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Modern determinations of the Avogadro constant (N(A)) are performed on a Si single crystal. Reproducibilities and total uncertainties of 3 x 1.0 E-5 have been attained by using a high precision gas mass spectrometer, but, more so, by developing highly refined measurement procedures. Measurement performance is so close to theory that the application of the same measurement procedure to the analysis of other gas isotope mixtures (Ar, Kr, Xe, N(2)) and even to mixtures of gaseous compounds (CO(2)/N(2)) leads to measurement results which are absolute at the 1.0 E-3 relative uncertainty level without calibration. The implication of this could be that: (i) near-absolute gas measurements become possible at the less than or equal to 1.0 E-3 uncertainty level; (ii) measurements of gas mixtures can be made which are traceable to the mole, the SI unit for amount of substance, since they are made according to exactly the same procedures as used in determining the Avogadro constant. The latter may be regarded, in fact, as a first realisation of the unit mole in the laboratory.

Additional information

Authors: DE BIEVRE P, JRC Geel (BE)
Bibliographic Reference: Paper presented: 3rd International Symposium on Separation Technology, Antwerpen (BE), August 22-27, 1993
Availability: Available from (1) as Paper EN 37936 ORA
Record Number: 199311444 / Last updated on: 1994-11-28
Original language: en
Available languages: en