154 TRANSACTIONS OF THE 
precipitator. The type of furnace best adapted to fume 
reduction is still a matter of experimentation. 
At the present stage of experimental development, 
the process seems best suited to oxidized ores, the gangue 
of which is of such a nature that it will withstand the 
necessary temperature in the roasting operation without 
excess clinkering. Zinc is not volatilized successfully, 
results so far being very erratic with this element. Lead, 
copper, gold, and silver are volatilized readily once the 
proper conditions are obtained and work already done 
indicates that the process may be extended to some of 
the other metals. The leach tailings from the extraction 
of zine from certain lead-zine ores should be a promising 
source for experimentation though little work has been 
done on such material so far as I am aware. 
The plant necessary for operation is simple and 
composed wholly of equipment which is already well 
standardized. It consists of an adequate crushing and 
grinding plant with facilities for cheaply handling the 
ore, a cement kiln, a flue system, a Cottrell precipitator 
and a furnace for the treatment of the resulting fume. 
This simplicity and standardization of equipment should 
be a thing decidedly in the favor of the process since it 
makes possible the erection of the plant near the source 
of the ore, a most desirable feature in the treatment of 
low grade ores. Further, the plant will require little 
water and it can therefore be operated in places where 
wet concentrating methods are excluded through lack 
of water. 
Although the process is as yet in the experimental 
stage, four plants of commercial size will soon be in 
operation. Two of these will handle an ore carrying 
copper, one a zinc-lead product, and one a tailing carry- 
ing values in silver, mercury, copper, lead and zinc. 
In conclusion it is of interest to note that these 
plants are all the direct results of the work carriel on at 
the Salt Lake City station of the Bureau of Mines and the 
Department of Metallurgical Research of the University 
of Utah. Their successful outcome will be a worthy 
contribution to metallurgy. 
