# Ternary Phase Diagram with Phase Envelope

Ternary Phase Diagram with Phase Envelope

This Demonstration shows a ternary phase diagram, including the phase envelope. This diagram is used to represent the phase behavior of mixtures of three components that are only partially miscible over a range of compositions so that phase separation occurs. The black point represents the overall composition of the mixture, while each corner of the triangle corresponds to 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. In "view phases" mode, the single-phase region is light red, and the two-phase region (phase envelope) is light blue. In "view diagram" mode, 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 ( phase and phase), and these compositions are shown when the "show phase" and "show phase" options are selected. The points along the left of the phase envelope boundary belong to the phase, and the points along the right belong to the phase. The point at which the phase switches to phase on the phase envelope is the plait point, which is found by following the tie lines up until a tie line is tangent to the phase envelope boundary. The point of intersection is the plait point. These diagrams could also be drawn with mole fractions instead of mass fractions.

α

β

α

β

α

β

α

β