Curie (unit)

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The curie (symbol Ci) is a non-SI unit of radioactivity originally defined in 1910. According to a notice in Nature at the time, it was to be named in honour of Pierre Curie, but was considered at least by some to be in honour of Marie Skłodowska-Curie as well, and is in later literature considered to be named for both. In 1910, it was originally defined as "the quantity or mass of radium emanation in equilibrium with one gram of radium (element)". In modern terms, 1 curie is the mass of Radon-222 in secular equilibrium with 1 gram of Radium-226. In 1964 was redefined as 1 Ci = 3.7×1010 decays per second after more accurate measurements of the activity of 226Ra (which has a specific activity of 3.66×1010 Bq/g). In 1975 the General Conference on Weights and Measures gave the becquerel (Bq), defined as one nuclear decay per second, official status as the SI unit of activity. Therefore: 1 Ci = 3.7×1010 Bq = 37 GBq and 1 Bq ≅ 2.703×10−11 Ci ≅ 27 pCi While its continued use is discouraged...

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