Rhodium

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William Hyde Wollaston discovered rhodium in 1803 in London, England in crude platinum ore from South America. He dissolved the ore in aqua regia, neutralised the acid with sodium hydroxide, and precipitated the platinum by treatment with ammonium chloride, as ammonium chloroplatinate. Palladium was then removed as palladium cyanide by treatment with mercuric cyanide. What remained was a red material containing rhodium chloride salts from which rhodium metal was obtained by reduction with hydrogen gas.

Symbol: Rh
Atomic number: 45
Atomic weight: 102.90550
Density (at room temperature and pressure): 12.4 g/cc
Melting point: 1,966°C
Boiling point: 3,695°C
Main valences: +1, +3
Ground state electron configuration: [Kr]4d⁸5s¹

Rho"di*um (?), n. [NL., fr. Gr. "ro`don the rose. So called from the rose-red color of certain of its solutions. See Rhododendron.] Chem.

A rare element of the light platinum group. It is found in platinum ores, and obtained free as a white inert metal which it is very difficult to fuse. Symbol Rh. Atomic weight 104.1. Specific gravity 12.

© Webster 1913.