cyanide process


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cyanide process

or

cyanidation,

method for extracting goldgold,
metallic chemical element; symbol Au [Lat. aurum=shining dawn]; at. no. 79; at. wt. 196.96657; m.p. 1,064.43°C;; b.p. 2,808°C;; sp. gr. 19.32 at 20°C;; valence +1 or +3.
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 from its ore. The ore is first finely ground and may be concentrated by flotation; if it contains certain impurities, it may be roasted. It is then mixed with a dilute solution of sodium cyanide (or potassium or calcium cyanide) while air is bubbled through it. The gold is oxidized and forms the soluble aurocyanide complex ion, Au(CN)2−1. (Silver, usually present as an impurity, forms a similar soluble ion.) The solution is separated from the ore by methods such as filtration, and the gold is precipitated by adding powdered zinc. The precipitate usually contains silver, which is also precipitated, and unreacted zinc. The precipitate is further refined, e.g., by smelting to remove the zinc and by treating with nitric acid to dissolve the silver. The cyanide process was developed (1887) by J. S. MacArthur and others in Glasgow, Scotland. It is now the most important and widely used process for extracting gold from ores.

cyanide process

[′sī·ə‚nīd ‚präs·əs]
(metallurgy)
Process of dissolving powdered gold and silver ores in a weak solution of sodium cyanide or potassium cyanide; the precious metals are precipitated from solution by zinc. Also known as cyanidation.
References in periodicals archive ?
Park, James 1906 The Cyanide Process of Gold Extraction, Fourth Edition, London: Charles Griffin & Co.
Before the cyanide process was developed, refractory gold ores were processed by smelting, using lead or copper collectors for the precious metals, or by chlorination.
In 1913, Dorr undertook the operation of a small mill in South Dakota for the extraction of gold by the cyanide process. The ore was treated with a cyanide solution and the dissolved metal was later precipitated from the solution, fused, and cast into ingots.
Germany banned cyanide processes in 2002, while Greece has ruled against numerous gold mining projects.
This new process claims to reduce the emission of environmentally dangerous compounds compared to traditional cyanide processes.