Bundesanstalt für Materialforschung und ‐prüfung (BAM), Berlin (Germany).Chinese Academy of Sciences (CAS), Beijing (China).Geological Survey, Reston, VA (United States) Not only has the Commission shielded users of the TSAW and TICE from unreliable measurements that appear in the literature as a result of unduly small uncertainties, but the aim of IUPAC has been fulfilled by which any scientist, taking any natural sample from commerce or research, can expect their sample atomic weight to lie within A r(E) ± its uncertainty almost all of the time. This footnote emphasizes that an atomic-weight uncertainty is a consensus (decisional) uncertainty. To clarify the definition of uncertainty, a new footnote has been added to the TSAW. ![]() ![]() In 2017, to eliminate this noncompliance with the GUM, a new format was adopted in which the uncertainty value is specified by the more » plus-minus symbol, e.g. A r (Se) = 78.971(8), is not in accord with the GUM, which suggests that this parenthetic notation be reserved to express standard uncertainty, not the expanded uncertainty used in the TSAW and TICE. In 2016, it was recognized by the Commission that a guideline recommending expression of uncertainty listed in parentheses following the standard atomic-weight value, e.g. The Commission strives to provide utmost clarity in products it disseminates, namely the TSAW and the Table of Isotopic Compositions of the Elements (TICE). The Commission on Isotopic Abundances and Atomic Weights of the International Union of Pure and Applied Chemistry (IUPAC) regularly evaluates the literature for new isotopic-abundance measurements that can lead to revised standard atomic-weight values, A r(E) for element E. Unlike most parameters in physical science whose values and uncertainties are evaluated using the “Guidelines for Uncertainty in Measurement” (GUM), the majority of standard atomic-weight values and their uncertainties are consensus values, not GUM-evaluated values. ![]() The present Table of Standard Atomic Weights (TSAW) of the elements is perhaps one of the most familiar datasets in science.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |