Predicting miscibility gaps in reciprocal liquids

There is a strong correlation between the appearance of liquid miscibility gaps in reciprocal phases and the standard Gibbs energy of the reciprocal reaction, Δ°G. The associate solution model does not predict such a correlation but the two-sublattice model does. ally, the critical temperature of a reciprocal miscibility gap is related to Δ°G and is also affected by the presence of short range order. The latter effect can be estimated from Δ°G using the conformal solution theory which was developed for reciprocal systems with univalent ions. In that approximation the short range order effect is described with a reciprocal parameter. The estimate of that parameter for systems with different valencies is now discussed. lculated phase diagram may be reasonable for low values of the reciprocal parameter, relative to Δ°G, but is not satisfactory for large values because two asymmetric miscibility gaps will appear when the critical temperature has been suppressed to 34 of the value predicted without a reciprocal term. An alternative form of the reciprocal term is now proposed, which does not produce the splitting into two miscibility gaps.