ATOMIC WEIGHTS OF THE ELEMENTS 1993

The biennial review of atomic weight, A(r)(E), determinations and othe r cognate data has resulted in changes for the standard atomic weight of titanium from 47.88+/-0.03 to 47.867+/-0.001, of iron from 55.847+/ -0.003 to 55.845+/-0.002, of antimony from 121.757+/-0.003 to 121.760/-0.001, and of iridium from 192.22+/-0.03 to 192.217+/-0.003. Recent investigations on chlorine and bromine confirmed the presently accepte d values of A(r)(Cl) and A(r)(Br). To emphasize the fact that the atom ic weight of lithium commonly available in laboratory reagents can var y significantly, the value of lithium, A(r)(Li), was enclosed in brack ets and a footnote was added. As a result of several changes, the Tabl e of Standard Atomic Weights Abridged to Five Significant Figures has been updated. Because relative isotope-ratio data for stable hydrogen, carbon, and oxygen are commonly being expressed on non-corresponding scales, the Commission recommends that such isotopic data be expressed only relative to the references VSMOW and VPDB. Because many elements have a different isotopic composition in some non-terrestrial materia ls, recent data on non-terrestrial materials are included in this repo rt for the information of the interested scientific community. (C) 199 5 American Institute of Physics and American Chemical Society.