METALLURGICAL METHODS AT BROKEN HILL. 29% 
silver. The bars of this Dore silver, as it is called, are put into a 
cast-iron kettle heated by a fire, filled with strong sulphuric acid, 
preferably of about 66° Baumé. This is boiled until complete 
solution of the silver takes place, the gold being left as a dense, 
black, finely-divided powder at the bottom of the kettle. The 
solution containing the silver is either ladled or siphoned out of 
the dissolving kettle into a settling tank warmed by steam passing 
through a leaden coil. Here any fine particles of gold which 
may not have settled in the dissolving kettle are collected. The 
silver solution is diluted to about 24° Baumé, and emptied into a 
precipitation vat in which plates of copper are arranged. The 
reaction between the metallic copper and the silver sulphate solu- 
tion causes the silver to precipitate and the copper to go into 
solution as a sulphate, so replacing the silver. The liquor left in 
the vat after the silver is all out, is siphoned into vats, where the 
copper sulphate is crystallised out. The silver precipitated on the 
copper plates is then taken to a vat and well washed in hot water 
to free it from the last trace of sulphate of copper. It is then 
melted up and sold as fine silver, and is about 997 fine. 
The gold is sometimes pure enough to melt up into bars, but if 
not it is boiled with fresh acid; then thoroughly washed, dried, 
and melted. Since this method has been adopted, the ‘“ Mcebius” 
electrolytic separation of gold and silver has come into prominence 
in America, and some writers claim for this process that the cost 
of separation does not exceed one-eighth of a halfpenny per ounce. 
CHLORIDISING AND LIXIVIATION. 
The ore which is handled in these portions of the works is too 
low grade to pay the expense of blast-furnace treatment, and it 
has to be mined to get at the other and richer ores; so there is a 
choice of two things, either use it for filling the stopes or treat it 
at a small profit. To get this small profit the chloridising and 
lixiviation works have been erected. The first part of this plant 
consists of the necessary crushing and power machinery for reduc- 
ing the ore to the required state of fineness. Salt is added during 
the crushing operation from 4} to 64 per cent., by weight. The 
mixture of crushed ore and salt is elevated into hoppers, from 
which the ore is automatically fed into a series of eight Howell 
Revolving Cylinder Furnaces, which chloridise from 30 to 40 tons 
of ore per furnace daily. All of the furnaces are not in constant 
work, some always being kept as stand-by furnaces, ready for use 
at any time. These furnaces automatically deliver the chloridised 
ore into trucks, which are picked up by arevolving steam crane, 
the ore being dumped out to cool on a large open floor. 
The quantity of ore treated weekly averages from 1,400 to 1,500 
tons, at a cost for all expenses, such as superintendence, coal, 
