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Rhodium
Rhodium is one of the six elements in the platinum group, which consists of platinum, palladium, rhodium, osmium, iridium, and ruthenium. Often found with deposits of platinum and commonly obtained from the mining and refining of platinum, it is considered the rarest and most valuable precious metal—more valuable than gold or silver. Rhodium is a silver-white metallic element with high melting and boiling points. It is highly reflective and resistant to corrosion and oxidation, which is why it is also classified as a noble metal. Rarely used by itself, rhodium metal is almost always used as an alloy.
Rhodium was discovered in 1803 by English chemist William Hyde Wollaston shortly after his discovery of palladium. Wollaston extracted rhodium from a piece of platinum ore that he had obtained from South America. Rhodium was named for the rose-red color of its salts, after the Greek word "rhodon," which means rose.
The Thermo Scientific portfolio of rhodium products can be used in a wide range of research applications. Explore our PremIon line of precious metal compounds and pure elements. The minimum purity of our PremIon line of products is 99.99% (metals basis). PremIon pure elements include platinum, palladium, iridium, ruthenium, osmium, silver, and gold.
In addition to our catalog offerings below, our products are available in bulk quantities and pack sizes that can be customized to your requirements.
Rhodium compounds
Rhodium alloys
Chemistry
Rhodium is used in research and industrial laboratories primarily as a catalyst. It is preferable to the other platinum group catalysts in the reduction of nitrogen oxides to nitrogen and oxygen. Rhodium is also used to catalyze the reduction of benzene to cyclohexane as well as the addition of hydrosilanes to double bonds, an important step in the manufacture of certain silicone rubbers. In industry, it is used in the catalytic carbonylation of methanol to produce acetic acid by the Monsanto process. The coordination complex of rhodium(I) with tris(triphenylphosphine)chloride, known as Wilkinson's catalyst, is widely used in the hydrogenation of alkenes. The rhodium complex with BINAP(2,2′-bis(diphenylphosphino)-1,1′-binaphthyl) is used for chiral synthesis, as in the synthesis of methanol. Rhodium's ability to withstand high temperatures makes it a perfect material for laboratory crucibles.
Emission control devices
Approximately 87.2% of world rhodium production is used in catalytic converters, often together with palladium and/or platinum, to clean vehicle emissions. It has by far the highest activity for the removal of nitrogen oxides (NOx) from exhaust fumes, as well as very high activity for the oxidation of hydrocarbons and carbon monoxide and very good resistance to the poisons present in the exhaust stream. Its primary drawback, however, is its high cost.
Jewelry and decoration
Its brilliance and resistance to wear and tarnishing make rhodium a perfect material for jewelry. It is electroplated on white gold and platinum jewelry with a surface that guards against scratches and gives a reflective white appearance, preventing tarnishing during wear. It is also used in coating sterling silver to protect against tarnish from the silver sulfide produced from atmospheric hydrogen sulfide. Rhodium has also been used to signify elite status, when more commonly used metals such as silver, gold, or platinum were deemed insufficient, as when in 1979 the Guinness Book of World Records gave Paul McCartney a rhodium-plated disc for being history's all-time best-selling songwriter and recording artist.
Industry
Rhodium is used in the glass industry, mostly for production of fiberglass and flat-panel glass, and in the chemical industry, such as in producing some herbicides, as well as acids such as nitric acid and acetic acid. In automobile manufacturing, rhodium is used in the construction of headlight reflectors. Because of its rarity and its inertness against corrosion and most aggressive chemicals, rhodium is usually alloyed with platinum or palladium for use in high-temperature and corrosion-resistive coatings. Rhodium is sometimes used to cure silicones. Rhodium plated by either electroplating or evaporation is used in the manufacture of optical instruments as well as filters for mammography systems because of the characteristic X-rays it produces. Rhodium neutron detectors are used in nuclear reactors to measure neutron flux levels, providing an accurate 3D "picture" of reactivity and allowing fine tuning to determine the most economical consumption of nuclear fuel.
Electrical applications
Rhodium is often alloyed with platinum and iridium to make an oxidation-resistant metal that can withstand high temperatures. These alloys are used in furnace coils, thermocouple and resistance wires, and electrodes for aircraft spark plugs. It is also used in electrical contacts, where it is valued for its low electrical resistance, low and stable contact resistance, and great corrosion resistance.
Rhodium compounds
Rhodium alloys
Chemistry
Rhodium is used in research and industrial laboratories primarily as a catalyst. It is preferable to the other platinum group catalysts in the reduction of nitrogen oxides to nitrogen and oxygen. Rhodium is also used to catalyze the reduction of benzene to cyclohexane as well as the addition of hydrosilanes to double bonds, an important step in the manufacture of certain silicone rubbers. In industry, it is used in the catalytic carbonylation of methanol to produce acetic acid by the Monsanto process. The coordination complex of rhodium(I) with tris(triphenylphosphine)chloride, known as Wilkinson's catalyst, is widely used in the hydrogenation of alkenes. The rhodium complex with BINAP(2,2′-bis(diphenylphosphino)-1,1′-binaphthyl) is used for chiral synthesis, as in the synthesis of methanol. Rhodium's ability to withstand high temperatures makes it a perfect material for laboratory crucibles.
Emission control devices
Approximately 87.2% of world rhodium production is used in catalytic converters, often together with palladium and/or platinum, to clean vehicle emissions. It has by far the highest activity for the removal of nitrogen oxides (NOx) from exhaust fumes, as well as very high activity for the oxidation of hydrocarbons and carbon monoxide and very good resistance to the poisons present in the exhaust stream. Its primary drawback, however, is its high cost.
Jewelry and decoration
Its brilliance and resistance to wear and tarnishing make rhodium a perfect material for jewelry. It is electroplated on white gold and platinum jewelry with a surface that guards against scratches and gives a reflective white appearance, preventing tarnishing during wear. It is also used in coating sterling silver to protect against tarnish from the silver sulfide produced from atmospheric hydrogen sulfide. Rhodium has also been used to signify elite status, when more commonly used metals such as silver, gold, or platinum were deemed insufficient, as when in 1979 the Guinness Book of World Records gave Paul McCartney a rhodium-plated disc for being history's all-time best-selling songwriter and recording artist.
Industry
Rhodium is used in the glass industry, mostly for production of fiberglass and flat-panel glass, and in the chemical industry, such as in producing some herbicides, as well as acids such as nitric acid and acetic acid. In automobile manufacturing, rhodium is used in the construction of headlight reflectors. Because of its rarity and its inertness against corrosion and most aggressive chemicals, rhodium is usually alloyed with platinum or palladium for use in high-temperature and corrosion-resistive coatings. Rhodium is sometimes used to cure silicones. Rhodium plated by either electroplating or evaporation is used in the manufacture of optical instruments as well as filters for mammography systems because of the characteristic X-rays it produces. Rhodium neutron detectors are used in nuclear reactors to measure neutron flux levels, providing an accurate 3D "picture" of reactivity and allowing fine tuning to determine the most economical consumption of nuclear fuel.
Electrical applications
Rhodium is often alloyed with platinum and iridium to make an oxidation-resistant metal that can withstand high temperatures. These alloys are used in furnace coils, thermocouple and resistance wires, and electrodes for aircraft spark plugs. It is also used in electrical contacts, where it is valued for its low electrical resistance, low and stable contact resistance, and great corrosion resistance.
Find rhodium in our interactive periodic table
Learn about the physical properties of rhodium or any element, select products by format, and find compounds and alloys.