and the parameter 0 ≤ ≤ y < ∞ ∞ is given physically by y = ( s g − − s f ) / ( 2 R ) . The values of all other property discontinuities across the saturation curve also follow from this solution. These functions define the coexistence curve which is the locus of the saturated liquid and saturated vapor states of the vdW fluid. The curve is plotted in Fig. 1 and Fig. 2, two projections of the state surface. These curves agree exactly with the numerical results referenced earlier.