Indium, a rare chemical element. Indium is a soft, silvery-white metal, easy to melt and mold. Traces occur in many ores, especially zinc ores, the main source. When used in alloys or as plating, indium lends hardness, strength, and resistance to corrosion. It is used to plate aircraft bearings and in lubricants, solders, jewelry, dentures, and atomic reactors (to detect free neutrons). Ferdinand Reich and H. T. Richter discovered indium in 1863.
Symbol: In. Atomic number: 49. Atomic weight: 114.82. Specific gravity: 7.31. Melting point: 313.9 F. (156.6 C.). Boiling point: 3,776 F. (2,080 C.). Indium belongs to Group III-A of the Periodic Table and has a common valence of +3.