Rhodium belongs to the platinum group metals. It is a silvery-white metal that is hard and durable that exhibits high reflectance.
When compared to platinum is has a lower density and a high melting point
The discovery of rhodium has been attributed to William Hyde Wollaston who discovered it in England in 1803. He successfully isolated it from a crude ore shortly after having discovered palladium.
The name rhodium is derived from the Russian word “rhodon” which means rose.
Rhodium is found in its elemental form in North America. It is also found in association with nickel and copper in Canada and South Africa. The latter is the largest exporter of Rhodium.
The production of rhodium is quite involved as it is usually found in ores along with metals such as platinum and palladium. Separation from such ores is quite complex. For this reason, rhodium is often produced as a by-product of other metals extraction, when its production becomes more economical.
Ores are treated to remove precious metals such as gold, silver, palladium and platinum. The resultant residue is melted using NaHSO4 and then treated to extract Rh2(SO4)3. Rhodium hydroxide is them precipitated out using sodium hydroxide. This is redissolved using hydrochloric acid to produce H3RhCl6. This is them treated with NaNO2 and NH4Cl which produces (NH4)3[Rh(NO2)6]. The precipitate is then dissolved in hydrochloric acid to produce pure (NH4)3RhCl6. This materials is then heated in a hydrogen atmosphere to yield rhodium metal.