Phase diagrams topological schemes

Methods of topological schemes for flrrid and complete phase diagrams derivation and main features of phase behavior at sub- and supercritical conditiorrs for ternary systems are discussed later in the chapter. The available experimental data are used to demorrstrate some regularity of sohd solubility, hquid immiscibility and critical behavior in ternary mixtures. 

Representation of three-component systems as a set of quasi-binary cross-sections is not quite rigorous for the most real ternary mixtures because a ratio of second and third components in equibbrium phases is not usually constant. However, if we intend to study the phase behavior from the point of view of topological schemes, the sequence of binary phase diagrams of quasi-binary sections (including the sections through the ternary nonvariant points) give an exhaustive description of possible phase equilibria and phase transformations in ternary systems. 

As one can see the experimental phase diagram in Figure 44a is the same as the left-hand parts of topological schemes IIIa-1, IIIa-2 or IIIa-3 (see Figure 37). The right-hand parts of these schemes are complicated with the another immiscibility regions which spread from binary subsystems A-C. The immiscibility phenomenon is absent in the binary subsystem H2O - NaCl as well as in intermediate quasibinary cross-sections of ternary systems A - B - C in Illa-1, IIIa-2 or IIIa-3 topological schemes. 

Experimental phase diagrams turn out to compare remarkably well to the calculated ones. Actually most of the experimental topologies exhibiting uniaxial phases only fall in one of the theoretical schemes of Figs. 6 and 7. 

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