g54 ®^ PREPARATIONS OF QOID. 



small quantity, when the washings have been conducted 



with due care. 

 Its raedicinai The sU;yht solubility of this oxide, and its very easy de- 

 qualities. composition, must render its action, as an oxigenizing 



substance, in the animal economy, prompt and certain. 



JJiroilar to The Ted oxide of mercury, which has some properties in 



those of the common with the oxide of ijold, namely those of dissoiving 



liiercurvr i" water and of being easily decomposed, possesses nearly 



Oxide ot silver similar medicinal virtues; and from ai..:logy we may 



probably ana- coniecture, that Oxide of silver also would have the same 

 logous. '' 



properties. , 



Action of ni- Nitric acid does not attack dry oxide of gold, unless 

 th*^^"d" ^^ ^^ employed in large quantity, and in a concentrated 

 state. In this it differs greatly from the muriatic acid, 

 which dissolves it immediately. The nitric solution of 

 gold has a brown hue; and water throws down from it a 

 flocculent precipitate, of the same colour as that occasioned 

 by alkalis. 



The first portions of nitric acid, that have been decanted 

 off the same oxide of gold, form a precipitate with the 

 solution of silver, after the gold has been thrown down from 

 them by water; but the latter portions are not precipitated, 

 which confirms what has been said above. 



The affinity of the oxide of gold for nitric acid appears 

 very weak, for part separates in, the metallic state by spon- 

 taneous evaporation. This no doubt is the reason why ni- 

 tric acid alone cannot dissolve this metal. 



Sect. II. Examination of tkt liquor, from which gold has" 

 been precipitated by fixed alkalis. 



The liquid, I have said, that this liquor has no perceptible colour, 



from which hut that it resumes a pretty deep yellow, wlien muriatic 



precipifttcdT *^''^ '' ''^^^^' ""''^ ^^'''^ afterward an addition of sulphate 



examined. of iron throws down metallic gold from it pretty copiously. 



Muriate of Having evaporated this liquor by a very gentle heat, I ob- 



potash first tained at first crystals of piuriate of potash; among which 



separated, yvere observable some other crystals of carbonate of potash, 



then carbon- , . , , • , , , , ■ n^i t- i ■ 



ate, this salt having been added ui excess. The liquor being 



decanted from these salts^, and evaporated anew with the 



same 



