Ternary Phase Diagram with Alternate Phase Envelope

This Demonstration illustrates a ternary phase diagram with a type-2 phase envelope. The diagram is used to represent mixtures of three components. The components are partially miscible within the phase envelope, which causes phase separation.

The black point represents the composition of the mixture, with each corner of the triangle being a pure component. The mass fraction of a component in the mixture is read off the axis that is the same color as that component in the standard view. A line is drawn through the point parallel to the base of the triangle that is opposite the corner corresponding to that pure component.

With the "view phases" option, the single-phase region is light red and the two-phase region (phase envelope) is light blue. With "view diagram," gray tie lines are shown in the two-phase region when the "show tie lines" option is selected. The endpoints of each tie line correspond to the compositions of the two phases in equilibrium (

α

phase and

β

phase), and these compositions are shown when the "show

α

phase" and "show

β

phase" options are selected. The points along the left of the phase envelope boundary belong to the

α

phase, and the points along the right belong to the

β

phase.

These diagrams could also be drawn in terms of mole fractions instead of mass fractions.