Volumetric and Thermodynamic Properties of Fluids. VI. Relationship of Molecular Properties to the Acentric Factor

Abstract

A method is developed for the derivation of improved intermolecular potentials from empirical second virial coefficient data together with the acentric factors of the fluids. The Kihara core model is considered first, and relationships are derived between the acentric factor and the core size for several shapes. The resulting cores for CH₄, CF₄, C(CH₃)₄, C₆H₆, and N₂ are reasonable in view of semiquantitative theoretical expectations, but the core for CO₂ is somewhat larger than expected. An approximate treatment is given which combines the Kihara core model with an electric quadrupole interaction. The core calculated for CO₂ on this model including the quadrupole moment is of a reasonable size.