Ternary Phase diagrams

Often, solutions are made with more than two components in significant amount.  This some times leads to  phase issues that require a new kind of phase diagram to represent.  A Ternary Phase Diagram shows the phases of a three component system.  Normally, we represent these phases in a triangular diagram where the apices of the triangle represent the three pure components and the distance from an apex is a measure of it's concentration.

Taken from http://home.c2i.net/astandne/help_htm/english/terplot1.htm

Here, we see a triangle for a system A,B,C.  If A is the top apex then the baseline BC represents the 2-component phase diagram between B and C.   Similarly, the edge opposite B is the two component AC region, etc.  any point on the diagram represents the composition of the three components.

Consider, first, a two-component water/dimethyl ether system.  If we consider only these two solvents, we find that they are immiscible over a large concentration range 0.34 < mass fraction < 0.95.  If we add at least 6% ethyl alcohol, we can make the solution totally miscible over the whole concentration range for the water/dimethyl ether.

http://www.rpi.edu/dept/chem-eng/Biotech-Environ/DOWNSTREAM/twophase.htm	Here is a phase diagram for three components A: water, B,C two different organic compounds B and C both are fully miscible with water but not with each other. Note that the tie-lines joining the two phases in the two-phase region are not parallel to each other.
http://www.brocku.ca/earthsciences/people/gfinn/petrology/ternary1.htm	This is a ternary diagram where the three binary diagrams each have a eutectic point.  The three eutectic curves converge to a single overall eutectic point for the ternary solution.  The curved lines represent the isotherms where T5>T4....
http://asymptotia.com/2006/11/18/a-tasty-phase-diagram/	Just for fun, here is a "phase diagram" for making pastry.