GB485089A - Improvements in electrolytic metal treatment - Google Patents

Abstract

485,089. Electrolytic treatment of metals. LANG, H. M. Oct. 13, 1936, No. 27822. Convention date, Oct. 14, 1935. [Class 41] Continuous conversion or corrosion, particularly solution of a metal anode is effected by alternating current by the use of a rectifying cathode. The process is particularly applicable to the refining of gold. In the gold refilling apparatus shown, cathodes 5, 6 of tantalum are connected across a transformer 14, the anode 1 being connected to the mid-point so as to provide whole - wave rectification. The cathodes are enclosed in porcelain containers 7, 8 to prevent deposition of metal thereon. The anolyte consists of 15-25 per cent hydrochloric acid together with a small amount of an oxidizing agent such as sodium nitrate or nitric acid and the catholyte consists of 36 per cent hydrochloric acid. The cathodes are tubular for the passage of a cooling medium. By the adjustment of resistances 19, 20 an alternating current may be superimposed on the direct current passing through the electrolyte. A resistance 17 may be inserted in the anode lead. By means of a tapping 18 direct current may be drawn off for operating another cell. The electrolyte may alternatively consist of alkali metal cyanide solution. When aluminium cathodes are employed, the catholyte may consist of sodium tetraborate solution with or without addition of boric acid. After electrolysis silver chloride in suspension is removed by settling, and gold is precipitated therefrom by a reducing agent such as sodium bisulphite and washed.