remaining after the Solution of Platina. 413 
separated from these metals, by the usual process of refining. 
It remains combined with either of them, after cupellatibn with 
lead ; and with the gold, after quartation with silver. The alloys 
retain considerable ductility ; and the colour of that with gold, 
is not materially different from pure gold. 
I shall now proceed to describe the analysis of the black 
powder, and the properties of the two metals which enter into 
its composition. The method which I used for dissolving it, 
was similar to that employed by M. Vauquelin, the alternate 
action of caustic alkali, and of an acid. I put a quantity of the 
powder into a crucible of silver, with a large proportion of pure 
dry soda, and kept it in a red heat for some time. The alkali 
being then dissolved in water, had acquired a deep orange, or 
brownish-yellow colour, but much of the powder remained un- 
dissolved. This powder, digested in marine acid, gave a dark 
blue solution, which afterwards became of a dusky olive-green, 
and finally, by continuing the heat, of a deep red colour. Part 
of the powder being yet undissolved by the marine acid, was 
heated as before with alkali; and, by the alternate action of the 
alkali and acid, the whole appeared capable of solution. At each 
operation, some silex was taken up by the alkali ; and, as this 
continued till the metallic part was entirely dissolved, it seems 
to have been chemically combined with it. 
The alkaline solution contains the oxide of a volatile metal, 
not yet noticed, but which I shall presently describe, and also 
a small proportion of the other metal. If this solution is kept 
for some weeks, the latter metal separates spontaneously from 
it, in the form of very thin flakes, of a dark colour. 
The acid solution also contains both the metals, but 
principally that which has been mentioned by the French 
