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iridium

[ ih-rid-ee-uhm, ahy-rid- ]

noun

, Chemistry.
  1. a precious metallic element resembling platinum: used in platinum alloys and for the points of gold pens. : Ir; : 192.2; : 77; : 22.4 at 20°C.


iridium

/ ɪˈrɪd-; aɪˈrɪdɪəm /

noun

  1. a very hard inert yellowish-white transition element that is the most corrosion-resistant metal known. It occurs in platinum ores and is used as an alloy with platinum. Symbol: Ir; atomic no: 77; atomic wt: 192.22; valency: 3 or 4; relative density: 22.42; melting pt: 2447°C; boiling pt: 4428°C
“Collins English Dictionary — Complete & Unabridged” 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

iridium

/ ĭ-rĭdē-əm /

  1. A rare, whitish-yellow element that is the most corrosion-resistant metal known. It is very dense, hard, and brittle, and is is used to make hard alloys of platinum for jewelry, pen points, and electrical contacts. Atomic number 77; atomic weight 192.2; melting point 2,410°C; boiling point 4,130°C; specific gravity 22.42 (at 17°C); valence 3, 4.
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Word History and Origins

Origin of iridium1

1804; < Latin īrid-, stem of īris rainbow ( iris ) + -ium; so named from its iridescence when dissolved in hydrochloric acid
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Word History and Origins

Origin of iridium1

C19: New Latin, from irido- + -ium ; from its colourful appearance when dissolving in certain acids
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A Closer Look

In 1978 geologist Walter Alvarez discovered a high concentration of iridium in a layer of clay that had formed between the Mesozoic and Cenozoic eras, a period about 65 million years ago during which dinosaurs and many other organisms became extinct. This finding was significant as iridium is rare at Earth's surface (an unusually high concentration is called an iridium anomaly ). Most surface iridium is thought to come from dust created when meteors disintegrate in the atmosphere or collide with Earth. Alvarez's father, the physicist Luis Alvarez, suggested that the iridium might have come from the impact of a meteor about 10 km (6.2 mi) across. Such an impact would have caused an enormous explosion, sending huge clouds of dust into the atmosphere. The dust, blocking out the Sun and causing extensive acid rain, would have triggered a worldwide ecological disaster. Many scientists think that such a disaster caused the extinction of the dinosaurs and at least 70 percent of all other species alive at the time, including most of Earth's land plants. Geologists have since found iridium deposits in rocks of a similar age in more than 100 places worldwide. Scientists in the early 1990s identified a large impact crater in the Yucatán peninsula of central Mexico that is the same age as the iridium deposit found by Alvarez. It is 200 km (125 mi) wide and may have been caused by the same impact.
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Example Sentences

Researchers report a new method that reduces the amount of iridium needed to produce hydrogen from water by 95%, without altering the rate of hydrogen production.

The sample is then coated with a thin layer of iridium metal to make it conductive.

From Salon

This will not only replace the rare, more costly ruthenium and iridium compounds, which today are still the most frequently used, but even enable reaction and substrate classes that are unavailable with the classical compounds.

However, OLEDs can include rare, expensive metals like iridium.

The research team focused on finding alternatives to precious metal catalysts like platinum and iridium, which exhibit stability in acidic conditions.

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