First and second thermodynamic mixing functions of ethylbenzene+n-nonane, +n-decane, and+n-dodecane at 25 and 45°C

Abstract

Isothermal compressibilities κ_T and isobaric thermal expansion coefficients α_p have been determined for mixtures of ethylbenzene+n-nonane, +n-decane, and +n-dodecane at 25 and 45°C in the whole range of composition. The excess functions$(\kappa _\nu ^V )^E = - (\partial V^{\text{E}} /\partial p)_{\text{T}}$ and$(\alpha p{\text{V}})^{\text{E}} = (\partial {\text{V}}^{\text{E}} /\partial T)_p$ have been obtained at each measured mole fraction. The first one$- (\partial {\text{V}}^{\text{E}} /\partial p)_{\text{T}} )$ is zero for ethylbenzene +n-nonane, positive for ethylbenzene +n-decane, and +n-dodecane and increases with chain length n of the n-alkane. The$(\partial {\text{V}}^{\text{E}} /\partial T)_{\text{P}}$ function is positive for the three studied systems and nearly constant with n. Both mixing functions increase slightly with temperature. From this measurement and supplementary literature data of molar heat capacities at constant pressure C _P , the isentropic compressibilities κ_S, the molar heat capacities at constant volume C _V and the corresponding mixing functions have been calculated at 25°C. Furthermore, the pressure dependence of excess enthalpy H^B,$(\partial H^{\text{E}} /\partial p)_{\text{T}}$ at zero pressure and at 25°C has been obtained from our experimental results of$(\partial V^{\text{E}} /\partial T)_{\text{P}}$ and experimental literature values for excess volume V^E.