Gold is too soft to make a durable ring out of at 24 karat purity (99.9% pure and up). EnvironmentalChemistry.Wedding bands have traditionally been made of gold with 14 karat (or 58.5% pure) being the most common and 18 karat (or 75% pure) also available.Iridium metal is generally non-toxic due to its relative unreactivity, but iridium compounds should be considered highly toxic. Ir-192 decays into platinum, while most of the other radioisotopes decay into osmium. There are two natural isotopes of iridium, and many radioisotopes, the most stable being Ir-192 with a half-life of 73.83 days. It is recovered commercially as a by-product from nickel mining and processing. Naturally occurring iridium alloys include osmiridium and iridiosmium, both of which are mixtures of iridium and osmium. Iridium is found uncombined in nature with platinum and other platinum group metals in alluvial deposits. The Earth's core is rich in iridium, and Piton de la Fournaise on Réunion, for example, is still releasing iridium today. McLean of Virginia Polytechnic Institute who argue that the iridium was of volcanic origin. However, there are others such as Dewey M. According to many scientists, such as Luis Alvarez of Berkeley, California, this iridium was of extraterrestrial origin, attributed to a comet thought to have struck near what is now the Yucatan Peninsula. The KT event, marking the temporal border between the Cretaceous and Tertiary eras of geological time, was identified by a thin stratum of iridium. In 1960 the Paris meter bar was replaced as definition of the fundamental unit of length (see krypton). This metal was to make the standard meter bar in Paris, which is an alloy of 90 % platinum and 10 % iridium. This element was named after the Latin word for rainbow because its salts are highly colored. Iridium ( Latin iris meaning "rainbow") was discovered in 1803 by Smithson Tennant in London, England along with osmium in the dark colored residue of dissolving crude platinum in aqua regia (a mixture of hydrochloric and nitric acid). Osmium/iridium alloys are used for ball point pen tips and for compass bearings.Īt one time iridium, as an alloy with platinum, was used in bushing the vents of heavy ordnance and in a finely powdered condition (iridium black), for painting porcelain black.Electrical contacts (notable example Pt/Ir sparkplugs).For making crucibles and devices that require high temperatures.The principal use of iridium is as a hardening agent in platinum alloys. Definitive selection between the two is therefore not possible at this time. However, calculations of density from the space lattice may produce more reliable data for these elements than actual measurements and give a density of 22650 for iridium versus 22661 for osmium. The specific gravity of this element is only slightly lower than osmium, which is generally considered to be the heaviest element known. Iridiuim can not be attacked by any acids or by aqua regia, but it can be attacked by molten salts, such as Na Cl and Na CN. Iridium is the most corrosion-resistant metal known Due to its extreme hardness and brittle properties, iridium is difficult to machine, form, or work. It is used in high temperature apparatus, electrical contacts, and as a hardening agent for platinum.Ī platinum family metal, iridium, is white, resembling platinum, but with a slight yellowish cast. Iridium is notable for being the most corrosion resistant element known and for its association with the demise of the dinosaurs. A heavy, very hard, brittle, silvery-white transition metal of the platinum family, iridium is used in high strength alloys that can withstand high temperatures and occurs in natural alloys with platinum or osmium. Iridium is a chemical element in the periodic table that has the symbol Ir and atomic number 77. SI units & STP are used except where noted.
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