Relationships between the internal pressure, the cohesive energy, and the surface tension of liquids

The relationship between the internal pressure P-int on the one hand and the cohesive energy density ced on the other and the ratio of the surface tension to the cube root of the molar volume sigma/V-1/3 (also called the Gordon parameter) was examined for a large number of liquids. These consisted of four classes: molecular liquids, liquid metals, room temperature ionic liquids (RTILs), and molten salts. Linear dependences, rather than proportionalities suggested by theory, were obtained in all cases, their slopes being independent of the type of the liquid (the exceptions being noted), but differ for P-int and ced.