the silk is kept wet with ether or alcohol1 depend entirely on water collected from the gas1 or deposited by them on the silk during their evaporation4 ,in order to compare the effects of hydrogen gas1 obtained from water1 iron nails1 and muriatic acid1 with that1 procured from the same materials1 by means of the sulphuric2 ,i made some experiments on gold1 silver1 mercury1 and lead1 in the same manner1 as the preceding2 and the principal difference was1 that the colours produced in all the pieces of silk1 except that1 which was dipped in acetite of lead1 were much brighter1 and more beautiful1 than any produced1 when the sulphuric acid was used4 ,the reduction of the lead was accompanied with its usual brown colour4 ,on the upper surface of a bit of silk1 which was dipped in a solution of gold1 a green colour instantly appeared2 and soon changed to a deep olive1 in proportion as the reduction advanced3 now examining the under surface1 ,i saw it coated with a bright film of reduced gold1 in the middle of which a blue spangle1 mixed with purple1 soon began to appear3 ,i then moistened the upper surface of the silk with water2 and in a few seconds1 it also was coated with reduced gold4 ,the blue on the other side of the silk became much more intense3 the piece was now turned2 and on each colour ,i let fall a drop of water3 the drop on the blue had a blue film1 the drop on the purple1 had a purple film1 and the drop on the yellow1 a film of reduced gold4 ,after some time1 these drops of water evaporated1 and the films came again in contact with the silk3 some parts of which were left bare1 as generally happens1 when too much water is applied4 ,on the under surface of a bit of silk1 which was immersed in a solution of nitrate of silver in water1 a coat of reduced metal was formed1 with various colours1 as green1 blue1 orange1 and yellow1 the beauty and brightness of which were remarkable4 ,in some time a muriate of silver is formed in the fibres of the silk1 which on exposure to light becomes of a bluish black colour3 but the whole of the silver does not undergo this change2 for part of it remains in its metallic state4 ,the colours remain a considerable time1 if the silk be removed from the gas before this muriate is formed4 ,hence it appears1 that hydrogen gas should not be prepared with an acid1 which forms an insoluble compound with the metal to be reduced4 ,i also found1 that hydrogen gas produces different effects not only according to the difference of the acid1 but also according to the difference of the metal employed to obtain it3 for this gas procured from zinc or tin1 and muriatic acid1 did not restore gold to its proper metallic lustre2 but formed on the silk1 a white metalline coat like silver4 ,the experiments related in this chapter indicate the following conclusions4 #a4 ,hydrogen is capable of reducing the metals in the ordinary temperature of the atmosphere4 #b4 ,water promotes1 and accelerates1 these reductions1 in a very remarkable manner4 #c4 ,ether1 and alcohol1 do not promote these reductions1 without the aid of water4 #d4 ,a variety of colours accompanies these reductions1 similar to what appears1 during the calcination of metals by heat and air2 and depends on the same cause3 viz4 the quantity of oxygen combined with the metal4 ,these colours have not been observed hitherto2 nor indeed could they2 as the metals were reduced in close vessels1 and in high degrees of heat4 #e4 ,these reductions often disappear4 ,this is commonly owing to an imperfect1 and partial reduction of the metal3 for the acid1 and water1 remaining in that part of the metallic solution1 not reduced1 recalcines these delicate films3 sometimes the disappearance of the metallic lustre depends on the nature of the metal itself3 thus arsenic1 lead1 silver1 c41 suffer some degree of calcination by water and atmospheric air4 ,messrs4 ,bergman and ,keir relate instances1 in which silver after being precipitated in its metallic state1 was recalcined1 and disappeared4 ,i first imagined1 that water promoted these reductions by minutely dividing the particles of the metallic salt1 and by condensing the gas1 and bringing its hydrogen1 and the metallic oxid1 within the sphere of attraction2 the hydrogen either uniting to the metallic earth and reducing it1 as the ,phlogistians suppose2 or uniting with1 and separating the oxygen of the metal1 and thus restoring it to the metallic form1 as the ,antiphlogistians maintain4 ,but it is evident from the experiments related1 that water does not promote these reductions solely1 by minutely dividing the particles of the metallic salt3 for were this the case2 ether1 and alcohol1 should promote the reduction of the metallic salts1 which they dissolve1 since they divide their particles1 as minutely as water can4 ,since then metallic solutions in ether1 and alcohol1 cannot be reduced by hydrogen gas2 it follows that the above supposition concerning the mode of agency of water does not account for the reduction of metals in this way4 ,and indeed were it true that hydrogen condensed by water reduced metals in the manner above mentioned1 it would follow1 that the reduction was effected by a single affinity1 which cannot be admitted2 #ast4 because the existence of a single affinity in such cases has not been proved2 #b;dly1 because a double affinity always takes place in preference to a single affinity1 which is demonstrated by the following facts1 transcribed from the works of ,mr4 ,kirwan4 8,if a solution of silver in the nitrous acid be thrown into a mixed solution of fixed alkali and common salt1 the silver will be precipitated by the marine acid of the common salt1 and not by the free alkali1 contained in the liquor3 for a luna cornea is found#ab40 8,i repeated the experiment with a solution of lead1 and also of mercury in the nitrous acid1 and the result was similar3 both lead and marine salt of mercury were formed#ac40 ,in these experiments of ,messrs4 ,monnet and ,kirwan1 'tis evident that a double affinity takes place in preference to a single one3 for the nitrous acid of these different nitrates unites with the alkali of the common salt1 while the muriatic acid of the latter seizes the silver1 mercury1 and lead1 of the nitrates1 and forms muriates of silver1 mercury1 and lead3 the free alkali remaining passive in the mixture4 ,m4 ,lavoisier says1 8,there exists only in nature1 as far as we can observe them1 cases of double affinity1 often triple1 and others perhaps still more complicated#ad40 ,now as water does not promote these reductions merely by dissolving1 and minutely dividing1 the particles of the metallic salts1 and condensing the hydrogen gas2 and since a double affinity takes place in preference to a single affinity2 it is obvious that the water must be decomposed in these reductions in the following manner4 ,the hydrogen of the gas unites to the oxygen of the water1 while the hydrogen of the latter unites in its nascent state to the oxygen of the metal1 reduces it1 and forms water4 ,thus what could never be effected by a single1 is readily performed by a double affinity4 ,hence it follows1 that the hydrogen of the gas is oxygenated by the oxygen of the water1 while the metal is1 at the same time1 restored to its combustible state4 ,it also follows1 that the quantity of water formed is double that decomposed4 ,,chapter ,,ii4 ,reduction of ,metals by ,phosphorus4 ,the next substance1 of whose effects in reducing metals in the fibres of silk1 ,i shall treat1 is ,phosphorus1 one of the most inflammable substances1 we are acquainted with4 ,i was for some time at a loss1 how to apply it to this purpose2 but learning from a note of ,mr4 ,lewis1 that it is soluble in ether2 ,i dissolved a small quantity of it in that fluid1 which can be easily effected1 if the ether be good4 ,the solution is considerably promoted by a gentle heat1 as that of the hand1 and may be made in a small phial1 which should be nearly filled with the ether1 and accurately corked3 a common cork is preferable1 for this purpose1 to a glass stopper2 and a single grain of phosphorus is sufficient for a great number of experiments4 ,i sometimes applied a much greater degree of heat than the above1 by placing the phial in hot sand1 pressing on the cork at the same time with my finger1 to prevent its being forced out by the expansion of the ether1 part of which is converted into an elastic fluid1 and holds some phosphorus in solution3 the ether soon begins to boil2 the phosphorus melts2 and a strong solution is obtained in a few minutes by shaking the phial4 ,if the solution be removed to a cool place it frequently deposits crystals4 ,this manner of preparing the solution is attended with some danger2 for should the phial burst1 or the cork be extruded1 the contents will be thrown out with considerable force1 and that part of the phosphorus not dissolved by the ether burn with great violence4 ,the only objection to this preparation of phosphorus is the ether1 which must necessarily modify the result1 and prevent that simplicity so desirable in experiment4 ,but1 after some observation1 it was perceived1 that the ether flies off1 and leaves the phosphorus pure1 and minutely divided in the fibres of the silk3 the ether1 from its great volatility1 first evaporates1 and1 at the same time1 produces a very considerable degree of cold1 which effectually prevents the evaporation1 and combustion1 of the phosphorus4 ,after the ether evaporates2 the cold ceases1 and the combustion of the phosphorus commences1 attended with white fumes1 which continue till the whole is consumed1 if no other power intervene4 ,hence it is evident1 that this preparation of phosphorus has a simplicity1 and elegance1 not always to be obtained4 ,it has also another great advantage in experiments of this kind2 for it does not change1 in the smallest degree1 the white colour of silk1 during its slow combustion1 which is not attended with heat sufficient to affect the most delicate colour4 ,this property of not affecting the colour of the silk renders observation1 and experiment1 more accurate2 as whatever change supervenes1 must depend either on the metallic solution itself1 or on the action of the phosphorus on the same4 ,but this advantage is confined to a certain range of the thermometer2 for if the heat be increased to about #hf of ,fahrenheit1 and the silk be dry1 the phosphorus is apt to set fire to it4 ,,exp4 #a4 ,,gold4 ,i immersed a bit of silk in a solution of gold in ether1 and after the ether evaporated1 dropped on it some of the solution of phosphorus1 which diffused itself through the silk1 like a drop of oil1 and formed a circumscribed spot1 whose limits1 as the ether evaporated1 assumed a brown colour1 which soon diffused itself equally over every part1 to which the solution of phosphorus was applied2 but the parts of the silk1 to which the latter did not reach1 retained the yellow colour1 which the solution of gold gave them4 ,the silk viewed by transmitted light presented the same colours1 except that the limits of the brown appeared more intense1 and seemed to border on a faint purple4 ,examining the silk next day1 ,i found1 that the whole of the brown stain acquired a faint shade of purple1 which was most evident on the margins of the stain4 ,,exp4 #b4 ,,gold4 ,i dipped a bit of silk in the solution of gold in ether1 and after it was well dried1 half of it was wetted with distilled water2 the other half remaining dry3 the solution of phosphorus was applied to both the moist and dry parts of the silk3 instantly the part wetted with the water began to acquire a purple colour2 and1 soon after1 the metallic splendour of the gold appeared2 but that part1 which was kept dry1 acquired only a brown stain1 similar to that described in the preceding experiment4 ,i repeated these experiments many times1 and always found1 that the gold was reduced only in proportion to the water applied4 ,finding water promoted the reduction of gold by phosphorus1 ,i began to form various conjectures about its mode of action3 ,i first supposed1 it acted by holding the particles of the salt minutely divided1 thus diminishing their attraction of cohesion1 and consequently increasing their chymical attraction4 ,the truth of this supposition might1 ,i thought1 be decided by using ether1 and alcohol1 instead of water1 to wet the silk1 avoiding aqueous moisture1 as much as possible2 accordingly1 ,i made the following experiments1 which were frequently repeated with nearly the same result4 ,,exp4 #c4 ,,gold4 ,a piece of silk was immersed in the solution of phosphorus2 as soon as the ether evaporated1 and the phosphorus began to fume1 an ethereal solution of gold was dropped on the silk1 which immediately got a brown colour2 the piece was kept constantly wet with ether2 in some time a purple tinge appeared on parts of the silk2 and1 shortly after1 small films of reduced gold appeared3 the silk was now remarkably wet1 and seemed to have a great power of collecting water2 this1 ,i supposed1 was partly attracted from the air by the salt1 and phosphorous acid formed during the combustion1 which has a powerful attraction for water2 and partly deposited in the silk by the ether during its evaporation4 ,in order to determine if the ether during its evaporation deposited water in the silk1 ,i kept a bit of silk wet with ether for a few minutes1 and found1 that1 after the evaporation ceased1 the silk was moist3 but this humidity was not so great1 as that observed in the silk1 to which the ethereal solutions of phosphorus1 and gold1 were applied4 ,another bit of silk was dipped in the ethereal solution of gold1 and after the ether evaporated1 the solution of phosphorus was applied3 a brown colour was produced2 the silk was kept wet with ether1 and1 in a short time1 a purple tinge appeared on parts of it2 but chiefly at the margin of the stain1 which gradually diffused itself over the whole4 ,the only difference between this and the preceding experiment on gold is the order1 in which the solution of gold1 and phosphorus1 were applied to the silk2 but there is a considerable difference in the result2 for in this the brown and purple colours were formed much more slowly1 and no particles of reduced gold appeared till after a much longer time4 ,,exp4 #d4 ,,gold4 ,a piece of silk was immersed in the solution of phosphorus1 and when the white fumes began to rise1 a solution of gold in alcohol was applied to the silk1 which was kept wet with alcohol2 a brown tinge1 which soon changed to a purple1 appeared on different parts2 and1 in a little time after1 a very small film of reduced gold was visible on a part of the margin4 ,in another experiment1 conducted in the same manner1 the reduction was more evident4 ,the solution of gold used in this experiment was very rich2 and had a great attraction for water2 for bits of silk tinged with it1 could not be dried without difficulty2 and after they were removed to a cool place1 they very soon became moist again4 ,this is more or less the case with solutions of gold in general4 ,,exp4 #e4 ,,gold4 ,a bit of silk was dipped in a solution of gold in alcohol1 and dried2 then some of the solution of phosphorus was poured on the silk2 a brown1 and then a purple colour1 appeared2 and in some parts a small portion of the gold was reduced3 the reduction was very obscure2 but became gradually more evident1 in proportion as it attracted water from the air4 ,the silk was occasionally wetted with alcohol4 ,this experiment was repeated1 with this difference1 that the silk was not kept wet with alcohol2 and no reduced gold could be perceived4 ,,exp4 #f4 ,,gold4 ,in order to exclude water more effectually1 a small phial was carefully dried by placing it in hot sand1 and then corked1 to prevent the access of moisture from the air2 when the phial cooled1 it was nearly filled with ether1 and a small bit of phosphorus dropped into it2 it was then corked1 and replaced on the hot sand2 the phosphorus soon melted1 and a strong solution was obtained by shaking the phial4 ,into this solution a small bit of silk1 which was dipped in a rich solution of gold1 and carefully dried1 was introduced3 the silk immediately got a brown tinge2 but not a particle of reduced gold could be perceived4 ,the solution in a short time became turbid1 and deposited a brown powder4 ,the colour of the precipitate was exactly the same1 as that which the silk acquired4 ,the experiment was continued about three months1 and carefully observed2 but no other change could be perceived3 at the end of this time the silk was taken out of the phial2 and the solution of phosphorus was found capable of reducing gold and silver by the aid of water4 ,,exp4 #g4 ,,gold4 ,in order to contrast the effects of water with those of ether1 and alcohol1 more fully1 a piece of silk was immersed in a solution of nitro-muriate of gold in water1 and dried in the air about twelve hours2 during which time the yellow tinge1 the solution of gold gave the silk1 remained unchanged3 the solution of phosphorus was then applied2 a brown stain appeared2 the ether soon evaporated2 the phosphorus began to fume2 and the silk acquired a purple colour2 but not a particle of reduced gold could be perceived4 ,the purple tinge in this bit of silk was much more intense1 and more equal1 than in the pieces1 in which ether and alcohol were used4 ,,exp4 #h4 ,,gold4 ,i dipped a piece of silk in the solution of phosphorus1 when the ether evaporated1 and the phosphorus began to fume1 a solution of gold in water was applied2 instantly the silk was covered with a splendid coat of reduced gold4 ,nothing can be more striking than this experiment1 which was repeated times without number1 or demonstrates the necessity of water in these reductions in a more convincing manner4 ,this piece1 viewed by transmitted light1 had a purple colour with a considerable tinge of blue2 and the margin of the reduced gold was fringed with purple4 ,,exp4 #i4 ,,gold4 ,thinking that phosphorus applied in the form of vapour through the medium of water might be more effectual than a solution of it in ether1 ,i immersed a small bit of silk in an aqueous solution of gold1 and suffered it to dry a little2 it was then suspended in a phial over a little water1 into which a small bit of phosphorus was previously introduced3 the phial was then corked1 and placed on hot sand3 the phosphorus began to melt1 and ascend in white vapours1 which1 as soon as they reached the lower end of the silk1 gave it a brown tinge1 succeeded by a purple2 and the gold began to assume its metallic splendour3 in a short time these appearances were evident over the whole silk4 ,the following propositions are deducible from these experiments4 #a4 ,water does not promote the reduction of gold merely by dissolving1 and minutely dividing1 the particles of the salt1 and thus diminishing their attraction of cohesion1 and consequently increasing their chymical attraction1 as ,i first supposed2 for were this the case1 ether and alcohol1 which equally dissolve1 and divide1 the salt1 should produce the same effect4 #b4 ,ether and alcohol do not promote these reductions without the aid of water2 for it is evident from the experiments related1 that the few particles of reduced gold1 which appear1 when they are employed1 depend entirely on the quantity of water1 which they leave in the silk during their evaporation1 and that attracted from the air by the solution of gold1 and by the phosphorus during its combustion1 both of which have a strong attraction for water4 #c4 ,phosphorus does not reduce gold by giving the metallic earth phlogiston1 as the ,phlogistians suppose2 for were this opinion true1 a solution of gold in ether1 or alcohol1 should be reduced by the phosphorus as effectually as a solution of gold in water is4 #d4 ,phosphorus does not reduce gold1 by combining with1 and separating1 the oxygen of the gold1 as the ,antiphlogistians assert2 for were this the case1 the particles of the phosphorus so attenuated by the ether1 should reduce a solution of gold in ether1 or alcohol1 as well as a solution of gold in water1 since the impediment opposed by the attraction of cohesion is equally removed in both cases4 ,i shall conclude these remarks on the reduction of gold with the following experiment1 which often amused me4 ,,exp4 #aj4 ,,gold4 ,a small bit of silk was immersed in a solution of gold in ether1 and dried2 then the solution of phosphorus was applied1 which changed the yellow colour of the silk to a brown3 when the phosphorus began to fume1 ,i placed the silk on the palm of my hand1 and breathed on it a considerable time2 a purple tinge gradually succeeded the brown1 and1 in some little time after1 the metallic lustre of the gold began to appear4 ,the same experiment succeeds with a solution of gold in alcohol4 ,another bit of silk1 treated in the same manner1 was placed over the vapour of warm water for some time2 the same appearances took place1 and particles of reduced gold were evident in the silk4 ,if the water1 whence the vapour arises1 be too hot2 the heat retards1 and sometimes prevents1 the reduction1 by volatilizing the phosphorus4 ,,exp4 #aa4 ,,silver4 ,i dipped a bit of silk in a solution of fused nitrate of silver in alcohol1 and dried it in the air3 then some of the solution of phosphorus was applied1 which produced a brown stain1 whose margin1 after a few minutes exposure to the air1 acquired a livid white appearance1 caused by a partial and imperfect reduction of the silver4 ,this1 however1 would not be taken by a person unacquainted with experiments of this kind for reduced silver4 ,,exp4 #ab4 ,,silver4 ,a bit of silk was immersed in the solution of phosphorus2 as soon as the ether evaporated1 and the phosphorus began to fume2 a few drops of the solution of silver in alcohol were applied3 immediately a black stain1 intermixed with some brown1 appeared3 and1 after some time1 obscure films of reduced silver presented themselves2 these appeared on different parts of the stain2 but were so minute as