Three or More Component Equilibria

Abstract

The maximum variance of a condensed, isobaric three-component system is 3. In a two-dimensional representation, the variance that can be described is restricted to values of 0, 1, and 2. The usual presentation is of a projection of the saturation surface of the single-phase liquid. An area (Φ = 2) is a two-phase region; a line or curve (Φ= 1) is a three-phase equilibrium, and the intersection of lines at a point (Φ = 0) represents the isobaric invariance of four-phase equilibria. A projection of the liquidus onto a single plane is unambiguous if the solid crystallizing phase compositions are reasonably constant, as unique isothermal sections can be determined from the diagram information.