From the CRC handbook of Chemistry and Physics, CRC Press, Cleveland, 55th ed., 1974-75 "The Elements" by C.R. Hammond. page B-6
INDIUM (from the brilliant indigo line in its spectrum), In; at. wt. 114.82; at. no. 49; m.p. 156.61 C; b.p. 2080 C; sp.gr. 7.31 (20 C); valence 1, 2, or 3. Discovered by Reich and Richter, who later isolated the metal. Indium is most frequently associated with zinc minerals, and it is from these that most commercial indium is now obtained; however, it is also found in iron, lead, and copper ores. Until 1924, a gram or so constituted the world's supply of this element in isolated form. It is probably about as abundant as silver. One to 1.5 million troy ounces of indium are now produced annually in the Free World. Japan is presently producing more than 250,000 troy oz. annually. The present cost of indium is about $1.50 to $5.00/troy oz., depending on quantity and purity. It is available in ultrapure form. Indium is a very soft, silvery-white metal with a brilliant luster. The pure metal gives a hig-pitched "cry" when bent. It wets glass, as does gallium. It has found application in making low-melting alloys; an alloy of 24% indium-76% gallium is liquid at room temperature. It is used in making bearing alloys, germanium transistors, rectifiers, thermistors, and photconductors. It can be plated onto metal and evaporated onto glass forming a mirror as good as that made with silver, but with more resistance to atmospheric corrosion. There is evidence that indium has a low order of toxicity. Normal hygienic precautions should provide adequate protection.
