Plathia and Mercury upon each other. e*> 



delivered by M. Vauquelin at the Ecole des Mines in Parij, 

 when he was professor at that estabHshment, it was his 

 constant custom to exhibit an experiment to prove that 

 mercury, precipitated from its solution by many of the al- 

 kaline and earthy hydro-sulphurets, was redissolved by 

 adding an excess of them. 



It is moreover well known that there is a strong affinity 

 between potash and the oxide of platina, and also that when 

 those substances are brought together in solution, a triple 

 salt, but little solutile, is ihc result. It was tr> avoid these 

 difficulties that I had employed uncombined sulphuretted 

 hydrogen gas; for the method adopted by Messrs. Rose 

 and Gehlen appearing to me to be the application of two 

 divellent forces, I presumed that it would produce a sepa- 

 ration. The result of their experiment, which, it appears 

 from their paper, ihey had not anticipated, shows the ne- 

 cessity of the precaution I had used. The operation which 

 they performed to unite platina and mercury was, in fact, 

 nearly the reverse of that which they supposed they had 

 repeated from me, and might have been applied perhaps 

 with a better prospect of success towards the d'econ^posiuon 

 of palladium. 



Messrs. Rose and Gehlen seem, in many parts of their 

 paper, to question ir.y having fused platina; and inform 

 us, that although ihey i\ad exposed this metal in the furnace 

 of the royal porcelain manuikctory of Berlin, in which 

 VVcdgewood's pyronielcr ceased to mark the degree of lieat, 

 they could not accomplish its fusion. Many of my friends 

 in England have, however, seen the buttons which I ob- 

 tained, and which were not le-v in number. The dux which 

 1 had used was borav. But no mentit-a is mad^j in any one 

 of the operations of xMessrs. Rose and Gehicu of borax hav- 

 ing been en) ployed. 



h\ many of their attempts they obtained an irrcoidar and 

 porous mass, which of course was of a specific gravitv ntuch 

 inferior to that of platina; and it might be inferred from 

 their paper that the diminution of specific gravity, which I 

 had observed, was owing to the san>e cause. ' It is true, 

 not only tliat I had very often obtained su.ch a mass, but 

 that I had frequently also observed no diminution whatso- 

 ever in tlic specific gravity of the button which resulted 

 from my operations. But all those upon which I had 

 founded the conclusions alluded to by Messrs. Rose and 

 Gehlen were performed. in the ioUowiiig n)aniier, and have 

 been repeated since. A Hessian crucible was filled with 

 lauip-black, and the contents pressed hard together. The 



lamp -black 



