Densities and derived thermodynamic properties of (2-methoxyethanol + 1-propanol, or 2-propanol, or 1,2-propandiol) at temperatures from T = (293.15 to 343.15) K

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Abstract

Densities of the binary liquid mixtures of (2-methoxyethanol + 1-propanol, or 2-propanol, or 1,2-propandiol) have been measured over the entire range of compositions at temperatures from (293.15 to 343.15) K and ambient pressure 81.5 kPa, using a vibrating-tube densimeter. The excess molar volumes VmE, thermal expansion coefficients α, and their excess values αE, and isothermal coefficient of pressure excess molar enthalpy HmE/PT,x, were calculated from experimental densities. The excess molar volume is positive for (2-methoxyethanol + 1-propanol) and becomes more positive with increasing temperature. The excess molar volume for (2-methoxyethanol + 2-propanol) shows a S-shaped dependence on composition with positive values in the 2-propanol rich-region and negative values at the opposite extreme. With increasing temperature from (293.15 to 313.15) K, it increases but beyond this range with increasing temperature from (313.15 to 343.15) K it decreases. The excess molar volume is negative for (2-methoxyethanol + 1,2-propandiol) and becomes more negative with increasing temperature. The excess molar volumes were correlated with a Redlich–Kister type equation.

Introduction

The compound 2-methoxyethanol, commonly known as methyl cellosolve, is a widely used industrial solvent that possesses unique solvating properties associated with its quasiprotic character. The 2-methoxyethanol, an ether alcohol, shows physicochemical characteristics midway between protic and dipolar aprotic solvents [1], [2]. From a theoretical point of view, mixtures containing hydroxyethers are very important, not only because of their self-association but also due to the strong intramolecular effects which is produced by the presence of –O– and –OH groups in the same molecule [3]. Physicochemical and thermodynamic investigations play an important role in helping to understand the nature and the extent of the patterns of molecular aggregation that exist in binary liquid mixtures and their sensitivities to variations in composition and the molecular structure of the pure components [4], [5]. The experimental data of excess thermodynamic properties of liquid mixtures provide useful information about molecular interactions and can be used to test thermodynamic models [6], [7], [8]. The 2-methoxyethanol binary mixtures systems with 1-propanol, 2-propanol and 1,2-propandiol help us to understand the effect of the position of the hydroxyl group in hydrogen bond systems on the excess thermodynamic properties.

We report in this paper the measurements on density and derived thermodynamic properties of (2-methoxyethanol + 1-propanol, or 2-propanol, or 1,2-propandiol) at temperatures from (293.15 to 343.15) K and ambient pressure 81.5 kPa, using an oscillating u-tube densimeter over the entire range of compositions. The excess molar volumes were correlated with a Redlich–Kister type equation. As far as we know there is not any reference for the studied binary mixtures at these temperatures.

Section snippets

Materials

All products were high purity Merck reagents (GC mass fraction purity ⩾0.995) and were used without further purification. The stated purities of the solvents by the manufacturer were further ascertained by comparing their density with the corresponding literature values [9], [10], [11], [12], [13], [14], [15] and they are in good agreement. Purity grades and density of the pure components are listed in table 1.

Apparatus and procedure

The apparatus used in this work is an Anton Paar digital vibrating u-tube densimeter

Results and discussions

The densities ρ, for pure liquids and for the binary mixtures at different concentrations were determined over the temperature range (293.15 to 343.15) K at intervals of 10 K. The excess molar volumes of the binary mixtures were computed by applying the following equation:VmE=i=12xiMi(ρ-1-ρi-1),where Mi and ρi are the molar mass and density of pure component, respectively, and ρ is the density of a mixture.

The average uncertainty in the excess molar volume is estimated to ±6 · 10−3 cm3 · mol−1. The

Acknowledgement

The author thanks the Bu-Ali-Sina University for providing the necessary facilities to carry out the research.

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