Indium is a soft, ductile, silver-white metal, which melts at 155° and is volatile at a red heat. It crystallises, like aluminium, but unlike zinc, in the cubic system, being electrolytically deposited from its sulphate solution in regular octahedra. Its density is 7.277 at 20°, its coefficient of expansion, 0.0000459, and its specific heat (0° to 100°) is 0.0570. The atomic refraction 6f indium in its compounds is 17.4 (for the Hα line; Gladstone and Dale's formula). Indium is diamagnetic.
The flame, arc, and spark spectra of indium are characterised in the visible region by two brilliant indigo-blue lines, 4511.55 and 4101.95. The most persistent lines in the spark spectrum of indium, and therefore the lines that should be looked for when seeking traces of the element, are (Exner and Haschek's wave-lengths) 4511.55* 4101.95,* 3256.22* 3039.46* 2941.39, 2890.35, 2710.39, 2306.20, those asterisked being the most sensitive. |
| Indium readily alloys with gallium, gold, lead, tin, and sodium, and easily forms an amalgam with mercury. When electrolytically deposited in a platinum dish it alloys with the platinum. |