The magenta curve, obtained for versus , is the spinodal line or locus of the turning points where . These points are readily obtained using the Mathematica built-in command WhenEvent. The spinodal curve envelops the regions where supercooling and superheating of a liquid can be achieved (i.e. metastable and unstable regions). The checkbox lets you zoom and clearly observe the black binodal curve. Also shown (1) are one of the two turning points (green) and (2) two blue dots corresponding to the saturation pressure at the user-set value of the reduced temperature, or . The binodal curve represents the curve where vapor and liquid coexist and the equilibrium state is stable.

The versus item of the second dropdown menu gives the limits of coexistence of vapor and liquid for a given value of the reduced pressure . These limits are indicated by the green dots. The dotted blue curve shows the limits of metastability (superheating and supercooling of a liquid).