Chemistry International
Vol. 22, No.2, March 2000

2000, Vol. 22
No. 2 (March)
..News from IUPAC
..West Africa Chemical Society
..Reports from Symposia

..Awards and Prizes
..New Books
..Reports from Commissions
..Conference Announcements

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Chemistry International
Vol. 22, No. 2
March 2000

Reports from Commissions

Commission on Atomic Weights and Isotopic Abundances (II.1)

Summary of Minutes of Commission Meeting at IUPAC General Assembly, Berlin, Germany, 8-10 August 1999

The Commission on Atomic Weights and Isotopic Abundances (II.1) met for three days of discussions under the chairmanship of Prof. Ludolf Schultz during the 40th IUPAC General Assembly in Berlin. The standard atomic weights of seven chemical elements have been changed significantly. Based on new determinations of isotopic abundances and reviews of previous isotopic abundances, the standard atomic weight of nitrogen was changed from 14.00674(7) to 14.0067(2), of sulfur from 32.066(6) to 32.065(5), of chlorine from 35.4527(9) to 35.453(2), of germanium from 72.61(2) to 72.64(1), of xenon from 131.29(2) to 131.293(6), of erbium from 167.26(3) to 167.259(3), and of uranium from 238.0289(1) to 238.02891(3). Many of these changes were adopted so that standard atomic-weight values more accurately reflect the values of these chemical elements in naturally occurring materials.

The changes in atomic-weight values will be reflected in the Table of Standard Atomic Weights 1999, which will be submitted for publication in Pure and Applied Chemistry (PAC) before the end of the year. Also planned for publication in PAC is a report on fourteen elements that show significant isotopic abundance variation in naturally occurring materials. This report demonstrates that the atomic weight of such elements can be significantly larger than the uncertainties of measurement. Publication of an element-by-element review was discussed and is planned for submission to PAC in 2000. The Commission discussed a glossary of definitions specific to atomic-weight and isotopic-abundance work in order that definitions generated would be submitted to nomenclature commissions for inclusion in future IUPAC documents. A large number of isotopic-abundance measurements in extraterrestrial materials is available; these data will be summarized and a draft will be available at the next General Assembly in Brisbane in 2001.

> Link to Commission

Tyler B. Coplen II
Chairman, IUPAC Commission II.1,
Subcommittee on Natural Isotopic Fractionation


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