  The subtle interplay between critical phenomena and electrostatics is
investigated by considering the effective force acting on two parallel walls
confining a near-critical binary liquid mixture with added salt. The
ion-solvent coupling can turn a non-critical repulsive electrostatic force into
an attractive one upon approaching the critical point. However, the effective
force is eventually dominated by the critical Casimir effect, the universal
properties of which are not altered by the presence of salt. This observation
allows a consistent interpretation of recent experimental data.
