Thermodynamic and Acoustic Properties of Mixtures of 1,6-Dichlorohexane with Heptane from (293 to 313) K

For {xCl(CH2)6Cl + (1 − x) n-C7H16}, densities ρ were measured with a vibrating-tube densimeter at (293.15, 298.15, 303.15, 308.15, and 313.15) K, covering the whole composition range. From the densities the corresponding isobaric expansivities α p and the excess molar volumes V E were calculated. At the same temperatures, the molar heat capacities at constant pressure C p were also measured over the whole composition range using a differential scanning calorimeter (DSC III from Setaram), and excess molar heat capacities at constant pressure C p E were calculated therefrom. In addition, ultrasound speeds u were determined with a pulse-echo-overlap apparatus. From these results, isentropic compressibilities κ S , isothermal compressibilities κ T , molar heat capacities at constant volume C V , and internal pressures Π were obtained for this system at all five temperatures. The V E are negative throughout; they are somewhat skewed with minima around x = 0.6, and they become less negative with decreasing temperature. The C p E are all negative and strongly asymmetric with minima around x = 0.3 and rather broad shoulders at larger mole fractions of 1,6-dichlorohexane. With decreasing temperature, the C p E(x) curves become less negative with more pronounced shoulders, which behavior is reminiscent of the onset of a W-shaped composition dependence.