ENTHALPIES OF SOLUTION OF ORTHO-TERPHENYLS, META-TERPHENYLS AND PARA-TERPHENYLS IN BENZENE AT 298.15-K

As a test of the overall performance of the calorimetric system used, the enthalpy of solution of tris(hydroxymethyl)aminomethane in 0.100 mol dm-3 aqueous HCl at 298.15 K was measured. For the crushed and vacuum-dried preparation it was -(29.794 ± 0.006) kJ mol-1 which agrees with -(29.790 ± 0.013) kJ mol-1 reported by Rychlý and Pekárek. By use of this calorimeter, the enthalpies of solution ΔHsoln/kJ mol-1 and standard deviations σ/kJ mol-1 of o-, m-, and p-terphenyls in benzene at 298.15 K were found to be (15.57+21.85 n2 n1), σ = 0.05; (24.04-2.83 n2 n1), σ = 0.08; (31.46-5.48 n2 n1), σ = 0.12; respectively, in very dilute solutions, where n2 and n1 are the amounts of terphenyl and benzene. The enthalpies of solution at higher mole fractions are also given for o- and m-terphenyls. The enthalpies of solvation have been estimated. © 1979.