The element is also alloyed with osmium and is used for fountain pen nibs and compass bearings. It is also used for electrical contacts and is slowly finding it way into medical devices that are implanted into the body.
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It is also recovered as a by-product from the nickel mining industry.Īlthough its principal use is as a hardening agent for platinum, iridium is also used to make crucibles and devices requiring high temperatures. It is commercially obtained from osmiridium a by-product of platinum production. Iridium occurs uncombined in nature with platinum and other metals of this family in alluvial deposits. At present, therefore, we know that either iridium or osmium is the densest known element, but the data do not yet allow selection between the two. These values may be more reliable than actual physical measurements. Calculations of the densities of iridium and osmium from the space lattices give values of 22.65 and 22.61 g/cm3, respectively. The specific gravity of iridium is only very slightly lower than osmium, which is generally credited as the heaviest known element. Iridium is not attacked by any of the acids nor by aqua regia, but is attacked by molten salts, such as NaCl and NaCN. This meter bar was replaced in 1960 as a fundamental unit of length. It is the most corrosion-resistant metal known, and was used in making the standard meter bar of Paris, which is a 90 percent platinum and 10 percent iridium alloy. Because iridium is very hard and brittle, it is hard to machine, form, or work. Iridium, a metal of the platinum family, is white, similar to platinum but with a slight yellowish cast.
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The name iridium is appropriate because its salts are multi-colored. iris, rainbow) Smithson Tennant discovered iridium in 1803 in the residue left when crude platinum is dissolved by aqua regia.