These expressions are the result of least squares best fitting to outputs from a database of the property measurements by numerous experimenters [Lemmon et al. 2002]. Equations 12 through 15 were fitted to data over the range of 270 K to 330 K. This range allows application of the correlations at the conditions found in the test section of the flow standard. However, it should be noted that the conditions in the collection tank are much narrower, with pressures ranging from 0 kPa to 101 kPa at a nearly constant temperature of 296.5 K. For these narrower conditions, the third virial coefficient could be ignored with negligible impact on the density uncertainty