16 
Copper. 
minute or two, invariably contain eighty parts of pure nie 
tallic copper. The ammoniated copper gives the same 
oxyd when boiled with potash * 
It is also produced at once by adding potash or soda to 
the'acid solutions of copper* and boiling for a minute or 
two ( which last is an essential circumstance) and this is a 
better method of proceeding in analysis* since an excess 
of carbonated alkali will redissolve a part of the green car- 
bonat, and vitiate the analysis, whereas no such effect is 
to be feared from an excess of the pure fixed alkalies at a 
boiling heat. 
O 
The leading steps of the actual analysis of sortie of the 
principal copper ores by the most accurate chemists may 
now be given in a few words, as a specimen of the mode 
of proceeding in different cases. 
Of the ores composed chiefly of Copper , Iron, and Sulphur \ 
The vitreous copper ore was thus analysed by Kla- 
proth. ^ 
To 200 grains of the powdered ore muriatic acid was 
added in a boiling heat, which had no immediate effect* 
but on dropping in a little nitrous acid, solution began with 
violent disengagement of nitrous gas. When every thing 
soluble was taken up, the solution consisted of a clear 
green liquor on which the sulphur was floating. The in- 
soluble part amounted to 38 1-2 grains, 37 of which were 
dissipated by calcination and were sulphur, leaving 11-2 
of silex behind. The solution was divided into two parts, ^ 
one to ascertain the copper, the other the iron. 
Into the former a bar of polished iron was immersed, 
and by rest 78 1-2 grains of copper were precipitated.— 
The other half was supersaturated with ammonia, which 
first precipitated both the iron and copper, and then re- 
dissolved only the copper, leaving 3 grains of oxyd of 
iron, equal to 2 1-2 of metallic iron. Hence the iron, cop- 
*Essays, Vol. I. 
