PhysChemBasics#8 Phase Diagrams 101 The best way to discuss phase diagrams is to first look for the homogeneous and heterogeneous regeions, then label the binodals and draw in some tie lines. Finaly depict the invariant points and specify the processes that take place at these points. Ideal phase diagrams, whether melting or boiling phase diagrams, show neither maximum nor minimum for the binodals. Non-ideal mixtures may have maxima and minima, which are called azeotrope, peritectic or eutectic, depending on the type of diagram. Gibbs' phase triangle has proven useful for the illustration of 3-component mixtures. Again there may be binodals and tie lines in this diagram. A tie line not only tells us the composition of the phases in the heterogeneous region, but also - after applying the lever rule - their quantity ratio..