17(J ACTION OF PLATINA AND MERCURY, 



ment ; that Is, he ufed 100 of gold and 300 of mercury, a,nd 

 obtained a precipitate weighing 102. He is furpriied at the 

 ditference of weight between our refults, which might be 

 owing to his method of repeating the experiment j but the real 

 caufe of this difference lies, as I fuppofe, in my having acci- 

 dentally ufed nitrate inftead of muriate of mercury. I had 

 never obferved that with mercury and filver this operation 

 had failed, and it muft have been, becaufe, on account of the 

 known €ffe6t of muriatic falls upon thofe of lilver, I had 

 naturally avoided ufing a muriate of mercury, 

 The (late of ox- But the ftate of the nitrate of mercury which is ufed with a 

 idationofthcni-fQJ^j^j^^ of gold IS not indifferent. As green fulphate of iron 



trate of mercury 6 v^ ,,-.... .. it 



ufed with the fo- reduces mercury when dmolvcd m nitric acid, as well as gold, 



liulonofgoldisof It j<j neceffary to mix the folutions of thofe metals before the 



the minimum of greei» fulphate of iron is added, in order that both maybe 



oxidation pre- atled upon together. If the nitrate be at the minimum of oxi- 



and mcTairic gold <^'zement, a precipitate is immediately formed upon mixing the 



falldoA-nj folutions of gold and mercury. Calomel is produced by the 



muriatic acid of the foKition of gold and the oxide of mercury ; 



whilft the gold is reduced to the metallic ftate by a portion of 



the oxide of mercury becoming more oxidized, and forming 



the foluble muriate. The precipitate confifts of calomel, of 



metallic gold, and of a very fmall portion of mercury which I 



believe to be in the fame ftate ; my reafon for thinking fo, is, 



that I have often obferved, that a glafs veflel in which I had 



fublimed fome of it, was lined with a thin gray metallic coat. 



fcut if thcroax. If, on the contrary, a nitrate of mercury be highly oxidized, 



fhin^faltstill^ne "^ precipitate nor redu6lIon of gold takes place until the green 



^een fulphate of fulphate of Iron is added. But at any rate the precipitation of 



iron is added. g^j^^j ^^^ mercury, or of filver and mercury by green fulphate 



of iron, cannot be adduced as an argument to fupport the 



affinity of thefe metals, fince the effed is the fame, whether 



they are feparate or united. 



Thefe preliminary confiderations were neceflary as well 

 for the rectification of ray former experiments as for the pur- 

 fuit of my prefent obje6^ ; and now to return to plalina. 

 £xp«rirr.ents Exper. I . If a folution of highly oxidized nitrate of mercury 



I MmcIi of'the ^^ poured into a rhixed folution of platina and green fulphate 

 highly oxid. fol. of iron, the firft a6^ion which takes place pafTes between 

 ofmprciuypour-jjj J tj j^ of the folution of platina and the oxide pf 



■fd jn;o a mixed . r • r j 



loiut'on of plat, mercury, by which a mnnate of mercury is formed, but retained 



in 



