Apparent molar volumes and apparent molar heat capacities of aqueous tetrahydrofuran, dimethyl sulfoxide, 1,4-dioxane, and 1,2-dimethoxyethane at temperatures from 278.15 K to 393.15 K and at the pressure 0.35 MPa

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Abstract

We determined apparent molar volumes Vϕ at 278.15  (T/K)  368.15 and apparent molar heat capacities Cp,ϕ at 278.15  (T/K)  393.15 at p = 0.35 MPa for aqueous solutions of tetrahydrofuran at m from (0.016 to 2.5) mol · kg−1, dimethyl sulfoxide at m from (0.02 to 3.0) mol · kg−1, 1,4-dioxane at m from (0.015 to 2.0) mol · kg−1, and 1,2-dimethoxyethane at m from (0.01 to 2.0) mol · kg−1. Values of Vϕ were determined from densities measured with a vibrating-tube densimeter, and values of Cp,ϕ were determined with a twin fixed-cell, differential, temperature-scanning calorimeter. Empirical functions of m and T for each compound were fitted to our Vϕ and Cp,ϕ results.

Introduction

Interactions between polar compounds and water have been studied extensively. Densities for aqueous solutions of many polar compounds have been reported in the literature at many concentrations and temperatures. While densities ρs and apparent molar volumes Vϕ have been studied extensively for aqueous solutions of polar nonelectrolytes, relatively little attention has been given to apparent molar heat capacities Cp,ϕ of these systems.

In this investigation, we report values of Vϕ and Cp,ϕ for aqueous solutions of tetrahydrofuran [THF], dimethyl sulfoxide [DMSO], 1,4-dioxane [DIOX], and 1,2-dimethoxyethane [DME] and their dependencies on temperature T and molality m. We have measured and report here values of Vϕ at 278.15  (T/K)  368.15 and Cp,ϕ at 278.15  (T/K)  393.15 at the pressure 0.35 MPa for aqueous solutions at the indicated molalities m: THF at 0.016  (m/mol · kg−1)  2.5, DMSO at 0.02  (m/mol · kg−1)  3.0, DIOX at 0.015  (m/mol · kg−1)  2.0, and DME at 0.01  (m/mol · kg−1)  2.0.

Section snippets

Experimental

We used THF (C4H8O, molar mass M2 = 72.1061 g · mol−1, Sigma–Aldrich product no. 186562, lot 03458DD, reported purity = 0.9987 mass fraction), DMSO (C2H6OS, M2 = 78.1287 g · mol−1, Sigma–Aldrich product no. 276855, lot 02734ED, reported purity = 0.9998 mass fraction), DIOX (C4H8O2, M2 = 88.1056 g · mol−1, Sigma–Aldrich product no. 296309, lot 05063ED, reported purity = 0.9998 mass fraction), and DME (C4H10O2, M2 = 90.1215 g · mol−1, Sigma–Aldrich product no. 307432, lot 03153MC, reported purity = 0.9998 mass fraction)

Results and discussion

Values of Vϕ for aqueous solutions were calculated using the following equation:Vϕ=(M2/ρs)-(ρs-ρw)/(ρs·ρw·m),where ρw is the density of water [3]. Our experimental values of ρs and the values of Vϕ(m, T) from equation (1) and their uncertainties are given in TABLE 1, TABLE 2, TABLE 3, TABLE 4 for aqueous THF, DMSO, DIOX, and DME, respectively. The estimated uncertainties in TABLE 1, TABLE 2, TABLE 3, TABLE 4 were obtained by using standard error propagation methods as described previously [2].

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