COMPRESSIBILITY FACTOR OF POLAR SUBSTANCES BASED ON A FOUR-PARAMETER CORRESPONDING STATES PRINCIPLE

Abstract

A fourth parameter, ψ_E, obtained from the second virial coefficients at low reduced temperatures, is proposed to correlate the compressibility factor Z of polar substances. The value is expressed in terms of ψ_E and the acentric factor ω as:
Z=Z⁽⁰⁾+ωZ⁽¹⁾+ψ_E(Z⁽²⁾+ωZ⁽³⁾)
Tables of Z⁽⁰⁾ through Z⁽³⁾ are presented over the range of reduced temperatures from 0.4 to 4.0 and of reduced pressures from 0.03 to 40.0, using an approximate BWR equation of state. For fifteen polar substances, the overall average absolute deviations in predicted compressibility factor for the gaseous and liquid regions are 1.3 and 3.3%, respectively. The parameter can be roughly related to dipole moments, whereas no strong correlations between ψ _E and the Stockmayer potential model parameter is observed.