A Picard et al 2008 Metrologia 45 149 doi:10.1088/0026-1394/45/2/004
A Picard1, R S Davis1, M Gläser2 and K Fujii3
Show affiliationsMeasurements of air density determined gravimetrically and by using the CIPM-81/91 formula, an equation of state, have a relative deviation of 6.4 × 10−5.
This difference is consistent with a new determination of the mole fraction of argon xAr carried out in 2002 by the Korea Research Institute of Standards and Science (KRISS) and with recently published results from the LNE. The CIPM equation is based on the molar mass of dry air, which is dependent on the contents of the atmospheric gases, including the concentration of argon. We accept the new argon value as definitive and amend the CIPM-81/91 formula accordingly. The KRISS results also provide a test of certain assumptions concerning the mole fractions of oxygen and carbon dioxide in air. An updated value of the molar gas constant R is available and has been incorporated in the CIPM-2007 equation. In making these changes, we have also calculated the uncertainty of the CIPM-2007 equation itself in conformance with the Guide to the Expression of Uncertainty in Measurement, which was not the case for previous versions of this equation. The 96th CIPM meeting has accepted these changes.
Issue 2 (April 2008)
Received 8 January 2008
Published 18 February 2008
A Picard et al 2008 Metrologia 45 149
Joële Viallon et al 2008 Metrologia 45 08009
C R Quétel et al 2007 Metrologia 44 08010
Joële Viallon et al 2006 Metrologia 43 08010
R Felder 2005 Metrologia 42 323
Adriaan M H van der Veen et al 2005 Metrologia 42 08004
T J Quinn 2003 Metrologia 40 103
C S J Wolff Briche 2003 Metrologia 40 08010
F Delahaye et al 2000 Metrologia 37 659
H Haitjema et al 1996 Metrologia 33 67