362 
CHEMICAL PRINCIPLES. 
Oxides of pla- phuret of hydrogen present. With an excess of the latter, it 
gives a precipitate of a reddish brown colour, which is decom- 
posed as fast as the sulphuret of hydrogen finds means to escape. 
The common precipitate appeared to me to be a sulphuret of 
platina. I have had an opportunity of verifying the observation 
of Proust that this sulphuret is decomposed, when we attempt 
to dry it, so that it produces the sulphuric acid, and leaves a 
sulphuret with a less portion of sulphur. In an experiment 
where I endeavoured to operate w’iih a sulphuret which had 
undergone the least possible decomposition by the formation of 
sulphuric acid, I found that it contained 77 hi 100 parts of 
metal with 23 of sulphur. That is to say, that 100 parts of 
metal had been combined with 30 parts of sulphur ; which 
proportion is somewhat smaller than it ought to be, according 
to the calculation of chemical proportions. But the difference 
must undoubtedly be attributed to a decomposition which had 
taken place previously to the commencement of the experi- 
ment. I found, also, that when the sulphuret was distilled in 
a retort, a part of its sulphur was disengaged, but another part 
remained combined with the metal. Hence I conclude, that 
there are two sulphurets of platina, of which the one is propor- 
tional to the oxidule, and the other to the oxide. The sul- 
phuret of platina is dissolved by the hydrosulphuret of kali. 
The solution is of a reddish brown. The acids precipitate* 
from it a flocculent mass, resembling crocus of antimony. 
It is the sulphuret of platina, containing sulphuret of hydrogeii ^ 
but the latter soon flies off when exposed to the air. 
VII. The Oxide and Sulphuret of Palladium. 
Through the complaisance of Dr. Wollaston, I became pos- 
sessed of a piece of palladium which weighed several grammes. 
I prepared a gramme in fine filings, which I mixed in a 
small glass phial with some sulphur. I then heated the 
mixture over the flame of a spirit lamp, until the metal and the 
sulphur were combined, which took place, accompanied with 
the production of fire. I next heated the phial over hot 
coals, until the excess of the sulphur was entirely got rid of. 
The sulphurated palladium weighed l*28t5 grains. V/hen 
mixed 
