High purity indium prodn. - by two=stage vacuum melting, electrorefining and remelting into molten indium

摘要

High purity indium is produced by (a) two-stage vacuum melting of the metal (i) at 850-940 deg.C for 1-5 hrs. and (ii) at 950-1100 deg.C for 0.5-2hrs.; (b) electrochemically refining the metal in a hydrochloric acid soln., pref. at an indium chloride concn. of 120-200 g/l in the presence of 0.1-0.7g/l thiourea and/or gelatin and at 0.015-0.03A/sq.cm. cathodic c.d.; and (c) remelting the indium residue evolved on the cathode by introducing into molten indium at 160-400 deg.C. The process produces indium contg. contaminants at a level of 0.000001 wt.% with metal losses reduced by 3-6%. The indium is useful in the mfr. of semiconductors.