Excess Gibbs’ energies of selected binary mixtures formed by N,N-dimethyl formamide at 95.5 kPa
Introduction
This investigation on the excess Gibbs’ energies of the binary mixtures formed by N,N-dimethyl formamide with the compounds noted in the abstract, is in continuation of our recent systematic studies leading to the phase equilibria of the binary mixtures formed by different types of compounds [1], [2]. There is no published vapor–liquid equilibrium data on the systems chosen for the present study. However, it was felt it appropriate to cite some important studies on similar systems. Vapor–liquid equilibria of N,N-dimethyl formamide: with methanol have been reported by Delzenne [3], Singh et al. [4] and Bittrich and Flischer [5], while those with n-propanol and n-butanol have been published by Wang et al. [6].
Section snippets
Method
Bubble point temperatures are measured making use of a Swietoslawski type ebulliometer, similar to the one described by Hala et al. [7] in construction and described in some detail in our earlier paper [1]. The ebulliometer is connected to a vacuum pump and a dry nitrogen gas cylinder, with a closed end manometer in line, to enables the measurement and maintenance of the total pressure of the system at 95.5 kPa, by adjusting the opening of the needle valve of the gas cylinder/the opening of the
Results and discussion
The experimental liquid phase composition (x1) versus temperature (T) data, summarized in Table 2, are fitted to the Wilson model, expressing the activity coefficients aswherewhere and are the molar volumes of the pure liquids and λs are the energies of interaction between the molecules denoted by the subscripts.The optimum Wilson parameters are
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