HISTORICAL NOTES: MIXING, METALLURGICAL AND STATISTICAL. 37
centrales were mixed with nitrate of potash or soda and roasted in a reverberatory furnace at a low heat.
Lieber stated * in 1856 that a process for roasting sulphurets, with subsequent amalgamation, had been introduced by a Mr. C. Ringel at a mine near Rutherfordton, X. C. (this was probably the Alta mine), and was afterwards practiced with success on old tailings at the Gold Hill and other mines in Xorth Carolina.
In the past history of the Southern mines a vast number of roasting processes and furnaces have been introduced, many of them approaching the ludicrous, but they have never lasted beyond the experimental stage. Heap-roasting with salt was also tried.
Some of the furnaces, particularly of the well-known reverberatory type, were successful enough so far as the roasting went; the fault lay in the prevalent and popular belief that, by oxidizing the sulphurets, the difficulty of amalgamating the precious metals, which had been set free, would be removed, when in fact the resulting coating of iron oxide was nearly as fatal to the work as the sulphide had been.
The Bartlett method of making white lead-zinc oxide was introduced at the Silver Hill mine, Xorth Carolina, in 1871-2. It consisted in roasting the concentrated galena-blende and condensing the zinc-lead oxide fumes, which made a good paint material. The process is said to have been carried on successfully until all the available suitable material was exhausted.
CHEMICAL TREATMENT.
The next step was in the direction of a chemical treatment of these refractory sulphurets. It would be useless to outline the numerous processes that were experimented with for this purpose. The South has been, much to its detriment, the " proving ground " of almost all the patent gold-saving processes invented, and the greater proportion of these have, as might have been predicted, resulted in utter failure. Of all these the chlorination process is practically the only survivor; and there is a possibility of the successful application of the cyanide process.
THE CHLORINATION PROCESS.
It was not until 1879 that the successful treatment of pyritic sulphurets was accomplished by the introduction of the chlorination process. In that year a Alears chlorination plant was erected at the Phoenix mine, Xorth Carolina, under the management of Jlr. A. Thies, who soon improved on and developed it into what is now universally known as tlie Thies process.
