![]() ![]() Copyright © 2023, Columbia University Press. The Columbia Electronic Encyclopedia, 6th ed. Iridium was discovered in 1804 by Smithson Tennant it is so named because of its various highly colored salts. ![]() It resists attack by fused bases and by most molten metals. It is oxidized slowly at high temperatures. Fluorine and chlorine attack it only at a red heat. Pure iridium metal is not attacked by acids or acid mixtures, not even by aqua regia, which dissolves gold. Platinum group PRONUNCIATION i-RI-dee-um. Formerly the international meter standard was the distance between two marks on a bar made of that same alloy it is now based on the wavelength of a line in the spectrum of an isotope of krypton. Overview SYMBOL Ir ATOMIC NUMBER 77 ATOMIC MASS 192.217 FAMILY Group 9 (VIIIB) Transition metal. ![]() An alloy of 10 parts iridium with 90 parts platinum is used in the international kilogram standard in Paris. Alloys with platinum are used in heavy-duty electrical contacts. An alloy with osmium is used to make fountain-pen nibs. It is also used in making chemical crucibles. The metal is used in pivot bearings and in scientific and other special equipment, such as surgical tools. It is obtained commercially from osmiridium, a byproduct of platinum production. Ir, Iridium, Latin: iris, rainbow (because of the colorful compounds that it forms). The chemical behaviour of these metals is paradoxical. Information about various chemical compounds and elements. The elements all possess a silvery white colourexcept osmium, which is bluish white. Chlorine is a yellow-green gas at room temperature. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Iridium is found uncombined in nature as the metal and in combination with osmium and platinum. Platinum group, six metals, in order of increasing atomic weight, ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), and platinum (Pt). Chlorine is a chemical element with the symbol Cl and atomic number 17. It is not certain whether osmium or iridium is the most dense element. It falls between platinum and osmium in Group 9 of the periodic table. Iridium is a very hard, usually brittle, extremely corrosion-resistant silver-white metal with a face-centered cubic crystalline structure. Iridium ĭrĭdˈēəm, metallic chemical element symbol Ir at. ![]()
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