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  2. Gold extraction - Wikipedia

    en.wikipedia.org/wiki/Gold_extraction

    The gold may then be further refined by gold parting, which removes other metals (principally silver) by blowing chlorine gas through the molten metal. Historically, small particles of gold were amalgamated with mercury, and then concentrated by boiling away the mercury. The mercury method is still used in some small operations.

  3. Wohlwill process - Wikipedia

    en.wikipedia.org/wiki/Wohlwill_process

    The resulting gold is 99.999% pure, and of higher purity than gold produced by the other common refining method, the Miller process, which produces gold of 99.5% purity. [1] [2] [3] For industrial gold production the Wohlwill process is necessary for highest purity gold applications.

  4. Gold parting - Wikipedia

    en.wikipedia.org/wiki/Gold_parting

    The very earliest attempts at refining gold can be shown by the surface enhancement of gold rings. Gold quality was increased at the surface by 80–95% gold compared to 64–75% gold at the interior found in Nahal Qanah Cave dated to the 4th millennium BC.

  5. Miller process - Wikipedia

    en.wikipedia.org/wiki/Miller_process

    The resulting gold is 99.5% pure, but of lower purity than gold produced by the other common refining method, the Wohlwill process, which produces gold of up to 99.999% purity. [1] [2] The Wohlwill process is commonly used for producing high-purity gold, such as in electronics work, where exacting standards of purity are required.

  6. Refining (metallurgy) - Wikipedia

    en.wikipedia.org/wiki/Refining_(metallurgy)

    In metallurgy, refining consists of purifying an impure metal. It is to be distinguished from other processes such as smelting and calcining in that those two involve a chemical change to the raw material, whereas in refining the final material is chemically identical to the raw material. Refining thus increases the purity of the raw material ...

  7. Cupellation - Wikipedia

    en.wikipedia.org/wiki/Cupellation

    16th century cupellation furnaces (per Agricola). Cupellation is a refining process in metallurgy in which ores or alloyed metals are treated under very high temperatures and subjected to controlled operations to separate noble metals, like gold and silver, from base metals, like lead, copper, zinc, arsenic, antimony, or bismuth, present in the ore.

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