Commission on Isotopic Abundances and Atomic Weights

The Commission on Isotopic Abundances and Atomic Weights (CIAAW) is an international scientific committee of the International Union of Pure and Applied Chemistry (IUPAC) under its Division of Inorganic Chemistry. Since 1899, it is entrusted with periodic critical evaluation of atomic weights of chemical elements and other cognate data, such as the isotopic composition of elements. The biennial CIAAW Standard Atomic Weights are accepted as the authoritative source in science and appear worldwide on the periodic table wall charts.

Commission on Isotopic Abundances and Atomic Weights
AbbreviationCIAAW
Formation1899 (1899)
TypeInternational scientific organization
PurposeTo provide internationally recommended values of isotopic composition and atomic weights of elements
Region served
Worldwide
Official language
English
Chair
Johanna Irrgeher
Secretary
Jochen Vogl
Parent organization
IUPAC (since 1920)
Websitewww.ciaaw.org

The use of CIAAW Standard Atomic Weights is also required legally, for example, in calculation of calorific value of natural gas (ISO 6976:1995), or in gravimetric preparation of primary reference standards in gas analysis (ISO 6142:2006). In addition, until 2019 the definition of kelvin, the SI unit for thermodynamic temperature, made direct reference to the isotopic composition of oxygen and hydrogen as recommended by CIAAW. The latest CIAAW report was published in May 2022.

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