. 
AND OTHER METALS FROM PYRITES. 108 
obtained as sulphuric acid, sone in the free state or in combina- 
tion with copper and iron—this quantity is nearly sufficient to 
dissolve both a copper and on the latter as ferrous sulphate, 
the theoretical quantity required with the ore Pap vet on Need 
29°6 r ; ul ed i se Bere 
and opened at once a prospect of the <n of the Span 
resu 
t. 
As it was ig es that such a result would not be attained on 
ge scal eeded aq 
large scale, I proceeded to examine the action of aqueous 
sulph a ‘Moaod that by treating ore calcined at a 
low temperature therewith, a considerable quantity of ate 
8 ned in solution along with the sulphate of 
orm the process now presented itself in, was, to calcine 
the ore at a low temperature and extract the sulphates of copper 
and iron formed with the mixed sulphurous and sulphuric acids 
formed during the roasting, then to reduce all the iron to the 
metallic state and remove it in the same manner, when the gold, 
metallic state, and to obtain the sia from solution. 
The reduction of the iron was necessary, because the Ti al 
acid obtained would be too dilute to ra on the ferric oxide, an 
divided carbon was deposited amongst the iron, which rend 
wetting it difficult, and the powder was very pyrop 
TL 5 finely ground carbon at a low-red heat, I aah 
ould be so managed as to obtain the iron as a metallic powder 
which was mere attacked. 
For the removal of ‘hee copper from solution the use of metallic 
iron had to be abandoned, on account of the quantity required to 
precipitate it from its solution as sulphate, which on the large 
seale is found to be about three times the q sored of the copper 
precipitated. As it would be advantageous to recover some of 
the sulphuric acid, the use of sulphuretted bh pas rogen presented 
itself, but after repeated trials the exceeding t bulk of the pre- 
cipitate presented an obstacle which on an erable scale 
would be insuperable, and has indeed been site to be so where 
tried. 
