The solar chemical composition is an important ingredient in our understanding of the formation, structure, and evolution of both the Sun and our Solar System. Furthermore, it is an essential refer ...

The Chemical Composition of the Sun

This paper gives the 2010 self-consistent set of values of the basic constants and conversion factors of physics and chemistry recommended by the Committee on Data for Science and Technology (CODATA) for international use. The 2010 adjustment takes into account the data considered in the 2006 adjustment as well as the data that became available from 1 January 2007, after the closing date of that adjustment, until 31 December 2010, the closing date of the new adjustment. Further, it describes in detail the adjustment of the values of the constants, including the selection of the final set of input data based on the results of least-squares analyses. The 2010 set replaces the previously recommended 2006 CODATA set and may also be found on the World Wide Web at physics.nist.gov/constants.

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CODATA Recommended Values of the Fundamental Physical Constants: 2006

To minimize confusion in the expression of measurement results of stable isotope and gas-ratio measurements, recommendations based on publications of the Commission on Isotopic Abundances and Atomic Weights of the International Union of Pure and Applied Chemistry (IUPAC) are presented. Whenever feasible, entries are consistent with the Systeme International d'Unites, the SI (known in English as the International System of Units), and the third edition of the International Vocabulary of Basic and General Terms in Metrology (VIM, 3rd edition). The recommendations presented herein are approved by the Commission on Isotopic Abundances and Atomic Weights and are designed to clarify expression of quantities related to measurement of isotope and gas ratios to ensure that quantity equations instead of numerical value equations are used for quantity definitions. Examples of column headings consistent with quantity calculus (also called the algebra of quantities) and examples of various deprecated usages connected with the terms recommended are presented.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/rcm.5129

Guidelines and recommended terms for expression of stable‐isotope‐ratio and gas‐ratio measurement results

Background
Structure elucidation of unknown small molecules by mass spectrometry is a challenge despite advances in instrumentation. The first crucial step is to obtain correct elemental compositions. In order to automatically constrain the thousands of possible candidate structures, rules need to be developed to select the most likely and chemically correct molecular formulas.

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Seven Golden Rules for heuristic filtering of molecular formulas obtained by accurate mass spectrometry

Stable isotope ratios are reported in the literature in terms of a deviation from an international standard (delta-values). The referencing procedures, however, differ from instrument to instrument and are not consistent between measurement facilities. This paper reviews an attempt to unify the strategy for referencing isotopic measurements. In particular, emphasis is given to the importance of identical treatment of sample and reference material ('IT principle'), which should guide all isotope ratio determinations and evaluations. The implementation of the principle in our laboratory, the monitoring of our measurement quality, the status of the international scales and reference materials and necessary correction procedures are discussed.

Referencing strategies and techniques in stable isotope ratio analysis

A consistent set of internationally accepted atomic weights has long been an essential aim of the scientific community because of the relevance of these values to science and technology, as well as to trade and commerce subject to ethical, legal, and international standards. The standard atomic weights of the elements are regularly evaluated, recommended, and published in updated tables by the Commission on Atomic Weights and Isotopic Abundances (CAWIA) of the International Union of Pure and Applied Chemistry (IUPAC). These values are invariably associated with carefully evaluated uncertainties. Atomic weights were originally determined by mass ratio measurements coupled with an understanding of chemical stoichiometry, but are now based almost exclusively on knowledge of the isotopic composition (derived from isotope-abundance ratio measurements) and the atomic masses of the isotopes of the elements. Atomic weights and atomic masses are now scaled to a numerical value of exactly 12 for the mass of the carbon isotope of mass number 12. Technological advances in mass spectrometry and nuclear-reaction energies have enabled atomic masses to be determined with a relative uncertainty of better than 1 x 10 - 7 . Isotope abundances for an increasing number of elements can be measured to better than 1 x 10 - 3 . The excellent precision of such measurements led to the discovery that many elements, in different specimens, display significant variations in their isotope-abundance ratios, caused by a variety of natural and industrial physicochemical processes. While such variations increasingly place a constraint on the uncertainties with which some standard atomic weights can be stated, they provide numerous opportunities for investigating a range of important phenomena in physical, chemical, cosmological, biological, and industrial processes. This review reflects the current and increasing interest of science in the measured differences between source-specific and even sample-specific atomic weights. These relative comparisons can often be made with a smaller uncertainty than is achieved in the best calibrated "absolute" (= SI-traceable) atomic-weight determinations. Accurate determinations of the atomic weights of certain elements also influence the values of fundamental constants such as the Avogadro, Faraday, and universal gas constants. This review is in two parts: the first summarizes the development of the science of atomic-weight determinations during the 20 t h century; the second summarizes the changes and variations that have been recognized in the values and uncertainties of atomic weights, on an element-by-element basis, in the latter part of the 20 t h century.

https://www.degruyter.com/downloadpdf/j/pac.2003.75.issue-6/pac200375060683/pac200375060683.xml

Atomic weights of the elements. Review 2000 (IUPAC Technical Report)

Documented variations in the isotopic compositions of some chemical elements are responsible for expanded uncertainties in the standard atomic weights published by the Commission on Atomic Weights and Isotopic Abundances of the International Union of Pure and Applied Chemistry. This report summarizes reported variations in the isotopic compositions of 20 elements that are due to physical and chemical fractionation processes (not due to radioactive decay) and their effects on the standard atomic-weight uncertainties. For 11 of those elements (hydrogen, lithium, boron, carbon, nitrogen, oxygen, silicon, sulfur, chlorine, copper, and selenium), standard atomic-weight uncertainties have been assigned values that are substantially larger than analytical uncertainties because of common isotope-abundance variations in materials of natural terrestrial origin. For 2 elements (chromium and thallium), recently reported isotope-abundance variations potentially are large enough to result in future expansion of their atomic-weight uncertainties. For 7 elements (magnesium, calcium, iron, zinc, molybdenum, palladium, and tellurium), documented isotope variations in materials of natural terrestrial origin are too small to have a significant effect on their standard atomic-weight uncertainties. This compilation indicates the extent to which the atomic weight of an element in a given material may differ from the standard atomic weight of the element. For most elements given above, data are graphically illustrated by a diagram in which the materials are specified in the ordinate and the compositional ranges are plotted along the abscissa in scales of (1) atomic weight, (2) mole fraction of a selected isotope, and (3) delta value of a selected isotope ratio.

