Second Virial Coefficients of Argon, Krypton, and Argon-Krypton Mixtures at Low Temperatures

Second virial coefficients of argon between 80–125°K, and krypton (105–140°K), have been measured. The experimental values are 5–15% larger in magnitude than those calculated from 12–6 or exp—6 potential functions by the substitution of parameters assigned to describe high-temperature virial coefficients. Second virial coefficients calculated from the potential-distance relationship proposed by Guggenheim and McGlashan are within 1% of the experimental values for argon, but are about 4% smaller in magnitude than the measured krypton coefficients. Argon-krypton mixed virial coefficients have been determined between 105–125°K. These experimental results are best expressed by a 12–6 potential energy parameter combining rule ε12=2ε1ε2/ε1+ε2.