Use of a Cubic Equation to Predict Surface Tension and Spinodal Limits

The very general ShamsundarMurali cubic equation is used to interpolate p-v-T data into the metastable and unstable regions. This y ields a spinodal line that closely matches the homogeneous nucleation limit predicted by an improved kinetic theory. Only the pressure, the saturated liquid and vapor volumes, and the liquid com­ pressibility at saturation, as well as one compressed liquid data point. are needed to use the cubic equation for the interpolation process. The equation also yields an ac curate prediction of the temperature dependence of surf ace tension when it is substituted in van der Waals'surface tension fo rmula. Thus, by capitalizing on the inherent relation among the p-v-T equation, the spinodal prediction, and the sur­ face tension all three it is possible to obtain each with high accuracy and minimal experimental data.