13 
Copper . 
when this metal is found it is generally in conjunction 
with iron ; and ammonia, which precipitates all the three 
metals from their acid solution, redissolves, when in ex- 
cess, both the nickel and copper $ but to obtain the cop- 
per singly, again supersaturate with muriatic acid, and 
immerse a piece of iron, which will separate the copper, 
and leave the nickel dissolved. 
Copper is obtained separate, in wet analysis, in three 
states, in each of which the weight may be taken, either 
in the metallic state, or as the green carbonat, or as the 
black oxyd. If a piece of polished iron is immersed in 
an acid solution of copper it is almost instantly covered 
with a brilliant coating of metallic copper, owing to an 
exchange having taken place, a portion of the iron being 
dissolved, and separating an equivalent quantity of cop- 
per from the solution. As this proceeds, the precipitate 
of metallic copper increases, and incrusts the remain- 
ing iron, forming a bundle of ragged filaments w hich 
the slightest force will detach if the solution is 
sufficiently diluted. At last the solution contains only 
iron, and the whole of the copper is thus obtained in 
the metallic state, which only requires washing and dry- 
ing. This precipitation is much assisted by boiling for a 
short time, especially at last, without which indeed the 
last portions of copper will hardly separate. The solution 
when purely cupreous is of a fine azure blue, but when 
converted to a solution of iron becomes green. It should 
be remembered, however, that for a perfect separation of 
copper from iron by this method, the solution should be 
in the sulphuric or muriatic acids and not the nitrous, for 
though iron will equally displace copper from the nitrous 
as from the other acids, the nitrat of iron is itself largely 
decomposed by mere heat or exposure to air, and lets fall 
a fully oxidated iron, which in this case mixes with the 
line filaments of the reduced copper, and vitiates the re- 
sult of the analysis. When, therefore* it has. been neces- 
