AUGUST,
1944
411
(3). Another method used is to add NaCl, evaporate to dryness, dissolve in cold water, and treat the resulting solution with H,S. Only a little iron precipitates as FeS and this procedure can be repeated several times for complete separation of the iron and indium. The indium is precipitated as In zS3. Still another method of removing iron is to add KCNS to a solution of the mixed chlorides and extract Fe(CNS), with ether. Indium remains in solution. The addition of alcoholic pyridine solution to the mixed chlorides precipitates InCI, 3C,H,N; FeCI, and AICh remain in solution. InBr, may be sublimed in a stream of CO,; FeBr, is left as a residue. The usual method of purification of indium is by electrolytic deposition. When 1020 3 is heated in hydrogen or in the presence of carbon, the metal is obtained. Metallic indium may be precipitated from an acid solution of an indium compound by the addition of zinc metal. The electrolysis of the chloride or sulfate in the presence of pyridine, hydroxylamine, or formic acid also yields the metal. Commercially, there are three methods of electrolytic deposition. The first is the cyanide bath process patented by the Indium
REFERENCES (1) HOPKINS, "Chapters in the Chemistry of the Less Familiar Elements," Stipes Publishing Company, Champaign, Illinois, 1939, Chapter 8. (2) MELLOR, "Comprehensive Treatise of Inorganic and Theoretical Chemistry," Longmans, Green & Company, London, 1924, Vol. V, pp. 387-405. (3) TREADWELL AND HALL, "Analytical Chemistry," 9th English Edition, John Wiley and Sons, Inc., New York, 1937, pp. 576-7. (4) DERGE, "Tin-indium alloys," Trans. Electrochern. Soc.,
LXXV, 469-71 (1939). (5) DYER, "Indium," Iron Age, 35-9 (Dec .. 1940). (6) DYER, "Recovery of indium from waste liquors," Metals and Alloys, 14,60 (July, 1941). (7) FRENCH, "A new low melting alloy," Ind. Eng. Chern., 27, 1464-5 (1935). (8) FRENCH, "The effect of thallium on the freezing point of indium-Lipowitz alloy," Metals and Alloys, 7, 64 (1936). (9) LUDWICK, "Indium and indium plating," Metal Finishing, 40,13-17 (1942). (10) LUDWICK, "Indium," Steel, III, 80, 122-4 (1942). (11) LAWRENCE AND WESTBROOK, "Indium--occurrence, re· covery and uses," Ind. Eng. Chern., 30, 611-14 (1938). (12) MURRAY, "Indium," Printed Proceedings of the 30th An· nual Convention of the American Electroplaters' Society, June, 1942. (13) RAYMOND, "Bearings and bearing corrosion," S. A. E. Journal (Trans.), 50, 533-37 (1942). (14) SANDERSON, "Indium," Canadian Mining Journal, 63, 156 (1942). (15) SYKES, "Rare and precious metals," Mining and Met., 24, 66-8 (1943). (16) "Handbook of Chemistry and Physics," 24th Ed., Chemical Rubber Publishing Company, Cleveland, 1940-41, pp. 1398 and 1886. (17) Indium News, I, 1-4 (1942). (18) Ibid., I, 1-4 (1943).
