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De - Pt| English Dictionary: iridium | by the DICT Development Group |
| 3 results for iridium | |
| From WordNet (r) 3.0 (2006) [wn]: | |
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| From Webster's Revised Unabridged Dictionary (1913) [web1913]: | |
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Iridium \I*rid"i*um\, n. [NL., fr. L. iris, iridis, the rainbow. So called from the iridescence of some of its solutions. See {Iris}.] (Chem.) A rare metallic element, of the same group as platinum, which it much resembles, being silver-white, but harder, and brittle, and indifferent to most corrosive agents. With the exception of osmium, it is the heaviest substance known, its specific gravity being 22.4. Symbol Ir. Atomic weight 192.5. Note: Iridium usually occurs as a native alloy with osmium (iridosmine or osmiridium), which may occur alone or with platinum. Iridium, as an alloy with platinum, is used in bushing the vents of heavy ordnance. It is also used for the points of gold pens, and in a finely powdered condition (iridium black), for painting porcelain black. | |
| From The Elements (22Oct97) [elements]: | |
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iridium Symbol: Ir Atomic number: 77 Atomic weight: 192.217 Very hard and brittle, silvery metallic transition element. It has a yellowish cast to it. Salts of iridium are highly colored. It is the most corrosion resistant metal known, not attacked by any acid, but is attacked by molten salts. There are two natural isotopes of iridium, and 4 radioisotopes, the most stable being Ir-192 with a half-life of 73.83 days. Ir-192 decays into {platinum}, while the other radioisotopes decay into {osmium}. Iridium is used in high temperature apparatus, electrical contacts, and as a hardening agent for platinum. Discovered in 1803 by Smithson Tennant in England. The name comes from the Greek word iris, which means rainbow. Iridium metal is generally non-toxic due to its relative unreactivity, but iridium compounds should be considered highly toxic. | |
