Inhaltsangabe
This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1917 edition. Excerpt: ... Preliminary to Cyanidation.--The objects of roasting an ore before subjecting it to the solvent action of some chemical, are: 1. To oxidize iron, copper, lead, zinc, aluminum, calcium, or magnesium. 2. To volatilize sulphur, arsenic, antimony, bismuth, or tellurium. 3. To sulphatize calcium, magnesium, and to some extent, lead, and zinc. 4. To dehydrate, with the object of agglomerating the ore particles to make them more susceptible to leaching, decantation, or filtration. Usually an ore, which will percolate or filter very slowly before roasting will percolate or filter quite rapidly after roasting. Mill dust, when raw, may be difficult to filter, but after roasting filtration is quite rapid. 5. To make the ore porous. Oxidation of sulphur and telluride ores, by the elimination of sulphur and tellurium, must necessarily make the ore particles more porous, and thus present a greater surface to the action of the solvent. Most ores will yield a much higher extraction after roasting than before, even though they are otherwise equally susceptible to treatment. 6. To free gold and silver particles. Cyanide is not a practical solvent of gold and silver in their telluride combination, and in their sulphide condition they present serious difficulties. After roasting, the gold and silver are reduced to their metallic state and are then readily soluble if the particles have not been fused. Since the cost of roasting entails a heavy additional expense, the increased extraction resulting from the roasting of the ore must be carefully balanced against the extra cost of roasting. After roasting, an ore may be so leachable as to make fine grinding unnecessary, thus giving a small margin of expense to be deducted from the cost of roasting. Tests on...
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