Isotope-abundance variations of selected elements (IUPAC Technical Report)

...................................................... Introduction...................................................................^ Basic Concepts ................................................................................................................................................2 Aclmowledgements...........................................^ Hydrogen...............................................................................................................................................^ Reference materials and reporting of isotope ratios......................................................................................5 Ranges in isotopic composition......................................................................................................................5 Water...................................................................................................................................... Silicates............................................................................................................................................^ Hydroxides...........:...............................................................................^ Organic hydrogen....................................................................................................................................8 Methane .................................................................................................................................................10 Hydrogen gas......................................................................................................................................... 10 Lithium................................................^ Reference materials and reporting of isotope ratios.................................................................................... 11 Ranges in isotopic composition.................................................................................................................... 11 Marine sources ......................................................................................................................................11 Non-marine sources............................................................................................................................... 13 Lithium in rocks.................................................................................................................................... 13 Phosphates............................................................................................................................................. 13 Silicates....... ... . ........... . .... . .. .. . . .... . ....... .._ Reagents............................ .. ..... ... . ... .. ... . . ..............J^ Boron......................................................................... Reference materials and reporting of isotope ratios.................................................................................... 15 Ranges in isotopic composition.................................................................................................................... 15 Marine sources ......................................................................................................................................15 Non-marine sources............................................................................................................................... 16 Igneous rocks......................................................................................................................................... 19 Metamorphic rocks................................................................................................................................ 19 Sediments............................................................................^ Organic boron........................................................................................................................................19 Carbon ......................................................................................20 Reference materials and reporting of isotope ratios....................................................................................20 Ranges in isotopic composition....................................................................................................................20 Carbonate and bicarbonate ...................................................................................................................20 Carbon dioxide......................................................................................................................................25 Oxalates...............................................................................26 Carbon monoxide..................................................................................................................................26 Organic carbon ......................................................................................................................................26 Elemental carbon...................................................................................................................................28 Ethane ....................................................................................................................................................28 Methane .................................................................................................................................................28 Nitrogen............................................................ Reference materials and reporting of isotope ratios....................................................................................29 Ranges in isotopic composition....................................................................................................................29 Nitrate................................................................................................................................ Nitrite............................................................................................ Nitrogen oxide gases.......................................................................................30 Nitrogen gas ................................................................................................30 Organic nitrogen....................................................................................................................................32 Nitrogen in rocks...................................................................................................................................34 Ammonium.................................................................................................................................^ Oxygen ........................................................... Reference materials and reporting of isotope ratios....................................................................................36 Ranges in isotopic composition....................................................................................................................37 Oxygen gas.............................................................................................................................................39 Water........................................................^ Carbon monoxide..................................................................................................................................41 Carbon dioxide ......................................................................................................................................41 Carbonates .............................................................................................................................................41 Nitrogen oxides.....................................................................................................................................42 Other Oxides..........................................................................................................................................42 Phosphates .............................................................................................................................................42 Silicates...................................................... Sulfates..................................................................................^ Plants and animals.................................................................................................................................43 Magnesium.....................................................................................................................................^ Reference materials and reporting of isotope ratios....................................................................................44 Ranges in isotopic composition....................................................................................................................44 Marine sources ......................................................................................................................................44 Elemental magnesium...........................................................................................................................46 SiHcon..............................................................^ Reference materials and reporting of isotope ratios....................................................................................46 Ranges in isotopic composition....................................................................................................................46 Igneous rocks.........................................................................................................................................47 Metamorphic rocks................................................................................................................................47 Vein quartz and silicified rocks ............................

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Compilation of minimum and maximum isotope ratios of selected elements in naturally occurring terrestrial materials and reagents

The Commission on Atomic Weights and Isotopic Abundances of the International Union of Pure and Applied Chemistry completed its last review of the isotopic compositions of the elements as determined by isotope-ratio mass spectrometry in 2001. That review involved a critical evaluation of the published literature, element by element, and forms the basis of the table of the isotopic compositions of the elements (TICE) presented here. For each element, TICE includes evaluated data from the “best measurement” of the isotope abundances in a single sample, along with a set of representative isotope abundances and uncertainties that accommodate known variations in normal terrestrial materials. The representative isotope abundances and uncertainties generally are consistent with the standard atomic weight of the element Ar(E) and its uncertainty U[Ar(E)] recommended by CAWIA in 2001.

Isotopic Compositions of the Elements, 2001

/pdf/atomic-weights-of-the-elements-review-2000-3pjbpf2uv5.pdf

H. S. Peiser

Papers

Atomic weights of the elements. Review 2000 (IUPAC Technical Report)

Isotope-abundance variations of selected elements (IUPAC Technical Report)

Compilation of minimum and maximum isotope ratios of selected elements in naturally occurring terrestrial materials and reagents

Isotopic Compositions of the Elements, 2001

Atomic weights of the elements: review 2000