G O L I). 



las been Rruck v:tli "'fic acid, impregnated with nitrous oxvd, and he fuppofes 

 1, tluis ohtamcd, con- t i;it it is owing to the nitrous oxyd tliat tli<- gold is oxydated 

 By precipitation from tins oxyd being fo much more cafily decompofod than thj 



'lioufes, or on tlie funiitinv which has been flruck wit): 



lightning. The purple oxyd of gold, 



tains five or fix per c.nl. of oxygen. By precijiitation troin tins oxyd being fo much more cafily Oecomud 



fome of its faliiie combinations, a yellow oxyd has been «b- "itric acid. The acid which, at firft, is deprived of its co 



tamed, in which the proportion of oxygen amounts to ten lour by the oxydation of the gold, as this oxyd is difTolved' 



percent. The oxyd in both inllances may be decompofed, ''liumes an orange-yellow colour, holding in (olution the ni ' 



and tiie oxygen completely expelled, by an elevation of tem- Irate of gold with an cxcefs of acid. I'he nitrate cannot be 



perature not much fupcrior to that of ignition. obtained in cry (lals, and it is decompofed bv heat or bv 



The attraction of gold to oxygen is fo weak, that it is being expofcd to the light of the fun ; it is alfo decompofed 

 fcarcely affected by the greater number of acids. It was by the alkalies, or bv introducing a plate of tin or filver into 

 formerly luppofed to lie perfectly iniblublc in the nitrous and the folution, and the purple oxyd is precipitated in the 

 „ nitric acids, whicli in general part with oxygen with fo form of powder ; and likewife by muriatic acid, which at 

 much facility, and when gold leaf is put into tlie acid cold, the inllaiit of combination converts the orange-colour to a 

 it f^ems to fuffer no change, but when nitric or nitrous acid is pure yellow. 



boiled on gold, it is capable of diflolving a* fmall portion of 2. Alurid/e of G«/,/— Muriatic acid of itfelf has no aftion 

 it. The quantity dilTolved is, however, fo inconfiderable, on gold, or on its purple oxyd, but gold is immediately oxy- 

 and depends on lo many conditions, which it is needlcfs to dated and tlien diffolved in oxymuriatic acid: or if nitric 

 enumerate, that the accuracy of the proceffes of affaying ^p'^l be added to the muriatic in certain proportions, the folu- 

 can fcarcely be affrfled by it. tion of gold in the mixture is readily effected : hence the ni- 



When gold is difiolved in the nitro-muriatic acid, or in a tro-muriatic acid wa,s dilliuguifhed bv tiie name of " aqui 

 mixture of equal parts of nitric and muriatic acids, an ef- regia," becaufe it difTolved gold, which was regarded by the 

 fervefcence takes place, and the folution becomes of a yellow alchemifts as the king of metals. The nature of the chemi- 

 colour. In this procefs the nitric acid is decompofed, its cal aftion is thus explained. Gold is oxydated with 

 oxygen combines with the gold, and the oxyd, as it is form- great difficulty, but it is effeded by oxymuriatic acid, which 

 ed, is dillblvcd in the muriatic acid. By adding hme-water readily parts with its oxygen, or bv the addition of the ni- 

 a precipitate is formed, whicli is the yellow oxyd of gold, trous to the muriatic, the former of which is decompofed 

 confifting of from eight to ten parts of oxygen in the hun- giving out its oxygen to the gold, which being now oxydated 

 dred. There is no artion between gold and azote, hydro- 's difiolved in the muriatic acid, forming with it a muriate 

 gen, carbon, or fulphur : but the oxyds of gold are readily "f gold. This folution of the muriate of gold is of a deep 

 decompofed by hydrogen, as will be foon feen. yellow colour, extremely acrid and eauftic • has an aftrin- 



Pliol'phorus combines with gold by heating together in a gent metallic taile,and ilains the fl<in of a deep purple colour 

 crucible a mixture of one lart of gold in filings, with two "'hich becomes darker by expofure to the air andlieht. It pro- 

 parts of phofphoric glafs, and an eighth part of charcoal. d"ces a fimilareffea on all vegetable and animal matters and 

 Great part of the phofphorus is feparated from the acid, and on marble and filiceous flones. Bv evaporating the folutioH 

 driven off, but there remains a fmall quantity united with the to one half, nitric acid is difengaged, and cryrtalsare obtaiii- 

 gold, formifig a phofphuret of gold. It may be done alfo by ^d. Thefe alTume a red colour by the action of llronfj light. 

 .idding phofphorus to gold in a red heat in a crucible. It is, They attract moitlure from the air, and fpontancoufly be- 

 in thiii itate, pale coloured, granulated, brittle, and a little come liquid. When oxymuriatic acid is ufed, the oxynrn 

 more fulible. The proportion of phofphorus is not more of this acid being retained even by a weaker affinity than the 

 than one part in twenty-four ; and the fubffancc may be dc- nitric acid, the gold attraAs it, and combines with the mu- 

 compofcd by being kept in fulion ; the phofphorus is driven riatic acid. In this cafe tlio folution is flow, and but a very 

 off in the flate of vapour, and inflamed. Bergman has ar- fmall quantity of gold can be diffolved, partly from the oxy- 



ranged the affinities of gold and its oxyds in the foUowi 



order : 



Go!J. Oxy.h of Gold. 



Mercury, Muriatic-acid, 



Copper, Nitric, 



Silver, S-ilpluiric, 



I.cad, Arfenic, 



Bifmulh, Fluoric, 



Tin, Tartaric, 



Antimony, Phofphoric, 



Iron, Pruific. 



Platin.-., 

 Zinc, 

 Nickel, 

 Arfenic, 

 Cobalt, 

 Mangariefe. 

 Sails of Gold. — Thefe are the nitrate and muriate 



muriatic acid not being in a very concentrated' ftate, and part- 

 ly, it is fuppofcd, from the quantity of oxygen prefent not 

 being fuch as to form a futficient quantity of oxyd to fatu- 

 rate the acid. It ought, however, to be obferved, that if 

 the late difcoveries of profeffor Davy he eifabLlhcd, which 

 make the oxy-muriatic acid a fimple fubilance, .iwd even pof- 

 fefPing no oxygen whatever, then a iiew^ theory mull be intro- 

 duced to account forthefachs above-Hated. In oxy-muri.Mic 

 gas, gold-leaf is inllantlv fufed with intlanmiation, and dif- 

 folved. 



Gold cannot be dilTolved by the other acids when in its 

 metallic Hate, but itsoxvds may be combined with thom, 

 and a number of tlie falts of gold be formed. The fulphate 

 and nitrate alio, as we have feen, do not cryilalli/e : the phof- 

 phate of gold may be fufed, and in this il,\te it fwrms a finr 

 red glafs. We ihall now briefly notice fome of the proper- 

 ties of the muriate of gold. In connexion with this fubjecl, 

 we mufl not omit the experiments of Mrs. Fulhame, which 



NhniteofGoU. When concentrated nitric acid is feve- fhe announced in an " Effay on Combuition." with a view 



ral times fuccelfively poured upon gold, boiled and dillilled to to a new art of dyeing and painting, &c. in the year 1794, 



drynefs, the gold is diffolved, and tlie folution ali'umes a yel- and w hich were, at that period, expvded to lead to fome 



Ijwilh colour. This folution is more readily effected in pro- important praclical refults. 



portion to the quantity of gas or nitrous gas which the acid The muriate of gold is very folublc in water, and it dc- 



contains. Gold-leaf, according to Fourcroy, is diffolved in compoled in hydrogen gas. If a piece of filk be moiftcned 



witU 



