Solid solution discontinuous, phase diagram

Solid solutions can be classified by two methods. According to the extent of miscibility of the two components, they may be classified as continuous or discontinuous. In continuous solid solutions, the two components are miscible in the solid state in all proportions. Typical phase diagrams of continuous and discontinuous solid solutions are shown in Figs. 2 and 3, respectively. Discontinuous solid solutions exist at extremes of composition. In general, some solid-state solubility can be expected for all two-component systems. 

Fig. 3 A typical phase diagram of a discontinuous solid solution for a binary system A and B a and P are regions of solid solution formation.

The construction of a ternary solubility phase diagram for two solid phases in equilibrium with one solution was discussed in detail by Jacques et al. in the context of solubility phase diagrams of enantiomers in achiral solvents,2 where the method of algebraic extrapolation or wet residues is used. The biggest challenge with this classic method is the avaUabUity of pure components, enantiomers, or diastereomeric salts. The discontinuous isoperibolic thermal analysis (DITA) method developed by Marchand et al.22 overcame this barrier. In the DITA method, a mixture of an equal amount of diastereomeric salts is used. 

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