A VSE equation of state for normal liquids—I. n-Heptane

A volume—entropy—energy (VSE) equation of state, unlike a PVT equation of state, can be used to calculate “all conceivable” thermodynamic quantities, including specific heats, without supplemental calorimetric data. A VSE equation for liquids, based on simple theoretical concepts, is proposed and, in this paper, applied specifically to n-heptane. This equation of state requires only ten arbitrary parameters, seven of which may be calculated from data at but three temperatures, e.g., 25°, 50° and the normal boiling point. It yields calculated values of many thermodynamic properties nearly as accurate as the best experimental data, from a few degrees above the melting temperature all the way to the critical temperature. PVT equations of state of comparable accuracy over such broad ranges would require at least as many parameters, as well as supplemental calorimetric data, to calculate many thermodynamic quantities that are obtainable directly from our VSE equation.