  We study the phase behavior of colloidal suspensions the solvents of which
are considered to be binary liquid mixtures undergoing phase segregation. We
focus on the thermodynamic region close to the critical point of the
accompanying miscibility gap. There, due to the colloidal particles acting as
cavities in the critical medium, the spatial confinements of the critical
fluctuations of the corresponding order parameter result in the effective,
so-called critical Casimir forces between the colloids. Employing an approach
in terms of effective, one-component colloidal systems, we explore the
possibility of phase coexistence between two phases of colloidal suspensions,
one being rich and the other being poor in colloidal particles. The reliability
of this effective approach is discussed.
