Ternary Phase Diagram with Alternate Phase Envelope

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This Demonstration shows a ternary phase diagram with a 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. Select "diagram" and move the black dot to any location within the triangle by clicking on that location, which represents the overall composition of the mixture. 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. These axes are labeled by drawing a line through the point; this line is parallel to the base of the triangle that is opposite the corner corresponding to a pure component. Select "phases" to view a diagram that shows the one- and two-phase regions.


When the black dot is in the two-phase region, a tie line (dashed black lines) is shown, and the endpoints of the tie line correspond to the compositions of the two phases ( and ) that are in equilibrium. Check "alpha phase" and "beta phase" to show the compositions of each phase. Check "tie lines" to view the gray tie lines. Check "grid lines" to view grid lines on the diagram. The points along the orange side of the phase envelope boundary belong to the phase, and the points along the magenta side belong to the phase. Ternary phase diagrams can also be drawn in terms of mole fractions instead of mass fractions.


Contributed by: Megan E. Maguire and Rachael L. Baumann (January 2015)
With additional contributions by: John L. Falconer and Nick Bongiardina
(University of Colorado Boulder, Department of Chemical and Biological Engineering)
Open content licensed under CC BY-NC-SA



For use of this Demonstration, view the page at [1]. For more information on how to use a ternary phase diagram, view the screencasts at [2] and [3].


[1] Ternary Phase Diagram with Alternate Phase Envelope. www.colorado.edu/learncheme/thermodynamics/TernaryAlternatePhaseEnvelope.html.

[2] Using a Triangular (Ternary) Phase Diagram [Video]. (Nov 16, 2011) www.youtube.com/watch?v=gGYHXhcKM5s.

[3] Interpolating Tie Lines on aTernary Diagram [Video]. (Mar 15, 2013) www.youtube.com/watch?v=n7DPiuHllZE.

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