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Farooq
Sep 16, 2021, 11:13 AM
Defined as the mass of a particular platinum cylinder – an iridium alloy stored at the International Bureau of Weights and Measures in Sevres, France. This weight level was established in 1887 and has not changed because platinum-iridium is an unusual compound. The Sèvres cylinder is kept at the National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland.
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