12 6 Purple Powder of Coffins. [Book VI. 



iblutions of other metals, this procefs may be ufed as 

 a means of refining gold j for the acid containing gold 

 is imbibed by the inflammable fluid, while that part 

 of it which is combined with any other metal remains 

 behind. 



Almoft all metallic fubftances precipirate gold from 

 its folution in aqua regia. Mercury and copper fe- 

 parate it in its mining metallic form ; lead, iron, and 

 filver, precipitate it of a deep and dull purple colour. 

 A plate of tin, plunged in a folution of gold, feparates 

 the perfect metal in the form of a deep violet powder, 

 called purple powder of Cafllub, which is ufed in 

 painting, in enamel, and in porcelain. This powder 

 confifts of the calces of gold and tin in combination, 

 and is capable of communicating a fine purple colour 

 to glafs. The folution of green vitriol precipitates no 

 other metal but gold, and the gold proves of uncom- 

 mon purity, and of .a very deep colour. Gold in its 

 metallic ftate is incapable of uniting with fulphur alone, 

 but if a piece of gold is dropped into a folution of 

 hepar fulphuris, efpecially if the latter is prepared 

 with equal parts of fulphur and alkali, the gold difiblves 

 with fome ebullition, and forms a mafs, which diflblves 

 in water like the combination of alkali and crude anti- 

 mony. 



Stahl fuppofes that this procefs was ufed by Mofes 

 to render the golden calf, adored by the Ifraelites, 

 loluble in water. 



But though gold will not unite with fulphur, it may 

 be purified by means of it, the fulphur uniting with the 

 metals with which it is alloyed. With this view it is 

 ufual to heat the gold with crude antimony, in which 

 Hate the fulphur is more fixed than when applied in a 

 feparate ftate. In this procefs, however, the gold 

 combines with a portion of antimony, which muft be 

 afterwards driven off by heat. 



There 



