Chemical Element: rhodium

(Modern Latin: from Greek, rhodon, "rose"; in reference to the red color of its salts; metal)

Chemical-Element Information

Symbol: Rh
Atomic number: 45
Year discovered: 1803 or 1804

Discovered by: William Hyde Wollaston (1766-1828), a British chemist.


  • William Hyde Wollaston discovered rhodium in crude platinum ore from South America rather soon after his discovery of another element, palladium.
  • He dissolved the ore in aqua regia (a mixture of hydrochloric and nitric acids), neutralized 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.
  • The remaining material was a red material containing rhodium chloride salts from which rhodium metal was obtained by reduction with hydrogen gas.
  • The surface of rhodium has a high reflectivity for light and is not corroded or tarnished by air at room temperature.
  • It is frequently electroplated onto metal objects and polished to give permanent attractive surfaces for jewelry and other decorative purposes.
  • The black tarnish of silver is prevented by the use of rhodium plate.
  • It also is particularly important as an element for the preparation of “silvered” surfaces for reflectors of searchlights and motion-picture projectors.
  • Rhodium is almost as resistant as iridium to chemical attack by acids.
  • This massive metal is not dissolved by hot concentrated nitric or hydrochloric acid or even by aqua regia which dissolves gold and platinum.

Name in other languages:

French: rhodium

German: Rhodium

Italian: rodio

Spanish: rodio


Information about other elements may be seen at this Chemical Elements List.

A special unit about words that include chemo-, chem- may be seen here.