Elsevier

Fluid Phase Equilibria

Volume 273, Issues 1–2, 25 November 2008, Pages 52-58
Fluid Phase Equilibria

Activity coefficients and excess Gibbs energy of binary mixtures of N,N-dimethyl formamide with selected compounds at 95.5 kPa

https://doi.org/10.1016/j.fluid.2008.07.018Get rights and content

Abstract

Bubble point temperatures at 95.5 kPa, over the entire composition range, are measured for the binary mixtures of N,N-dimethyl formamide with: acetophenone, aniline, bromobenzene, chlorobenzene and N,N-dimethyl acetamide, employing a Swietoslawski-type ebulliometer. Liquid phase mole fraction versus bubble point temperature measurements are well represented by the Wilson model. Computed values of the activity coefficients and excess Gibbs energy are presented and discussed.

Introduction

N,N-Dimethyl formamide is a widely used aprotic solvent and reagent in organic synthesis and chemical analysis. The uses of the other components chosen for this study as solvents and in other applications needs no fresh mention. Information leading to the vapor–liquid equilibrium of the binary mixtures of N,N-dimethyl formamide with the selected compounds is expected to be of use in the design and operation of the separation processes for the compounds contained in the mixtures. This investigation, on the bubble point temperatures of the binary mixtures noted in the abstract, is a continuation of our recent studies on the phase equilibrium of the binary mixtures containing hydrocarbons or alcohols [1], [2]. We could not locate any phase equilibrium data on the selected mixtures for comparison.

Section snippets

Methods

A Swietoslawski-type ebulliometer, very similar to the one described by Hala et al. [3] is used for this experimental investigation. Connection of the ebulliometer to a good vacuum system and dry nitrogen gas cylinder helped in the creation and maintenance of the chosen pressure within ±0.05 kPa of the selected value of 95.5 kPa. An open end manometer, provided in line, is read frequently and the needed corrective action of – adjusting the opening of the needle valve attached to the gas cylinder

Results and discussion

The experimental liquid phase composition (x1) versus temperature (T) data, summarized in

Table 2, are fitted to the Wilson [5] equation:lnγ1=ln(x1+Λ12x2)+x2Λ12x1+Λ12x2Λ21x2+Λ21x1lnγ2=ln(x2+Λ21x1)+x1Λ21x2+Λ21x1Λ12x1+Λ12x2whereΛ12=V2LV1Lexpλ12λ11RTΛ21=V1LV2Lexpλ12λ22RTwhere V1L and V2L are the liquid molar volumes of the pure components and λ ‘s are the energies of interaction between the molecules designated by the subscripts. It is assumed that the interaction energies λ12 and λ21

Conclusion

Phase equilibria in the binary mixtures of N,N-dimethyl formamide with: acetophenone, aniline, bromobenzene, chlorobenzene and N,N-dimethyl acetamide have been investigated. The observed values of the liquid phase mole fraction versus bubble point on all the mixtures investigated could be well represented by the Wilson model. Among the mixtures investigated, the mixtures with bromobenzene, chlorobenzene and N,N-dimethyl acetamide show positive values for excess Gibbs energy while the mixtures

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