Thermodynamic properties of some binary mixtures of specifically interacting non-electrolytes. Part 1.—Aniline + toluene

Abstract

Heats of mixing h^M of aniline + toluene have been measured at 30 and 50°C over the entire composition range and have been correlated with published values of the excess free energy g^E to obtain the excess functions of the system between 30 and 100°C. The results have been interpreted assuming aniline to be associated. The excess functions calculated by means of the Mecke-Kempter model, characterized by only two adjustable parameters, agree excellently with the experimental g^E, very satisfactorily with h^M, and predict correctly the almost zero excess heat capacity c^E_p of the mixture. The association constant K, the enthalpy of association ΔH°(energy of the N—H … N bond), and the entropy of association ΔS° have been derived. K is given by the equation log K= 442/T–1.06, from which ΔH°=–2025 ± 50 cal/mole (in agreement with spectroscopic and other data), and ΔS°=–4.85 ± 0.20 cal/deg mole.