Solubilities of eight aromatic hydrocarbon solids, biphenyl, naphthalene, fluorene, phenanthrene, acenaphthene, fluoranthene, pyrene, and 0 -terphenyl, have been determined in two pure solvents, pyridine and thiophene, from around room temperature to temperatures near the melting point of the solids. The solubility data of the first five solids are correlated well by the Scatchard-Hildebrand regular solution theory if solubility parameters of the components in each binary system are evaluated at the melting temperatures of the solutes rather than at 298 K, the conventional datum temperature. In this case activity coefficients of the solutes are predicted on average to within 3%. When the binary parameter, /,2, determined from the lowest solubility datum point temperature is used in the Scatchard-Hildebrand equation, the activity coefficients are predicted to within an average of 0.6%.

The solubilities of five solutes, biphenyl, naphthalene, fluorene, phenanthrene, and acenaphthene, In pure benzene and cyclohexane and In mixtures of benzene and cyclohexane, have been determined. The activity coefficients of the five solutes In cyclohexane are correlated to within an average of 0.6% by Wilson's equation compared to 9.3 % by the Scatchard-Hlldebrand expression. Similarly for the solutes In benzene, the activity coefficients were correlated to within an average of 0.5 % and 1.2%, respectively, by the same two methods. For the ternary mixtures Wilson's method correlates the activity coefficients for the 78 measured data points within 1.4% compared to 2.6% by the Scatchard-Hlldebrand expression. As expected, when the solution exhibits a significant deviation from Ideal behavior, regular solution theory becomes Inadequate and Wilson's equation Is proposed as a more appropriate correlation. The solubility data can also be correlated as functions of reduced temperature T"/T where 7m Is the melting point temperature.

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