Platina and Mercury vpon each other. 1 07 



some of it, was lined with a thin gray metallic coat. If, on 

 the contrary, a nitrate of niercury be highly oxidized, no 

 precipitate nor reduction of gold takes place until the green 

 sulphate of iron is added. But at any rate the precipitation 

 of gold and mercury, or of silver and mercury, by green 

 sulphate of iron, cannot be adduced as an argument to sup- 

 port the affinity of these metals, since the effect is the same 

 whether they are separate or united. 



These preliminary considerations were necessary, as well 

 for the rectification of mv former experiments, as for the 

 pursuit of mv present object : and now to return to platina. 



Exp. 1. if a solution of highly oxidized nitrate of mer- 

 cury be poured into a mixerj solution of platina and green 

 sulphate of iron, the first action which takes place passes 

 between the muriatic acid of the solution of platma and the 

 oxide of mercury, by whicri a muriate of mercury is formed, 

 but retained in solution. This eiTect makes it advantageous 

 to use a greater quantity of the solution of mercury than is 

 merely capable of drawing down the given quantity of pla- 

 tina along with itself in the form oi a metallic precipitate. 

 When this precipitate is washed and dried, it will be found 

 to weigh nuieh more than the original quantity of platina ; 

 and the augmentation of weight has no limit but those of 

 the mercury and the green sulphate of iron employed. But 

 even after nitric acid has been boiled for a long time and 

 in great quantities upon tl;is precipitate, until it no longer 

 dissolves any part of it, there still remains more undissolved 

 matter than the original weight of the platiua used in the 

 experiment. By exposure to heat, little more is left in ge- 

 neral than the original platina; and sometimes even a di- 

 minution maybe observed; for, as the experiment is not 

 attended with uniform success, it docs not always happen 

 that the whole of the platina is precipitated, but a portion 

 of it will sometimes resist the action of the green sulphate 

 f)f iron, even when sufficient mercury has been used. Be- 

 fore the precipitate has been exposed to heat it is dissolved 

 more easily than platina by nitro-muriatic acid ; and the 

 solution, when nearly in a neutral state, gives a copious 

 metallic precipitate (yet' not equal to the quantity employed) 

 when boiled with a solution of green sulphate of iron. 



E.vf). 2. When a mixed solution of platina and mercurv 

 is precipitaied by metallic iron, a (piantitv equal to the sum 

 oi the former metals is generailv obtained. After nitric 

 acid has been boili'cl for a long time upon the precipitate so 

 formed, the orisrinal weight of platina, together with a con- 

 siderable increase, reniains behind, nor can nitric acid sen- 

 sibly 



