Thermodynamic Excess Functions for the Liquid System Water + Acetic Acid from Calorimetric Data

Abstract

For the liquid system water + acetic acid, we give the results of new calorimetric measurements regarding the molar excess enthalpy [FORMULA OMITTED] for 25 °C, 30 °C, 35 °C, 40 °C, 55 °C, and 70 °C, covering nearly the entire range of compositions. The experimental data show that [FORMULA OMITTED] is positive for all compositions and temperatures except in the region of low acid concentrations at temperatures below 55 °C where the process of mixing the pure liquid components is exothermic ([FORMULA OMITTED]σ0). Using values of the molar excess Gibbs function [FORMULA OMITTED] (always positive) derived from earlier data on vapour-liquid equilibria, we compute the molar excess entropy [FORMULA OMITTED] which is always negative. The “symmetry rule” concerning the composition dependence of [FORMULA OMITTED] (as compared to that of [FORMULA OMITTED] and [FORMULA OMITTED]) has again been confirmed. The composition dependence of [FORMULA OMITTED] is similar to that of the molar excess volume. © 1977, Walter de Gruyter. All rights reserved.