Rhodium metal is lustrous and silvery white. Rhodium has a higher melting point and lower density than platinum. It has a high reflectance and is hard and durable. Upon heating it turns to the oxide when red and at higher temperatures turns back to the element. Rhodium it is unaffected by air and water up to 600 C. It is insoluble in most acids, including aqua regia, but is dissolved in hot concentrated sulfuric acid and it is attacked by molten alkalis.
Used as catalytic converters for cars.
Furnace windings, pen nibs, phonograph needles, high-temperature thermocouple and resistance wires, electrodes for aircraft spark plugs, bearings and electrical contacts.
Used to plate jewelry and the reflectors of searchlights, due to its brilliance and resistance to tarnish.
It is also a highly useful catalyst in a number of industrial processes, such as the BP-Monsanto process.