5/31/2023 0 Comments Iridium silver metallic![]() However, corrosion-resistance is not quantifiable in absolute terms although only certain molten salts and halogens are corrosive to solid iridium, finely divided iridium dust is much more reactive and can be flammable, whereas gold dust is not flammable but can be attacked by substances that iridium resists, such as aqua regia. It is one of the most corrosion-resistant metals, even at temperatures as high as 2,000 ☌ (3,630 ☏). A very hard, brittle, silvery-white transition metal of the platinum group, it is considered the second-densest naturally occurring metal (after osmium) with a density of 22.56 g/cm 3 (0.815 lb/cu in) as defined by experimental X-ray crystallography. ![]() The international prototype standard kilogram of mass is made from an alloy containing 90 percent platinum and 10 percent iridium.Iridium is a chemical element with the symbol Ir and atomic number 77. Such alloys are used for jewelry, pen points, surgical pins and pivots, and electrical contacts and sparking points. Platinum-iridium alloys (5 to 10 percent iridium) are readily workable metals that are much harder and stiffer and more resistant to chemical attack than the soft pure platinum. Iridium is chiefly used in the form of platinum alloys. It can be dissolved in concentrated hydrochloric acid in the presence of sodium perchlorate at 125° to 150° C (257° to 302° F).īecause of difficulties in preparation and fabrication, the pure metal has few applications. In the massive state the metal is practically insoluble in acids and is not attacked even by aqua regia. It is one of the densest terrestrial substances. A precious, silver-white metal, iridium is hard and brittle, but it becomes ductile and can be worked at a white heat, from 1,200° to 1,500° C (2,200° to 2,700° F). It is very dense and rare and is used in platinum alloys. Iridium (Ir), chemical element, one of the platinum metals of Groups 8–10 (VIIIb), Periods 5 and 6, of the periodic table.
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