The generalized hypernetted-chain free-energy formulas derived earlier are used for an accurate analysis of the phase properties in the binary ionic mixtures with dielectric screening of the electrons. The miscibility of iron atoms in the hydrogenic solar plasmas has been treated as a specific example. It is found that while the extent of the electronic screening effect is substantial, the resulting change in the phase diagram is not sufficiently large as to be able to account for the solar-neutrino problem. © 1986 The American Physical Society.