Elsevier

Thermochimica Acta

Volume 589, 10 August 2014, Pages 90-99
Thermochimica Acta

Dynamic and kinematic viscosities, excess volumes and excess Gibbs energies of activation for viscous flow in the ternary mixture {1- propanol+ N,N-dimethylformamide + chloroform} at temperatures between 293.15 K and 323.15 K

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Highlights

  • •

    Many engineering applications require quantitative thermodynamic data of the fluids.

  • •

    Excess properties of mixtures are important in the understanding of mixing process.

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    The results are used to explain the molecular interaction in the mixtures.

Abstract

Dynamic and kinematic viscosities, and densities of the ternary mixture {x1 propanol + x2 DMF + x3 chloroform} and of the three corresponding binary systems have been measured at 293.15, 303.15, 313.15 and 323.15 K and atmospheric pressure. The thermophysical properties, viscosity deviations (Δη), kinematic viscosity (γ), excess Gibbs energies of activation of viscous flow (G*E) and excess molar volumes (VE) have been calculated from experimental values of dynamic viscosity, η, and density, ρ. The different results have been correlated by the Redlich–Kister equation for the binary mixtures and the Cibulka equation for equation for the ternary ones.

Introduction

Excess properties of mixtures provide information about the molecular interactions between the various components and can be used for the development of molecular models describing their thermodynamic behavior.

Experimental results of multicomponent mixtures are very important for industrial applications. Therefore the properties of multi-component mixtures are often estimated from the corresponding data of the constituent binary mixtures but the reliability of such estimation is always questionable and has to be tested. Mixtures of alcohol with chloroform have been the subject of a extended investigation [1]. They are highly non-ideal systems with large negative excess thermodynamic properties as a result of strong cross-association through the formation of hydrogen bonds. Experimental data and excess thermodynamic properties of liquid mixtures are necessary in drawing information on their structure and interactions [2], [3]. The aim of this work is to show the influence of molecular interactions and the effect of the temperature on the thermodynamic and transport properties studied.

N,N-dimethylformamide (DMF) is an industrial solvent with polar character used widely in a variety of industrial processes, among them the manufacture of synthetic fibers, leathers, films, and surface coatings [4]. The negative pole in DMF is on an oxygen atom that is situated just out of he rest of the molecule, this oxygen atom is the best hydrogen bond acceptor. Through unshared pairs of electrons on it, is negatively charged. This well exposed atom is solvated very strongly. The positive pole on the other hand, is buried within the molecule itself. In DMF, the presence of two electron-repelling single bondCH3 groups make the lone pair on the nitrogen atom still more perceptible toward donation. Thus, it may be argued that the DMF is actually the donator of nitrogen–electron pairs [5]. The resonance structure of DMF is shown in below.

Section snippets

Materials

The liquids used were N,N-dimethylformamide (DMF), purity (>99.8%), chloroform purity (>99%), and 1-propanol purity (>99.5%) obtained from Sigma–Aldrich. All chemicals were used without further purification. The purities of all the substances were checked by comparing the measured densities (ρ) and dynamic viscosity (η), and kinematic viscosity (γ) of the components to those reported in literature. The values and references are listed in Table 1.

Apparatus and procedures

Densities and viscosities of the pure liquid

Experimental results and correlations

Viscosity deviations, Δη, excess molar volumes, VE, and excess Gibbs energies of activation of viscous flow, G*E, for binary and ternary mixtures were determined through the following equations:Δη(mPas)=η−∑i=1nXiηiVE(cm3/mol)=∑i=1nXiMiρ−1−ρi−1G*E(J   mol−1)=RTLn(γM)−∑i=1nXiLn(γiMi)where M=∑i=1nXiMi is the molar mass of mixture, R, the gas constant, T, the absolute temperature, η, the absolute viscosity (dynamic viscosity), ρ, the density, and γ the kinematic viscosity of the mixture.

Results and discussion

The observed excess molar volume values in the present investigation may be discussed in terms of several effects which can be arbitrarily divided into physical, chemical and geometrical contributions. The physical interactions involve mainly dispersion forces giving a positive contribution to VE. The chemical or specific interactions between constituent molecules of the mixture components result in a volume decrease. The structural contributions arising from the geometrical fitting of one

Acknowledgments

A. Hassein-bey-Larouci gratefully acknowledges the existing International Cooperation Agreement between the University of Valladolid (Valladolid, Spain) and the Université des Sciences et de la Technologie Houari Boumediene (Alger, Algeria) as well as the financial support of the Spanish Agency for International Cooperation and Development (AECID/MAEC) – International Project: C/033908/10, using the experimental equipment TERMOCAL Research Group.

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