Thermophysical Properties of Chlorine from Speed-of-Sound Measurements
John J. Hurly
The speed of sound was measured in gaseous chlorine using a highly precise acoustic resonance technique. The data span the temperature range 260 K to 440 K and the pressure range 100 kPa to the lesser of 1500 kPa or 80 % of the sample's vapor pressure. A small correction ( 0.003 % to 0.06 %) to the observed resonance frequencies was required to account for dispersioncaused by the vibrational relaxation of chlorine. The speed-of-sound measurements have a relative standard uncertainty of 0.01 %. The data were analyzed to obtain the ideal-gas heat capacity as a function of the temperature with a relative standard uncertainty of 0.1 %.The reported values of C_p are in agreement with those determined from spectroscopic data. The speed-of-sound data were fitted by virial equationsof state to obtain the temperature dependent density virial coefficients. Two virial coefficient models were employed, one based on square-well intermolecular potentials, and the second based on a hard-core Lennard-Jones intermolecular potential. The resulting virial equations reproduced the sound speed data to within 0.01 %, and may be used to calculate vapordensities with relative standard uncertainties of 0.1 % or less.