Adjacent Words

Iridium definitions

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Webster's 1828 Dictionary

IRID'IUM, n. [from iris.] A metal of a whitish color, not malleable, found in the ore of platinum, and in a native allow with osmium. Its specific gravity is above 18. It takes its name from the variety of colors which it exhibits while dissolving in muriatic acid. The native allow with osmium, or native iridium, is of a steel gray color and shining metallic luster. It usually occurs in small irregular flat grains, in alluvial soil, in S. America.

WordNet (r) 3.0 (2005)

n
1: a heavy brittle metallic element of the platinum group; used in alloys; occurs in natural alloys with platinum or osmium [syn: iridium, Ir, atomic number 77]

Merriam Webster's

noun Etymology: New Latin, from Latin irid-, iris; from the colors produced by its dissolving in hydrochloric acid Date: 1804 a rare silver-white hard brittle very heavy metallic element — see element table

Britannica Concise

Metallic chemical element, one of the transition elements, chemical symbol Ir, atomic number 77. A very rare, precious, silvery-white, hard, brittle metal that even resists most acids, it is one of the densest substances known on earth. It probably does not occur uncombined in nature but is found in natural alloys with other noble (i.e., chemically inactive or inert) metals. The pure metal is too hard to work with to have any significant uses; alloys with platinum are used in jewelry, pen points, surgical pins and pivots, electrical contacts and sparking points, and extrusion dies. The international primary standards (see weights and measures) for weight and length are 90% platinum, 10% iridium. The discovery of abnormally high amounts of iridium in rocks dating to between the Cretaceous and Tertiary periods has given rise to a controversial hypothesis that an iridium-containing meteorite crashing into the earth led to a catastrophic chain of events incl. extinction of dinosaurs and many other forms of life.

Dictionary of the Elements

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.

Oxford Reference Dictionary

n. Chem. a hard white metallic element of the transition series used esp. in alloys. Usage: Symb.: Ir. Etymology: mod.L f. L IRIS + -IUM

Webster's 1913 Dictionary

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.