Excess volumes for ethanol + water mixtures at 10-K intervals from 278.15 to 338.15 K

Abstract

The excess volumes of mixtures of x_A ethanol+ x_B water have been measured at 10-K intervals from 278.15 to 338.15 K over the whole composition range, various dilution dilatometers being used. Particular attention has been paid to regions dilute in both ethanol and water. The partial molar excess volume of ethanol at infinite dilution in water is extremely temperature-dependent, becoming more negative as the temperature increases. The partial molar excess volume of ethanol in dilute solutions is very concentration-dependent at low temperatures but the dependence approaches zero at 362 K. At an x_A value of 0.038, the partial molar excess volume of ethanol V^E_A is independent of temperature, having a value of -5.23 cm³ mol^-1, while the excess volume V^E_A is independent of temperature at x_A = 0.082, having a value of -0.420 cm₃ mol^-1. These unusual observations are explained in terms of the variation of the temperature of maximum density with composition for dilute ethanol solutions. At high mole fractions of ethanol the excess volume and the partial molar excess volume of water do not show unusual behaviour.