Product Reference

Physical and chemical characteristics:

• Latin name Rhodium (Rh);
• chemical element of Group VIII in Mendeleev's periodic table;
• Atomic number 45;
• Atomic weight 102.9055;
• Density 12.41 g/cmі
• Melting point 1,963°C

A bluish-white metal resembling aluminium, hard and fragile. Highly reflective, becomes more flexible when heated.

Rhodium is chemically resistant. Under normal conditions it does not oxidize in air and in water. When heated it gets covered by a black film of oxide, which disappears at temperatures higher than 1,200°C. Rhodium is resistant to the effects of acids (with the exception of concentrated sulphuric acid) and aqua regia, as well as sulphur, chlorine and fluorine.

It is one of the platinum group metals.

History:

Rhodium was discovered in 1804 by the British scientist William Hyde-Woollaston, immediately after his discovery of palladium. Woollaston dissolved virgin platinum in aqua regia, and then neutralized the excess acid with caustic soda. From the neutralised solution, he precipitated platinum with ammonium chloride, and palladium with mercury cyanide. The filtrate, processed with muriatic acid to get rid of the excess of mercury cyanide, was boiled dry. The residue, after having been treated with alcohol, turned out to be a dark red powder of double sodium rhodium salts of muriatic acid (chloride). The metal is then easily obtained by heating this powder in a stream of hydrogen.

Rhodium gets its name from the Greek "rhodon", which means "rose", on account of the pinkish red colour of its salts.

Uses:

Rhodium is used in alloys with platinum (for the manufacture of catalysts, thermocouples, etc.), and is used to cover mirrored surfaces in astronomical instruments. It is used in jewellery production as decorative and protective plating. Objects made from non-precious metals and silver become very resistant to wear and tear when covered with a layer of rhodium. It is also used in the manufacture of reflectors, electrical contacts, and in the chemical industry.