to be scarce visible4 ,the only difference between this and the preceding experiment is the order1 in which1 the solutions were applied2 but even this modifies the result in some measure4 ,that these imperfect reductions depended on water1 deposited in the silk1 by the alcohol during its evaporation1 or attracted from the air by the phosphorus during its combustion1 will appear from the following experiment4 ,,exp4 #ac4 ,,silver4 ,a small phial was well dried in hot sand1 then corked1 and removed to a cool place2 after the phial cooled1 it was nearly filled with ether1 and a small bit of phosphorus1 which was repeatedly washed in alcohol to free it from any aqueous moisture1 that might adhere to it1 was introduced2 the phial was then corked1 and placed in hot sand2 when the phosphorus melted1 ,i shook the phial1 and obtained a strong solution4 ,into this solution a small bit of silk1 which was dipped in a solution of silver in alcohol1 and dried1 was introduced3 the phial was corked2 the silk instantly assumed a brown colour2 but not a particle of reduced silver could be seen1 though the experiment was continued about three months2 nor did the solution of phosphorus become turbid1 or deposit any precipitate1 as happened in similar experiments on gold4 ,at the end of this period the silk was taken out of the phial1 wetted with water1 and suspended in a window2 and1 after a considerable time1 reduced silver was manifest on different parts of the silk4 ,with the solution of phosphorus1 in which the silk stood during that time1 ,i reduced gold1 and silver1 with the assistance of water4 ,in order to compare the effects of water with those of ether and alcohol1 ,i made the following experiments4 ,,exp4 #ad4 ,,silver4 ,i dipped a bit of silk in a solution of nitrate of silver in water1 and dried it at the fire3 the silk thus dried retained its white colour3 the solution of phosphorus was then applied1 and immediately produced a brown colour1 which soon1 in proportion as the phosphorus fumed1 acquired a deeper tinge1 verging on black2 and slight signs of reduction appeared after a little time on the margin of the stain4 ,another bit of silk1 treated in the same manner1 but dried much better1 exhibited still fainter signs of reduction3 for the brown stain did not appear on this piece as soon as on the former1 nor was it so intense2 however1 after some minutes exposure to the air1 the stain became deeper1 and its margin acquired a livid white appearance1 owing to a partial reduction of the silver4 ,it has been often remarked1 that the reduction commences first on the margin of the stain1 which the solution of phosphorus1 and that of the metal1 produce in the silk3 ,i was a long time at a loss to account for this appearance2 but the cause was accidentally discovered2 for happening to spill a few drops of the solution of phosphorus on a table1 ,i observed1 that1 as they evaporated1 watery circles were formed round the spaces1 on which the drops fell2 and1 that all the parts within the circles were dry4 ,this explains why the reduction begins on the margin of the stain4 ,i observed the same of alcohol2 for if it be dropped on a level surface1 it leaves a watery ring behind1 though not near so soon1 as a solution of phosphorus in ether does3 this is the reason why alcohol seems to promote the reduction of some metals2 ,i say seems2 for it does not promote it1 but in proportion to the quantity of water it contains1 or attracts from the air1 and deposits in the silk during its evaporation4 ,how essential water is to the reduction of metals will appear from the following experiment4 ,,exp4 #ae4 ,,silver4 ,i immersed a piece of silk in the solution of phosphorus1 and after the ether evaporated1 and the phosphorus began to fume1 a solution of nitrate of silver in water was applied2 instantly the silver was restored to its metallic splendour4 ,this experiment is very amusing1 and well calculated to strike the beholder with surprise4 ,the reduction is sometimes attended with spangles of a beautiful blue1 which appear chiefly where the solution of silver is most abundant4 ,the solution of silver is commodiously applied by a camel hair pencil4 ,i also tried the effects of the vapour of phosphorus on bits of silk dipped in a solution of nitrate of silver in water1 and exposed to the vapour1 in the same manner as in experiment the #ith2 and the silver was always reduced3 but a solution of phosphorus in ether seems preferable to the vapour4 ,a small glass tube1 resembling a thermometer1 with its bulb terminating in a smaller and nearly capillary tube1 ,i found useful1 and economic1 especially in experiments on gold3 by immersing the smaller end in the metallic solution1 and inspiring through the tube at the same time1 the bulb may be filled3 by this means a single drop1 or more1 if necessary1 may be applied to the silk2 and1 thus1 a great number of experiments can be made on a single grain1 or a much less quantity1 of gold1 or any other metal4 ,this little instrument may be used also to apply the solution of phosphorus to the silk2 and it was by using it for this purpose1 ,i discovered1 that phosphorus has not the power of reducing silver without the aid of water2 for blowing the solution of phosphorus from the tube on bits of silk1 which had been dipped in a solution of silver1 and dried1 ,i was surprised to find films of reduced silver frequently appear2 whereas none appeared1 when ,i applied the solution of phosphorus in a different manner3 this unexpected event often occurred1 before ,i learned the cause2 at length ,i suspected1 it might depend on the moisture of the breath2 and ,i was soon convinced by moistening the silk with water1 that the suspicion was well founded4 ,it is evident from these experiments on silver1 that water is essential to the reduction of this metal by phosphorus2 and that ether1 and alcohol1 do not promote it4 ,it is also evident1 that these experiments1 and those1 made on the reduction of gold1 mutually illustrate each other2 and confirm the conclusions drawn from them4 ,,exp4 #af4 ,,platina4 ,i immersed a bit of silk in a solution of nitro-muriate of platina in distilled water1 and dried it in the air2 the solution of phosphorus was then applied to the silk2 but no appearance of reduction could be perceived4 ,another bit of silk was dipped in the solution of phosphorus2 when the ether evaporated1 and the phosphorus began to fume1 the solution of platina was applied to the silk2 and1 in some time1 delicate films of reduced platina were visible where the water was most abundant4 ,these films of platina commonly disappear2 and nothing remains but a brown tinge1 which1 however1 is more intense1 than what the solution of platina alone gives the silk4 ,to succeed in this experiment1 the silk should be replete with phosphorus2 which is easily done by applying the solution twice or thrice1 and waiting after each application1 till the fumes begin to appear4 ,it is also necessary to keep the silk constantly wet with water4 ,sometimes it requires from ten to twenty minutes to reduce platina in this manner4 ,,exp4 #ag4 ,,mercury4 ,i dipped a bit of silk in a solution of oxygenated muriate of mercury1 and dried it in the air2 then the solution of phosphorus was applied2 when the ether evaporated1 and the phosphorus began to fume1 a yellow stain commenced on the margin1 and gradually appeared over the whole4 ,to compare the effects of different degrees of moisture1 ,i immersed a bit of silk in the same solution of mercury1 and dried it carefully at the fire2 the solution of phosphorus was then applied2 the silk began to fume2 but no change1 except a very slight ring of a yellow hue1 appeared4 ,the rest of the silk retained its white colour4 ,another bit of silk was immersed in the solution of phosphorus1 when the ether evaporated1 and the phosphorus began to fume1 the same solution of mercury in distilled water was applied2 and1 in a few seconds1 a bright film of reduced mercury was visible on the margin of the part1 to which the metallic solution was applied1 and after some time appeared on the whole4 ,the reduction was attended with the colours of the rainbow4 ,after a little time1 these colours vanish1 and the metallic film becomes much more obscure1 according as the silk dries1 and is succeeded by a yellow stain4 ,,exp4 #ah4 ,,mercury4 ,a bit of silk was dipped in a solution of nitrate of mercury in distilled water1 and dried at the fire2 then the solution of phosphorus was applied2 and1 when it began to fume1 a brown stain commenced at the margin1 which soon diffused itself over the whole1 and gradually acquired a faint tinge of black4 ,another piece of silk1 treated in the same manner1 but dried in the air1 exhibited the same appearances2 except that the brown tinge verged more on black4 ,another bit of silk was immersed in the solution of phosphorus1 and when it began to fume1 the solution of nitrate of mercury was applied2 a brown colour instantly appeared1 accompanied with a film of reduced mercury1 which was most evident where the metallic solution was most abundant4 ,this film soon disappeared1 and was succeeded by a black stain1 in which1 however1 reduced mercury was visible4 ,no colours but black1 and brown1 appeared in this experiment4 ,it appears from these experiments on mercury1 that the reduction kept pace with the quantity of water present4 ,,exp4 #ai4 ,,copper4 ,a piece of silk was immersed in a solution of sulphate of copper1 and dried in the air3 then a strong solution of phosphorus was applied2 the silk acquired a brown colour2 but no other visible alteration occurred4 ,another piece of silk was dipped in the same solution of copper1 and dried at the fire much better than the preceding2 the solution of phosphorus was applied2 when the ether evaporated1 and the phosphorus began to fume1 a brown tinge commenced on the margin of the silk1 and gradually diffused itself over the whole2 but the stain was by no means so intense as that produced in the preceding piece3 so that there can be no doubt that the difference was owing to the different degrees of moisture in the silk4 ,after this piece remained in the air for some time1 the brown tinge became more intense1 a proof that it attracted water from the air4 ,this difference in the appearances of pieces dried in the air1 and at the fire1 ,i frequently remarked4 ,,exp4 #bj4 ,,copper4 ,a strong solution of phosphorus was applied to a piece of silk1 when the ether evaporated1 and the phosphorus began to fume1 a solution of sulphate of copper was applied2 a brown stain was instantly produced1 and its margins were soon covered with a white metallic film1 parts of which1 after some time1 verged on the colour of copper1 intermixed with purple1 green1 and blue4 ,if the solution of phosphorus be weak1 which is always the case1 when the ether is bad1 nothing appears on the silk but the brown stain1 and the white metallic film4 ,as the silk dries most of these appearances vanish2 but some of the blue tinge survives2 and the silk looks very unseemly4 ,a bit of silk was immersed in the same solution of copper1 and exposed to the vapour of phosphorus1 as in experiment the #ith2 but no change was produced on the silk1 except a few brown spots1 though the heat was such that the vapour filled the phial1 and circulated through it3 the vapour corroded a brass pin1 which was used to suspend the silk in the phial4 ,this induced me to try its effects on copper1 which was corroded by it in a remarkable manner1 and changed into a black substance resembling a mixture of charcoal and oil4 ,it appears then that phosphorus is ill adapted to the reduction of this metal4 ,,exp4 #ba4 ,,tin4 ,a bit of silk was immersed in a solution of muriate of tin in distilled water1 and dried in the air2 the solution of phosphorus was then applied to the silk1 and though it fumed considerably1 no change whatever could be perceived in the colour of the silk2 nor was there the smallest appearance of reduction4 ,i poured some of the solution of phosphorus on a bit of silk1 and when it began to fume1 the solution of tin was applied3 after a few seconds1 white metallic films appeared1 first on the margin1 and were gradually diffused over that part of the silk1 to which the muriate of tin was applied3 a yellow colour intermixed with red sometimes attends the reduction4 ,after some little time these films of reduced tin vanish1 and scarcely leave a stain behind4 ,i did not succeed in reducing acetite of lead1 muriate of arsenic1 or sulphates of iron1 and zinc1 in this way4 ,these experiments on tin shew that water is essential to its reduction by phosphorus1 and give additional force to the preceding conclusions4 ,m4 ,sage discovered that gold1 silver1 c4 are precipitated from their solutions in the metallic form1 by pieces of phosphorus1 which are covered at the same time with bright coats of gold1 silver1 c4 ,to determine if water were essential to these reductions performed by ,m4 ,sage1 ,i made the following experiments4 ,,exp4 #bb4 ,,gold4 ,some solution of phosphorus in ether was poured into a china cup1 and a few drops of the ethereal solution of gold were added2 instantly a brown powder was precipitated similar to what appeared in experiment the #fth1 but no gold in its metallic form could be perceived4 ,,exp4 #bc4 ,,gold4 ,a solution of nitro-muriate of gold in water was poured into a china cup1 containing a solution of phosphorus in ether2 instantly the gold began to assume its metallic splendour1 attended with a variety of colours1 as purple1 blue1 and red1 the beauty of which cannot be described3 the quantity of the blue was gradually diminished1 and what remained1 was dispersed over the surface in small films1 intermixed with spangles of reduced gold4 ,most of the blue films were of a circular figure2 some had a central speck of ruby red1 and were fringed with purple2 some had a round central speck of a darker blue than the surrounding parts3 and some were of an irregular figure1 fringed with purple1 or ruby red4 ,i often observed these blue films assume the real colour of gold without suffering any intermediate change of colour2 and1 ,i think1 ,i observed the same of one of the largest specks of ruby red1 that appeared in this experiment4 ,all these colours disappeared1 when the reduction was completed4 ,the variety of colours1 which those films assume1 depends on the different degrees of reduction2 that is to say1 on the quantity of oxygen combined with the metal3 in proportion as the metal is deprived of the oxygen1 it assumes various colours1 which often succeed each other in a regular order1 showing the different stages of the reduction3 thus when gold is reduced2 the first perceptible change is a green1 which soon becomes olive2 this is succeeded by blue1 and purple2 and sometimes by a ruby red3 the purple tinge is a mixture of blue1 and red4 ,the various colours1 which metals1 and their calces1 communicate to glass1 and other substances1 are explicable on these principles3 and the difficulty of obtaining a ruby-coloured glass by gold is readily understood from the facility1 with which that metal parts with oxygen4 ,,exp4 #bd4 ,,gold4 ,a thread was passed by means of a needle through a small bit of phosphorus1 which was freed from any moisture1 that might adhere to it1 by immersing it for some time in alcohol2 it was then suspended by means of the thread in a solution of gold in ether1 contained in a phial1 which was carefully dried in hot sand3 in a few minutes1 the solution became turbid1 an effervescence commenced1 and a brown precipitate was formed3 according as the precipitate fell1 the solution became clear1 lost its yellow colour2 and the whole of the gold seemed to have been precipitated3 but not a particle of reduced gold could be seen4 ,another bit of phosphorus was suspended in the same manner in a solution of nitro-muriate of gold in water2 and in a few minutes got a splendid coat of reduced gold4 ,,exp4 #be4 ,,silver4 ,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 ether3 instantly a black precipitate1 with a tinge of brown1 was formed2 but no silver in its metallic state could be perceived4 ,after some time the precipitate attracted moisture from the air2 and some films of reduced silver appeared4 ,the same experiment was made in a phial1 which was corked1 to exclude the moisture of the air2 and nothing1 but the black precipitate1 appeared4 ,some of the same solution of silver was diluted with water1 and dropped on a solution of phosphorus in ether2 and instantly films of reduced silver floated on the surface4 ,,exp4 #bf4 ,,silver4 ,a bit of phosphorus was suspended by a thread in some of the same solution of silver in alcohol1 contained in a phial carefully dried3 a black precipitate with a tinge of brown soon appeared2 but no silver in its metallic state could be observed2 part of the precipitate adhered to the phosphorus1 and part fell to the bottom of the phial4 ,in another experiment made in a phial not sufficiently dried1 a few small films of reduced silver were observed on the sides of the phial2 but not a particle of silver in its metallic form could be seen on the phosphorus4 ,another bit of phosphorus was suspended in a diluted solution of nitrate of silver in water3 and in some hours1 the phosphorus was covered with reduced silver4 ,the case of silver1 which covered the phosphorus1 prevented its spontaneous combustion in the air2 the same was observed of the bit of phosphorus coated with gold4 ,hence it appears1 that ,m4 ,sage's success in reducing metals by phosphorus depended on the water of the metallic solution4 ,these experiments were often repeated with nearly the same result2 but some variety often occurs1 depending on various circumstances2 as the strength of the metallic solution1 and that of the phosphorus2 the quantity of water present1 and the purity of the materials employed4 ,it is difficult to obtain ether1 or alcohol1 with the least possible quantity of water2 and equally difficult to expel all moisture from the surface of glass2 for this reason1 the bits of phosphorus in the experiments made with alcohol and ether were suspended by threads1 so as not to touch the sides of the glass4 ,i shall conclude this chapter with a general view of the inferences1 which seem naturally to flow from these experiments with phosphorus4 #a4 ,water is essential to the reduction of metals by phosphorus2 for these experiments show that the reduction is effected only in proportion to the quantity of water present4 #b4 ,phosphorus does not reduce the metals by giving them phlogiston4 #c4 ,phosphorus does not reduce the metals by uniting with1 and separating1 their oxygen4 ,how then is the reduction effected8 are we not to conclude1 that it is effected by the decomposition of the water1 in the following manner8 ,the phosphorus attracts the oxygen of the water1 while the hydrogen of the latter unites1 in its nascent state1 with the oxygen of the metal1 and effects the reduction4 ,hence it follows1 that the phosphorus is oxygenated by the oxygen of the water1 while the metal is restored to its combustible state4 ,thus what could never be effected by a single1 is readily performed by a double affinity2 which always takes place in preference to a single affinity1 as the experiments of ,messrs4 ,monnet1 and ,kirwan1 mentioned in the preceding chapter1 show4 ,it is well known1 that phosphorus kept in water acquires an oxygenated crust1 which could not happen without a decomposition of the water3 this fact serves to confirm the explanation here offered4 ,and indeed the decomposition of water in these experiments must be granted1 or it must be supposed1 that water itself reduces the metals1 by uniting with their earths1 and constituting their phlogiston2 or by uniting with1 and separating1 their oxygen2 suppositions repugnant to our present knowledge of chymistry4 ,,chapter ,,iii4 ,reduction of ,metals by ,sulphur4 ,though ,sulphur1 as far as my reading extends1 has seldom been considered as a reducer of the metals1 yet as it holds a distinguished rank among combustible bodies1 analogy led me to examine its powers in reducing and fixing the metals in the fibres of silk4 ,the vapour of sulphur appeared to be the most simple form1 in which it could be applied to this purpose2 and may be obtained by placing a phial containing flowers of sulphur in hot sand3 as the sulphur melts1 it assumes the form of vapour1 which soon fills the phial1 expels the atmospheric air1 and bears a considerable heat1 before it inflames2 a bit of silk1 prepared for the experiment1 may be held over the vapour1 as it issues from the phial1 or immersed in it4 ,the neck of the phial should be of a convenient size for this purpose4 ,but these experiments are more conveniently made by means of a sulphurous match1 and a glass funnel1 in which the silk imbued with the metallic solution may be suspended by a thread passed through it1 and made fast with a cork1 which also serves to confine the vapour4 ,the glass is then placed on a table1 and by moving it a little beyond the verge of the same1 a lighted match is readily introduced1 which1 as soon as the glass is filled with vapour1 may be withdrawn2 the vapour is confined by making the glass glide back on the table2 and thus the phenomena of the experiment can be easily observed4 ,though the vapour obtained in this manner be chiefly sulphurous acid gas2 yet its effects are not less interesting on that account4 ,,exp4 #a4 ,,gold4 ,a bit of silk was dipped in a solution of gold in ether1 and dried3 it was then suspended in the glass funnel1 and exposed for some time to the vapour obtained from a burning match3 but no change could be perceived1 except that the silk became a little brown4 ,another bit of silk1 prepared in the same manner1 was immersed in the vapour of sulphur1 formed in a phial placed in hot sand1 with the same result4 ,,exp4 #b4 ,,gold4 ,a piece of silk was immersed in a solution of nitro-muriate of gold in water1 suspended in the glass