ic8 Mr. Chenevix on the Action of 
metals, as to combine palladium with sulphur, I hoped that 
those effects might be produced before the total dissipation of 
the mercury. How far my expectation was fulfilled has been 
stated in my former Paper. 
The sulphuretted hydrogen gas which Mess. Rose and 
Gehlen presented to those metals was combined with potash. 
Now, in the course of docimastic lectures annually delivered by 
M. Vauouelin at the Ecole des Mines in Paris, when he was 
Professor at that establishment, it was his constant custom to 
exhibit an experiment to prove that mercury, precipitated from 
its solution by many of the alkaline and earthy hydrosulphurets, 
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 soluble, is the result. It was to avoid these difficulties 
that I had employed uncombined sulphuretted hydrogen gas ; for 
the method adopted by Mess. Rose and Gehlen appearing to me 
to be the application of two divellent forces, I presumed that it 
would produce a separation. The result of their experiment, 
which, it appears from their paper, they had not anticipated, 
shews the necessity of the precaution I had used. The opera- 
tion 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 decomposition of 
palladium. 
Mess. Rose and Gehlen seem, in many parts of their paper, 
to question my having fused platina; and inform us that 
although they had exposed this metal in the furnace of the 
