GB800153A - Process for the electrolytic production of indium of high purity - Google Patents

Abstract

800,153. Electrolytic production of indium. RARE METALS FOUNDATION. Jan. 6, 1955 [Jan. 11, 1954], No. 482/55. Class 41. Indium of at least 99.99 per cent purity is electrolytically deposited on a fixed cathode in a cell having an anode consisting of an indium amalgam in which the only impurity metals are more noble than indium by applying across the cell a potential of 680 mV. measured against a IN mercurous chloride electrode. The amalgam may be produced either by dissolving impure indium directly in mercury or by electrolysis of an aqueous solution of an impure indium salt such as indium chloride buffered with hydrochloric and acetic acids using a mercury cathode, the salt concentration being maintained either by periodic addition if a graphite anode is used or by employing a soluble anode of impure indium. Electrolytically produced amalgam may be continuously fed as anode into the decomposition cell, where it is agitated, and is returned with a reduced indium content, preferably not less than 1 per cent, as cathode of the amalgamating cell. The electrolyte in the amalgam decomposition cell may be a solution of pure indium chloride in an aliphatic alcohol of not more than 4 carbon atoms, e.g. methyl or ethyl alcohol, or an aqueous solution in which case hydrolysis of the indium salt is prevented by the addition of an acid, preferably a mixture of hydrochlorics, acetic acids, or a complexing agent such as an alkali metal cyanide.