funnel1 and exposed1 while wet1 to vapour of sulphur1 formed by a burning match2 no sooner did the vapour touch the silk1 than the reduction commenced2 and in a few seconds the whole piece was covered with a splendid coat of reduced gold1 permanent1 and retentive of its lustre2 but had a few specks of a dull violet hue4 ,the silk viewed by transmitted light appeared of a beautiful blue colour2 and being removed from the vapour1 and suspended in the air1 began in about ten minutes to exhale a vapour1 which continued about two hours1 and smelled acid1 and pungent4 ,another bit of silk1 dipped in the same solution of gold1 and dried1 was wetted with alcohol1 and exposed to the same vapour3 the silk acquired a brownish hue2 and a small white metallic film appeared on its lower end1 where the alcohol most abounded3 the silk was then wetted with water1 and replaced in the vapour2 instantly a lively purple with a bright pellicle of reduced gold appeared4 ,,exp4 #c4 ,,silver4 ,a piece of silk was immersed in a solution of nitrate of silver in water1 and suspended in the air of a dark closet to dry2 the silk retained its white colour1 though it remained in the air twenty-four hours2 it was then exposed fourteen hours to the vapour obtained from a burning match2 but suffered no change1 except that it acquired a brown tinge3 it was now wetted with alcohol1 and replaced in the vapour for some time2 no signs of reduction appearing1 it was wetted again with the alcohol1 and exposed to the vapour2 but still no signs of reduction could be perceived3 ,i then wetted the silk with distilled water1 replaced it in the sulphureous vapour2 and in about a minute reduced silver appeared4 ,,exp4 #d4 ,,silver4 ,i dipped a bit of silk in a solution of nitrate of silver in distilled water1 and exposed it1 while wet1 to the vapour of sulphur1 as in the preceding experiment2 in a few seconds the silver appeared in its metallic form1 attended with a variety of lively colours3 the most remarkable of these were a pleasant blue1 orange1 purple1 and yellow1 which soon disappeared3 the reduced silver also disappeared in a great measure1 some faint traces only remaining4 ,the silk was removed from the vapour into the air1 but exhaled no vapour1 as happened in experiment the second4 ,a small bit of sulphur was suspended in a phial containing a solution of nitrate of silver in water2 and after some weeks the sulphur was coated with reduced silver of no great lustre4 ,,exp4 #e4 ,,platina4 ,a bit of silk was immersed in a solution of nitro-muriate of the ore of platina in distilled water1 and dried in the air2 it was then suspended in the glass funnel1 and exposed to the vapour of a burning match3 but no signs of reduction could be observed3 the silk retained the colour1 the solution gave it4 ,another bit of silk was dipped in the same solution of platina1 and exposed1 while wet1 to the sulphureous vapour2 in a few seconds the reduction was very evident4 ,the silk was immerged in a glass of clear water1 and transferred bright films of reduced platina to the surface of that fluid2 most of them were of the same colour as the spangles in the ore of platina2 and some were distinguished by lively blue and purple colours4 ,another bit of silk1 dipped in the same solution of platina1 was immersed1 while wet1 in the vapour of sulphur1 formed in a phial placed in hot sand2 the reduction soon commenced1 and was much more perfect1 and permanent1 than in pieces exposed to the vapour obtained from ignited matches4 ,it is remarkable that sulphur reduced this metal much better1 than phosphorus or hydrogen gas did3 but the reduced platina disappears after some time1 and leaves nothing behind but a brown stain4 ,if the films be transferred from the silk to water1 they may be preserved in their metallic form4 ,,exp4 #f4 ,,mercury4 ,a bit of silk was immersed in a solution of nitrate of mercury in distilled water1 and dried2 parts of the silk immediately acquired a slate colour3 the silk was then exposed to the vapour of sulphur1 obtained from a burning match2 but it suffered no change1 except that the colour became a little more intense4 ,another bit of silk was dipped in the same solution of mercury1 and exposed1 while wet1 to the same vapour3 the reduction instantly commenced in a very evident manner1 accompanied with several colours1 as blue1 purple1 and yellow4 ,the silk was removed from the vapour1 and soon lost most of its lustre1 which was succeeded by a slate colour1 through which some particles of reduced mercury were observed to shine4 ,,exp4 #g4 ,,mercury4 ,a bit of silk was immersed in a solution of oxygenated muriate of mercury in water1 and dried in the air3 it was then exposed to the sulphureous vapour obtained from a burning match2 but the silk underwent no visible change4 ,this solution of mercury does not change the white colour of silk1 as that of nitrate does4 ,another bit of silk was dipped in the same solution of oxygenated muriate of mercury1 and exposed1 while wet1 to the vapour2 in a few seconds reduced mercury appeared1 unattended by any colour1 except a slight tinge of citron yellow on part of the silk4 ,after some time the whole of the reduced mercury vanished4 ,,exp4 #h4 ,,copper4 ,a piece of silk was immersed in a solution of sulphate of copper1 and dried2 it was then suspended in the glass funnel1 and exposed to the vapour obtained from a burning match2 but the silk suffered no change1 retaining the colour1 which the solution gave it4 ,another bit of silk was dipped in the same solution of copper1 and exposed1 while wet1 to the vapour of an ignited match2 in a short time a white metallic film appeared1 accompanied with a brown tinge2 the silk becoming dry1 was wetted with water1 and exposed to a brisk vapour from another match3 the film became more evident1 and parts of it verged on yellow1 bordering on a copper colour4 ,after some time this white metallic film disappears1 and nothing remains but a light brown stain4 ,,exp4 #i4 ,,lead4 ,a bit of silk was immersed in a solution of acetite of lead in distilled water1 and dried in the air3 it was then exposed to the sulphureous vapour of a burning match2 but underwent no visible change whatever4 ,another bit of silk was dipped in the same solution of lead1 and exposed1 while wet1 to the vapour2 reduced lead soon appeared all over the silk2 but after some time this reduced lead disappears1 unless it be transferred to the surface of water4 ,,exp4 #aj4 ,,tin4 ,a bit of silk was immersed in a solution of muriate of tin in distilled water1 and dried in the air3 it was then exposed to the vapour obtained from a burning match1 which soon filled the glass2 but produced no visible change on the silk4 ,another bit of silk was dipped in the same solution of tin1 and exposed1 while wet1 to the sulphureous vapour2 and in a few seconds reduced tin appeared all over the silk2 but the tin soon disappears1 if not transferred to water4 ,,exp4 #aa4 ,,arsenic4 ,a bit of silk was immersed in a solution of muriate of arsenic in distilled water1 and dried in the air2 it was then exposed to the vapour of sulphur1 obtained from a burning match2 but the silk suffered no apparent alteration4 ,another bit of silk was dipped in the same solution of arsenic1 and exposed1 while wet1 to the vapour3 in a few seconds the arsenic was reduced1 but not in a very evident manner2 the silk was immerged in water1 and several bright films of reduced arsenic floated on the surface of that fluid4 ,,exp4 #ab4 ,,bismuth4 ,a bit of silk was immersed in a solution of nitrate of bismuth in distilled water1 and dried in the air2 it was then exposed to the vapour of sulphur obtained from a burning match2 but no signs of reduction appeared4 ,another bit of silk was dipped in the same solution of bismuth1 and exposed1 while wet1 to the sulphureous vapour2 the bismuth was soon reduced1 accompanied with a brown stain3 but the metallic lustre soon disappeared4 ,,exp4 #ac4 ,,antimony4 ,a piece of silk was immersed in a solution of tartarite of antimony in water1 and dried2 it was then exposed to the vapour of a burning match2 but no change could be observed2 nor did the silk immerged in water deposit any films on its surface4 ,another piece of silk was dipped in the same solution of antimony1 and exposed1 while wet1 to the vapour3 the silk1 in a few seconds1 acquired a yellow colour1 and a bright bluish film of reduced antimony appeared on the lower end of the silk1 where the water was most abundant3 the silk was then immerged in a glass of water1 and transferred a large pellicle of reduced antimony to the surface of that fluid4 ,,exp4 #ad4 ,,iron4 ,a bit of silk was immersed in a largely diluted solution of sulphate of iron in distilled water1 and dried in the air2 it was then exposed to the vapour of sulphur obtained from a burning match2 after some time the colour of the silk became a little brown2 but no reduced iron could be seen2 nor did the silk immerged in a glass of clear water transfer any thing metallic to its surface4 ,another bit of silk was dipped in the same solution of iron1 and exposed1 while wet1 to the sulphureous vapour2 in a short time the silk was withdrawn1 and a minute shining film1 of a livid white colour1 was visible on its lower margin1 where the water most abounded3 the silk was then immerged in a glass of water1 and transferred a large film of reduced iron to its surface4 ,this experiment succeeded also with the vapour of sulphur formed in a phial placed on hot sand4 ,the films of reduced iron were seldom visible on the silk2 but were soon rendered visible1 by transferring them to water4 ,,exp4 #ae4 ,,zinc4 ,a piece of silk was dipped in a diluted solution of sulphate of zinc1 and dried2 it was then exposed to the vapour obtained from a burning match2 no change whatever could be perceived3 the silk was immerged in a glass of water1 but deposited no film on its surface4 ,another piece of silk was dipped in the same solution of zinc1 and immersed while wet in the vapour of sulphur formed in a phial placed on hot sand2 in about half a minute the silk was withdrawn from the vapour1 and some parts of it had a shining livid appearance1 which ,i took for reduced zinc3 in order to determine if the reduction were real1 the silk was immerged in a glass of clear water1 and transferred to its surface a bright film of reduced zinc4 ,if the silk be kept too long in the vapour1 some sulphur will be condensed on its surface1 and give it a yellow colour3 if it be then dipped in a glass of water1 it will deposit both the sulphur1 and the metallic films on its surface2 but the appearance of the sulphur is so different from that of the reduced metal1 that they are easily distinguished4 ,another bit of silk was immersed in a largely diluted solution of muriate of zinc1 and exposed1 while wet1 to the vapour obtained from a burning match3 the silk being withdrawn exhibited a few minute shining films on its lower end1 and on immersion in water1 left bright films of reduced zinc floating on the surface of that fluid4 ,very often these films cannot be seen1 until they are transferred to water1 which ,i found a very useful test in doubtful cases3 they are better seen in the gray light than in sunshine4 ,these experiments on the reduction of metals by sulphur were often repeated with nearly the same result3 but some variety occurs depending on the quantity of water present1 the strength of the metallic solution1 and sulphureous vapour1 and also on the time the silk is exposed to the vapour4 ,when the experiments are made in a phial placed in hot sand1 part of the metallic solution frequently drops from the silk1 and falling on the bottom1 or sides of the phial1 is reduced1 covering these parts with a metallic crust2 on which the sulphur soon reacts1 and changes the greater part into a sulphure4 ,the phial commonly cracks4 ,the following conclusions are deducible from the experiments related in this chapter4 #a4 ,water is essential to the reduction of metals by sulphur2 for this effect is always in proportion to the quantity of water present4 #b4 ,alcohol does not promote these reductions without the aid of water4 #c4 ,sulphur does not reduce the metals by giving them phlogiston2 nor by uniting with and separating their oxygen2 for were either of these opinions just1 the sulphur1 so minutely divided by heat1 should reduce metallic solutions in alcohol as effectually as it does metallic solutions in water4 ,when we compare these reductions by sulphur1 with those effected by phosphorus1 and consider that water is essential to both2 we must conclude1 that the reduction is effected in the same manner1 viz4 by the decomposition of water2 which may be thus explained4 ,the sulphur attracts the oxygen of the water1 while the hydrogen of the latter unites1 in its nascent state1 to the oxygen of the metal1 and restores it to the metallic form4 ,hence it follows1 that the sulphur is oxygenated by the oxygen of the water1 while the metal is restored to its combustible state4 ,it also follows1 that a quantity of water equal to that consumed is formed by the hydrogen of the water1 and the oxygen of the metal4 ,this explanation is supported by a fine experiment of ,dr4 ,priestley1 who obtained inflammable air by passing the vapour of water through sulphur heated in an earthen tube#ae2 and farther confirmed by the experience of some judicious makers of oil of vitriol1 who always sprinkle the sulphur with a certain proportion of water1 before they inflame it4 ,the decomposition of water in these reductions must be granted1 or it must be supposed1 that a single takes place in preference to a double affinity2 which cannot be admitted4 ,these experiments point out several errors in ,m4 ,lavoisier's ,table of the ,affinities of the ,oxygenous ,principle2 for he has placed sulphur at a much greater distance from that principle than any of the metals treated of in this chapter1 except gold2 and even in this instance his table is erroneous1 unless it be proved1 that sulphur reduces metals by directly uniting with1 and separating their oxygen2 a supposition which implies1 that the reduction is effected by a single affinity2 and therefore inadmissible4 ,i shall close this chapter with a short extract from the chemical essays of ,bishop ,watson2 as it seems to have some relation to the experiments related here4 ,his lordship says1 that his experiments on 8the ,derbyshire lead ore instruct us to believe1 that the lead in this kind of ore is in its metallic state2 as the ore was changed into lead without the addition of any substance containing the inflammable principle#af40 ,but the reduction of lead by sulphur and water1 related in this chapter1 points out an evident source of the inflammable principle2 for the ore itself must contain some water1 a constituent part of which is hydrogen1 or the base of inflammable air3 beside his lordship thinks1 no appearance of lead would have taken place1 had there been no communication with the external air3 but as air always holds water in solution1 an ample source of the inflammable principle is evident4 ,,chapter ,,iv4 ,reduction of ,metals by ,alkaline ,sulphure4 ,the ,sulphure1 ,i made use of1 was prepared by fusing equal parts of carbonate of potash1 and flowers of sulphur1 till the effervescence ceased4 ,m4 ,gengembre has made a very important observation on alkaline sulphure1 prepared in this way1 which is1 that this substance has no smell1 and that it exhales no gas1 while it continues dry2 but that1 when it is dissolved in water1 or attracts humidity from the air1 it diffuses an offensive smell4 ,from this circumstance ,m4 ,gengembre inferred1 that the disengagement of this gas depended on the decomposition of water2 for he discovered both by analysis1 and synthesis1 that this air consists of hydrogen1 one of the principles of water1 combined with sulphur1 and caloric4 ,there can then be no doubt1 but alkaline sulphure has the power of decomposing water2 and may therefore be happily employed to illustrate the mode of action of sulphur1 and other combustible substances1 treated of in this essay4 ,when dilated acids are poured on solid alkaline sulphure1 the decomposition of the water is promoted1 and accelerated1 sulphurated hydrogen gas being formed in great abundance4 ,i made two solutions of this alkaline sulphure1 one in water1 and the other in alcohol4 ,,exp4 #a4 ,,gold4 ,a bit of silk was immersed in the solution of sulphure in alcohol1 and then a solution of gold in ether was applied3 a brown matter was formed in the silk2 but no reduced gold could be perceived4 ,another bit of silk was dipped in the same solution of sulphure in alcohol1 and a solution of nitro-muriate of gold in water was applied2 a white metallic film was slowly formed2 but no other signs of reduction were visible4 ,this experiment was repeated on another bit of silk1 with this difference1 that the solutions of the gold1 and sulphure1 were both in water2 and the white metallic film was instantly formed1 accompanied by a considerable precipitate of a brown matter4 ,it is obvious then1 that water accelerates1 and is necessary to the appearance of this film3 for when both solutions were in water1 it appeared much sooner4 ,,exp4 #b4 ,,gold4 ,a piece of silk was immersed in an aqueous solution of gold1 in which the acid predominated1 then a few drops of the aqueous solution of sulphure were applied3 a white pellicle1 which looked like silver1 was immediately formed1 and the silk got a deep brown colour4 ,to another piece of silk1 dipped in the same solution of gold1 the solution of sulphure in alcohol was applied1 a white metallic film appeared2 but not so evident1 or so soon1 as in the preceding experiment1 wherein the solution of sulphure in water was used3 beside the film produced by the aqueous solution of sulphure was more permanent1 and the stain1 which the silk acquired1 was more intense1 than those produced by the solution of sulphure in alcohol4 ,,exp4 #c4 ,,silver4 ,i immersed a piece of silk in a solution of the sulphure in alcohol1 and after most of the spirit evaporated1 a solution of nitrate of silver in alcohol was applied3 nothing appeared on the silk1 but a brown stain4 ,the nitrate of silver1 used in this experiment1 was fused1 to expel as much water as possible4 ,another piece of silk was dipped in the same solution of sulphure2 when most of the alcohol evaporated1 a solution of crystallized nitrate of silver in water was applied to the silk2 and instantly the metallic lustre of the silver appeared1 attended with a brown stain4 ,,exp4 #d4 ,,silver4 ,a piece of silk was dipped in the solution of alkaline sulphure in water1 and an aqueous solution of crystallized nitrate of silver was applied2 the silver was immediately reduced in greater quantity than in the preceding experiment1 in which the alkaline sulphure employed was dissolved in alcohol4 ,the stain produced in the silk was also more intense4 ,,exp4 #e4 ,,silver4 ,a bit of silk was immersed in a solution of the sulphure in water1 and then a solution of nitrate of silver in alcohol was applied3 but nothing appeared on the silk1 except a brown stain4 ,the nitrate of silver1 used in this experiment1 was fused1 which deprived it of a great part of its acid4 ,that this was the circumstance1 which prevented the reduction of the silver1 appears from the following experiment4 ,a bit of silk was immersed in the same solution of silver in alcohol1 then some diluted nitric acid was applied1 lastly the aqueous solution of sulphure was dropped on the silk3 and instantly the silver was restored to its metallic splendour4 ,it is evident then1 that acids contribute to the reduction of silver by alkaline sulphure1 which they effect by promoting the decomposition of water4 ,in some time the reduced silver disappears for the most part3 and indeed the white metallic films1 which were produced in the experiments on gold1 totally disappeared4 ,,exp4 #f4 ,,platina4 ,a bit of silk was immersed in a solution of nitro-muriate of the ore of platina in distilled water1 and dried2 then the solution of sulphure in alcohol was dropped on the silk3 nothing appeared but a brown stain4 ,another bit of silk was dipped in the aqueous solution of sulphure1 and a little of the solution of platina applied2 in a short time1 a film of reduced platina appeared4 ,to another bit of silk1 which was dipped in the solution of platina1 a few drops of distilled vinegar were applied1 and then the solution of sulphure in water was added2 a brown stain was immediately produced1 and more platina reduced than in the preceding experiment4 ,,exp4 #g4 ,,mercury4 ,to a bit of silk1 which was immersed in a solution of oxygenated muriate of mercury in water1 and dried in the air2 some of the solution of sulphure in alcohol was applied2 but no change1 except a light yellowish brown1 was produced4 ,after the silk was some time exposed to the air1 some very faint shades of black were visible on parts of it4 ,to a piece of silk1 which was immersed in the solution of sulphure in water1 some of the same solution of mercury was applied2 immediately the metal was restored to its metallic lustre1 in a very striking manner2 and it was remarkable1 that the precipitate on the silk was very small4 ,this experiment was repeated with this difference1 that the silk was first wetted with distilled vinegar3 and more of the mercury was reduced1 than in the preceding experiment1 attended with an olive precipitate1 which gradually turned blackish3 the quantity of precipitated matter in this was much greater than in the former experiment2 but the reduced metal was not so bright4 ,,exp4 #h4 ,,mercury4 ,a bit of silk1 which was dipped in a solution of nitrate of mercury1 and dried in the air1 had no change produced on it by a solution of sulphure in alcohol1 except a stain compounded of the slate colour1 which the nitrate imparts1 and the yellow of the sulphure4 ,to another bit of silk1 which was immersed in the aqueous solution of sulphure1 some of the same solution