Forces between Unlike Molecules and the Properties of Gaseous Mixtures

The intermolecular potentials for a number of pairs of unlike molecules have been calculated from the known potentials for pairs of like molecules, by means of semi‐empirical combination rules. The intermolecular potential used was of the exp‐six form, ${\text{[open phi](r)=ε/(1−6/α)[(6/α)e}}^{{\text{α(1−r/r}}_m)}{\mathrm{-(r}}_m{\mathrm{/r)}}^6]$ . The validity of the combination rules were tested by calculating a number of properties of binary gas mixtures for comparison with experimental values. The resulting agreement was quite reasonable, and it was concluded that the combination rules can be used with some confidence.