is 
Copptr* 
both the zinc and iron, and the latter being again separat- 
ed by the zinc that remains. On this account, perhaps,, 
iron is a more accurate reagent than zinc in these analy* 
sis. As the muriat of copper seems to yield its metal 
with more ease than the sulphat, it might perhaps be of 
use previously to convert the sulphat into a muriat by the 
addition of common salt. The colour immediately 
changes to green, which is a proof of this change of the 
cupreous salt. 
The report of the assay will probably be still more ac- 
curate, if the precipitated copper, after being washed and 
dried, instead of being immediately weighed, is put into a 
small crucible, moistened with a drop or two of oil, co- 
vered with borax, and strongly heated for a few minutes 
whereby it becomes a solid button of good malleable cop- 
per. 
The second state is that of the green carbonat If car- 
bonated potash or soda be added to a solution of copper, 
a green precipitate is formed, which, when washed and 
dried at the heat of boiling water, gives an uniform green 
powder. Its exact nature will be mentioned when de- 
scribing the carbonat of copper, but it may be here added, 
that 180 parts of this carbonat are equivalent to 100 of 
metallic copper, and may be reckoned as such in all ana- 
lysis. But as the pure fixed alkalies give a precipitate 
which may occasionally be confounded with this carbonat, 
this method of estimation is not quite so good as the fob 
lowing. 
The third state in which copper may be estimated is 
that of black oxyd. If the green carbonat last mention- 
ed (and it need not be washed with particular care nor 
dried) be boiled for a few moments in caustic potash, it 
at once shrinks considerably and becomes a deep brown- 
ish black fine powder, which is a pure oxyd of copper in 
its highest state of oxygenation. Gne hundred parts of 
this oxyd, well washed and dried in a low red heat for a 