of mercury was applied3 the metal was immediately reduced2 and a very black stain attended the reduction4 ,,exp4 #i4 ,,copper4 ,a piece of silk was dipped in a solution of sulphate of copper1 and dried in the air2 a solution of the sulphure in alcohol was applied to it2 but no change1 except a brown stain1 was produced4 ,to another bit of silk1 immersed in the aqueous solution of sulphure1 some of the same solution of copper was applied3 a white metallic film was slowly formed1 attended with a brown colour4 ,on another bit of silk1 which was dipped in the same solution of copper1 and placed on a saucer1 some distilled vinegar was dropped1 and then a few drops of the aqueous solution of sulphure were added3 immediately a white metallic film appeared in greater quantity than in the preceding experiment4 ,,exp4 #aj4 ,,lead4 ,a piece of silk was immersed in a solution of acetite of lead in distilled water1 and dried in the air2 then the solution of sulphure in alcohol was applied3 but nothing appeared on the silk1 except a brown stain4 ,a bit of the same silk was dipped in the same solution of lead1 then the solution of sulphure in water was applied3 the lead was soon reduced to its metallic state3 a brown stain1 and precipitate of the same colour1 attending the reduction4 ,the same experiment was repeated with this difference1 that the silk was first wetted with distilled vinegar1 and instantly the lead was reduced of greater lustre1 and in greater quantity1 than in the preceding experiment4 ,this experiment was tried on a bit of white calico1 dipped in distilled vinegar1 and placed on the palm of my hand2 and instantly the metallic lustre of the lead1 which was reduced in great quantity1 appeared in a very remarkable manner1 attended with a brown stain4 ,,exp4 #aa4 ,,tin4 ,to a bit of silk dipped in a solution of muriate of tin in distilled water1 and dried in the air1 the solution of sulphure in alcohol was applied3 nothing appeared but a brown stain4 ,another bit of silk was immersed in the solution of sulphure in water1 then the same solution of muriate of tin was applied2 in a short time some reduced tin appeared on the silk4 ,vinegar promoted the reduction of this metal also1 in a remarkable manner4 ,,exp4 #ab4 ,,arsenic4 ,a bit of silk was immersed in a solution of muriate of arsenic in distilled water1 and dried in the air3 the solution of sulphure in alcohol was then applied3 the silk first looked yellow1 in a short time the yellow colour almost entirely disappeared1 leaving behind a whitish precipitate2 but no other change was produced4 ,another bit of silk was dipped in the solution of sulphure in water2 then some of the same solution of arsenic was applied2 a yellow precipitate was formed2 and shortly after1 this precipitate was surrounded by a violet margin2 but no other change could be observed4 ,i immersed another bit of the same silk in the same solution of arsenic1 some distilled vinegar was then dropped on it2 and lastly the aqueous solution of sulphure was applied3 after some time1 a few minute films of reduced arsenic bright as silver were visible4 ,some attention is necessary to discover the reduced arsenic1 as the particles reduced are few1 and minute2 and sometimes none can be seen4 ,,exp4 #ac4 ,,bismuth4 ,to a bit of silk1 which was dipped in a solution of nitrate of ,bismuth in distilled water1 and dried in the air1 the solution of sulphure in alcohol was applied3 the silk appeared first yellow1 then brown2 but no farther change could be observed4 ,another bit of silk was immersed in the solution of sulphure in water2 some of the same solution of bismuth was then applied to it2 the metal was immediately reduced2 and a brown precipitate was formed4 ,vinegar seems neither to promote1 nor retard the reduction4 ,two bits of white calico were dipped in the same solution of bismuth2 to one of these placed on a saucer some distilled vinegar was added2 then a single drop of the solution of sulphure in water was applied2 and the whole of the calico1 except that part on which the drop fell1 was covered with reduced bismuth1 which looked exceedingly bright3 the same appearance was observed on the other bit1 to which no vinegar was added4 ,,exp4 #ad4 ,,antimony4 ,to a bit of silk1 which was dipped in a solution of tartarite of antimony in distilled water1 and dried in the air1 the solution of sulphure in alcohol was applied2 the silk got a yellow colour1 whose margins1 some time after1 acquired an orange hue2 but no other change was perceived4 ,another bit of the same silk was immersed in the aqueous solution of sulphure1 the same solution of antimony was then applied3 part of the metal was reduced1 though in small quantity1 attended with an orange precipitate4 ,the acids of vinegar1 and tartar1 seemed to impede the reduction2 the muriatic acid also seemed to have the same effect1 though not in so great a degree as the two former4 ,,exp4 #ae4 ,,cobalt4 ,to a bit of silk1 which was dipped in a solution of nitrate of cobalt1 and dried in the air1 the solution of sulphure in alcohol was applied2 the silk soon became brown2 but no farther change could be perceived4 ,to another bit of silk1 which was immersed in the solution of sulphure in water1 a few drops of the same solution of cobalt were applied3 the silk immediately acquired a dark colour1 and1 in a little time1 some of the metal was reduced1 attended with a dull blue precipitate1 which changed to a blackish brown4 ,muriate of cobalt was reduced in the same manner3 vinegar promoted the reduction of both these preparations of cobalt4 ,,exp4 #af4 ,,iron4 ,to a piece of silk1 which was immersed in a solution of sulphate of iron largely diluted1 and dried in the air1 the solution of sulphure in alcohol was applied3 the silk soon became black2 but no other change could be perceived4 ,another bit of silk was dipped in the solution of sulphure in water1 some of the same solution of iron was then applied3 the silk instantly assumed a black colour2 but no reduced iron appearing1 it was immerged in a glass of water1 and transferred a bright film of reduced iron to the surface of that fluid4 ,sometimes part of the film has not the metallic lustre1 which is very evident in other parts of it2 so that the parts completely reduced can be easily distinguished from the dull and imperfectly reduced black oxid of iron1 intermixed with these bright films4 ,the same experiments were repeated on bits of calico with the same result3 the calico from its spongy texture is better suited to produce strong films than silk is4 ,vinegar did not promote the reduction of iron in these experiments4 ,,exp4 #ag4 ,,zinc4 ,to a bit of silk1 which was immersed in a largely diluted solution of muriate of zinc1 and dried in the air1 some of the solution of sulphure in alcohol was applied2 nothing appeared on the silk1 but the yellow colour1 which the solution of sulphure imparts4 ,another bit of silk was dipped in the solution of sulphure in water1 and some of the same solution of zinc was applied3 the yellow colour1 which the solution of sulphure gave the silk1 soon became white2 but no reduced zinc could be seen4 ,the silk was then immerged in a glass of clear water1 and transferred a bright film of reduced zinc to its surface4 ,in another experiment1 made with white calico1 the pellicle transferred to the surface of water was brighter2 and more zinc was reduced1 than in the preceding experiment4 ,sulphate of zinc also was reduced both on silk1 and calico1 with this difference that black1 and olive1 precipitates1 attended the reduction4 ,,exp4 #ah4 ,,manganese4 ,i dipped a bit of silk in a diluted solution of nitrate of manganese1 and dried it in the air2 the solution of sulphure in alcohol was then applied3 the silk acquired a yellow colour1 which soon disappeared2 but no other change could be observed4 ,to another bit of silk1 which was immersed in the solution of sulphure in water1 a drop of the same solution of manganese was applied3 instantly a pearl-white precipitate was formed1 the margin of which soon acquired a bright film of reduced manganese4 ,under this film a violet tinge was evident4 ,the nitrate of manganese used in this experiment was very acid4 ,a solution of alkaline sulphure in water after a certain length of time loses the power of reducing the metals1 in which respect it resembles an old solution of sulphate of iron4 ,having procured a more neutral solution of nitrate of manganese1 ,i immersed a bit of silk in the solution of sulphure in alcohol1 when most of the spirit evaporated2 a single drop of this solution of manganese was applied2 instantly a bright film of reduced manganese appeared1 attended with a violet tinge1 and a brown precipitate4 ,after some time the violet tinge disappears4 ,on another bit of silk immersed in the same solution of sulphure in alcohol1 a drop of a solution of sulphate of manganese in distilled water was applied3 instantly films of reduced manganese bright as silver appeared1 accompanied with a faint violet tinge1 and a pearl-white precipitate4 ,these films soon disappear4 ,a solution of alkaline sulphure in alcohol does not by age lose its power of reducing the metals1 as that in water does2 ,i kept the former solution more than two years1 and found it1 at the end of that time1 as capable of reducing the metals1 as when it was made4 ,it is manifest from the experiments related in this chapter1 #a4 ,that water is essential to the reduction of metals by alkaline sulphure4 #b4 ,that alcohol does not promote these reductions1 without the aid of water4 #c4 ,that alkaline sulphure does not reduce the metals by giving them phlogiston2 nor by uniting with1 and separating1 their oxygen2 for were either of these opinions true1 a solution of alkaline sulphure in alcohol should reduce them as effectually1 as a solution of the same in water does4 #d4 ,that acids contribute to these reductions by promoting the decomposition of water4 ,now since ,m4 ,gengembre has demonstrated1 that water is decomposed by alkaline sulphure2 who can doubt1 that it is decomposed in these reductions8 ,the manner1 in which metals are reduced by this substance1 seems to be the following4 ,an hydrure of sulphur1 that is1 a combination of hydrogen1 and sulphur1 is formed3 this hydrure of sulphur attracts the oxygen of the water1 while the hydrogen of the latter unites1 in its nascent state1 with the oxygen of the metal1 and reduces it4 ,the experiments in this chapter leave us no room to doubt of the decomposition of water in metallic reductions by alkaline sulphure1 and serve to illustrate1 and confirm1 the manner1 in which sulphur1 phosphorus1 and other combustible bodies1 effect the reduction of metals4 ,,chapter ,v4 ,,reduction ,,of ,,metals ,,by ,,sulphurated ,,hydrogen ,,gas4 ,having treated of the effects of hydrogen gas1 and sulphur1 separately1 ,i shall next treat of their effects1 when combined in the form of sulphurated hydrogen gas4 ,i obtained this elastic fluid by pouring water1 acidulated with sulphuric acid1 on alkaline sulphure1 prepared in the manner mentioned in the preceding chapter2 but had it been prepared with a caustic alkali1 it is probable1 the gas would be more powerful4 ,the sulphure of the shops is generally unfit for these experiments4 ,it is necessary in experiments with sulphurated hydrogen gas1 hydrogen gas1 c4 to have some mode of conveying them into a chimney2 as they are offensive1 and unwholesome4 ,,exp4 #a4 ,,gold ,a piece of silk1 which was immersed in a solution of nitro-muriate of gold in water1 and dried in the air1 was exposed to sulphurated hydrogen gas3 the silk got a slight tinge of brown2 but no other change occurred3 it was then wetted with alcohol1 and after some time1 the brown became more intense2 and white films appeared on some parts of the silk1 owing to moisture collected from the gas1 which is always replete with water4 ,another bit of silk was dipped in the same solution of gold1 and exposed1 while wet1 to the gas3 the yellow colour1 which the solution of gold gave the silk1 was immediately changed to a brown2 and a white metallic pellicle appeared1 and covered the whole surface of the silk opposed to the gas2 but no purple1 or other colours1 that usually attend the reduction of this metal by other agents1 could be perceived4 ,this pellicle did not entirely disappear1 as the silk became dry2 though it lost most of its lustre1 and looked more like silver1 or some other white metal imperfectly reduced1 than gold4 ,this elastic fluid1 and alkaline sulphure1 have an effect on the reduction of gold1 very different from that of the vapour of sulphur1 obtained from a burning match1 which further appears from the following experiment1 made with sulphurated hydrogen gas1 that happened to be mixed with some sulphurous acid gas4 ,,exp4 #b4 ,,gold4 ,a piece of silk1 which was dipped in a solution of gold in ether1 and dried in the air1 was exposed to a current of sulphurated hydrogen gas1 containing some sulphurous acid gas2 but no signs of reduction could be perceived3 the silk was then wetted with alcohol2 still no visible change was produced1 except a brown stain1 where the alcohol most abounded3 this stain1 after some minutes exposure to atmospheric air1 was covered with a white metallic film1 which soon disappeared3 after some minutes1 the silk was wetted with water1 and exposed again to the gas2 a white metallic film immediately appeared1 and the brown stain began to change slowly to a purple2 the silk was soon covered with various colours1 as blue1 red1 and orange2 and some spots of reduced gold of its own proper colour appeared3 after some time the white film1 and all the colours1 except the purple1 disappeared3 some specks of the perfectly reduced gold were permanent4 ,another bit of silk1 which was immersed in an aqueous solution of gold1 and exposed to the same mixed gas1 exhibited nearly the same appearances4 ,,exp4 #c4 ,,gold4 ,having found that sulphurated hydrogen gas had a powerful effect in reducing other metals1 ,i was desirous of trying its effects on a larger scale1 thinking it might be attended with more success3 ,i therefore immersed a quarter of a yard of silk in an aqueous solution of gold1 and exposed it1 while wet1 to this gas in close vessels3 the silk was soon covered with a white metallic pellicle1 which disappeared in a short time3 the experiment was continued about twelve hours1 and1 on withdrawing the silk from the gas1 ,i could not perceive the smallest vestige of reduced metal1 or purple1 or other colours1 that constantly attend the reduction of gold4 ,the silk had a dull brown hue verging on a slate colour4 ,,exp4 #d4 ,,silver4 ,a piece of silk1 which was immersed in a solution of nitrate of silver in water1 and dried in the air1 was exposed to a current of sulphurated hydrogen gas2 but no change could be perceived for some time2 at length1 when the silk collected moisture from the gas1 some particles of reduced silver were visible1 accompanied by a brown stain4 ,another piece of silk was dipped in the same solution of nitrate of silver1 and exposed1 while wet1 to the gas3 the silver was instantly reduced all over the side of the silk opposed to the current3 a great variety of beautiful colours1 as red1 orange1 yellow1 green1 and blue1 attended the reduction3 most of these disappeared2 but part of the silver remained permanently reduced4 ,i found1 that1 if the silk be immersed in a solution of silver in alcohol1 and dried1 and then moistened with water1 and exposed1 while wet1 to the gas1 none of these colours appear4 ,this experiment was repeated on a quarter of a yard of silk in close vessels1 and immediately both sides of the silk were covered with reduced silver1 attended with the same beautiful colours3 the silk was left exposed to the gas seven or eight hours2 and being then examined1 no reduced silver could be seen3 nothing remained1 but a strange medley of colours1 chiefly blue1 green1 purple1 and orange1 unequally mixed1 some prevailing more than others in certain parts of the silk3 however the die is by no means disagreeable4 ,,exp4 #e4 ,,silver4 ,a piece of silk1 which was immersed in a solution of fused nitrate of silver in alcohol1 and dried in the air1 was exposed to a current of the gas2 but no change could be perceived for some time3 it was then wetted with alcohol1 still no alteration could be observed1 till the silk attracted moisture from the gas1 when small particles of reduced silver began to appear1 attended with a brown stain4 ,if the silk immersed in the solution of silver in alcohol1 and exposed while wet to the gas1 be kept constantly wet with alcohol1 these appearances take place sooner4 ,a piece of silk1 which was dipped in a solution of muriate of silver in ammonia1 and exposed1 while wet1 to the gas1 had in a short time its surface covered with reduced silver3 but another piece of silk dipped in the same solution of silver1 and dried1 underwent no such change4 ,,exp4 #f4 ,,platina4 ,a bit of silk1 which was dipped in a solution of nitro-muriate of the ore of platina in distilled water1 and dried in the air1 was exposed to a current of sulphurated hydrogen gas2 but underwent no perceptible change4 ,another bit of silk was immersed in the same solution of platina1 and exposed1 while wet1 to the gas2 the whole surface of the silk1 opposed to the current1 was instantly covered with reduced platina1 which soon lost its lustre2 nothing remaining but a brown colour1 with some faint vestiges of the reduced metal4 ,this experiment was repeated on a bit of linen with the same result4 ,,exp4 #g4 ,,mercury4 ,a bit of silk1 which was dipped in a solution of oxygenated muriate of mercury in distilled water1 and dried in the air1 was exposed to a current of the gas2 the only visible change produced was a slight shade of yellow on part of the silk4 ,another bit of silk was immersed in the same solution of mercury1 and exposed1 while wet1 to the gas3 the mercury was immediately reduced2 but soon lost its lustre3 the gas reacting changed most of it to a substance of a dull white colour4 ,the same experiments were made with nitrate of mercury1 with the same result4 ,,exp4 #h4 ,,copper4 ,a bit of silk was immersed in a solution of sulphate of copper in distilled water1 and suspended in the air to dry2 it was then exposed to a current of the gas3 the silk assumed a brown colour2 but no other change appeared4 ,another bit of silk was dipped in the same solution of copper1 and exposed1 while wet1 to the gas3 a white metallic film1 attended with a brown stain1 immediately appeared3 some parts had a yellow film approaching to the colour of copper3 these films all disappeared1 leaving behind a brown stain3 the parts1 which were covered with the yellow film1 resembling copper1 exhibited1 after some time1 a dull bluish disagreeable matter4 ,,exp4 #i4 ,,lead4 ,having dipped a piece of silk in a solution of acetite of lead in distilled water1 and dried it in the air1 ,i exposed it to a stream of the gas3 the silk became a little brown2 but no other change could be observed4 ,another bit of silk was immersed in the same solution of lead1 and exposed while wet to the gas2 no sooner did it touch the silk1 than a brown tinge diffused itself1 like a passing shadow1 over the whole surface of the silk1 accompanied with a bright coat of reduced lead1 which resembled silver4 ,the brown tinge1 which the silk acquires1 resembles what happens when white paper is slightly singed by holding it near a burning body4 ,this experiment was repeated on a quarter of a yard of silk in close vessels2 and the silk was immediately covered with a coat of reduced lead1 which had the brilliance of silver1 and was attended with a brown tinge3 the experiment was continued several hours1 after which the silk was examined1 and found to have lost all the argentine lustre1 which was succeeded by a sparkling gray die3 a sulphure of lead1 or galena1 being formed in the fibres of the silk4 ,the same experiment was repeated on two other pieces of silk with the same result4 ,this elastic fluid is so powerful a reducer of the metals1 that if chambers1 painted with white lead1 have any considerable degree of moisture1 and are exposed to its influence1 the lead on the surface of the walls is reduced1 and that chiefly where the humidity is most abundant3 this effect1 ,i observed1 was produced1 even at the distance of three chambers from the place1 where the gas was formed3 and the lead was reduced most evidently behind the window-shutters where the moisture of the wall was most considerable4 ,it is a common experiment with chymists1 in order to show the effects of this gas1 to draw characters with a solution of sugar of lead on paper1 which they place over a glass of water1 containing some alkaline sulphure3 in some time the characters drawn on the paper acquire a brown1 or black colour1 and become visible2 which amuses the spectators4 ,but it is surprising1 that the metal has never been reduced in this experiment even by chance2 and not less so1 why lead should be singled out for this trial of skill1 in preference to other metals1 which are equally affected by this gas4 ,,exp4 #aj4 ,,tin4 ,a piece of silk was dipped in a solution of muriate of tin in distilled water1 and dried in the air2 the silk1 on exposure to a current of the gas1 scarce underwent any change1 except a few brown specks dispersed over its surface4 ,another bit of silk was immersed in the same solution of tin1 and exposed1 while wet1 to the gas1 which no sooner touched the silk1 than the surface opposed to the current was covered with reduced tin of great brightness3 in some time various colours1 as blue1 orange1 and a faint purple1 appeared1 and became more evident1 as the reduction proceeded4 ,the gas does not react on this metal so much as on mercury1 and some other metals3 part of the reduced tin remained permanent2 but most of it disappeared1 and left behind a disagreeable brown stain4 ,,exp4 #aa4 ,,arsenic4 ,a bit of silk was immersed in a solution of muriate