The cyanide process for the extraction of gold and its practical application on the Witwatersrand goldfields and elsewhere - Softcover

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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1898 Excerpt: ...to the success of the MacArthur-Forrest process. The ores of the Black Reef series, near Johannesburg, carry a small quantity of copper pyrites, and consequently the extraction of gold by cyanide does not give as good results as on the Main Reef series. In this connection it is important to mention here a point which the inventors of the cyanide process have strongly emphasised--namely, the selective action of weak solutions of cyanide for gold in preference to other metals. It is a strange fact that, while gold is one of the most difficult of metals to dissolve in acids, it is extremely susceptible to the weakest solution of cyanide, when copper and other metals might According to Mr. Bettel. remain unaffected in it. The successful use of very weak solutions may have much wider and more important consequences. It is well known that the MacArthur-Forrest process has failed in some mining districts in the treatment of complex ores; and it has seemed to me not unlikely that when experimenters with the cyanide process have met with difficulties such as this, they have increased the strength of their solutions, using more cyanide in the hope of overcoming the disturbing presence of the baser metals. I shall presently give an account of the process introduced by Messrs. Siemens and Halske, who have adopted the diametrically opposite course; they have taken weaker solutions. If they had confined themselves to the chemical precipitation of the gold upon zinc or some other metal, as in the MacArthurForrest patent, they would have failed, because a point arrives at which chemical precipitation, in exceedingly dilute solutions, becomes imperfect. But the introduction by Messrs. Siemens and Halske of the agency of electricity solved the problem at once. Now it is quit...