Rhodium

DescriptionRhodium is one of the platinum group elements, and is found at very low concentrations in the Earths crust. Rhodium was discovered by William Hyde Wollaston (England) in 1804. The origin of the name comes from the Greek word rhodon, meaning rose. The plated solid is very corrosion resistant and exceptionally hard. While inert in air and acids, it can produce a violent reaction to chlorine, bromine pentafluoride, bromine trifluoride, and fluorine monoxide.

OccurrenceRhodium is rare, but not as rare as ruthenium. It makes up only 1 part in 20 million of theelements found in the Earth’s crust. Even so, it is considered the 79th most abundant elementand is found mixed with platinum ore, and to a lesser extent, it is found with copper andnickel ores. It is found in Siberia, South Africa, and Ontario, Canada.Rhodium is recovered from platinum and other ores by refining and purification processesthat start by dissolving the other platinum group metals and related impurities with strongacids that do not affect the rhodium itself. Any remaining platinum group elements areremoved by oxidation and bathing the mixture in chlorine and ammonia.Rhodium is usually produced as a powder and can be formed by either casting or powdermetallurgy.

HistoryWollaston discovered rhodium in 1803-4 in crude platinum ore he presumably obtained from South America. Rhodium occurs native with other platinum metals in river sands of the Urals and in North and South America. It is also found with other platinum metals in the copper-nickel sulfide ores of the Sudbury, Ontario region. Although the quantity occurring here is very small, the large tonnages of nickel processed make the recovery commercially feasible. The annual world production of rhodium in 1999 was only about 9000 kg. The metal is silvery white and at red heat slowly changes in air to the sesquioxide. At higher temperatures it converts back to the element. Rhodium has a higher melting point and lower density than platinum. Its major use is as an alloying agent to harden platinum and palladium. Such alloys are used for furnace windings, thermocouple elements, bushings for glass fiber production, electrodes for aircraft spark plugs, and laboratory crucibles. It is useful as an electrical contact material as it has a low electrical resistance, a low and stable contact resistance, and is highly resistant to corrosion. Plated rhodium, produced by electroplating or evaporation, is exceptionally hard and is used for optical instruments. It has a high reflectance and is hard and durable. Rhodium is also used for jewelry, for decoration, and as a catalyst. Fifty-two and isomers are now known. Rhodium metal (powder) costs about $180/g (99.9%).isotopes

UsesAs an alloy with platinum; as a corrosion-resistant electroplate for protecting silverware from tarnishing; for making high-reflectivity mirrors for cinema projectors, searchlights. Spongy or black rhodium is used as a catalyst in various organic hydrogenation and oxidation reactions.

UsesRhodium is commercially used as an alloy metal with other metals to form durable hightemperatureelectrical equipment, thermocouples, electrical contacts and switches, and laboratorycrucibles.Because of its high reflectivity, it is used to electroplate jewelry, silverware, optical instruments,mirrors, and reflectors in lighting devices.When rhodium is combined with platinum and palladium, the elements together form theinternal metals of automobile catalytic converters, which convert hot unburned hydrocarbonexhaust gases to less harmful CO2 and H2O. Similar alloys are used to manufacture hightemperatureproducts such as electric coils for metal refining furnaces and high-temperaturespark plugs.

UsesRhodium is a transition metal catalyst used in a multitude of inorganic synthesis.

General DescriptionThis product has been enhanced for energy efficiency.

DefinitionA rare silvery hard transition metal. It is difficult to work and highly resistant to corrosion. Rhodium occurs native but most is obtained from copper and nickel ores. It is used in protective finishes, alloys, and as a catalyst. Symbol: Rh; m.p. 1966°C; b.p. 3730°C; r.d. 12.41 (20°C); p.n. 45; r.a.m. 102.90550.

Definitionrhodium: Symbol Rh. A silvery whitemetallic transition element;a.n. 45; r.a.m. 102.9; r.d. 12.4; m.p.1966°C; b.p. 3727°C. It occurs withplatinum and is used in certain platinumalloys (e.g. for thermocouples)and in plating jewellery and opticalreflectors. Chemically, it is not attackedby acids (dissolves only slowlyin aqua regia) and reacts with nonmetals(e.g. oxygen and chlorine) atred heat. Its main oxidation state is+3 although it also forms complexesin the +4 state. The element was discoveredin 1803 by William Wollaston(1766–1828).

DefinitionMetallic element having atomic number 45, group VIII of the periodic table, aw 102.9055, no isotopes, valence = 3.