cyanide process

cyanide process or cyanidation, method for extracting gold 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.

The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.

More on cyanide process from Fact Monster:

  • refining - refining refining, any of various processes for separating impurities from crude or semifinished ...
  • cyanide - cyanide cyanide , chemical compound containing the cyano group, -CN. Cyanides are salts or esters ...
  • silver - silver silver, metallic chemical element; symbol Ag [Lat. argentum]; at. no. 47; at. wt. 107.8682; ...
  • metallurgy: Separation of the Metal - Separation of the Metal Processes for separating the metal from the impurities it is found with or ...
  • gold - gold gold, metallic chemical element; symbol Au [Lat. aurum=shining dawn]; at. no. 79; at. wt. ...

See more Encyclopedia articles on: Compounds and Elements