Indium - (from the brilliant indigo line in its spectrum),In; at. wt. 114.818(3); at. no. 49; f.p. 156.5985 deg C; b.p. 2072 deg C; sp. gr. 7.31 (20 deg C); valence 1, 2, or 3. Discovered by Reich and Richter, who later isolated the metal. Indium is most frequently associated with zinc materials, and it is from these that most commercial indium is now obtained; however, it is also found in iron, lead, and copper ores. Until l924, a gram or so constituted the world's supply of this element in isolated form. It is probably about as abundant as silver. About 4 million troy ounces of indium are now produced annually in the Free World. Canada is presently producincg more than 1,000,000 troy ounces annually. The present cost of indium is, about $2 to $10/g, 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 high-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 photoconductors. 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; however, care should be taken until further information is available. Sixty seven isotopes and isomers are now recognized (more than any other element). Natural indium contains two isotopes. One is stable. The other, 115In, comprising 95.71% of natural indium is slightly radioactive with a very long half-life.