Specifications: Rhodium Rhodium is a chemical element with the symbol Rh and atomic number 45. A rare silvery-white hard transition metal and a member of the platinum group, rhodium is found in platinum ores and is used in alloys with platinum and as a catalyst. It is usually the most expensive precious metal, though it is sometimes surpassed by rhenium, depending on the market.
Rhodium is a hard silvery white and durable metal that has a high reflectance. Rhodium metal does not normally form an oxide, even when heated. Oxygen is absorbed from the atmosphere at the melting point of rhodium, but on solidification the oxygen is released.[3] Rhodium has both a higher melting point and lower density than platinum. It is not attacked by acids: it is completely insoluble in nitric acid and dissolves slightly in aqua regia. A complete dissolution of rhodium in powder form is only obtained in sulfuric acid.
Applications
The primary use of this element is as an alloying agent for hardening and improving the corrosion resistance[4] of platinum and palladium. These alloys are used in furnace windings, bushings for glass fiber production, thermocouple elements, electrodes for aircraft spark plugs, and laboratory crucibles. Other uses include:
* It is used as an electrical contact material due to its low electrical resistance, low and stable contact resistance, and its high corrosion resistance.
* Plated rhodium, made by electroplating or evaporation, is extremely hard and is used for optical instruments.
* This metal finds use in jewelry and for decorations. It is electroplated on white gold and platinum to give it a reflective white surface. This is known as rhodium flashing in the jewelry business. It also may be used in coating sterling silver in order to strengthen the metal from tarnish, as a result from the copper compound found in sterling silver.
* It is also a highly useful catalyst in a number of industrial processes (notably it is used in the catalytic system of automobile catalytic converters and for catalytic carbonylation of methanol to produce acetic acid by the Monsanto process). It is used to catalyse addition of hydrosilanes to a double bond, a process important in manufacture of certain silicone rubbers.
* The complex of a rhodium ion with BINAP gives a widely used chiral catalyst for chiral synthesis, as in the synthesis of menthol.
* It is also used as a filter in mammography systems because of the characteristic x-rays it produces.
* It is also used in high quality pen surfaces due to its high-resistance characteristics. These pens include Graf von Faber-Castell, Caran D'ache which are rather less famous than Montblanc, but produces very limited pens.
