  Exploiting the mapping between a binary mixture and the Ising model we have
analyzed the critical fluctuations by means of the density-matrix
renormalization group technique. The calculations have been carried out for a
two-dimensional Ising strip subject to equal strong surface fields. It was
found that the critical Casimir force displays significantly different behavior
on opposite sides of the capillary condensation line, especially below the
critical temperature. It can be concluded that in a real binary mixtures the
most attractive force appears at temperatures near T_C and at reservoir
compositions slightly away from the critical composition.
