934 Transactions of the American Institute. 



mostly a previous roasting of the ore, we will give at fii'st to this 

 interesting topic some attention. 



We have, in the first part of this paper, shown that when sul- 

 phurets in powder form are treated with mercuiy, the gold was 

 very imperfectly amalgamated, and could not all be extracted, 

 only a comparatively small amount of the precious metal uniting 

 with the mercury; and that a perfect and careful roasting of the 

 ore is requu-ed, as well as also a condensation of the resulting vapors. 



I studied carefully the various processes in use, such as Keith's, 

 Whelpley and Storer's, Dr. Hagan's, Crosby and Thompson's, Dr. 

 Ott's, Ryason's and several others, all of which ai*e said to give 

 perfect satisfaction. We will only give to them a rapid glance 

 without comments. 



The furnaces of Messrs. Whelpley and Storer, in Boston, have 

 been described in most of our mining journals; they certainly look 

 as if they could do some good work when properly managed. 



The ore, finely pulverized in their centrifugal crushing and 

 pulverizing machine, is blown, together with charcoal-powder, down 

 a vertical shaft or tower, the gases condensed, and then treated 

 for the dififerent metals. Keith oxidizes the pulverized sulphurets 

 by air in an upward or horizontal direction. Crosby and Thompson 

 do the same in a revolving retort; they condense most of the volatile 

 products. (I learned lately that they get from the condensed smoke 

 as much gold as they extract from the roasted ore.) 



A very neat arrangement for roasting has been patented, and 

 is now being tested in Washington, D. C, by Dr. Adolph Ott, of 

 this city. The sulphurets pass successively through three separate 

 superposed furnaces, in which automatic stirrers keep the ore in 

 motion, and cause it to fall from one oven into the other, receiving 

 three successive treatments, by which the ore is fully decomposed. 



The lighter metals, zinc, antimony, ai"senic and bismuth are con- 

 densed in separate chambers, and the sulphurous gases subjected 

 to a spray before they are allowed to escape through the chimney. 



The desulphurized ore is then moistened by steam, and placed 

 into a large tank, where it is treated with oxy chlorine gas, which 

 rapidly converts the present gold into a soluble salt, the terchloride 

 of gold Au CP which is leached out afterwards, either by pressure 

 or by a centrifugal machine. The solution is then treated with 

 sulphate of iron, or other precipitant, and the pure gold taken from 

 it as a dark brown powder. This is quite an improvement on Prof. 

 Plattner's successful chlorination process, and shows that the origi- 



