METALLURGICAL METHODS AT BROKEN HILL. 305 
Broken Hill a difficultly marketable bye-product of zinc tailings 
is produced, running high in zine and silver (up to 40 per cent. 
zinc, and 25 to 35 oz. of silver per ton). The higher grades of 
this particular material are produced at Block 10, and they are 
content to accept as low as 10s. per ton for this product when a 
buyer is to be found. 
ZINC RECOVERY. 
No effort has been made until very late times in Australia to 
recover the zinc from the ore, either directly or from the bye- 
products of the zinc tailings. The Ashcroft process for the recovery 
of zinc has now been at work some time, but so far no results 
have been published as to its success or otherwise. The process 
this company originally started with was an electrolytic one. The 
ore was to be roasted and then leached with ferric chloride, oxide 
of iron depositing with the residual ore and a zinc chloride being 
produced. This, on purification from any gold, silver, or copper 
dissolved, was then subjected to the electric current in vats, the 
anodes being iron and the cathodes zinc. The idea was to re- 
generate the ferric chloride again ; but it is said that some difficulty 
has been experienced in making the cycle of operations act 
properly—ain fact, that the chlorine, instead of being all liberated 
as hydrochloric acid, and therefore in a condition to act on the 
iron anodes, is liberated as free chlorine and is lost. The amount 
of manganese in the ore, and which goes in solution on leaching 
the roasted ore with the ferric chloride, is also said to have inter- 
fered considerably with the deposition of the zinc, more especially 
after the leaching solution has got somewhat charged with the 
salt of this metal. By their latest reports, however, they claim to 
have overcome all the difficulties which have delayed them in the 
past, and we may hope to hear in the near future of the results of 
their efforts. It takes but half an eye to see how important to 
the mining industry at Broken Hill if some zine recovery process 
be made commercially, as well as chemically, successful. The 
chief ore supplies which the mines now have left are, apparently, 
unlimited supplies of zincose lead sulphide, and there is no doubt 
of the effect a good process for zinc would have on the prosperity 
of the whole of the sulphide mines. 
Other attempts have been made to recover the zinc, amongst 
which is an ammonia process, brought out by Mr. Carmichael, 
late of Block 10 and now of the Proprietary. This is based on 
the following reaction :— 
1, ZnO + (NH, ), SO, = ZnSO, + 2NH, + H,O 
and 
2, ZnSO, + INH, + H,O = ZnO + (NH,); SO, 
U 
