THERMOCHEMICAL INVESTIGATIONS OF HYDROGEN-BONDED SOLUTIONS .5. DEVELOPMENT OF PREDICTIVE EQUATIONS FOR THE SOLUBILITY OF ANTHRACENE IN BINARY ALCOHOL PLUS ALCOHOL MIXTURES BASED UPON MOBILE ORDER THEORY

The unconventional solution model of Mobile Order, which had previously been shown to provide a very accurate thermodynamic description of anthracene solubilities and chemical potentials in binary hydrocarbon + alcohol solvent mixtures, is extended to binary solvent systems containing two self-associating alcohol co-solvents. Expressions are derived for predicting the solubility of crystalline solutes from a prior knowledge of the solubility in the two pure alcohol solvents. Applications and limitations of the newly derived equations are assessed using anthracene solubilities in binary 2-propanol + 1 -propanol, 1-butanol + 1-propanol, 2-butanol + 1-propanol, 1-octanol + 1-propanol, 1-butanol + 2-propanol, 2-butanol + 2-propanol, and 1-octanol + 2-butanol mixtures which are measured as part of the present study. The two most successful expressions permit each individual alcohol co-solvent to form homogeneous hydrogen-bonded complexes. Both equations predict the experimental anthracene solubilities to within an average absolute deviation of about +2%. Inclusion of terms to account for heterogeneous complex formation between two dissimilar alcohols has little effect on the predicted values.