of arsenic in distilled water1 and dried in the air2 it was then exposed to a stream of sulphurated hydrogen gas2 but no change could be observed1 except a faint tinge of citron yellow1 which appeared on some parts of the silk4 ,another bit of silk was dipped in the same solution of arsenic1 and exposed1 while wet1 to the gas3 the arsenic was instantly reduced all over the surface1 opposed to the gas1 attended with a citron yellow colour4 ,the gas soon reacted on the reduced arsenic2 and nothing remained but the yellow stain4 ,,exp4 #ab4 ,,bismuth4 ,i dissolved some bismuth in nitric acid1 and evaporated the solution to dryness2 the salt was then dissolved in distilled water1 and the solution deposited a copious white precipitate1 but retained a quantity of the metal sufficient for these experiments4 ,in this solution of bismuth a piece of silk was immersed1 and dried in the air2 it was then exposed to a stream of the gas3 and the only visible effect produced was a very faint tinge of brown4 ,another bit of silk was dipped in the same solution of bismuth1 and exposed wet to the gas3 the silk was instantly covered with a bright pellicle of reduced bismuth1 which soon lost most of its metallic lustre1 being changed by the reaction of the gas to a sulphure4 ,mr4 ,kirwan in his experiments on hepatic air1 found1 that nitrous solution of bismuth1 by mixture with a solution of hepatic air in water1 changes to a reddish brown1 and even assumes a metallic appearance4 ,he also found that nitrates of silver1 lead1 and acetite of lead1 were precipitated black4 ,,exp4 #ac4 ,,antimony4 ,a piece of silk1 which was immersed in a solution of tartarite of antimony in distilled water1 and dried in the air1 was exposed to a stream of the gas2 but suffered no visible change1 except that a few specks of yellow1 and orange appeared4 ,a bit of silk was dipped in the same solution of antimony1 and exposed1 while wet1 to the gas2 the antimony was immediately reduced to its metallic form1 attended with a deep orange colour3 in some time1 most of the metallic lustre disappeared1 a few specks only remaining permanent4 ,,exp4 #ad4 ,,iron4 ,a piece of silk was immersed in a diluted solution of sulphate of iron in distilled water1 and dried2 it was then exposed to a current of the gas2 but underwent no visible change4 ,another bit of silk was dipped in the same solution of iron1 and exposed1 while wet1 to the gas3 the silk soon began to acquire a dark colour1 which gradually increased1 and1 at length1 became black1 attended with an obscure metallic film4 ,the silk was immersed in water1 and deposited a bright metallic film on the surface of that fluid4 ,,exp4 #ae4 ,,zinc4 ,a bit of silk1 which was immersed in a diluted solution of sulphate of zinc in distilled water1 and dried in the air1 was exposed to a current of the gas2 but underwent no visible change4 ,another bit of silk was dipped in the same solution of zinc1 and exposed1 while wet1 to the gas2 but no change in the colour of the silk1 or sign of reduction could be perceived3 the silk was then immerged in a glass of clear water1 and transferred to its surface a bright metallic film of the colour of zinc4 ,when a languid stream of gas was employed in these experiments1 the films transferred to water were scarce visible4 ,,exp4 #af4 ,,zinc4 ,a piece of silk1 which was immersed in a largely diluted solution of muriate of zinc1 and dried in the air1 was exposed to a brisk current of sulphurated hydrogen gas2 but underwent no visible alteration4 ,another bit of silk was dipped in the same solution of zinc1 and exposed1 while wet1 to the same brisk current of gas2 instantly the surface of the silk1 opposed to the gas1 was covered with a bright coat of reduced zinc1 attended with faint orange1 and purple colours4 ,though the reduced zinc was quite evident2 yet ,i had the curiosity to examine its appearance on the surface of water2 ,i therefore immersed the silk in a glass of that fluid1 and a bright metallic pellicle1 which retained the texture of the silk1 as wax retains the impression of a seal1 was transferred to its surface4 ,another bit of silk1 dipped in the same solution of zinc1 and exposed for a longer time to the gas1 lost its metallic lustre1 the zinc being changed to a sulphure by the reaction of the gas4 ,these experiments on sulphate1 and muriate of zinc1 show1 that the acid1 in which the metal is dissolved1 influences the reduction in a remarkable manner4 ,it is evident from the experiments related in this chapter1 #a4 ,that water is essential to the reduction of metals by sulphurated hydrogen gas4 #b4 ,that alcohol does not promote these reductions1 without the aid of water4 #c4 ,that sulphurated hydrogen gas does not reduce the metals by giving them phlogiston2 nor by uniting with1 and separating1 their oxygen3 for were either of these opinions well founded2 metallic solutions in alcohol should be as effectually reduced by this gas1 as metallic solutions in water are4 ,when we consider1 that alkaline sulphure reduces the metals by decomposing water2 we have every reason to conclude1 that sulphurated hydrogen gas reduces them in the same manner2 since the same circumstances are necessary to both3 the hydrure of sulphur1 which constitutes the base of this gas1 attracts the oxygen of the water1 while the hydrogen of the latter unites1 in its nascent state1 with the oxygen of the metal1 and reduces it4 ,hence it follows1 that the hydrure of sulphur is oxygenated by the oxygen of the water1 while the metal is restored to its combustible state4 ,,chapter ,,vi4 ,,reduction ,,of ,,metals ,,by ,,phosphorated ,,hydrogen ,,gas4 ,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 chapters2 in this1 ,i shall briefly treat of their effects1 when combined in the form of phosphorated hydrogen gas1 which from its high degree of inflammability seemed well adapted to this purpose4 ,the spontaneous inflammation of this kind of air was known to ,m4 ,gengembre in #aghc2 and his experiments were published in ,rosier's journal for ,october #aghe4 ,mr4 ,kirwan also1 without any knowledge of ,m4 ,gengembre's experiments1 discovered the same air1 which he calls phosphoric air1 and published his experiments in the #gfth volume of the ,philosophical ,transactions for #aghf4 ,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 latter2 and may be received in glass vessels over mercury4 ,but finding it inconvenient to introduce pieces of silk prepared for these experiments over mercury in close vessels1 ,i exposed them to the gas1 as it issued from the neck of the phial in which it was prepared4 ,part of this elastic fluid is spontaneously inflammable2 but the other has not that property1 which ,m4 ,gengembre imputes to the presence of carbonic acid2 for the sake of brevity1 ,i shall design the latter by the term gas1 or phosphorated hydrogen gas2 and the former by the epithets spontaneously inflammable1 or detonating gas1 which1 ,i found1 does not burn or scorch silk wetted with metallic solutions4 ,,exp4 #a4 ,,gold4 ,a piece of silk1 which was immersed in a solution of nitro-muriate of gold in distilled water1 and suspended in the air twelve hours to dry1 was divided into three parts4 ,one of these was exposed to a stream of phosphorated hydrogen gas3 the silk became brown1 and its margins1 which happened to touch the sides of the phial1 acquired a violet tinge3 but no reduction took place4 ,another of these parts was wetted with alcohol1 and exposed to the gas2 but no signs of reduction could be perceived4 ,the remaining part was wetted with water1 and was no sooner exposed to the gas1 than the reduction commenced over the whole silk1 which was soon covered with a bright coat of reduced gold4 ,,exp4 #b4 ,,silver4 ,a piece of silk was dipped in a solution of fused nitrate of silver in alcohol1 and dried in the air3 it was then divided into three parts4 ,one of these1 in order to dissipate moisture more effectually1 was dried still better by a gentle heat1 and exposed to the gas2 the silk acquired a brownish dark colour3 but no other alteration could be perceived4 ,another of these parts1 which was also better dried by a gentle heat1 was wetted with alcohol1 and exposed to the gas3 the silk acquired a dark brown colour2 but no other change could be observed4 ,the remaining part was wetted with water1 and exposed to the gas3 the reduction commenced immediately1 and in a short time the silk was covered with reduced silver4 ,,exp4 #c4 ,,platina4 ,a piece of silk was immersed in a solution of nitro-muriate of the ore of platina in distilled water1 and dried in the air2 it was then divided into three parts4 ,one of these parts was exposed to the gas2 but suffered no visible change4 ,another of them was wetted with alcohol1 and exposed to the gas2 but underwent no perceptible change4 ,the remaining part was wetted with water1 and exposed to the gas3 in about three or four minutes1 a bright metallic film1 of great lustre1 appeared on the side of the silk1 opposed to the gas4 ,another bit of silk1 which was dipped in the same solution of platina1 and exposed1 while wet1 to the spontaneously inflammable gas1 was immediately covered with reduced platina1 which being transferred to the surface of water looked bright as silver1 and retained the impression of the silk4 ,,exp4 #d4 ,,mercury4 ,a bit of silk1 which was immersed in a solution of nitrate of mercury in distilled water1 and dried in the air1 was exposed to the gas2 but underwent no visible change4 ,another bit of silk was dipped in the same solution of mercury1 and dried3 it was then wetted with alcohol1 and exposed to the gas2 but no sign of reduction appeared4 ,another bit of silk was immersed in the same solution of mercury1 and exposed to the gas2 the metal was instantly reduced all over the silk2 a great variety of beautiful colours attending4 ,a piece of silk was dipped in a solution of oxygenated muriate of mercury in distilled water1 and dried in the air3 it was then divided into two parts4 ,one of these was exposed to the gas3 no change appearing1 it was wetted with alcohol1 and exposed again to the gas2 but still no alteration could be perceived4 ,the remaining part was wetted with water1 and was no sooner exposed to the gas1 than the mercury was reduced over the whole silk4 ,no colours attended the reduction4 ,mr4 ,kirwan introduced some precipitate per se to a small portion of phosphoric air3 the precipitate soon grew black2 and a white smoke appeared2 in two days the precipitate remained solid2 yet acquired a pale white colour1 like that of steel3 the air lost its spontaneous inflammability#ag4 ,,exp4 #e4 ,,copper4 ,a piece of silk1 which was immersed in a solution of sulphate of copper in distilled water1 and dried in the air1 was divided into two parts4 ,one of these was exposed to the gas2 but no visible change occurred4 ,the remaining part was wetted with water1 and exposed to the gas3 in a few minutes a brownish matter appeared in the silk2 but nothing metallic could be seen3 the silk was then dipped in a glass of clear water1 and transferred a small white metallic pellicle to its surface4 ,in another experiment1 made with the spontaneously inflammable gas1 a white metallic pellicle was immediately formed1 attended with a brown stain2 this pellicle resembled silver1 or a white metal3 but the gas soon reacted on it1 and formed a disagreeable brown matter in the fibres of the silk4 ,,exp4 #f4 ,,lead4 ,a bit of silk1 which was dipped in a solution of acetite of lead in distilled water1 and dried in the air1 was exposed to the gas2 but suffered no visible change4 ,another bit of silk was immersed in the same solution of lead1 and exposed1 while wet1 to the gas2 but nothing metallic could be seen3 the silk1 however1 on immersion in water1 transferred a few minute bright films to the surface of that fluid4 ,in another experiment1 made with the detonating gas1 the reduced films were more evident4 ,,exp4 #g4 ,,tin4 ,a bit of silk1 which was dipped in a solution of muriate of tin in distilled water1 and dried in the air1 was exposed to the action of the gas1 without suffering any visible alteration4 ,another piece of silk was immersed in the same solution of tin1 and exposed1 while wet1 to the gas2 but no signs of reduction could be perceived3 the silk was then immersed in water1 and transferred a delicate metallic film to its surface4 ,,exp4 #h4 ,,arsenic4 ,a bit of silk1 which was immersed in a solution of muriate of arsenic in distilled water1 and dried in the air1 was exposed to the gas2 but no change could be perceived4 ,another bit of silk1 immersed in the same solution of arsenic1 and exposed1 while wet1 to the gas1 acquired in a few minutes a brown stain2 but nothing metallic could be seen on the silk2 which1 however1 on being dipped in water1 transferred a very minute film of reduced arsenic to its surface4 ,in another experiment1 made with the detonating gas1 the films of reduced arsenic were much more evident1 of greater brilliance1 and attended with a brown stain produced in the fibres of the silk4 ,,exp4 #i4 ,,bismuth4 ,a piece of silk1 which was dipped in a solution of nitrate of bismuth in distilled water1 and dried in the air1 was exposed to the gas2 but no alteration could be observed4 ,another bit of silk was immersed in the same solution of bismuth1 and exposed1 while wet1 to the gas3 the silk in two or three minutes got a brown stain1 which gradually became more intense2 and a very delicate metallic film appeared3 the silk was then immerged in water1 and transferred a bright film of reduced bismuth to the surface of that fluid3 the film retained the impression of the silk4 ,,exp4 #aj4 ,,antimony4 ,a bit of silk1 immersed in a solution of tartarite of antimony in distilled water1 and dried in the air1 was exposed to the gas2 but suffered no apparent change4 ,another piece of silk was dipped in the same solution of antimony1 and exposed1 while wet1 to the gas2 but no signs of reduction appeared3 the silk was then immerged in water1 to the surface of which1 it transferred one small spangle4 ,this experiment was repeated with the detonating gas1 which with difficulty produced some sparkling films3 the silk was immersed in water1 and transferred the films to its surface4 ,a white matter was visible in the fibres of the silk4 ,,exp4 #aa4 ,,cobalt4 ,a piece of silk1 immersed in a solution of muriate of cobalt1 and dried in the air1 was exposed to the gas2 but suffered no visible alteration4 ,another bit of silk was dipped in the same solution of cobalt1 and exposed1 while wet1 to the gas3 but no sign of reduction appeared2 nor did the silk transfer a film to water4 ,another bit of silk was immersed in a solution of nitrate of cobalt1 and exposed1 while wet1 to the detonating gas3 no signs of reduction were visible for some time2 but at length a few small spangles of the metal appeared on the silk1 and were very brilliant1 and when transferred to water1 were still more so3 a white matter could be seen in the fibres of the silk4 ,,exp4 #ab4 ,,iron4 ,a bit of silk was immersed in a largely diluted solution of sulphate of iron in distilled water1 and dried3 it was then exposed to the action of the gas2 but no alteration could be perceived4 ,another bit of silk was dipped in the same solution of iron1 and exposed1 while wet1 to the gas3 in a few minutes some parts of the silk acquired a light brown colour2 but no reduced iron could be seen on the silk1 which however transferred a very minute1 and delicate film to water4 ,this experiment was repeated with a strong detonating gas1 and a very brilliant metallic film about four lines in diameter was reduced on the silk accompanied with a brown stain3 but nothing like the black oxid of iron appeared4 ,,exp4 #ac4 ,,zinc4 ,a bit of silk1 which was immersed in a largely diluted solution of muriate of zinc1 was exposed dry to the gas2 but underwent no visible alteration4 ,another piece of silk was dipped in the same solution of zinc1 and exposed wet to the gas2 no signs of reduction appearing1 the silk was immerged in water1 and left a very minute metallic film on its surface1 which could with difficulty be seen4 ,the experiment was repeated with the detonating gas1 and a very bright metallic film of zinc1 four or five lines in diameter1 was reduced on the silk4 ,this experiment succeeded also with a largely diluted solution of sulphate of zinc4 ,the silk1 viewed by transmitted light1 exhibited a brown stain beneath these films of iron and zinc4 ,the experiments detailed in this chapter show1 #a4 ,that water is essential to the reduction of metals by phosphorated hydrogen gas4 #b4 ,that alcohol does not promote these reductions1 without the aid of water4 #c4 ,that this elastic fluid does not reduce metals by giving them phlogiston2 nor by combining with1 and separating1 their oxygen2 for were either of these suppositions true1 it should reduce them as well with alcohol1 as with water4 ,after explaining the manner1 in which sulphurated hydrogen gas reduces the metals2 the mode of agency of phosphorated hydrogen gas is sufficiently obvious4 ,the gas attracts the oxygen of the water1 while the hydrogen of the latter unites1 in its nascent state1 with the oxygen of the metal1 and reduces it4 ,hence it follows1 that the hydrure of phosphorus1 which constitutes the base of this gas1 is oxygenated by the oxygen of the water1 while the metal is1 at the same time1 restored to its combustible state4 ,by hydrure of phosphorus is meant1 a combination of hydrogen and phosphorus1 containing less caloric1 than is necessary to the gazeous state4 ,,chapter ,,vii4 ,,reduction ,,of ,,metals ,,by ,,charcoal4 ,finding several combustible bodies1 as hydrogen1 phosphorus1 sulphur1 and combinations of these1 capable of reducing the metals in the ordinary temperature of the atmosphere2 ,i was desirous of knowing1 if ,charcoal also possessed that power4 ,charcoal may be applied with this view in several forms4 ,m4 ,rouelle has observed that caustic fixed alkali dissolves a considerable quantity of this substance4 ,charcoal also exists in a very attenuated state in ether1 alcohol1 gum1 c4 ,i have examined some of its effects on the reduction of metals1 in these different forms1 in which it probably exists combined with hydrogen1 and also some of its effects in the solid form4 ,,exp4 #a4 ,,gold4 ,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 water3 some air bubbles soon appeared on the charcoal3 and in about two hours reduced gold was evident on its lower surface1 and increased gradually1 till the charcoal was nearly coated with gold of its proper colour4 ,this experiment was repeated with a richer solution of gold2 the reduction did not commence near so soon1 nor was the quantity reduced so great1 or brilliant1 as in the preceding experiment4 ,,exp4 #b4 ,,gold4 ,a small bit of charcoal was suspended in a solution of gold in ether3 an effervescence immediately commenced1 and continued for a considerable time3 but the solution suffered no change of colour2 nor was there a particle of the gold reduced4 ,i should not be surprised1 if the gold were reduced in this experiment1 as charcoal contains a large quantity of water1 which it powerfully attracts from the surrounding air3 however not a vestige of reduced gold could be perceived4 ,bits of charcoal were suspended in the same manner in most of the metallic solutions treated of in this essay3 no change was perceived on those immersed in solutions of arsenic1 manganese1 and fused nitrate of silver in water3 but a bit immersed in a solution of the same nitrate in alcohol1 had parts of it covered with bright sparkling particles1 which seemed to vegetate from the charcoal1 and were evidently reduced silver3 for they were not soluble in water1 on the surface of which the bit of charcoal deposited some small spangles of great lustre4 ,the bits immersed in solutions of sulphate of iron and zinc exhibited some very faint signs of reduction4 ,but these experiments were not repeated1 nor sufficiently varied1 to enable us to form a just opinion of the power of charcoal in reducing metals in this way4 ,a small quantity of charcoal1 reduced to fine powder1 was digested several days in a strong solution of caustic potash in alcohol2 the phial was frequently shaken to promote the solution4 ,some of the clear solution1 which was of a reddish colour1 was poured into a phial for use4 ,,exp4 #c4 ,,gold4 ,a few drops of this solution of charcoal1 or carbone1 were applied to a bit of silk2 after the alcohol evaporated1 a solution of gold in ether was dropped on1 and immediately produced a brown1 which1 in about half an hour1 was changed to a purple hue1 owing to water attracted from the air2 but no other sign of reduction appeared4 ,another bit of silk was immersed in the solution of carbone1 and when the alcohol evaporated1 a few drops of an aqueous solution of gold were applied2 a brown stain was instantly formed2 the silk was kept wet with water2 the stain gradually assumed a purple tinge1 and1 in about five minutes1 some reduced gold of its proper splendour1 and colour1 appeared3 and in some time after every part of the silk1 to which the solutions of carbone and gold were applied1 was coated with reduced gold1 which remained permanent4 ,during the experiment1 it is necessary to keep the silk constantly wet with water4 ,if the solution of gold be applied before the alcohol evaporates1 a black precipitate is formed1 along with the brown stain4 ,in an experiment made in this manner1 a metallic film1 whitish1 and obscure1 appeared in the beginning2 but soon vanished3 and in some time after the gold was reduced of its proper colour2 and a speck of ruby red appeared on the margin4 ,the silk viewed by transmitted light presented various colours1 as purple1 blue1 and some green4 ,,exp4 #d4 ,,silver4 ,a few drops of the solution of carbone were applied to a bit of silk2 when the alcohol evaporated1 a solution of fused nitrate of silver in alcohol was applied3 a light brown stain was immediately