INDUSTRIAL AND ENGINEERING CHEMISTRY
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From the above brief consideration of the problems which have been partially solved by the chemists and those on which little headway has been made, it can be seen that, although quick-freezing has progressed a long way commercially, a great deal still needs to be done by the research worker if all of the problems are to be satisfactorily solved.
(3) Kohman, E. F.. Paper presented before the Pea Section a t the (4)
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LITERATURE CITED (1) Birdseye, C., Food Ind., 3, 213 (1931). (2) Birdseye, C., and Fitzgerald, G. A., IND.ENQ. CHEM.,24, 676 (1932).
Vol. 24, No. 6
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25th Annual Convention of the Nat. Cannera Assoc., Chicago, Ill.. Januarv 25 to 29., 1932. ~ ~ Overholser, E. L.,and Cruess, w. V., Calif. Agr. Exp. Sta., Tech. Paper 7 (1923). Plank, R., Ehrenbaum. E.. and Reuter, K.. “Die Konservierunn von Fischen durch das Gefrierverfshrung,” Zentral Einkaufgesellschaft, Berlin, 1916. Taylor, H. F., Bur. Fisheries, Document 1016 (1927). Tressler, D. K., and Murray, W. T., Fishing Gaz., 49, No. 2, 24-6 (1932).
RECEIVED April 7, 1932. [ E N DOF SYMPOSIUM]
Indium Available in Commercial Quantities WILLIAMS. MURRAY,805 Watson Place, Utica, N. Y.
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I K E many other elements, indium was discovered several years before sources and processes of recovery made it available for commercial use. Reich and Richter (4) are accredited with having discovered this element in 1863. Because of the indigo-blue lines which are in its spectrum, it.was named “indium.” It was one of those elements which was supposed to be widely distributed in several kinds of ores, but always in minute amounts. Later a zinc ore in Germany was reported to contain as high as 0.1 per cent. So far as the writer knows, no definite and serious effort was made to find lasting sources for this metal until a careful survey of all known ores was made. Because of the success of these efforts, indium can now be made available in substantial commercial amounts.
PROPERTIES OF INDIUM The properties of this element are fairly well known. It is a white lustrous metal, very soft and ductile, and slightly
heavier than zinc; it melts a t 155” C. and is said to boil at about 1450” C. It has very great surface stability at ordinary temperatures, but oxidizes and burns a t temperatures above its melting point, especially if finely divided. Indium is supposed to be trivalent in its stable compounds. Several of these are listed in the usual references. Especial attention has been given to its halogen compounds which are quite unstable. The cyanide is reported to be insoluble in water but soluble in cyanides of other elements. There are also listed the hydroxide, oxides, sulfide, and sulfite. It is believed that little is really known about indium and its compounds; the reason for this is that there have been heretofore but small amounts available for research, and therefore little interest was shown in such work. The physical properties are very concisely stated in a paper by Westbrook (6) from which the following is taken: Atomic weieht 114.8 3 (usually); also 2 and 1 Valence 115 Melting point, C. 1450 Boiling point, C. 7 .12 Specific gravity5 L.31 ‘27;3 Specific heat, joules per gram atom Electrical resistivity: A t 20’ C., ohms 9 x 10-6 29 X 10-6 At 155’C ohms Thermal expLnsion (Z/Ldl/dt) at 20’ C . 33 x 10-6 Hardness O Brinell 1 7.99 Tensile sirength (99.71% pure). tons per sq in. a According t o two different authorities.
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It is believed by several that changes will be made in the above values accredited to its specific gravity, its hardness, and its tensile strength.
USESFOR INDIUM Considerable work has been done on the electrolytic deposition of the element. Thiele (5) in 1904 deposited indium from a bath slightly acidified with sulfuric acid. Dennis and Geer ( 1 ) in 1904 used formic acid. Kollock and Smith (8) in 1910 used gelatin as an addition agent in the presence of free sulfuric acid, acetic acid, or sodium acetate. Mathers (3) used fractional electrolysis as a means for purifying the element. Recent work has shown that all of the above baths are very unstable. Daniel Gray found that sugars or carbohydrates added to a cyanide bath would stabilize it. Westbrook (6) reviewed the work of all except Gray and finally turned to a sulfuric acid bath containing sodium citrate. Fortunately Gray perfected a bath which is entirely stable. Kot only can indium be plated from this bath, but it can be plated simultaneously with other elements. Work has been concentrated not only on the plating of indium but also on its combinations with other metals. I n every case the addition of indium to other elements has especially increased the surface stability and also the hardness of the combination until indium is in excess. Patented processes have been developed which make the recovery of this element in substantial amounts entirely practical. By careful and systematic search of all known ores, a district was found which has very rich indium ore deposits. The indium seems to be a replacement in the ore of this particular district. By concentration, the ore has been made to yield a very high percentage of its indium content. These deposits will furnish substantial amounts of this element. Assistance can be furnished to those who wish to work with this metal, not only in the pure state but also in the form of many of its salts. Already several uses have been found for this element. It would seem to have use in the automotive, electrical, jewelry, and dental fields. There are undoubtedly many other places in which this element may be used. It would be desirable to know what it will do in medicine, radio, thermometry, and many other lines of work. Indium is no longer in the gram class, but is surely an ounce of metal. LITERATURE CITED (1) Dennis and Geer, J. Am. Chem. SOC.,26, 438 (1904). (2) Kollock and Smith, Zhid., 32. 1248 (1910). (3) Mathers, F. C., Ihid., 29, 485 (1907). (4) Reich and Richter, J . prakt. Chem., 89, 441; 90, 179; 92, 480 (1863). (5) Thiele, 2. anorg. Chem., 39, 119; 40. 280 (1904). (6) Westbrook, L. R., Trans. Am. Electrochem. SOC.,57, 289 (1930). RECEIVEDApril 18, 1832.
