Abstract:
The data needed to evaluate the specific heat, virial, and relaxation corrections for the sound speed have been compiled from the literature for over 40 pure gases. Theoretical and published experimental sound speeds are compared in several case studies. (1) In precision measurements in a spherical resonator (argon, nitrogen), agreement between theory and experiment falls within 0.04% and 0.02%, respectively, over the entire ranges of temperature and pressure. (2) In high-pressure measurements (argon, helium, methane), agreement remains within 1% or better up to a certain pressure, typically 20 to 50 times the critical pressure, beyond which the increasing disagreement is attributed to truncation of the virial expansion. (3) In a measurement with large dispersion due to molecular relaxation (sulfur hexafluoride), agreement is well within 0.5%. The specific heat, virial, and relaxation corrections are analyzed in detail.