Process for the manufacture of indium of high purity

Indium chloride is purified by extracting a solution of indium chloride in 7-11 N hydrochloric acid with a mixture of dibutyl and/or tributyl phosphate and an organic solvent, thallium, nickel and cadmium impurities are left in the aqueous hydrochloric acid phase, the purified indium chloride being contained in the organic phase. The aqueous phase preferably contains 40-50 grm. of indium per litre and the organic phase preferably contains 30-50% by weight of dibutyl and/or tributyl phosphate. The inert solvent can be benzene, toluene, chlorobenzene or aliphatic hydrocarbons. Extraction is preferably carried out with equal volumes of organic and aqueous phases. After extraction the organic phase is washed with 8-11 NHCl. The organic phase is then extracted with water or 0.1-0.5N hydrochloric acid and the aqueous solution of indium chloride is subjected to electrolysis either directly or after conversion of the chloride into the sulphate (see Division C7). French Specification 1,286,101 is referred to.ALSO:Indium chloride which has been extensively purified (see Division C1) is subjected to electrolysis either directly or after conversion of the chloride to the sulphate. The electrolysis is carried out firstly, with a potential adapted to deposit on a first cathode, impurities which are less electro-negative than indium and, secondly, with a higher potential adapted to deposit on a second cathode the indium. The solution contains 200 g. of indium per litre and has a pH of 1-1.5. The first electrolysis is carried out with a cathodic potential of -560 millivolts measured against a saturated calomel electrode, with a mean current density of 0.05 milliampere/cm.2, and the second electrolysis is carried out with a cathodic potential of -700 millivolts and a current density of 2 milliamperes/cm.2. French Specification 1,286,101 is referred to.