Thermochemical Investigations of Associated Solutions. 3. Effect of the Inert Cosolvent on Solute-Solvent Association Constants Calculated from Solubility Measurements

Solubility are reported for caracole in binary solvent mixtures containing dibutyl ether with n-hexane, n-heptanes, n-octane, cyclopean, cyclostomes, methylcyclohexane and isooctane at 25°C. The results of these measurements are compared to solution models previously developed for solubility in systems containing specific solute-solvent interactions. A simple stoichiometric compellation model based primarily on specific solute-solvent interactions required two equilibrium constants to mathematically describe the experimental solubility's in binary deputy ether mixtures. Calculated equilibrium constants in cyclostomes co solvent were significantly different from values for the isooctane co solvent system. In comparison, an expression derived by including nonspecific interaction contributions described the solubility data to within an average absolute deviation of 2% using a single carbazole-dibutyl ether association constant, which varied from KΦ = 22 for n-heptanes to KΦ = 30 for isooctane.