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Osmium–iridium is used for compass bearings and for balances. [13] Because of their resistance to arc erosion, iridium alloys are used by some manufacturers for the centre electrodes of spark plugs, [88] [91] and iridium-based spark plugs are particularly used in aviation.
Iridium Communications Inc. (formerly Iridium Satellite LLC) is a publicly traded American company headquartered in McLean, Virginia, United States.Iridium operates the Iridium satellite constellation, a system of 80 satellites: 66 are active satellites and the remaining fourteen function as in-orbit spares. [2]
The Iridium system was designed to be accessed by small handheld phones, the size of a cell phone. While "the weight of a typical cell phone in the early 1990s was 10.5 ounces" [6] (300 grams) Advertising Age wrote in mid 1999 that "when its phone debuted, weighing 1 pound (453 grams) and costing $3,000, it was viewed as both unwieldly and expensive."
Iridium is mainly used as a hardening agent for platinum alloys. Iridium is the most corrosion-resistant metal known as it is not attacked by acids, including aqua regia. In the presence of oxygen, it reacts with cyanide salts. Traditional oxidants also react, including the halogens and oxygen at higher temperatures.
Metallic iridium is found with platinum and other platinum group metals in alluvial deposits. [23] Naturally occurring iridium alloys include osmiridium and iridosmine, both of which are mixtures of iridium and osmium. It is recovered commercially as a by-product from nickel mining and processing. [20]
Iridium-192 (symbol 192 Ir) is a radioactive isotope of iridium, with a half-life of 73.827 days. [1] It decays by emitting beta (β) particles and gamma (γ) radiation. About 96% of 192 Ir decays occur via emission of β and γ radiation, leading to 192 Pt .
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Natural alloys also occur in the systems Ir-Os-Rh, Os-Ir-Pt, Ru-Ir-Pt, Ir-Ru-Rh and Pd-Ir-Pt. Names used in these systems have included platiniridium (or platinian iridium) and iridrhodruthenium. However, there is no universally accepted method of plotting these compositions and their names, especially in the ternary systems.