Correlations of Surface Free Energy and Solubility Parameter with Dielectric Constant and Density for Inorganic Solids

There should be some intrinsic correlations between the surface free energy (γ) and solubility (δ) parameters, called characteristic parameters here, of substances with their basic physical properties such as the relative dielectric constant (ε r ) and density (ρ), because they are all related to intermolecular interactions. Several correlations have been proposed empirically (or semiempirically) for liquids, but not for solids. It is essential to establish such correlations for solids because the estimation of γ and δ for solids is difficult and/or time-consuming. In the current work, the γ, δ, ε r, and ρ data of 34 inorganic solids were chosen, and possible relationships between the characteristic parameters (γ and δ) and the physical quantities (ε r and ρ) were explored by a trial-and-error fitting method based on the data of the solids. Six equations relating γ and δ to ε r and δ were established. The γ parameters include total (γ t ), dispersive (γ d ), and polar (γ p ) ones, and the δ parameters include the Hildebrand parameter (δ t ) and the Hansen-dispersive (δ d ), polar (δ p ), and hydrogen-bonding (δ h ) ones. The empirical equations can be used to estimate the characteristic parameters of inorganic solids from their easily measurable physical quantities.