Pure and Applied Chemistry

Abstract: The latest evaluation of atomic weight determinations and other cognate data has warranted five changes for the standard atomic weights of the elements, A_r(E), from those published previously in the Table of Atomic Weights 2005. The revised standard atomic weight of nickel, A_r(Ni), is 58.6934(4); zinc, A_r(Zn), is 65.38(2); molybdenum, A_r(Mo), is 95.96(2); ytterbium, A_r(Yb), is 173.054(5); and lutetium, A_r(Lu), is 174.9668(1). Standard atomic weight tables abridged to four and five significant figures were also evaluated. The Commission-recommended value for the isotope-amount ratio of n(⁴⁰Ar)/n(³⁶Ar), which is of importance in geochronology and geochemistry, has been changed to 298.56(31) from 296.03(53) based on new measurements. Atmospheric O₂ is recognized as an international measurement standard, along with Vienna Standard Mean Ocean Water (VSMOW) and Vienna Pee Dee Belemnite (VPDB) carbonate for measurement and reporting of differences in relative oxygen isotope-amount ratios δ(¹⁷O) and δ(¹⁸O).