Project Details Evaluated Published Isotope Ratio Data (2010-2011)

Project No.:
Start Date:
01 May 2010
End Date:
01 June 2013


Evaluate isotope ratio publications between 2009 and early 2011, to determine “best isotope ratio measurements” for compilation and publication in a 2011 TICE, recommend “new” standard atomic weights, and publish “Atomic Weights of the Elements 2011” in Pure and Applied Chemistry, which will also include a table of relative atomic masses.


The aim of the task group is to evaluate new isotope ratio publications between early-2009 and early 2011, and reevaluate 24 elements according to evaluation protocols developed in projects 2003-031-2-200 and 2005-027-1-200. The evaluated data will be incorporated into the CIAAW Table of Isotopic Composition of the elements (TICE21) and Table of Standard Atomic Weights.

The SIAM in CIAAW recognizes that there are a number of elements that need particular attention and for which significant publications are expected as an outcome of this project.

The task group members will evaluate recently published isotope ratios and resulting atomic-weights reports. Detailed discussions and calculations will be carried out on any chemical element for which new isotope ratio information exists. Particular attention will be paid to authors’ evaluations of uncertainty, the selection of materials for analysis, and the variability of isotope ratio measurements in these materials. The task group will than present their recommendations for adoption of best isotopic ratios and new standard atomic weights to the Commission on Isotopic Abundances and Atomic Weights.

It is anticipated that new standard atomic weights will be recommended, and a press release announcing these recommendations will be made available. Subsequently, a publication titled “Atomic Weights of the Elements 2011” will be prepared for Pure and Applied Chemistry. Subsequently, publication in J. Phys. Chem. Ref. Data is anticipated.


May 2013 – Atomic weights of the elements 2011 (IUPAC Technical Report) published in Pure Appl. Chem., 2013, Vol. 85, No. 5, pp. 1047-1078;

This biennial review of atomic-weight determinations and other cognate data has resulted in changes for the standard atomic weights of five elements. The atomic weight of bromine has changed from 79.904(1) to the interval [79.901, 79.907], germanium from 72.63(1) to 72.630(8), indium from 114.818(3) to 114.818(1), magnesium from 24.3050(6) to the interval [24.304, 24.307], and mercury from 200.59(2) to 200.592(3). For bromine and magnesium, assignment of intervals for the new standard atomic weights reflects the common occurrence of variations in the atomic weights of those elements in normal terrestrial materials.

project completed

Last updated 7 June 2013