Iridium

:Alternate meaning: Iridium (satellite)

History

Iridium was discovered in 1803 by Smithson Tennant in London, England along with osmium in the dark-colored residue of dissolving crude platinum in aqua regia (a mixture of hydrochloric and nitric acid). The element was named after the Latin word for rainbow (iris; iridium means "of rainbows") because many of its salts are strongly colored.

Related Topics:
1803 - Smithson Tennant - Osmium - Platinum - Aqua regia - Hydrochloric - Nitric acid - Rainbow

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An alloy of 90% platinum and 10% iridium was used in 1889 to construct the standard metre bar and kilogram mass, kept by the International Bureau of Weights and Measures near Paris. The metre bar has been replaced as the definition of the fundamental unit of length in 1960 (see krypton), but the kilogram prototype is still the international standard of mass.

Related Topics:
1889 - Metre - Kilogram - International Bureau of Weights and Measures - Paris - 1960 - Krypton

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The KT event of 65 million years ago, marking the temporal border between the Cretaceous and Tertiary eras of geological time, was identified by a thin stratum of iridium-rich clay. A team led by Luis Alvarez (1980) proposed an extraterrestrial origin for this iridium, attributing it to an asteroid or comet impact near what is now Yucatan Peninsula. Their theory is widely accepted to explain the demise of the dinosaurs. Dewey M. McLean and others argue that the iridium may have been of volcanic origin instead. The Earth's core is rich in iridium, and Piton de la Fournaise on Réunion, for example, is still releasing iridium today.

Related Topics:
KT event - Cretaceous - Tertiary - Geological time - Stratum - Luis Alvarez - 1980 - Asteroid - Comet - Yucatan Peninsula - Dinosaur - Volcanic - Earth - Réunion

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