Phase separation in regular solutions

In the preceding paragraphs we have given the general equations relating to critical solution phenomena. To obtain more specific conclusions we must know how the activity coefficients depend upon the independent variables T, p and Xg. 

We shall consider the special case in which the activity coefficients and given by 

The physical significance of this law wiU be examined later but for the moment we may use it to study the general behaviour of the conditions of stability when the activity coefficients are of this particular form. Similar calculations may be made starting from any other 

The chemical potentials follow directly from (16.48) in the form (cf, 7.63) 

If the system is to be in stable equilibrium with respect to phase separation, it is necessary and sufficient that, in accordance with (16.14), 

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Examples of Liquid-Liquid Phase Separation in Regular Solutions, van Laar parameters at ambient pressure are provided in Table 29-1 for three binary mixtures that exhibit concentration-dependent miscibility. The corresponding graphs of Agmixing VS. Composition at constant T and p are provided in Figures 29-1 and 29-2. There is a range of compositions where... 

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