Definition

Iridium is the chemical component with atomic number 77. A very solid, brittle, silvery-white transition metal of the platinum family, iridium is the second densest component and is the most corrosion-resistant metal, even at temperatures as high as 2000 °C. Although only firm molten salts and halogens are corrosive to solid iridium, finely divided iridium dust is much more reactive and can even be flammable. The most important iridium compounds in conditions of use are the salts and acids it forms with chlorine, though iridium also forms a number of organometallic compounds used in catalysis and in research.

Properties

A member of the platinum group metals, iridium is white, similar to platinum, but with a slight yellowish cast. Due to its stiffness, brittleness, and very high melting point, solid iridium is hard to machine, form, or work, and thus powder metallurgy is commonly employed instead. It is the only metal to maintain good mechanical properties in air at temperatures above 1600 °C.

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