NEW PROCESS FOR EXTRACTION OF SILVER.

Thames Guardian and Mining Record, Volume I, Issue 26, 6 November 1871, Page 3

NEW PROCESS FOR EXTRACTION OF SILVER.

The chemistry of Kroncke’s method of amalgamating silver ores has beeu investigated by Louis Eich. On treating the finely-ground red ore with a hot solution of chloride of copper and salt, the powder becomes black. Mr. Eich finds that this arises from the formation of sulphide of copper and sulphide of the ore of silver, the antimony being converted into the chloride, and entering the solution. The addition of a second portion of chloride of copper and salt to the precipitated sulphide of silver, in the presence of zinc, reduces the silver almost immediately to the metallic state. In this case the copper again forms a sulphide with the sulphur, in combination with the silver, thus forming chloride of silver, which in its turn parts with its chlorine of zinc In working this process, it is necessary to take care that the solutions of copper and salt are very concentrated, and the finelyground ores must he used dry, as otherwise they could not be rapidly saturated with the solutions, and the basic salts would also be formed. Another difficulty sometimes arises from the precipitation of copoer by the zinc amalgam if it he in excess ; when this happens Kruncke redissolves it from the pressed amalgam with hot chloride of copper. This process is the one most commonly employed for treatment of the South American silver ores of the West Coast.