235 
the Arseniates of Copper , and of Iron. 
to be attributed. All the acids above mentioned are capable of 
producing the same change, but in a manner, perhaps, not quite 
so distinct or satisfactory. 
From the foregoing experiments it appears, that copper ex- 
ists in this ore in a state hitherto unknown in nature ; and that 
it contains much less oxygen than has ever been suspected in any 
oxide of copper ; for, from the quantity which was precipitated 
in the metallic state by iron, it appears to be combined in the 
proportion of about 11,5 per cent. To confirm this idea, and 
ascertain as nearly as I could the precise quantity, I dissolved 
100 parts in nitric acid ; then boiled with potash, and filtered. 
Gne hundred and eleven remained upon the filter, which, as they 
had combined with a new portion of oxygen from the nitric 
acid, were in the state of black oxide, and correspond exactly to 
88,75 ; so that I believe I shall be within one per cent, of the 
truth, in asserting the proportions to be, 
Copper - - - 88,5 
Oxygen - - -11,5 
100,0 
When, into a solution of muriate of suboxide of copper, liquid 
potash or soda is poured, a bright yellow precipitate, not unlike 
the precipitate of platina, takes place. This precipitate differs 
only in colour from the original ore ; for it is soluble in muriatic 
acid, and affords the same solution and precipitation by water, 
and the same appearance with alcohol. It is likewise soluble in 
nitric acid, but with disengagement of nitrous gas, and gives 
the same appearances with the other acids above enumerated. 
The difference of colour seems to arise merely from the tenuity 
of its molecules, compared to the mechanical pulverisation of 
H h 2 
