Fundamental Studies on Dissolution of Gold in Cyanide Solutions. III : Effects of Alkalis, Lead Acetate, and Some Impurities Contained in Foul Cyanide Solutions

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By dissolving a pure gold plate under air agitation in potassium cyanide solutions, the effects of alkalis, lead acetate and impurities contained in foul cyanide solutions upon the rate of dissolution of gold were examined. It was found that calcium hydroxide, at a lower concentration, rapidly reduces the rate of dissolution, and this seems to be mainly due to the fact that calcium hydroxide would convert the hydrogen peroxide, formed as the intermediate substance of Bodlaender's equations, into rather insoluble calcium peroxide. The addition of lead acetate was found to cause both accelerated and retarded dissolution aud it seems probable that, as lead is electronegative to gold, the gold would deposit lead on its surface, resulting in the formation of local circuits on its surface. Passivity caused by lead acetate seems to be due to the fact that the lead thus deposited would be converted to some insoluble lead compound which would coat gold and prevent the further dissolution of gold. Furthermore the results of the study of the effects of some impurities usually contained in foul cyanide solutions are also given.
東北大学の論文