produced in the silk2 but no reduced silver could be seen4 ,the solution of carbone was applied to another bit of silk1 and when the alcohol evaporated1 an aqueous solution of fused nitrate of silver was dropped on3 a brown stain was instantly formed1 and1 in about ten minutes1 minute films of reduced silver were visible4 ,the silk was kept wet with water during the experiment2 and the brown stain was gradually changed to black4 ,in some little time the metallic films disappeared4 ,if the solution of silver be applied to the silk1 before the alcohol evaporates1 black and brown precipitates are immediately formed2 and commonly no reduced silver can be seen2 but sometimes very minute films appear4 ,,exp4 #e4 ,,platina4 ,to a bit of silk1 which was immersed in a solution of nitro-muriate of platina in distilled water1 and dried in the air1 a few drops of the solution of carbone were applied2 but no visible change was produced4 ,another bit of silk was dipped in the solution of carbone1 and when the alcohol evaporated1 a few drops of the solution of platina were applied3 a yellow precipitate was immediately formed1 and1 in about ten minutes delicate films of reduced platina were visible3 these metallic films soon vanished2 and nothing but a yellow stain and the precipitate remained4 ,a bit of calico1 on which this experiment was repeated1 transferred a bright film of reduced platina to the surface of water4 ,during the experiments1 the silk and calico were kept wet with water4 ,,exp4 #f4 ,,mercury4 ,on a bit of silk1 which was immersed in a solution of oxygenated muriate of mercury in distilled water1 and dried in the air1 a little of the solution of carbone was dropped2 but the silk underwent no visible change4 ,another bit of silk was dipped in the solution of carbone1 and1 when the alcohol evaporated1 a little of the same solution of mercury was applied2 a yellow precipitate was immediately formed2 and soon after small films of reduced mercury appeared on the margin of the stain4 ,this experiment was repeated with a solution of nitrate of mercury1 and the reduction of the metal was very evident on the margin of the stain1 which was black3 the precipitate on the bit of silk was of the colour of sulphur4 ,,exp4 #g4 ,,copper4 ,to a bit of calico1 which was immersed in a solution of acetite of copper in distilled water1 and dried in the air1 a few drops of the solution of carbone were applied2 but no visible change was produced4 ,on another bit of calico1 which was dipped in the same solution of copper1 some of the solution of carbone was dropped3 the calico acquired a slight tinge of brown2 it was kept wet with water2 and1 in about twenty minutes1 several white metallic films were evident4 ,a bit of silk1 on which this experiment was made1 acquired a beautiful red colour1 similar to the ruby red1 with which copper tinges glass1 and depending on the same cause1 viz4 the quantity of oxygen combined with the metal4 ,,exp4 #h4 ,,lead4 ,a bit of white calico was immersed in a solution of acetite of lead in distilled water1 and dried in the air3 then a few drops of the solution of carbone were applied2 but no visible alteration took place4 ,on another bit of the same calico1 which was dipped in the solution of carbone1 a little of the same solution of lead was dropped2 and in a few seconds films of reduced lead1 bright as silver1 appeared3 the calico was then immerged in water1 and transferred a continuous pellicle of reduced lead to its surface4 ,this experiment was often repeated both on silk1 and calico3 sometimes the lead is reduced in an instant2 but at other times five or six seconds elapse1 before any reduced lead becomes visible4 ,i also found1 that a solution of potash in alcohol reduces lead2 but not so soon1 or effectually1 or in such quantity1 as the former solution does2 but it is evident1 that these solutions differ only in the quantity of carbone1 which they contain4 ,,exp4 #i4 ,,tin4 ,to a bit of calico1 which was immersed in a solution of muriate of tin in distilled water1 and dried in the air1 some of the solution of carbone was applied3 but no signs of reduction appeared1 nor was the colour of the calico much altered4 ,on another bit of calico1 which was dipped in the solution of carbone1 some of the same solution of tin was dropped3 a white precipitate was instantly formed1 attended with bright films of reduced tin3 the calico was immerged in water2 and left a bright metallic film on the surface of that fluid4 ,the same experiment succeeds on silk4 ,,exp4 #aj4 ,,bismuth4 ,a piece of silk1 which was immersed in a solution of nitrate of ,bismuth in distilled water1 and dried in the air1 suffered no visible alteration1 on applying the solution of carbone4 ,to a bit of calico1 which was dipped in the solution of carbone1 a few drops of the same solution of bismuth were applied2 and immediately films of reduced bismuth were evident4 ,the calico was immerged in water1 and transferred a bright metallic film to its surface4 ,this experiment succeeded also on silk4 ,,exp4 #aa4 ,,arsenic4 ,a bit of silk was immersed in a solution of muriate of arsenic in distilled water1 and dried in the air1 then a little of the solution of carbone was dropped on the silk2 but no visible alteration took place4 ,another bit of silk was dipped in the solution of carbone1 and when the alcohol evaporated1 some drops of the same solution of arsenic were applied2 and in a short time a few minute metallic films were visible on the silk1 which1 when transferred to water1 were still more so4 ,tartarite of antimony1 treated in the same manner1 transferred a very delicate film1 scarcely visible1 to the surface of water4 ,,exp4 #ab4 ,,iron4 ,a bit of calico1 which was dipped in a largely diluted solution of sulphate of iron1 and dried in the air1 suffered no perceptible change1 on applying the solution of carbone1 except a slight tinge of brown4 ,another bit of calico was immersed in the same solution of iron1 and placed on a bit of deal board1 a few drops of the solution of carbone were then applied3 the calico was kept constantly wet with water1 and in about fifteen minutes films of reduced iron were visible3 the calico was immersed in water1 and left a bright metallic film on its surface4 ,,exp4 #ac4 ,,zinc4 ,to a bit of silk1 which was dipped in a largely diluted solution of muriate of zinc1 and dried in the air1 a few drops of the solution of carbone were applied2 but scarce any alteration of colour1 or other visible change1 occurred4 ,a piece of calico was immersed in the same solution of zinc1 and placed on a bit of thin deal board1 a few drops of the solution of carbone were then applied3 the calico was kept constantly wet with water2 and in about fifteen minutes films of reduced zinc were evident3 the calico was immerged in water1 and transferred a very bright metallic film of the colour of zinc to its surface4 ,i also reduced muriate of cobalt in this manner4 ,,exp4 #ad4 ,,manganese4 ,to a bit of silk1 which was dipped in a diluted solution of nitrate of manganese1 and dried in the air1 some drops of the solution of carbone were applied2 but nothing appeared1 except a brown stain4 ,another bit of silk was immersed in the solution of carbone1 when the alcohol evaporated1 a few drops of the same solution of manganese were applied3 a brown stain was soon produced2 the silk was kept wet with water1 and in about twenty minutes films of reduced manganese of a bluish white colour were evident on the silk4 ,this experiment did not succeed with a strong solution of nitrate of manganese4 ,the same experiment succeeds also on linen1 and calico1 both with nitrate1 and sulphate of manganese2 the reduction is attended with violet1 and purple1 colours1 such as this metal imparts to glass1 and other substances1 in which it exists combined with different proportions of oxygen3 this difference is the cause of the different colours1 which solutions of manganese assume4 ,the bright films of reduced manganese soon disappear1 the cause of which has been explained in the first chapter of this essay3 the explanation there offered is confirmed by the following facts4 8,regulus of ,manganese10 says ,mr4 ,bergman1 8when well fused generally persists in a dry place1 but sometimes undergoes spontaneous calcination1 and falls down in a brownish black powder4 8,moisture1 but particularly the access of aerial acid1 assists this operation4 ,a small piece1 put into a dry bottle1 well corked1 remained perfect for the space of six months1 but afterwards1 exposed to the open air of a chamber for two days1 contracted a browness on its surface1 together with so much friability as to crumble between the fingers4 ,the internal parts1 however1 retained an obscure metallic splendour1 which disappeared in a few hours#ah40 ,i shall now relate a few experiments made with ether1 alcohol1 and gum4 ,,exp4 #ae4 ,,gold4 ,i evaporated a solution of gold in nitro-muriatic acid to dryness1 and dissolved the salt in pure alcohol3 the solution was poured into a phial carefully dried in hot sand1 and rinced with pure alcohol3 the solution filled about of the phial1 which was carefully corked1 and though it was nine months exposed to the gray light1 no films of reduced gold appeared4 ,part of the same solution was poured into a phial1 and diluted with water2 films of reduced gold soon appeared4 ,,exp4 #af4 ,,gold4 ,a phial half filled with a solution of gold in sulphuric ether was exposed nine months to the gray light2 but no films of reduced gold were produced4 ,on a bit of silk1 which was dipped in part of the same solution of gold1 and exposed to the gray light1 and kept wet with water1 reduced gold appeared in the space of a few hours4 ,,exp4 #ag4 ,,gold4 ,i mixed an aqueous solution of gold with a solution of gum arabic in distilled water1 in such proportion1 as to prevent the solution from spreading in the silk4 ,with this solution ,i drew several stripes on a piece of silk1 and exposed it to the gray light of a chambre3 in some time the gold was reduced attended with blue1 and purple1 colours4 ,similar stripes were drawn on another piece of silk1 which1 after the stripes became sufficiently dry1 was placed over the vapour of hot water2 and in about fifteen minutes the gold was reduced in a beautiful manner4 ,this solution was applied to another bit of silk1 which1 after it became sufficiently dry1 was placed between the leaves of a blank book1 to exclude the action of light2 the gold1 after some time1 was reduced4 ,i found that small stripes1 and spots1 made with this solution1 were reduced by breathing on them for some time4 ,sugar also1 mixed with the solution of gold1 promotes the reduction2 but not so well as gum4 ,a bit of silk was dipped in a solution of nitrate of silver in distilled water1 and exposed1 while wet1 to the smoke of a common fire2 in a short time reduced silver appeared4 ,the following inferences are deducible from the experiments related in this chapter4 #a4 ,charcoal is capable of reducing the metals in the ordinary temperature of the atmosphere4 #b4 ,water is essential to the reduction of metals by charcoal3 for these experiments prove1 that the reduction cannot be effected without water4 #c4 ,charcoal does not reduce the metals by giving them phlogiston2 nor by uniting with1 and separating1 their oxygen2 for were either of these opinions true1 metallic solutions in ether1 and alcohol1 should be as effectually reduced by charcoal1 as metallic solutions in water are4 #d4 ,ether1 and alcohol do not promote the reduction of metals without the aid of water3 but when this is present in sufficient quantity1 they effect the reduction1 in the same manner1 that charcoal1 and other combustible bodies do4 ,it is evident then that charcoal reduces the metals by decomposing water2 which seems to be effected in the following manner4 ,the carbone of the charcoal attracts the oxygen of the water1 while the hydrogen of the latter unites1 in its nascent state1 with the oxygen of the metal1 and reduces it4 ,hence it follows that the carbone is oxygenated by the oxygen of the water1 and forms carbonic acid1 while the metal is restored to its combustible state4 ,this explanation is supported by the following fact3 ,m4 ,gengembre has observed1 that if charcoal be immersed in water1 and kept at a temperature of #cj degrees of the thermometer of ,m4 ,de ,reaumur1 the water is gradually decomposed1 and inflammable gas is formed#ai4 ,that charcoal effects the reduction of metals1 in high degrees of heat also1 by decomposing water1 is evident from the following observations4 ,the great force with which charcoal attracts water is a fact sufficiently established2 ,dr4 ,priestley is so convinced of this1 that he expresses himself in the following strong terms4 8,i did not know1 nor could believe the powerful attraction1 that charcoal1 or iron1 appear to have for water2 when they are intensely heated1 they will find1 and attract it in the midst of the hottest fire through any pores in the retort#bj40 ,now since water is essential to the reduction of metals in low degrees of heat2 and since that fluid is always present1 when metals are reduced by charcoal in high degrees of heat2 it is manifest1 that charcoal acts in the same manner in both these temperatures2 and since water is easily1 and instantly1 decomposed by charcoal at a red heat1 as the ,antiphlogistians themselves allow2 it clearly follows that their theory of metallic reduction is erroneous3 for since the water is instantly decomposed by the charcoal1 it is a necessary consequence1 that its carbone must unite with the oxygen of the water1 while the hydrogen of the latter unites1 in its nascent state1 with the oxygen of the metal1 and reduces it1 forming a new quantity of water equal to that decomposed3 this new quantity of water may be decomposed in its turn3 so that a thimble full of water would be sufficient to reduce any quantity of metal2 provided the water were prevented from escaping1 and time enough allowed4 ,beside this source of water1 the air of the atmosphere1 which contributes to support the fire is an inexhaustible magazine of water3 and the hotter the air is1 the more water it holds in solution2 as ,m4 ,le ,roy has demonstrated#ba4 ,moreover all metallic oxids and ores contain a large proportion of water4 ,from this view it appears1 that the manner1 in which charcoal1 and other combustible bodies1 effect the reduction of metals1 is by assisting to decompose water1 the hydrogen of which is therefore the only reducer of the metals4 ,in order to point out the difference between this opinion1 and that of the ,antiphlogistians1 ,i shall present the reader with ,m4 ,lavoisier's idea of metallic reduction4 8,it can not be doubted10 says that celebrated chymist1 8that charcoal at a red heat takes oxygen from all metallic substances3 this is a fact against which no exception can be made3 and it is the foundation of the whole theory of metallic reduction40 ,but the experiments in this essay demonstrate1 that this assertion is erroneous in every instance of metallic reduction3 for so far is it from being true1 that charcoal takes oxygen from all metallic substances1 that it never does so in one single instance2 since its carbone always unites with the oxygen of the water1 the hydrogen of which unites immediately to the oxygen of the metal1 and reduces it4 8,but this action of charcoal on oxygen10 adds ,m4 ,lavoisier1 8this property1 which it possesses of taking it from metallic subsubstances1 is not so strong in the cold1 as at a red heat1 since we are unacquainted with any metallic revivification effected by charcoal without heat#bb40 ,it is evident that this mode of reasoning is no longer of any weight2 since charcoal does reduce metals in the ordinary temperature of the atmosphere4 ,the reason charcoal is more powerful in high degrees of heat1 than other reducers of the metals1 is its great fixity in the fire1 and the immense force1 with which it attracts1 and imprisons water in its pores3 thus preventing its escape till it be decomposed by an affinity1 which is much more complex than has been hitherto imagined4 ,another reason of the superior power of charcoal in metallic reduction is1 that it forms a volatile elastic fluid with the oxygen of the water1 which flies off2 and consequently does not react on the metal1 or disturb1 or impede1 by its presence1 the action of the reducing powers3 advantages that phosphorus1 or any other combustible substance1 which forms a fixed acid1 that reacts on the metal1 can never possess4 ,,chapter ,,viii4 ,,reduction ,,of ,,metals ,,by ,,light4 ,the next substance1 ,i shall treat of1 is ,light1 which seems well adapted to illustrate the theory of metallic reduction2 as in experiments made with this substance1 water can be more effectually excluded1 than in trials with any other reducer of the metals4 ,before any decisive experiments could be made on light1 or indeed any other reducer of the metals1 it is obvious that we should first ascertain the effects of water itself in the ordinary temperature of the atmosphere3 to determine this point1 the two following experiments were made4 ,,exp4 #a4 ,,gold4 ,a piece of silk was immersed in an aqueous solution of nitro-muriate of gold1 and suspended in a phial over water3 the phial was corked1 covered with black silk1 and placed in a dark closet1 to prevent the action of light4 ,the experiment was continued from the #bjth of ,july to the #bjth of ,october1 during which time the silk was frequently observed1 and found to continue moist3 but no alteration could be perceived1 except that the yellow colour1 which the solution of gold gave the silk1 was changed to a light brown4 ,the silk was now taken out of the phial1 and a solution of phosphorus in ether applied to it3 shortly after1 a white metallic film appeared3 the silk was then kept wet with water1 and in some time1 reduced gold of its proper colour appeared4 ,,exp4 #b4 ,,silver4 ,a bit of silk1 which was dipped in an aqueous solution of nitrate of silver1 was suspended in a phial over water1 and placed in a dark closet1 from the #bjth of ,july to the #bjth of ,october1 and examined from time to time2 but no alteration could be observed2 its white colour continued pure1 and unchanged4 ,the silk was now taken out of the phial1 and the silver was immediately reduced by means of a solution of phosphorus in ether4 ,hence it appears1 that water alone has not the power of reducing metals in the ordinary temperature of the atmosphere4 ,,exp4 #c4 ,,gold4 ,on the #bdth of ,july a piece of silk was immersed in a solution of nitro-muriate of gold in water1 and dried by a gentle heat2 it was then suspended in a window1 exposed to the sunbeams1 as much as possible3 no change was perceived on it1 till the #bfth1 when the margin of the silk began to assume a purple tinge1 which increased gradually1 and on the #bith exhibited a few obscure specks of reduced gold on the side of the silk opposed to the light4 ,the purple tinge continued to increase1 and the yellow1 which the solution of gold gave the silk1 decreased gradually1 till on the #bgth of ,august the colour was a mixture of purple1 and light brown4 ,the reduction of the gold seemed to keep pace with these changes of colour1 and was very evident on some parts of the silk even in the gray light2 but much more so in sunshine3 these changes were observed till the #bjth of ,october2 the experiment was then discontinued2 and scarce any reduced gold could be seen on the side of the silk not opposed to the light4 ,that this slight reduction of the gold1 and changes of colour in the silk1 depended on water absorbed from the air of the chambre1 will appear from the following experiments4 ,,exp4 #d4 ,,gold4 ,a bit of silk1 which was dipped in the solution of gold employed in the preceding experiment1 was dried1 and suspended in a crystal phial over dry carbonate of potash3 the phial was then corked1 and further secured from external humidity by covering the cork with wax3 it was now placed in a dark closet #bd hours1 that the carbonate of potash might have sufficient time to attract all the moisture1 it could1 from the air of the phial1 before exposing it to the action of light4 ,the phial was then placed in a window1 exposed1 as much as possible1 to the solar light1 from the #bdth of ,july to the #bjth of ,october1 and carefully observed3 the same side of the silk was always opposed to the light1 and had the yellow tinge1 which the solution of gold gave1 altered to a brownish yellow3 but the other side of the silk suffered no visible change whatever2 nor could any purple tint1 or the smallest vestige of reduced gold be perceived4 ,another bit of silk1 which was immersed in the same solution of gold1 and dried by a gentle heat1 was suspended over some dry carbonate of potash1 contained in a crystal phial covered with black silk1 and placed in a dark closet1 during the same space of time1 underwent no visible change whatever4 ,both these bits of silk were now taken out of the phials1 and the gold was instantly restored to its metallic splendour by means of water and a solution of phosphorus in ether3 a proof that the nitro-muriate of gold1 in these bits of silk1 suffered no change1 during that space of time4 ,,exp4 #e4 ,,gold4 ,a piece of silk1 which was dipped in the same solution of gold1 and placed on a china plate exposed to the sunbeams1 was kept moderately wet with water during the experiment3 the first alteration observed was1 that the yellow colour of the silk began to change to a faint green1 succeeded by a purple tinge1 which in about fifteen minutes exhibited some particles of reduced gold3 soon after the threads of the silk1 which acquired this purple tint1 were gilded with gold2 and1 in about an hour1 the whole of the silk was covered with a superb coat of reduced gold1 exhibiting the texture of the silk in a beautiful manner4 ,the purple tinge1 which attended the reduction verged in some parts on red1 and in others on blue4 ,this experiment1 