A Primary Isotopic Gas Standard for Sulfur in the Form of SF6 with Système International d'Unités Traceable Values for Isotopic Composition and Molar Mass.

A batch of SF6 gas prepared by Messer (Germany) was metrologically certified for isotope abundance ratios and molar mass (mean relative atomic weight) of sulfur. It is now commercially available as a Primary Isotopic Gas Standard (PIGS). The values for these sulfur PIGS are demonstrated to be traceable to the SI (Systeme International d'Unites). All sulfur isotope abundance ratio measurements have been monitored against values directly derived from kinetic gas theory by demonstrating that close-to-ideal gas behaviour was realized in the Avogadro II "amount comparator" during the measurement. Synthetic mixtures of isotopically enriched sulfur isotopes were used to verify the presence/ absence of small systematic effects in the measurements of this PIGS. Identical measurements instument and procedures were used as for the high accuracy measurements of the isotope amount ratios of Si in SiF4 in the framework of the re-determination of the Avogadro constant. The PIGS are intended as primary standard (i.e. with smallest achievable combined uncertainties) for differential measurements (performed on the "delta" -scale.

VALKIERS Staf;  KIPPHARDT Heinrich;  DING Tiping;  DAMEN Rene;  DE BIEVRE Paul Jan Cyriel;  TAYLOR P.D.P.; 

1998-10-28

JRC17196