Derivation and classification of ternary phase diagrams

The experimental investigations were and are the main sources of information about phase behavior in ternary systems. In the beginning of the twentieth century Smiths (1910, 1913, 1915) using the topological method and available experimental information has considered 12 versions of complete phase diagrams with various types of fluid phase behavior and solid phase transformations. But it was not a systematic classification. 

The first systematic approach to a derivation the global phase diagram of ternary fluid mixture using an analytical investigation of the Van der Waals equation of state with standard one-fluid mixing rules was developed by Bluma and Deiters (1999). Eight major classes of ternary fluid phase diagrams were outlined and their relationship to the main types of binary subsystems were established. 

Row I contains the fluid phase diagrams of ternary class (la-lb-lb), row II - ternary class (la-lc-lc), row III - ternary class (la-ld-ld), row IV - ternary class (la-lb-ld), row V - ternary class (la-lb-lc), row VI - ternary class (la-lc-ld). 

Ternary system consists of one volatile and two nonvolatile components, such phenomena as an azeotropy in liquid-gas equilibria and a formation of binary or ternary compounds are absent. Solid phases of volatile and each non-volatile components are completely immiscible and have the eutectic relations in equilibrium with fluid phases, whereas the solid phases of non-volatile components form a continuous solid solution. 

Binary subsystems with volatile component are complicated with the immiscibility phenomena. However, the immiscibility regions spreading from the binary subsystems are not necessarily joined to form a unifled immiscibility region, they can be separated in ternary solutions by the miscibility region. 

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