Correlations of Surface Free Energy and Solubility Parameters with Dielectric Constant, Refractive Index, and Density for Liquids

There should be some intrinsic correlations between the surface free energy (gamma) and solubility (delta) parameters, called characteristic parameters here, of substances with their fundamental physical properties such as the refractive index (n(D)), relative dielectric constant (epsilon(r)), and density (rho) because they are all related to intermolecular interactions. Understanding the correlations between characteristic parameters and fundamental physical quantities is of great fundamental and practical importance. In the current work, possible relationships between the characteristic parameters (gamma and delta) and the physical quantities (n(D), epsilon(r), and rho) were explored by a trial-and-error fitting method based on the data of 92 liquids (including 14 nonpolar, 37 polar, and 41 hydrogen-bonded liquids). The gamma parameters include total (gamma(t)), dispersive (gamma(d)), and polar (gamma(p)) ones, and the delta parameters include the Hildebrand parameter (delta(t)) and the Hansen-dispersive (delta(d)), polar (delta(p)), and hydrogen-bonded (delta(h)) ones. For each characteristic parameter, its relationship with the physical quantities was established. The applicability of the so-obtained relationships was confirmed using the data of another 66 liquids as an external data set. The empirical relationships can be used to estimate the characteristic parameters of liquids from their easily measurable physical quantities.