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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. 1911 edition. Excerpt: ...for at least 20 or 30 minutes, to separate the silver from gold. The ratio of 2 and 2.5 to 1 is used practically only in the bullion assay. In parting beads from ore assays, it is considered necessary to have at least five times as much silver as gold present. The addition of silver to gold or to the gold-silver alloy in order to prepare for parting is termed inquartation, from the fact that at least 3 parts of silver to 1 part of gold were formerly considered necessary. The nitric acid used for parting must be free from hydrochloric acid and chlorine in order not to have a solvent action on the gold.1 Nitric acid should be examined for chlorides before being used for parting. In order to part silver from gold successfully, the following points must receive careful consideration: (1) The strength of the acid used; (2) the temperature of the acid; (3) the ratio of gold to silver in the bead to be parted. 1. The proper strength of acid is of great importance. Formerly, most authorities recommended that acids of 1.16 and 1.26 sp. gr. respectively--2 parts water to 1 of acid (1.42 sp. gr.) and 1 of water to 1 of acid--be used, first the weak acid and then the stronger acid. T. K. Rose recommends 4 parts acid to 3 parts water, which strength, if the acid be heated, will not break up the gold in the bead into fine particles, even if 50 parts of silver are present to 1 part of gold. Gold is less apt to break up when it is less than 0.10 mg. in weight. Keller2 recommends i Consult the caption Solution of Gold by HN03, in Chapter XI. 2 Keller, Trans. A. I. M. E., XXXVI, 3. acid of the following strength: 1 part acid (sp. gr. 1.42) to 9 parts distilled water. In this strength of acid the gold almost invariably remains in a coherent...

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