Thermodynamic and acoustic properties of mixtures of dibromomethane + heptane

Abstract

Densities and speeds of ultrasound in binarymixtures of dibromomethane with heptane have been measured within the temperature range from 288.15K to 318.15 K. From the experimental data, the thermodynamic excess volume, molar isobaric expansion, molar isentropic compression, and ultrasonic speed were calculated. The excess volume and excess isentropic compression have opposite signs, whereas the excess isobaric expansion is an S-shaped function of the mole fraction. An explanation was suggested to account for the excesses in terms of intermolecular interactions. It involved energetic and steric factors. Moreover, itwas shown that the positive excess sound speed results almost entirely from the negative excess compression.