the Arseniates of Copper, and of Iron. 237 
Such were the principal experiments, which the fleeting and 
precarious existence of the salt allowed me to make upon it. 
But, from some properties which I had remarked, I could per- 
ceive that this ore was a natural oxide of copper, nearly in the 
same state as that artificial oxide which M. Proust had 
found in the white muriate of copper, obtained by pouring a 
recent solution of muriate of tin into a solution of muriate of 
copper. 
If, however, by the very nature of the substance, (which, as 
I saw it ever changing, I thought it would be loss of time to 
examine farther,) I have been turned aside from more certain 
results, I have been more successful in imitating by art the 
state of this natural product. 
By exposing oxide, hydrate, or carbonate of copper, without 
addition, to a violent heat, in an open crucible, I frequently 
obtained the suboxide, which then presented all the properties 
already recognized in the above species of copper ore. In one 
instance, I so far succeeded, that, upon the very first inspection, 
the well experienced eye of the Count de Bournon, recognized 
a lump of it to be a mass of semi-fused, artificial, red copper ore. 
But I have found a method of producing at pleasure, in the 
humid way, all the new salts, and the oxide above described. 
As I had found about 11,5 per cent, of oxygen to be the quan- 
tity contained in the ore, I took that quantity of black oxide of 
copper which corresponded to 11,5 of oxygen ; (57,5 of black 
oxide was the proportion thus indicated ;) on the other hand, I 
took 50 parts of metallic copper, which had been precipitated 
by iron from muriate of copper, and which was in a state of 
tenuity not inferior to the finest powder. These were well 
mixed, by trituration in a mortar, and put, with muriatic acid, 
