Excess thermodynamic properties of some 2-alkoxyethanol–water systems

Abstract

Measurements have been made of the densities, ultrasonic velocities and heats of mixing of the 2-methoxyethanol–water, 2-ethoxyethanol–water and 2-butoxyethanol–water systems at 25 °C across their entire composition ranges. These data have been combined with estimates of the isobaric molar expansivities and isobaric molar heat capacities, taken from the literature, to generate a variety of excess molar thermodynamic properties. The excess molar properties of the 2-butoxyethanol system are found to possess intriguing composition dependence in the range 0.02 < X_BE < 0.2. This is particularly evident for the derived quantities C^E_V, A^E_S and [Vβ_S]^E. In order to provide an acceptable fit to these quantities it was necessary to devise a modified version of the four-segment composition model. An attempt has been made to reconcile the form of the excess molar data curves with the existence of a miscibility gap in the 2-butoxyethanol–water system above 49 °C.