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In his book "The Extractive Metallurgy of Gold", published 1991 by Van Nostrand Reinhold, ISBN 0 442 31797 2, the author J.C. Yannopoulos writes : "The solubility of gold in an aqueous solution of potassium cyanide was known by alchemists of the 18th century. J.W. Mellor (1923) specifically mentions that Scheele, in 1783, and Bagraton, in 1843, noted that aqueous solutions of alkali cyanide could dissolve gold. Potassium cyanide was mainly used to prepare the electrolyte necessary for electroplating gold and silver by the Elkington process, patented in 1843. "However, L. Elsner was the first to realise the importance of oxygen in the dissolution of gold and silver by aqueous solution of potassium cyanide in 1846...... "Metallurgists....experimented with alkali cyanides as gold solvents for the next 40 years, obtaining results of little or no practical importance. It was J.S. MacArthur and his coworkers R.W. Forrest and W. Forrest who first grasped the practical importance of cyanide leaching of auriferous ores...in 1887. MacArthur and the Forrest brothers patented the dissolution of gold from ground ores by a weak cyanide solution. They also patented its subsequent precipitation from the pregnant solution by zinc shavings, and thus radically changed the gold extraction process." I believe it is true to say that, had the MacArthur/Forrest process not been introduced when it was, the South African gold mining industry would have collapsed in the 1890s. Tony Brewis %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%