Solubility of anthracene in ternary propanol + 2,2,4-trimethylpentane + cyclohexane and butanol + 2,2,4-trimethylpentane + cyclohexane solvent mixtures

Experimental solubilities are reported for anthracene dissolved in ternary 1-propanol + 2,2,4-trimeth- ylpentane + cyclohexane, 2-propanol + 2,2,4-trimethylpentane + cyclohexane, 1-butanol + 2,2,4- trimethylpentane + cyclohexane, and 2-butanol + 2,2,4-trimethylpentane + cyclohexane solvent mixtures at 25 °C. Nineteen compositions were studied for each of the four solvent systems. Results of these measurements are used to test the predictive ability of the ternary solvent form of the combined NIMS/ Redlich-Kister equation. Computations showed that the model predicted the observed solubility behavior to within an overall average absolute deviation of about 1.6%. To address this problem, researchers have turned to group contribution methods and semiempirical equations to predict desired quantities from either pure component properties or measured binary data. In earlier studies we have used the binary solvent reduction of a predictive expression derived from a combined two- and three-body interactional mixing model as a mathematical representa- tion for describing how the measured isothermal solubility of a crystalline solute varies with binary solvent composi- tion. The binary reduction, referred to as the combined NIBS/Redlich-Kister equation, was found to accurately describe the observed solubility behavior in a large number of different binary solvent systems. We now extend our solubility studies to ternary solvent mixtures. Anthracene solubilities have been measured in the two ternary pro- panol + 2,2,4-trimethylpentane + cyclohexane systems and two ternary butanol + 2,2,4-trimethylpentane + cyclohex- ane systems at 25 °C. Nineteen ternary compositions were studied for each of the four systems. Results of these measurements are used to test the predictive ability of expressions based upon the general mixing model used in deriving the combined NIBS/Redlich-Kister equation. Experimental Methods Anthracene (Acros, 99.9+ %) was recrystallized three times from 2-propanone. 1-Propanol (Aldrich, 99+ %, anhydrous), 2-propanol (Aldrich, 99%, anhydrous), 1-bu- tanol (Aldrich, HPLC, 99.8+ %), 2-butanol (Aldrich, 99+ %, anhydrous), 2,2,4-trimethylpentane (Aldrich, HPLC, 99.7+ %), and cyclohexane (Aldrich, HPLC, 99.9+ %) were stored over molecular sieves and distilled shortly before use. Gas chromatographic analysis showed solvent purities to be 99.7 mol % or better. Ternary solvent mixtures were prepared by mass so that compositions could be calculated to 0.0001 mole fraction. Karl Fischer titrations performed on select samples both prior to and after equilibration gave, to within experimental uncertainty, identical water con- tents (mass/mass %) of <0.01%. The methods of sample equilibration and spectrophotometric analysis are dis- cussed in an earlier paper (Powell et al., 1997). Experi- mental anthracene solubilities in the two propanol + 2,2,4- trimethylpentane + cyclohexane and two butanol + 2,2,4- trimethylpentane + cyclohexane solvent mixtures are listed in Table 1. Numerical values represent the average of between four and eight independent determinations, with the measured values being reproducible to within (1.5%.