Solubility curve of an addition compound in a non-ideal solution

Solubility Curve of an Addition Compound in a Non-Ideal Solution. 

In general, we can neglect the second term of the right hand side of (23.24), but in (23.23) both terms are of the same order of magnitude. An approximate form of (23.10) is, for this case, 

We must now consider two cases, depending upon whether the deviations from Raoult s law are positive or negative. 

First we consider a 0, corresponding to activity coefiicients less than unity and so to negative deviations from Raoult s law (c/. chap. XXI, 3). In this instance, (23.25) shows that when 

as usual, the superscript id refers to the behaviour of an ideal system. Thus, approaching the indifferent point from the left (lower values of Xg), the curve rises more rapidly than in the case of an ideal system. 

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