Free-volume fraction in hard-sphere mixtures and the osmotic spinodal curve

The sensitivity of the theoretical spinodal curve deduced from the osmotic equilibrium equation for asymmetric hard-sphere mixtures is examined by evaluating the free-volume fraction from three expressions of the excess chemical potential. The conditions for predicting a reduction of the stability domain with increasing asymmetry are discussed. The necessity of modifying this approach in the presence of attractions between the smaller species is underlined.