13-09E

We study the gas-liquid phase diagram and the crossover temperature of a model binary fluid in which hard-core  particles interact via   screened Coulomb potentials with the inverse screening length $z$: like particles repel each other and unlike particles attract (YRPM). Using the mean-field theory we find that the gas-liquid coexistence region reduces with an increase of  $z$ and completely vanishes at $z\approx 3$. This is in qualitative agreement with the simulation findings.  It is also shown that an increase in the interaction range leads to the decrease of the crossover temperature. For  $z\leq 0.05$, the crossover temperature is the same as for the restricted primitive model.