which is very amusing1 ,i have repeated times unnumbered3 and when the sun is powerful1 and the solution of gold properly prepared1 and of due strength1 the coat of reduced gold is so bright1 and dazzling1 as to distress the eye of the beholder4 ,i find1 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 ether4 ,the silk may be dipped in this solution1 and when the ether evaporates1 kept moderately wet with distilled water4 ,it was with this solution in ether that ,i first reduced gold in the fibres of silk1 and it was by means of the same1 ,i discovered1 that water was a necessary condition in these reductions by light4 ,,exp4 #f4 ,,gold4 ,a bit of silk1 which was dipped in a solution of nitro-muriate of gold in alcohol1 and placed on a china saucer1 exposed to the sunbeams1 was kept wet with alcohol for the space of an hour2 but no change even in the colour1 which the solution of gold gave the silk1 could be perceived4 ,the alcohol diffused the solution of gold unequally through the silk3 the rays of the sun being intercepted1 suspended the experiment3 there was no sunshine on the following day3 on the third day the silk was again exposed to the sunbeams1 and kept wet with alcohol1 which extracted a yellow tincture2 a proof that the gold in the silk suffered no degree of reduction3 the sun shone pretty strong for an hour1 or more2 and1 at length1 a faint tinge of purple1 followed by some reduced gold1 appeared4 ,the preceding experiments leave us no room to doubt1 that the purple tinge and the small quantity of reduced gold1 that appeared in this experiment1 depended on water attracted from the air1 or deposited in the silk by the alcohol during its evaporation4 ,mr4 ,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#bc4 ,mr4 ,lewis also made many experiments on the staining of marble1 and other substances with metallic solutions1 and light#bd4 ,,exp4 #g4 ,,silver4 ,a piece of silk1 which was immersed in a solution of nitrate of silver in water1 was dried by a gentle heat1 and exposed to the light of the sun as much as possible in the window of a chambre from the #bjth of ,july to the #bjth of ,october4 ,in less than an hour the silk acquired a reddish brown colour3 next day the colour became more intense1 and gradually increased1 till1 on the third day1 it bordered on black1 which increased slowly3 at length part of it became gray1 and a few minute particles of reduced silver could be distinguished3 the black tinge gradually disappeared1 and the silk was of a reddish brown colour3 the reduced silver had a gray cast4 ,the following experiments demonstrate1 that the changes of colour1 and the few particles of semireduced silver depended on water attracted from the atmosphere4 ,,exp4 #h4 ,,silver4 ,a bit of silk was immersed in part of the same solution of nitrate of silver in water1 and dried in the dark3 the silk retained its white colour3 it was then suspended over dry carbonate of potash in a crystal phial1 which was corked1 and secured from the ingress of moisture by covering the cork with wax4 ,the phial was left in a dark closet #bd hours1 that the salt might imbibe as much moisture as possible from the silk1 and air4 ,the phial was then placed in a window1 exposed1 as much as possible1 to the rays of the sun1 from the #bdth of ,july to the #bjth of ,october3 the silk scarcely suffered any visible change1 except a very faint tinge of reddish brown2 which was best seen by transmitted light2 for the silk viewed by reflected light appeared nearly white3 but that even this tinge1 slight as it was1 depended on a minute quantity of moisture1 which the carbonate of potash was unable to extract1 appears from the next experiment4 ,,exp4 #i4 ,,silver4 ,a piece of silk was dipped in a solution of fused nitrate of silver in alcohol1 and carefully dried3 it was then suspended over a quantity of concentrated sulphuric acid in a crystal phial1 which was coated with a double fold of black paper1 and gum arabic1 reaching somewhat above the level of the acid1 to prevent the light from acting on it3 the phial was corked1 and to exclude moisture more effectually1 the cork was covered with wax4 ,the phial was now placed in a dark closet #bd hours1 that the humidity of the enclosed silk and air might be attracted by the acid3 it was then placed in a window1 exposed as much as possible to the rays of the sun1 from the #aith of ,july to the #bfth of ,october3 but the silk underwent no visible change whatever3 its white colour remained pure1 and unaltered4 ,the silk1 at the end of this period1 was taken out of the phial1 and wetted with water3 a solution of phosphorus in ether was then applied to it2 and instantly the metallic splendour of the silver appeared4 ,another bit of silk1 which was immersed in a solution of nitrate of silver in water1 and dried in the dark1 was suspended over dry carbonate of potash in a phial1 and placed in a dark closet about two months2 the silk underwent no visible alteration whatever2 its white colour remained pure4 ,i was desirous of knowing1 if the nitrate of silver in this bit of silk suffered any change1 that might render it incapable of reduction3 ,i therefore took it out of the phial1 and divided it into two parts3 one of these was wetted with water1 and the silver was instantly reduced by a solution of phosphorus in ether4 ,the other part1 which was suspended in a window1 exposed to the air of the chamber1 and rays of the sun1 soon acquired a reddish brown colour4 ,hence it is evident1 that these changes of colour indicate partial reductions of the metal2 and that they never happen without the presence of water4 ,,exp4 #aj4 ,,silver4 ,a bit of silk1 which was dipped in a solution of nitrate of silver in water1 was placed on a ,china saucer1 exposed to the rays of the sun1 and kept moderately wet with water3 in a few minutes the white colour of the silk was changed to a reddish brown1 which by degrees became darker2 and1 in about three or four hours1 though the solar rays were often languid1 and intercepted1 acquired a blackish gray colour1 most of the reddish brown having disappeared3 next day there was no sunshine2 but towards the evening particles of reduced silver were visible on the side of the silk opposed to the light4 ,,exp4 #aa4 ,,silver4 ,a bit of silk1 which was immersed in a solution of nitrate of silver in alcohol1 and exposed to the beams of the sun1 as in the preceding experiment1 was kept moderately wet with alcohol2 but resisted the action of the light much longer than the preceding3 however1 in some time1 specks1 and lines1 of a reddish brown1 began to appear on some parts of the silk3 next day1 though there was no sunshine1 the reddish brown colour increased a little3 on the third day1 it became more intense2 but no black1 or gray colour1 or particle of reduced silver1 could be observed4 ,whoever compares this with the preceding experiments1 can have no doubt that the changes of colour1 which appeared in this experiment1 depended on water attracted from the air1 or deposited in the silk by the alcohol during its evaporation4 ,the experiments detailed in this ,chapter1 prove beyond the power of contradiction1 #a4 ,that water is essential to the reduction of metals by light3 for these experiments demonstrate1 that the reduction can not take place without water1 and that it is always in proportion to the quantity of that fluid present4 #b4 ,that light does not reduce metals by giving them phlogiston1 as ,messrs4 ,macquer and ,scheele supposed2 for were this opinion true1 light should reduce them without the aid of water1 and as well with alcohol as with water4 #c4 ,light does not reduce metals by fusing and expelling their oxygen1 as the antiphlogistians imagine2 for were this its mode of agency1 the reduction should happen without the assistance of water1 and as well with alcohol as with water4 #d4 ,light is a combustible body2 for it acts like hydrogen1 phosphorus1 sulphur1 and charcoal1 in the reduction of metals4 ,since water then is essential to the reduction of metals by light1 and since light does not reduce metals by giving them phlogiston1 nor by fusing1 and expelling their oxygen1 it follows1 that the water is either decomposed1 or that it unites with metallic earths1 and constitutes their phlogiston1 or that it unites with1 and separates their oxygenous principle3 but as the two last suppositions are inadmissible1 it is obvious that light reduces the metals by decomposing water4 ,after explaining the manner in which other combustible bodies reduce the metals by decomposing water2 it will not be difficult to explain how light too produces the same effect4 ,but in order to facilitate the explanation1 it must be premised1 #a4 ,that it is a law of attraction1 that1 when any body is deprived1 to a certain degree1 of another1 for which it has a strong affinity1 the attraction of the former for the latter is much increased4 #b4 ,that light has a strong attraction for oxygen1 or the base of vital air4 #c4 ,that when oxygen is condensed1 and fixed in any substance1 it contains much less light1 and caloric1 than it does in the gazeous state4 #d4 ,that the oxygenous principle exists in water in this condensed state1 and consequently has a strong attraction for light4 ,therefore1 when light reduces the metals1 it attracts the oxygen of the water1 while the hydrogen of the latter unites1 in its nascent state1 to the oxygen of the metal1 and reduces it1 forming at the same time a quantity of water equal to that decomposed4 ,hence it follows that the light is oxygenated1 and changed into vital air1 while the metal is restored to its combustible state4 ,,chapter ,,ix4 ,,reduction ,,of ,,metals ,,by ,,acids4 ,it is well known that solutions of gold throw up films of the reduced metal to the surface of the fluid1 and sides of the phials that contain them4 ,it has been shown1 chap4 #gth1 that this effect depends on the presence of water1 which is further illustrated by the following experiments4 ,,exp4 #a4 ,,silver4 ,a dram of saturated solution of nitrate of silver in distilled water was mixed with half an ounce of vinegar1 in a few minutes1 a precipitate was formed3 the whole was then poured on a filter1 and washed with distilled water3 the precipitate acquired a bluish gray metallic appearance3 the liquor1 which passed the filter1 got a brown colour1 and became blackish3 next day bright films of reduced silver floated on the liquor2 and in some months after1 a considerable part of the inner surface of the phial was coated with reduced silver4 ,distilled vinegar did not produce this effect4 ,,exp4 #b4 ,,platina4 ,if a solution of the ore of platina in nitro-muriatic acid be evaporated to dryness2 and the salt dissolved in water1 films of a livid white metallic appearance are thrown up to the surface4 ,,exp4 #c4 ,,tin4 ,some tin1 which was dissolved in a china cup in muriatic acid1 and evaporated to dryness1 was dissolved in distilled water2 immediately white metallic films appeared on the surface of the liquor2 and after some hours1 the whole surface of the solution was covered with a continuous metallic pellicle1 which reflected all the colours of the rainbow1 in a beautiful manner4 ,,exp4 #d4 ,,mercury4 ,mr4 ,bergman says1 8calcined mercury is reduced by digestion in acid of salt2 but the cause has not yet been sufficiently explored#be40 ,as this reduction of mercury by muriatic acid is doubted of by some2 ,i made the following experiment4 ,a quantity of precipitate per se was put into a china cup1 placed on hot sand1 and some muriatic acid was poured on it3 the oxid was gradually dissolved1 and the digestion continued1 till the acid was nearly evaporated3 some distilled water was then poured on the salt1 and minute films of a bright metallic appearance floated on the surface4 ,a nitrate of mercury was evaporated to dryness2 the salt acquired a slight tinge of yellow2 the cup was removed from the hot sand1 and some water poured on the salt3 immediately bright films of reduced mercury appeared2 and in about three or four hours the whole surface of the solution was covered with a metallic pellicle1 parts of which had the colour and splendour of the metal2 and other parts reflected a wonderful variety of the most beautiful colours4 ,,exp4 #e4 ,,arsenic4 ,a quantity of white oxid of arsenic and muriatic acid was digested in the same manner in a china cup2 a smart heat was continued1 till most of the acid evaporated1 and left behind a mass of the consistence of tar3 the surface of which had a gray appearance2 after it cooled1 some distilled water was poured on1 it diffused a disagreeable smell1 and films of reduced arsenic were thrown up to the surface2 these were for some time remarkably bright1 but soon became of a dull gray colour1 owing to the rapid tendency of this metal to spontaneous calcination4 ,,exp4 #f4 ,,manganese4 ,some concentrated sulphuric acid was poured on a quantity of the black oxid of manganese in a china cup1 placed on hot sand3 an effervescence was visible1 but no sulphurous acid gas was exhaled3 the cup was removed from the sand1 before any perceptible quantity of the acid evaporated3 then some water was poured on the mixture3 and instantly the surface of the fluid was covered with very brilliant metallic films3 and1 at the same time1 the solution acquired a rose colour4 ,some of the same oxid of manganese was dissolved in nitric acid1 in which a bit of sugar was put3 the solution was poured into a china cup1 placed on hot sand1 and1 as the evaporation proceeded1 bright metallic films appeared on the surface4 ,mr4 ,bindheim of ,moscow relates1 that he reduced the arated calx of manganese dissolved in nitrous acid3 8the solution was placed upon an open fire in a glass retort#bf40 ,happening to pour out a very largely diluted solution of sulphate of iron1 ,i was surprised to find the flags of the court in an hour or two after1 covered with large films of a livid white metallic aspect3 these films1 after the water evaporated1 remained on the flags several days4 ,in consequence of this ,i poured a largely diluted solution of sulphate of iron into several shallow vessels1 and always found the surface of the solution covered with abundance of bright metallic films4 ,i also found that a largely diluted solution of muriate of zinc throws up bright metallic films to the surface4 ,the reduction of metals by acids is a very convincing proof of the decomposition of water1 and seems inexplicable on any other principle4 ,the reduction and calcination of metals by heat and electricity are naturally explained on the same principle3 ,doctor ,priestley informs us in his ,history of ,electricity1 ,vol4 ,i4 p4 #cdd1 that ,s4 ,beccaria revived several of the metals by the electric shock4 ,it is obvious that the electric fluid produces this effect in the same manner1 that other combustible bodies do1 viz4 by decomposing water4 ,when the red oxid of mercury is reduced in close vessels by heat2 the latter attracts the oxygen of the water1 contained both in the oxid1 and in the air of the vessels1 while the hydrogen of the water unites to the oxygen of the mercury1 reduces it1 and forms a quantity of water equal to that decomposed4 ,it is found1 that if light and caloric act both at the same time1 the reduction is effected with more facility1 than if either acted separately3 in this case1 the superior efficacy of the combined action of light1 and caloric resembles that of other compound reducers of the metals2 as that of sulphurated hydrogen gas1 phosphorated hydrogen gas1 alkaline sulphure1 c4 which are more powerful than simple hydrogen gas1 sulphur1 or phosphorus4 ,this superior efficacy of compound reducers1 is similar to what happens with some other combinations of combustible bodies1 as pyrites1 pyrophori1 a mixture of lead and tin1 c4 which have a more powerful attraction for oxygen1 than any of their ingredients1 in a separate state4 ,other acids1 as the gallic1 the tartarous1 the formic1 c4 and also alkalis1 as ammonia1 and soda1 have the power of reducing some of the metals1 facts well known to chymists4 ,,chapter ,x4 ,,oxygenation ,,of ,,combustible ,,bodies4 ,it has been shown1 in the preceding chapters1 that water is essential to the reduction of metals2 that it is always decomposed in that process2 and that the reducing substances are oxygenated by the oxygen of the water1 while the hydrogen of the latter reduces the metals4 ,that water is also decomposed in every instance of oxygenation1 and that the oxygen of water alone oxygenates combustible bodies1 will appear from the following observations4 ,,azote4 ,the first case of oxygenation1 we shall consider1 is that of azote1 in an experiment of ,dr4 ,priestley1 which has been urged by ,mr4 ,kirwan with great success against the ,antiphlogistians4 8,if the electric spark be taken in nitrous air1 it will be reduced to of its bulk1 and the residuum is mere phlogisticated air1 and a little acid is deposited4 ,now the ,antiphlogistians own that nitrous air contains both pure air and phlogisticated air2 since1 therefore1 this pure air disappears1 is it not evident that it was converted into water8 and since the formation of water requires the presence of inflammable air1 does it not follow that the nitrous air contained this also#bg80 ,to this objection ,m4 ,berthollet replies1 that the diminution of the nitrous gas 8is owing to the combination of the mercury with the oxygene1 which existed in the gas#bh40 ,but this answer is insufficient2 as it does not account for the water1 and acid1 that appeared3 and indeed1 by this experiment1 the ,antiphlogistians are refuted on their own principles1 and the decomposition of water is incontestably proved2 for as nitrous acid could not be formed without more oxygen than what existed in the nitrous air1 is it not evident1 that this oxygen must be derived from the water contained in the nitrous air8 ,it is obvious then1 that the water of the gas was decomposed2 which seems to have been effected in the following manner4 ,the electric spark diminishes the attraction of the constituent principles of the water for each other2 hence the azote of the gas unites with the oxygen of the water1 while the hydrogen of the latter combines with the oxygen of the gas2 and thus water and nitrous acid are formed4 ,the formation of nitrous acid in ,mr4 ,cavendish's noted experiment1 cannot be explained on any other principle than the decomposition of water3 when the electric spark is taken in a mixture of azotic gas1 and vital air2 the water of these airs is decomposed3 the electric flame lessens the force1 with which the oxygen and hydrogen of the water adhere2 hence the azote seizes the oxygen of the water1 and forms nitrous acid1 while the hydrogen of the water unites with the oxygen of the vital air1 and forms a quantity of water equal to that decomposed4 ,when nitrous1 and vital air1 are mixed2 the whole mass 8hisses1 turns red1 grows warm1 and contracts in bulk10 the azote of the nitrous air attracts the oxygen of the water1 and forms nitrous acid1 while the hydrogen of the water unites in its nascent state with the oxygen of the vital air1 and forms a quantity of water equal to that decomposed4 ,hence while the azote of the nitrous air is oxygenated2 the caloric is restored to its combustible state4 8,but it is to be observed10 says ,m4 ,bergman1 treating of this experiment1 8that the decomposition of nitrous air is the effect of a double attraction2 the phlogiston is attracted by the vital air1 and the acid part by the water4 ,therefore1 when the mixture is made in a phial immersed in mercury1 the experiment fails#bi40 ,,hydrogen4 ,the combustion of hydrogen gas with vital air is explicable only on the decomposition of the water contained in these airs3 thus when flame1 or a glowing body is applied to a mixture of them2 the attraction of the principles of the water for each other is diminished2 therefore the hydrogen of the inflammable air unites with the oxygen of the water1 while the hydrogen of the latter seizes the oxygen of the vital air3 thus the whole bulk of the airs1 which are changed into water1 disappears2 and their light1 and caloric1 are restored to the combustible state4 ,hence it appears that water is not formed during the combustion of vital1 and inflammable air1 in the manner the ,antiphlogistians suppose4 ,indeed it is obvious1 that1 if these airs contained no water1 they could never be burned3 for since they are already saturated with light1 and caloric1 they can have no attraction for any additional quantity of these fluids2 and consequently can suffer no other change from the light1 or caloric1 of a glowing body1 than a greater degree of expansion1 and therefore could never unite4 ,the same reasoning applies to the combustion of all elastic fluids4 ,,phosphorus4 ,vital air always contains a large proportion of water3 when phosphorus is burned in this air1 it attracts the oxygen of the water1 and forms phosphoric acid1 while the hydrogen of the water unites with the oxygen of the gas1 and forms water1 which unites with the acid4 ,hence the weight of the acid formed is equal to the weights of the oxygen gas1 and phosphorus1 consumed2 and the light and caloric1 which appear during the combustion1 are restored to their combustible state4 ,this explanation is confirmed by an observation of ,mr4 ,bergman1 who says1 8,in vital air1 without the aid of external heat1 phosphorus is consumed very slowly1 and scarce at all1 unless water be present#cj40 ,therefore the phosphorus does not unite to the oxygen of the vital air1 as ,m4 ,lavoisier supposes1 but to the oxygen of the water contained in the oxygen gas4 ,,sulphur4 ,when sulphur is burned in vital air1 it attracts the oxygen of the water1 and forms sulphuric acid1 while the hydrogen of the water attracts the oxygen of the gas1 and forms a quantity of water equal to that decomposed3 the light and caloric are at the same time restored to their combustible state4 ,the sulphur then does not unite with the oxygen of the vital air1 