the Arseniates of Copper, and of Iron. 229 
One hundred parts of very pure and regularly crystallized 
red copper ore were reduced to a fine powder, and dissolved* 
without the assistance of heat, in nitric acid. 
During the operation, a very violent effervescence, accom- 
panied by a disengagement of nitrous gas, unusually copious 
and rapid, took place. When these phenomena had subsided, 
the solution was blue, like every other nitrate of copper; and 
the ore had entirely disappeared. The liquor, perfectly limpid, was 
evaporated to dryness : muriatic acid was poured in; and the nitric 
acid was expelled, by a second evaporation. Into the muriate of 
copper, which remained behind, a plate of polished iron was 
immersed, which, after the usual phenomena, gave a precipitate, 
that was found, upon examination, to be copper, and amounted 
to 88,5. In order to complete the hundred parts, it would 
be necessary to add 1 1,5. But fire expelled from the ore neither 
water nor any other volatile substance ; nor did the weight of a 
given quantity appear either to diminish or to increase, by long 
exposure to a moderately elevated temperature. The only oxide 
of copper with which I was acquainted, as existing in nature, 
contains 20 per cent, of oxygen. I had therefore, 8,5 of copper 
exceeding the quantity I should have obtained, had the ore been 
wholly composed of black oxide of copper. And, on the other 
hand, as I had convinced myself, that no loss of weight had 
been occasioned by any part of the metal remaining unprecipi- 
tated by the iron from its solution, I could not conclude the ore 
to be in the state of native copper. I was led, therefore, to 
imagine, that it might be a mixture of those two substances ; and 
that muriatic acid, by dissolving the one, and leaving the other 
untouched, would be the most effectual means of producing 
