ioU On the Action of 



mercury, no reduction takes place; but if mercurv, whe- 

 ther al the maxiniuin or (lie minimum of osidizeinent, be 

 dissolved in nitric acid, and green sulphate of iron be added, 

 the mercury is precipitated in the metallic state. 



These experiments are much stronger examples than the 

 former of the effects produced bv complicated affinities. 

 They are of inijiortance not only as objects of general con- 

 sideration, but in their application to the pj-esent subject. 

 They most materially modify and are indispensable to the 

 accuracy of the results I formerly stated ; but I was not 

 aware of them at the lime I first engaged in the investiga- 

 tion of this subject. I can also now explain a verv material 

 difference between some proportions observed by M. Richter 

 and myself in an experiment u hich that chemist had made 

 as a repetition of one of mine. 



I had poured a solution of green sulphate of iron into a 

 solution of 100 parts of gold and 1200 of mercur}', and had 

 obtained a precipitate consisting of 100 of cold and 774 of 

 mercury. M. Hichter repeated, as he terms it, this expe- 

 riment; that is, he used luO of gold and 300 of mercurv, 

 and obtained a precipitate weighing 102. He is surprised 

 at the difference of weight between our results, which might 

 be owing to his method of repeating the experiment ; but 

 the real cause of this difference lies, as 1 suppose, in ray 

 having accidentally used nitrate instead of muriate of mer- 

 cury,. 1 had never observed that with mercury and .silver 

 this operation had failed, and it must have been, because, 

 on account of the known effect of niuriatic salts upon those 

 or silver, 1 had naturally avoided using a muriate of mer- 

 cury. 



But the state of the nitrate of mercury which is used with 

 a solution of gold is not indifferent. As gr<>en sulphate of 

 iron reduces mercurv when dissolved in nitric acid as well 

 as gold, it is necessary to mix the solutions of those metals 

 before the green sulphate of iron is added, in order that 

 both may be acted upon together. If the nitrate be at 

 the minimum of oxidizement, a precipitate is immediately 

 formed upon mixing the solutions of gold and mercury. 

 Calomel is produced by the muriatic acid of the solution of 

 gold and the oxide of mercury; whilst the gold is reduced 

 to the metallic state' by a portion of the oxide of mercury 

 becoming more oxidized, and forming the soluble nuiriate. 

 The precipitate consists of calomel, of metallic gold, and 

 of a very small portion of mercury, which I believe to be 

 in the same stale ; my reason for thinking so is, that I have 

 often observed, that a glass vessel^ in which I had sublimed 



some 



