Equation of state for all phases. Part 1.—Basic isothermal equation

Abstract

An open-ended isothermal equation of state developed from the van der Waals equation has the excluded volume term, B, as a function of (P+A/νⁿ). As values of (P+A/νⁿ) become large, the equation becomes simple in form while at low pressures it is most complex. A non-linear optimization technique was used to fit the equation parameters to various sets of PνT data which included the vapour, liquid and solid phases. The equation can represent the extremes of the pressure ranges of all the isotherms investigated including some at near critical temperatures within the experimental accuracies.