Excess properties (VE, εE, and HE) of the binary system pyridine (1) + sulfolane (2)

Volumes of mixing and dielectric constants of the binary system pyridine (1) + sulfolane (2) were measured over the entire composition range, 0 ≤ x ≤ 1, at selected temperatures ranging between 293.16 and 323.16 K. Mixing enthalpies were also measured at 303.16 K. Deviations from ideality of the measured properties are consistent with the regular behaviour of sulfolane systems, as evidenced by previous works. Nevertheless the occurrence, in the pyridine-rich region, of a sharp maximum in excess dielectric constants versus composition curves, and of a deep minimum in enthalpies of mixing curves, substantiates the supposition that small dipolar interactions occur between molecules of the components. These steadily decrease in magnitude with increasing temperature and sulfolane content in solution.