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Hydroch
loric acid. This method consists in exchange aurocyanide anion by chloride ions provided by hychloric acid. The hydrogen cyanide obtained during the reaction can be adsorbed onto a sodium hydroxide so that can be recycled to the cyanidation process. The quantity of sodium cyanide determined in the absorber can exceed more than 36% the whole quantity of free cyanide absorbed by the ion exchange resin indicating that partial decomposition of the adsorbed complex cyanides takes place. The main disadvantages are the evolution of hydrogen cyanide, and its low efficiency for practical applications.
] - +NR3Au(CN)2- + 2HCl = ] - +NR3 Cl + AuCl + 2HCN
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