The validity of the concept of “hard-sphere-like” particles for mixtures of colloids is questioned from a theoretical point of view. This concerns the class of pseudobinary mixtures in which the nonsteric interactions between the colloids are “residual” (with very small range and moderate strength). It is shown that contrary to common expectation, such interactions may have unexpected consequences on the theoretical phase diagram. The distinction between this situation and true solute-solvent mixtures is emphasized.

• Received 14 June 2003

DOI:https://doi.org/10.1103/PhysRevE.70.041409