Study of solute-solvent and solvent-solvent interactions in pure and mixed binary solvents

Solute-solvent and solvent-solvent interactions have been studied in fifteen pure solvents and seven binary aqueous mixtures by monitoring the solubility of a dye in the solvents. The standard Gibbs energy of solvation, as given by log s, where s is the solubility has been found to depend on various modes of solute-solvent interaction and also on the Hildebrand solubility parameter representing the cohesive energy density (solvent-solvent interaction) of solvent. In all the binary mixtures the value of log s has been found to deviate from the average of log s values in component pure solvents weighted with respect to their mole fractions. A dimensionless quantity has been defined to represent the deviation of the observed log s values from the mole fraction average. Results have been explained in terms of various modes of solvation interaction.