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    Isotope Atomic mass (Da) Isotopic abundance (amount fraction)
    191Ir190.960 5893(21)0.373(2)
    193Ir192.962 9216(21)0.627(2)

    In 1969, the Commission recommended Ar(Ir) = 190.22(3) based on a closer analysis of earlier mass-spectrometric determinations. In 1993, the Commission changed the recommended value for the standard atomic weight of iridium to Ar(Ir) = 192.217(3) based on recent high-precision measurements using both positive and negative thermal ionization mass spectrometry. The new value represents a significant improvement in the precision of the atomic weight and is in agreement with the previous measurements.

    SOURCE  Atomic weights of the elements: Review 2000 by John R de Laeter et al. Pure Appl. Chem. 2003 (75) 683-800
    © IUPAC 2003


    Ar(Ir) = 192.217(3) since 1993

    The name derives from the Latin Iris, the Greek goddess of rainbows, because of the variety of colours in the element's salt solutions. Iridium and osmium were both discovered in a crude platinum ore in 1803 by the English chemist Smithson Tennant. Iridium was discovered independently by the French chemist H. V. Collet-Descotils, who actually published his paper one month before Tennant, but Tennant is given credit for the discovery, perhaps because he alone also found osmium in the ore.