Thermodynamic speed of sound of xenon

Thermodynamic speed of sound data are an important basis for the development of Helmholtz energy equations of state because of their thermal and caloric nature. Moreover, they can be measured rapidly and with a high accuracy. Xenon is sampled with the pulse-echo technique to provide speed of sound data covering a temperature range from 217 K to 500 K with a pressure of up to 100 MPa. The measurement cell’s path length is calibrated with water and validated with the reference equation of state by Wagner and Pruß (2002). At a confidence level of 95% (k=2), the data have an overall expanded uncertainty of up to 0.17% near the critical point and less than 0.1% in the liquid and supercritical regions. The results are in good agreement with the Helmholtz energy equation of state by Lemmon and Span (2006) with a maximum deviation of up to 1.1%. The present data are also used to optimize the parameters of the Lennard-Jones potential and its truncated and shifted form for xenon. This parameterization leads to a convincingly better performance for the speed of sound calculation, but the representation of other properties, like the vapor-liquid two phase region, is significantly deteriorated