PDE: 3 Phases
2-phase plots used to freak me out so I had no hope with the sorts of 3-phase plots that occur with microemulsions.
Again, with an app showing what you would see in the test tube at each point, there is no need to panic.
Having mastered the 2-phase plot this 3-phase version should be relatively easy to grasp. The scenario here is that X is an oil. As before, you specify phase height, width and symmetry but this time 4 regions are created (though this is a highly unusual diagram, usually the 3-phase triangle would reside near the base with a residual "solubility" rectangle beneath it). The three 2-phase regions both have tie-lines that behave as in the 2-Phase app. The difference is the 3-phase region consisting of a middle microemulsion phase with the composition of the top of the triangle then the Water and Oil phases which contain the compositions at the lower corners of the triangle. The ratio of these phases comes from a more complex lever rule.
The act of moving the Symmetry slider is the same as changing the temperature for (especially) an ethoxylate surfactant system, changing the salt concentration for (especially) an ionic system or simply changing the oil. These effects are, of course, nicely described via HLD-NAC theory.
As with the 2-phase system, the colours of the 3 phases represent the red/green/blue combination of the respective components.
Now look at the same sort of thing through the eyes of the Gibbs Phase Rule.