VIRIAL EQUATION OF STATE OF HELIUM, XENON, AND HELIUM-XENON MIXTURES FROM SPEED-OF-SOUND AND BURNETT P-RHO-T MEASUREMENTS

The virial equation of state was determined for helium, xenon, and hel ium-xenon mixtures for the pressure and temperature ranges 0.5 to 5 MP a and 210 to 400 K. Two independent experimental techniques were emplo yed: Burnett P rho T measurements and speed-of-sound measurements. The temperature-dependent second and third density virial coefficients Fo r pure xenon and the second and third interaction density virial coeff icients For helium-xenon mixtures were determined. The present density virial equations of state for xenon and helium-xenon mixtures reprodu ce the speed-of-sound data within 0.01% and the P rho T data within 0. 02% of the pressures. All the results for helium are consistent, withi n experimental errors, with recent ab initio calculations, confirming the accuracy of the experimental techniques.