? 
96 ON A METHOD OF EXTRACTING GOLD, SILVER, 
oran acidified hypochlorite. This introduced a source of diffi- 
eulty, as the chlorine- would have to convert the sulphide into 
ferric sulphate before any gold coul uld be obtained in solution. 
_Ziervogel proposed bree — pyrites with chlorine, and 
process was us 
This process was esr nana in the United States by 
G. F. Deetken, in 1863, and has been used with tolerably satis- 
factory cee in California in two establishments. The process 
is there carried out as follows :—The concentrated pyrites are 
| when sul 
am 
chlorine gas from a generator is admitted below until it is seen 
floating above the material. e tank is then closed, the current 
of gas stopped, and the whole left at rest for ten or twelve hours, 
when the cover is removed and waterisrun on. This rae the 
chloride of gold formed, and the solution is run into earthen- 
ware or glass vessels, where the gold is precipitated as a bronze- 
black powder by the ‘addition of a ckilie n of ferrous ee 
e disadvantage of the chlorine method of extraction is, that 
with ores containing copper, the whole of that metal has to be 
removed before the chlorine becomes available, and also all the 
sulphur which otherwise becomes first sede to sulphuric atid. 
With a view to removing ie vel I vote roasted a 
quantit “of ore in a mufile, at a rn eat, with constant 
sulphate e dried residue was found to contain 1°5 per cent. 
of sulphur, and I therefore recalcined the whole for seven hours 
longer, and extracted the copp efore, when the sulphur 
was fonnd to be reduced to 046 per cent. A similar result was 
obtain in successive trials, and as this amount of sulphur 
would require as much chlorine, as upwards of 3,300 ozs. of gold 
per ton, a more perfect method of getting rid of it was evidently 
required. 
Another portion of ore was therefore partially calcined, cooled, 
and damped with tine and the whole again calcined until fumes 
were no longer ev 
e residue ennad with water and acid as before was found 
to contain. 0:12 per cent. of sulphur and traces only of co copper. 
* 
- » 
RE Re ee ee lt rae a Pion 
Bo Re Se eee Ne AE ene ST OS eae En eee See Pee eee ce? ae ae, ee re ae 
‘ 
ACT ETE Ons ee ov Sef eee 
