GB483741A - Improvements in process of gold refining - Google Patents

Abstract

483,741. Electrolysis. BLAUT, S. J. Oct. 26, 1936, No. 29102. Convention date; Oct. 25, 1935. [Class 41] In the parting and refining of gold from an impure gold anode, the gold is electrolytically dissolved in a bath initially comprising concentrated hydrochloric acid free of gold salts. The current density may be between 100 and 900 amperes per square foot, and an alternating current may be superposed to prevent polarization. The concentration of the acid may be restored as it is consumed, and an alkali or alkaline earth chloride may be added to the bath. The temperature may be maintained below 35‹ C. The gold content of the anode may be as low as 4 per cent. The gold deposits on the cathode as a loose spongy mass which drops off and falls to the bottom of the bath. In refining gold parted by the method of the invention, the silver present as chloride may be removed by treatment with ammonia, or sodium thiosulphate, by reduction and solution in nitric acid, or by melting the deposit and floating off the silver chloride, Or the deposit may be dissolved in aqua regia, the nitric acid driven off, the silver precipitated by hydrochloric acid, and the gold then precipitated by adding a reducing agent. Alternatively, the deposit may be refined by electrolysis, using a chlorauric acid bath. After removal of the silver chloride, the deposit may be refined by electrolysis as in parting, the gold being obtained wholly or in part as a solution..