The Solubility of Biphenyl in Non-Polar Solvents

The solubilities of biphenyl, between 30 degrees and 60 degrees, in benzene, carbon disulphide, carbon tetrachloride, heptane, dioxane and p-dichlorobenzene have been determined. The solubilities, in all cases, are lower than ideal. The freezing point-composition diagram for the system biphenyl-p-dichlorobenzene has been determined. These components yield a simple eutectic at 27.7 degrees and at 42.5 mole percent biphenyl. Hildebrand's equation, based upon the simple Baud-Heider equation for the heat of mixing, yields fairly satisfactory results for solutions of biphenyl in benzene, carbon disulphide, p-dichlorobenzene and dioxane. The results are not very satisfactory when the equation is applied to the solutions of biphenyl in carbon tetrachloride and heptane. Hildebrand's more recent equation, based upon the Menke probability function, yields fairly satisfactory results considering the nature of the assumptions made in its derivation. It is concluded that regular solution behavior should be expected only when the molecules of the constituents, in addition to being non-polar, possess spherical symmetry.