Elsevier

Fluid Phase Equilibria

Volume 249, Issues 1–2, 15 November 2006, Pages 49-54
Fluid Phase Equilibria

Excess Gibbs’ energies of selected binary mixtures formed by N,N-dimethyl formamide at 95.5 kPa

https://doi.org/10.1016/j.fluid.2006.08.018Get rights and content

Abstract

Bubble point temperatures at 95.5 kPa, over the entire composition range are measured for the binary mixtures formed by N,N-dimethyl formamide with 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, trichloroethylene, tetrachloroethylene, ethanol, and iso-, sec-, and tert-butanols, by means of a Swietoslawski type ebulliometer. The measurements are fitted to the Wilson model and computed values of vapor–liquid equilibria and excess Gibbs’ energies are tabulated and discussed.

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 aslnγ1=ln(x1+Λ12x2)+x2Λ12(x1+Λ12x2)Λ21x2+Λ21x1lnγ2=ln(x2+Λ21x1)+x1Λ21x2+Λ21x1Λ12x1+Λ12x2whereΛ12=V2LV1Lexpλ12λ11RTΛ21=V1LV2Lexpλ12λ22RTwhere V1L and V2L 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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    The activity coefficients of the solutions were correlated with its composition by the Wilson, NRTL and UNIQUAC models. Bubble point temperatures at 95.5 kPa, over the entire composition range were measured for the binary mixtures formed by DMF with isomeric (iso-, sec-, and tert-butanol) aliphatic alcohols with help of a Swietoslawski type ebulliometer [133]. The measured values were fitted with the Wilson model and computed the GE values.

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