Excess Isochoric Heat Capacities Research Articles

Density, speed of sound and derived thermodynamic properties of binary liquid mixtures of 1-chlorohexane with toluene and tetradecane under high pressures

The densities and speeds of sound of binary mixtures of 1-chlorohexane with toluene and tetradecane were measured at temperatures from 298.15 K to 433.15 K, and the pressures up to 100.1 MPa. The parameters of the Redlich–Kister equation were determined. The values of isentropic and isothermal compressibility, isobaric thermal expansivity, isobaric and isochoric heat capacity were calculated. Thereafter, excess molar volumes, excess speed of sounds, excess isentropic compressibilities, excess isothermal compressibilities, excess isobaric thermal expansivity, excess isobaric heat capacities, and excess isochoric heat capacities, were estimated.

Binary mixtures of cyclohexanone, 2-butanone, 1,4-dioxane and 1,2-dimethoxyethane

Densities and sound velocities of binary mixtures of cyclohexanone, 2-butanone, 1,4-dioxane and 1,2-dimethoxyethane were measured at 298.15 K and also the densities at 303.15 K. Excess volumes were determined from densities. Isentropic compressibilities were determined from densities and sound velocities, and excess thermal expansion factors were determined from excess volumes of two temperatures. Excess isothermal compressibilities and excess isochoric heat capacities were then estimated using excess isobaric heat capacities previously reported. Excess volumes and excess isentropic and isothermal compressibilities were negative except for cyclohexanone+1,4-dioxane system.

Thermodynamic properties of binary mixtures { x(2-alkoxyethanol)+(1− x) n-octane}: densities at 298.15 and 303.15 K and speeds of sound at 298.15 K

Densities and speeds of sound of the mixtures { x(2-ethoxyethanol), or x(2-propoxyethanol), or x(2-isopropoxyethanol), or x(2-butoxyethanol), or x(2-isobutoxyethanol)+(1− x)( n-octane)} were measured at 298.15 K, densities were also measured at 303.15 K. Excess molar volumes, excess isentropic and isothermal compressibilities, excess isochoric heat capacities and excess isobaric thermal expansivities were calculated therefrom. The excess molar volumes are positive and rather large. The excess isobaric thermal expansivities are positive and large as usual for polar mixtures but the excess isothermal and isentropic compressibilities are small. Derived excess molar isobaric heat capacities are in good agreement with the predicted values obtained with UNIFAC and DISQUAC group contribution models.

Thermodynamic properties of the mixture of methoxyethanol and cyclohexane: Measurements at the temperatures 293.15, 298.15 and 303.15 K above and below UCST

Excess enthalpies, excess isobaric heat capacities, densities and speeds of sound of the mixture of methoxyethanol and cyclohexane were measured at the temperatures 293.15, 298.15 and 303.15 K above and below UCST, approximately 295 K. Excess volumes obtained from the densities and isentropic compressibilities from the densities and speeds of sound. Excess isentropic and isothermal compressibilities and excess isochoric heat capacities were calculated from thermodynamic relations. From the properties obtained for the temperature 298.15 K just above UCST, microphase equilibria exist in the mixture at the temperature.

Thermodynamic properties of (an alkylbenzene + cyclohexane) at the temperature 298.15 K

Excess enthalpies, excess heat capacities, densities, and speeds of sound of (ethylbenzene or 1-methylethylbenzene + cyclohexane) were measured at the temperature 298.15 K. From these measurement, excess volumes, excess isentropic and isothermal compressibilities, and excess isochoric heat capacities were estimated. The excess values are compared with those for (toluene or benzene + cyclohexane). The excess enthalpies and excess volumes are positive and the excess isobaric and isochoric heat capacities are negative for all mixtures. The excess isothermal and isentropic compressibilities are positive along with positive excess volumes. Effects of excess thermal expansivities on isothermal compressibility and isochoric heat capacity are discussed. For these mixtures, the excess thermal expansivity seems to be sufficiently small to be neglected.

Thermodynamics of aqueous mixtures of nonelectrolytes. III. Compressibilities and isochoric heat capacities of water-n-alcohol mixtures at 25�C

Speeds of ultrasound in binary mixtures of water with methanol, ethanol, and 1-propanol were measured at 25°C over the whole composition range by a pulseecho-overlap method. Excess isentropic compressibilities, excess isothermal compressibilities and excess isochoric heat capacities were derived from the results in combination with the results of our previous studies of thermal expansibilities and isobaric heat capacities.

Evaluation of excess isentropic compressibilities and isochoric heat capacities

Two approximations commonly used to evaluate the ideal contribution to excess isentropic compressibilities and to excess isochoric heat capacities are compared for several binary mixtures.