as the ,antiphlogistians imagine1 but with the oxygen of the water contained in that gas4 ,,charcoal4 ,in like manner during the combustion of charcoal in vital air1 the carbone attracts the oxygen of the water1 and forms carbonic acid1 while the hydrogen of the water unites with the oxygen of the vital air1 and forms a new quantity of water equal to that decomposed4 ,hence the carbone of the charcoal does not unite with the oxygen of the vital air1 as ,m4 ,lavoisier supposes1 but with the oxygen of the water contained in that gas4 ,that water is decomposed in every instance of combustion1 is further proved by attending to what passes during the burning of a common fire3 the carbone of the fuel combines with the oxygen of the water1 and forms carbonic acid1 while the hydrogen of the water unites partly with the oxygen1 and partly with the azote of the atmosphere1 and forms water1 and the ammonia1 which abounds in soot4 ,from these observations it is evident1 that ,m4 ,lavoisier's account of the formation of water1 and acids1 is erroneous1 and inadequate to explain the phenomena4 ,the different kinds of fermentation are so many instances of the decomposition of water3 in every case of them1 combustible bodies are oxygenated by the oxygen of the water1 while others are restored by its hydrogen to their combustible state4 ,hence the azote1 ammonia1 and carbonic acid of fermentation1 the inflammable air of marshes1 mines1 c4 the azotic1 and hydrogen gas1 ascending into the atmosphere1 and there meeting the vital air discharged from the water of plants1 c4 form new quantities of air1 and water4 ,when the azote is oxygenated1 it unites with the oxygen of the water contained in the air1 and forms atmospheric air1 and sometimes perhaps nitrous acid1 the hydrogen of the water combines1 at the same time1 with the oxygen of the vital air1 and forms a quantity of water equal to that decomposed4 ,but when the hydrogen is oxygenated1 a quantity of water double that decomposed is regenerated2 for the hydrogen of the gas unites with the oxygen of the water1 while the hydrogen of the latter seizes the oxygen of the vital air3 and thus a quantity of water double that decomposed is formed1 and that part of it which the atmosphere cannot suspend descends in the form of rain4 ,when these decompositions are rapid1 the phenomena of thunder and lightning appear4 ,this account of the renovation of our atmosphere explains why the phenomena of thunder and lightning appear sometimes with1 and sometimes without rain1 and also accounts for the production of the nitrous acid1 which ,mr4 ,margraaf discovered in the purest snow4 ,the breathing of fishes is a striking proof of the decomposition of water in respiration4 ,for this view of the formation of our atmosphere ,i am indebted to a friend well acquainted with the experiments related in this essay1 and also for the application of the opinion which ,i venture to advance1 to the respiration of animals4 ,the phenomena of vegetation cannot be explained on any other principle1 than the decomposition of water by heat1 and light1 which uniting to the oxygen of the water contained in vegetables change it into streams of vital air1 that serve to renovate our atmosphere3 the hydrogen of the water1 at the same time1 contributes to form the oil and other principles of plants1 and when these are decomposed by the various processes of combustion1 forms a quantity of water equal to that consumed in their formation4 ,the changes1 which nitric acid suffers by exposure to heat1 or light1 are explained with ease on this principle3 the light unites with the oxygen of the water contained in the nitric acid1 and forms vital air1 while the hydrogen of the water combines with the oxygen of the acid1 and forms a new quantity of water equal to that decomposed3 thus the nitric is converted into the ruddy nitrous acid4 ,,metals4 ,according to the ,antiphlogistians1 8,in every metallic solution by an acid1 the metal1 in order to become oxided1 decomposes either the acid itself1 or the water of solution1 or it obtains from the atmosphere the requisite quantity of oxygene4 ,in the second case1 hydrogenous gas1 in a state of greater or less purity is disengaged2 and the acid remains entire without decomposition1 which is proved by the quantity of alkali necessary to saturate it4 ,in the first case1 one of the principles of the acid1 or the acid deprived of part of its oxygene1 is disengaged1 and fused in the caloric1 which is separated at the same time2 such are nitrous gas1 and sulphurous acid gas4 ,in the third case1 neither the water nor the acid are changed2 such is the solution of copper by the acetous acid4 8,the muriatic acid1 and the vegetable acids1 which are formed of radicals1 or acidifiable principles1 which have more affinity with oxygene1 than the metals have1 are not decomposed by these metals1 and the oxygene is always afforded to these last by the water or atmosphere4 ,hence the solutions by these acids afford only hydrogenous gas1 or do not effervese at all4 8,there are some cases in which the water and the acid are at the same time decomposed by the metal1 as in the solution of tin in the nitric acid1 according to the observation of ,m4 ,de ,morveau40 8,tin is so greedy of oxygene1 and requires so large a quantity for its saturation1 that after having absorbed that of the nitric acid1 and reduced it to the state of azote1 it decomposes likewise the water1 and disengages hydrogene4 ,these two principles being separated from their first compounds1 unite together1 and immediately form ammoniac4 ,hence there is no disengagement of elastic fluid4 ,in this case it appears1 that the formation of ammoniac1 in the solution of tin by the nitric acid1 always takes place2 for by throwing quicklime1 or caustic fixed alkali1 into this solution1 there is always a disengagement of ammoniac#ca40 ,it is evident1 then1 that this account of the oxygenation of metals1 given by the ,antiphlogistians1 is equally complex1 as their account of metallic reduction1 and improbable2 since every case1 in which they deny the decomposition of water1 and derive the oxygen from other sources1 is easily1 and naturally explained on that principle1 as will appear from what follows4 ,thus when mercury1 or silver1 is dissolved in nitric acid2 the metal attracts the oxygen of the water1 while the hydrogen of the latter unites with1 and separates1 more or less of the oxygen of the acid1 which is thus changed into nitrous air4 ,the same thing happens during the solution of other metals in this acid2 the only difference being the greater or less energy1 and rapidity1 with which they combine with the oxygen of the water4 ,this decomposition of water is confirmed by the solution of tin in this acid2 in which the ,antiphlogistians allow the decomposition of the acid1 and the water too2 for ammonia is formed by part of the hydrogen of the water1 and azote of the acid4 ,in every case of metallic solution by sulphuric1 and muriatic acids1 whether concentrated1 or diluted1 water is decomposed3 the metals attracting the oxygen of the water1 while its hydrogen escapes in the form of inflammable air1 or unites partly with the oxygen of the acid1 and partly with caloric3 hence the volatile sulphurous acid1 and muriatic acid air1 obtained1 always contain some hydrogen gas1 as appears from the following observation of ,m4 ,bergman4 8,by means of vitriolic acid1 inflammable air is obtained from zinc1 and iron1 as also by means of marine acid2 but1 from the other metals dissolved in vitriolic acid1 we obtain another species of air1 called vitriolic acid air2 and1 by the marine acid1 another similar to the former1 called muriatic air1 but both more or less mixed with inflammable air#cb40 ,again1 when copper is dissolved in the acetous acid2 the copper attracts the oxygen of the water1 while the hydrogen of the latter unites with the oxygen of the atmosphere1 and forms water3 hence no effervescence appears4 ,when alkalies dissolve metals1 the latter are always oxygenated at the expence of the water1 which holds the alkali in solution3 thus when lead1 and copper1 are dissolved2 the metals combine with the oxygen of the water1 while its hydrogen unites to the oxygen of the atmosphere1 and forms water3 hence no hydrogen gas appears4 ,the oxygenation of metals1 and other substances by heat1 and air1 is easily explained on the same principle3 the metals1 c4 unite with the oxygen of the water contained in atmospheric air1 while the hydrogen of the water combines with the oxygen of the air1 and forms a quantity of water equal to that decomposed4 ,this explanation is clearly proved by an experiment of ,mr4 ,bergman on the regulus of manganese1 which1 if kept in a dry place1 retains its metallic splendour2 but1 if exposed to moisture1 is soon oxygenated1 and loses its lustre#cc4 ,it is further confirmed by the authority of the distinguished ,mr4 ,scheele1 who says1 that 8the water contained in common atmospheric air is the chief cause of the ignition of pyrophorus10 which he proved by the following experiment4 8,i made a very dry air by putting some very small pieces of quicklime into a small matrass3 then ,i put the neck of another matrass into that of the first1 so that the air of both might communicate2 and ,i luted the crevices with wax4 ,two days afterwards ,i separated the empty matrass1 and poured half an ounce of pyrophorus from my phial into it1 and immediately carefully shut the aperture up3 but ,i did not observe1 that it grew in the least warm3 an hour after this1 ,i put a sponge moistened in water into the matrass1 and shut it up again3 a few minutes after the pyrophorus began strongly to be heated1 and some pieces kindled spontaneously#cd40 ,many other facts might be adduced to prove1 that oxygenation cannot take place without water1 as the combustion of mixtures of iron filings1 sulphur and water1 of alkaline sulphure and water1 c4 in which the water is decomposed1 and the combustible bodies oxygenated by its oxygen4 ,it is evident then from the experiments and observations related in this essay1 that water is essential to the oxygenation of combustible bodies2 and that it is the only source of the oxygen that oxygenates them3 it is also evident1 that when one body is oxygenated1 another1 at least1 is restored to the combustible state3 hence it appears that the oxygenation of combustible bodies is never effected by a single affinity4 ,the ,antiphlogistians treating of the precipitation of metals by each other1 say1 8,since the metals cannot remain united to the acids1 but in the state of oxides of a determinate degree1 it is easily conceived1 that by plunging into a metallic solution a metal which has a stronger affinity with oxygene than that which is dissolved1 the former must deprive the latter of its oxygene1 take its place in the acid1 and cause the second to subside in a form more or less metallic1 accordingly as it has deprived it of more or less oxygene4 ,this is the reason of the precipitation of silver by copper1 copper by iron#ce10 c4 ,but this account of the precipitation of metals by one another cannot be admitted2 for it has been proved in every instance of reduction related in this essay1 that water is decomposed1 and that its hydrogen is the only substance that restores bodies to their combustible state4 ,there is no reason then to suppose that nature deviates1 in this particular case1 from that uniform simplicity1 which she constantly observes in all her operations4 ,therefore it is obvious1 that1 when one metal precipitates another in a form more or less metallic2 the precipitant unites with the oxygen of the water1 while the hydrogen of the latter combines with1 and separates1 the oxygen of the precipitated metal1 and thus reduces it4 ,the experiments made with phosphorus and metallic solutions in ether1 alcohol1 and water1 prove the truth of this explanation2 and show that when one metal precipitates another in the metallic form1 it acts like a stick of phosphorus1 decomposing the water4 ,this account of the reduction of one metal by another is supported by the opinion of ,mr4 ,bergman1 who says1 8,it is well known1 that the calx of copper1 dissolved in vitriolic acid1 is precipitated in its metallic form on the addition of iron2 and that by means of a double elective attraction2 for the iron dissolving in the acid would form an inflammable air by its phlogiston1 were not the copper present1 which takes it up#cf40 ,the same author remarks1 that a small excess of acid is necessary1 and that without it no precipitation begins4 ,now since water is decomposed by iron and sulphuric acid1 it must be allowed1 that1 when iron is immersed in a solution of sulphate of copper1 the water is decomposed by the iron and excess of acid1 the iron attracting the oxygen of the water1 while the hydrogen of the latter1 unites to the oxygen of the copper1 reduces it1 and forms a quantity of water equal to that decomposed4 ,the precipitation of silver in its metallic form by iron and other metals is to be explained in the same manner3 and not by a single affinity1 as the ,antiphlogistians imagine4 ,the reduction of gold1 and some other metals1 by solutions of sulphate of iron1 and muriate of tin1 is readily accounted for on the principles advanced here2 for fresh made solutions of sulphate of iron1 and muriate of tin1 contain hydrogen1 and have the power of decomposing water3 the oxygen of which unites with the iron1 and tin1 while its hydrogen seizes the oxygen of the gold1 c4 reduces it1 and forms a quantity of water equal to that decomposed4 ,the decomposition of water is further proved by the large dilution necessary to form the arbor ,dian1 the purple precipitate of ,cassius1 and other instances of the reduction of metals by one another4 ,,chapter ,,xi4 ,,conclusion4 ,i shall conclude with a general view of the inferences1 which ,i ventured to advance in this essay4 #a4 ,neither the ,phlogistians1 nor ,antiphlogistians1 account in a satisfactory manner for the increase of weight1 which bodies acquire during combustion4 #b4 ,their account of the formation of water1 acids1 and oxids1 is erroneous2 for it has been shown that the oxygen of water alone oxygenates combustible bodies4 #c4 ,combustible bodies1 as hydrogen1 phosphorus1 sulphur1 charcoal1 light1 c4 are capable of reducing the metals in the ordinary temperature of the atmosphere2 and indeed ,i might add1 at a much lower temperature1 as ,i frequently experienced4 #d4 ,combustible bodies do not reduce the metals by giving them phlogiston1 as the ,phlogistians suppose2 nor by uniting with1 and separating their oxygen1 as the ,antiphlogistians maintain4 #e4 ,water is essential both to the reduction and oxygenation of bodies1 and is always decomposed in these operations4 #f4 ,water does not contribute to metallic reduction merely by dissolving and minutely dividing the particles of metallic salts1 and thus removing the impediment opposed to chymical attraction by the attraction of cohesion3 for were this the case1 metallic solutions in ether and alcohol1 in which that impediment is equally removed1 should be as readily and effectually reduced1 as metallic solutions in water are4 ,this circumstance1 in which all the experiments on metallic reduction detailed in this essay exactly coincide1 merits particular attention1 and shows that the manner1 in which combustible bodies effect the reduction1 is the same in them all4 #g4 ,when one body is oxygenated1 another1 at least1 is restored at the same time to its combustible state2 and v4 v4 when one body is restored to its combustible state1 another at least is at the same time oxygenated4 #h4 ,quantities of air1 and water1 equal to those decomposed in the different species of combustion1 are constantly a forming4 ,thus nature1 by maintaining this balance of power between combustible and oxygenated bodies1 prevents the return of original chaos4 ,since then in every act of combustion1 one body1 at least1 is oxygenated1 and another restored1 at the same time1 to its combustible state1 the phenomena of combustion may be referred to two heads1 viz4 ,oxygenation1 or the union of oxygen with combustible bodies1 and ,reduction1 or the restoration of oxygenated bodies to their combustible state4 ,and since in every instance of combustion water is decomposed1 and one body oxygenated by the oxygen of the water1 while another is restored to its combustible state by the hydrogen of the same fluid1 it follows1 #a4 ,that the hydrogen of water is the only substance1 that restores bodies to their combustible state4 #b4 ,that water is the only source of the oxygen1 which oxygenates combustible bodies4 #c4 ,that no case of combustion is effected by a single affinity4 ,this view of combustion may serve to show how nature is always the same1 and maintains her equilibrium by preserving the same quantities of air and water on the surface of our globe3 for as fast as these are consumed in the various processes of combustion1 equal quantities are formed1 and rise regenerated like the ,phenix from her ashes4 ,,nomenclature of the ,chymical ,terms used in this ,essay4 ,,new ,,names4 ,,old ,,names4 ,ammonia ,caustic vol4 alkali4 ,acetite of lead ,sugar of lead4 ---------- copper ,verdirgris4 ,azote ,base of phlogisticated air4 ,azotic gas ,phlogisticated air4 ,alkaline sulphure ,liver of sulphur4 ,alcohol ,highly rectified spirit of wine4 ,carbone ,pure coal4 ,carbonic acid ,fixed air4 ,caloric ,heat4 ,hydrogen ,base of inflammable air4 ,hydrogen gas ,inflammable air4 ,hydrure of sulphur ,a compound of hydrogen and sulphur4 ---------- phosphorus ,a compound of hydrogen and phosphorus4 ,muriate of tin ,salt of ,jupiter4 ---------- silver ,luna cornea4 ---------- arsenic ,arsenic combined with muriatic acid4 ---------- zinc ,marine salt of zinc4 ---------- cobalt ,marine salt of cobalt4 ,nitric acid ,dephlogisticated nitrous acid4 ,nitro-muriatic acid ,aqua regia4 ,nitro-muriate of gold ,a compound of gold and aqua regia4 ---------------- platina ,a compound of platina and aqua regia4 ,nitrate of silver ,lunar nitre1 crystals of the moon4 ------- of mercury ,mercurial nitre4 ------- of bismuth ,nitre of bismuth4 ------- of manganese ,nitre of manganese4 ,oxygen ,base of vital air4 ,oxygen gas ,vital air4 ,oxygenated muriate of mercury ,corrosive sublimate4 ,prussiate of mercury ,a compound of mercury and prussic acid4 ,phosphorated hydrogen gas ,phosphoric air4 ,potash ,caustic vegetable alkali4 ,sulphuric ether ,vitriolic ether4 ,sulphureous acid gas ,vol4 sulphureous acid4 ,sulphurated hydrogen gas ,hepatic acid4 ,sulphate of copper ,blue vitriol4 ----------- zinc ,white ditto4 ----------- iron ,green ditto4 ----------- manganese ,vitriol of manganese4 ,soda ,caustic mineral alkali4 ,tartarite of antimony ,emetic tartar4 ,,finis4 ,,footnotes3 #a ,essay on ,phlogiston1 by ,m4 ,kirwan1 a new edition1 p4 #ba1 and #af4 #b ,experiments on ,air and ,fire4 ,eng4 trans4 p4 #agd4 #c ,essay on ,phlogiston1 a new edition1 p4 #ch-aff4 #d ,essay on ,phlogiston1 p4 #bjg4 #e ,essay on ,phlogiston1 p4 #bje4 #f ,essay on ,phlogiston1 p4 #ad4 #g ,essay on ,phlogiston1 p4 #ac-ae4 #h ,ibid4 p4 #be4 and ,philo4 ,trans4 ,vol4 #gh4 p4 #cad4 #i ,scheele1 p4 #afb1 ,french translation4 #aj ,roz4 ,journ4 ,feb4 #aghb4 #aa ,elective ,attractions1 ,english ,translation1 p4 #hg4 #ab ,m4 ,monnet ,dissolution de ,metaux1 p4 #aei4 #ac ,phil4 ,trans4 ,vol4 #gc4 ,an4 #aghc4 #ad ,essay on ,phlogiston1 a new ,edit1 by ,m4 ,kirwan1 p4 #df4 #ae ,priestley1 ,vol4 ,,vi4 p4 #aej4 #af ,chem4 ,essays1 ,vol4 ,,iii4 p4 #bai4 #ag ,m4 ,kirwan1 ,phil4 ,trans4 for #aghf4 #ah ,chem4 ,essay4 ,vol4 ,,ii4 p4 #bjf and #bjg4 ,eng4 ,trans4 #ai ,essay on ,phlogiston1 new ,ed4 by ,m4 ,kirwan1 p4 #fa4 #bj ,phil4 ,trans4 #aghe4 ,vol4 ,,lxxv4 p4 #bhi4 #ba ,el4 ,nat4 ,hist4 ,chem4 ,eng4 ,trans4 in three volumes1 p4 #afc4 ,vol4 ,i4 #bb ,ess4 on ,phlog4 a new ,ed4 by ,m4 ,kirwan1 p4 #fj4 #bc ,experiments on ,air and ,fire1 ,eng4 ,trans4 p4 #hb4 #bd ,commerce of the ,arts4 #be ,elec4 ,attrac4 ,eng4 ,tran4 p4 #bbc4 #bf ,crell's ,chem4 ,jour4 ,vol4 ,,ii4 p4 #dh4 ,eng4 ,trans4 #bg ,essay on ,phlogiston1 new ,ed4 p4 #hb4 #bh ,ibid4 p4 #abb4 #bi ,elec4 ,attr4 ,eng4 ,trans4 p4 #baa4 #cj ,el4 ,att4 ,eng4 ,trans4 p4 #bac4 #ca ,essay on ,phlog4 new ,ed4 by ,mr4 ,kirwan1 p4 #bcc-bce4 #cb ,chem4 ,ess4 ,vol4 ,,ii4 p4 #ceh4 ,eng4 ,trans4 #cc ,chem ,ess4 ,vol4 ,,ii4 p4 #bjf-bjg4 ,eng4 ,trans4 #cd ,exper4 on ,air and ,fire1 ,eng4 ,trans4 p4 #aab1 and #acj4 #ce ,ess4 on ,phlog4 new ,ed4 by ,mr4 ,kirwan1 p4 #bcf1 and #bcg4 #cf ,chem4 ,essays1 ,vol4 ,,ii4 p4 #chd1 ,eng4 ,trans4 ,,transcriber',s ,,note ,obvious punctuation errors have been corrected after careful comparison with other occurrences within the text4 ,inconsistent hyphenations have been left as is4 ,the tables in this book are best viewed using a monospace font4 ,the original book used the character 7long-form s74 ,this has been changed to the modern s in this e,book4 ,footnotes have been renumbered consecutively and moved to the end of the text4 ,except for those changes noted below1 all misspellings in the text1 and inconsistent or archaic usage1 have been retained4 ,page #bh4 8hygrogen0 replaced by 8hydrogen04 ,page #ci4 ,unclear image of potentially 8horn0 replaced by 8both04 ,page #dh4 8theprecipitate0 replaced by 8the precipitate04 ,page #gg4 8evident manmer0 replaced by 8evident manner04 ,page #hd4 8,,chapter ,,iii0 replaced by 8,,chapter ,,iv04 ,page #hh4 8immediaaely0 replaced by 8immediately04 ,page #ajf4 8is influence0 replaced by 8its influence04 ,page #aef4 ,added full stop after 8,exp4 #d4 ,mercury0 for consistency4 ,errata from the publisher has been applied as described below4 ,page viii4 8ere long0 replaced by 8erelong04 ,page #ae4 8particles of reduced gold were observed0 replaced by 8,i observed many particles of reduced gold04 ,page #ag4 ,removed #c duplicated lines of text4 ,page #acg4 8or by uniting0 replaced by 8nor by uniting04 ,page #afc4 8and the caloric0 replaced by 8the caloric04