25 
Copper . 
fore separated from the copper in this analysis* and from 
100 grains (exclusive of the quartz) 138 grains of phos- 
phat of lead were formed, the phosphoric acid of which 
was estimated from other experiments to amount to 30.95 
grains® The cupreous solution was then treated with a 
little sulphat of soda, to separate the lead from the excess 
of the acetite remaining ; some naked sulphuric acid was 
then added, and the copper was separated by iron in the 
metallic state, which (increased in the proportion of 125 
to 100), was found equal to 68.13 of oxyd of copper® 
The above analyses include almost all the important 
ores of copper, except those in which it is combined with 
tin, which will be treated of under that metal® It may be 
mentioned however that the most accurate way of sepa- 
rating copper from tin appears to be to immerse in a so- 
lution of both metals a stick of tin, which will precipitate 
all the copper, whilst the loss of weight of the immersed 
tin subtracted from the entire quantity of tin afterwards 
obtained from the solution, will indicate the quantity of 
tin belonging to the ore. [1 Aikins Die . 327, 
Of the Reduction of Copper Ores . 
The only ores of copper in fact that are wrought in the 
large way, and from which the copper of commerce is for 
the most part supplied, are the sulphureous and arsenical 
ores of this metal. The method of reducing them, though 
consisting of a great number of processes, on account of 
the powerful affinity, both of the arsenic and sulphur, is 
yet upon the whole very simple, being little more than re- 
peated roastings and fusions, till the metal has acquired 
the necessary ductility, for it is never brought to a state of 
absolute purity, and the commoner sorts contain both ar- 
senic and antimony, in such proportions, as to be wholly 
unfit for alloying with either gold or silver® 
The rough ore, if simply sulphureous, is broken into 
pieces not larger than an egg, and separated as much as 
