306 PROCEEDINGS OF SECTION B. 
A short description of the process is as follows :—The ore is 
first finely ground and roasted, to leave as much of the zinc as 
possible in the state of the soluble sulphate. It is then placed in 
iron retorts and heated with sulphate of ammonia to complete 
this part of the process and bring about the first reaction given. 
The ammonia distils off through a pipe leading from the end of 
the retort, and dips below the surface of a solution of zinc sulphate 
obtained by leaching with water ore which has been subjected to 
the retort treatment. The second reaction 
ZnSO, + INH, + H,O = ZnO + (NH,), SO, 
is then obtained. The precipitated zinc oxide is: filter-pressed 
out, and the filtrate of dilute regenerated sulphate of ammonia 
has then to be evaporated and crystallised out ready for use again. 
Like all ammonia processes, the extreme difficulty of making 
the joints in the various parts tight, when free ammonia is present, 
has been, in this process, the stumbling block. It is now stated 
that this difliculty has been overcome, and, if so, we may soon 
hear of oxide of zine being prepared by the Proprietary Company 
from their ores. The process is a beautiful one in its chemical 
reactions, but hitherto the loss of ammonia has been prohibitive 
of its use. 
Other oxide processes are the magnesite and the calcium chloride 
processes, both owned by the Smelting Company of Australia ; but 
so far no attempts have been made to start work with them on a 
large scale. This company also owns the Siemens-Halske electro- 
lytic process for the production of metallic zinc. The solvent 
used with this process to extract the zinc from the roasted ore is 
either sulphuric acid or sulphate of iron and alumina, or sulphate 
of alumina alone. There is no doubt that sulphate of iron would 
act as a good solvent for the zinc, and, unlike the leaching solution 
of the Ashcroft process, all of them could be regenerated with no 
loss, except leakage from pipes and waste of that kind. 
I am trenching on the delicate ground of the problem of the 
sulphide ores, and therefore will say no more on the zinc recovery 
processes ; but before leaving the subject I may be permitted to 
hope that so vast a field will continue to find workers, and that in 
time the just reward of their efforts will be obtained, and the 
wealth of the immense sulphide mines of Broken Hill be brought 
within reach. 
