Key words: phase equilibrium, phase diagram, supercritical fluid, binary system, ternary component system
The main feature of supercritical (SC) fluids is a continuous increase of fluid density at increasing pressure (from values typical for gas to liquid-like) without an appearance of heterogeneity and "liquid - gas" (L-G) equilibria. In binary and more complex systems composed of components of different volatility SC fluid equilibria occur not only at temperatures above the critical point (CP) of less volatile component(s). They can also appear at much lower temperatures - below the melting point of nonvolatile compound, but necessarily above the CP of low-boiling component. Namely these "low-temperature" equilibria occur and are used in various SC fluid technologies. Therefore, an information about the displacement of homogeneity boundaries in SC fluid region, if a third component is added, is very important for practical application of ternary systems. The method of continuous topological transformation of phase diagrams permits to introduce the systematic classification for binary systems and also to derive both fluid and complete phase diagrams for ternary systems with one volatile and two nonvolatile components. The examination of theoretically derived ternary phase diagrams combined with the results of experimental measurements allowed to formulate some general regularities of the behavior of phase diagrams for ternary systems in the region of SC fluid heterogenization.