Volumetric and dielectric properties in liquid phase of dimethyl ether - ethanol at (293.2 - 313.2) K and 1.00 MPa

Abstract

Abstract Density and dielectric spectra were investigated in liquid phase of dimethyl ether (DME) – ethanol by an oscillating U-tube densimeter and a complex dielectric spectrometer under 1.00 MPa. The density was measured at 303.15 and 313.15 K, and converted to the excess molar volume. The excess molar volumes were no smaller than − 0.880 and − 0.909 cm3 mol–1 at 303.15 and 313.15 K, respectively. The mole fraction dependence can be correlated with Redlich-Kister equation, whose minimum was found around 0.58 for the mole fraction of DME. The dielectric constant and the dielectric relaxation time were evaluated form the complex dielectric spectra in the frequency range from 0.5 to 18 GHz at (293.2–313.2) K and 1.00 MPa. The dielectric constants and the relaxation time were decreased with the mole fraction of DME, and the latter tended to be around 25 ps in the range of mole fraction higher than 0.6. The logarithmic dielectric constants can be correlated with a similar function to Hildebrand equation with the volume fraction. The effective Kirkwood g-factor was evaluated at 293.2–313.2 K and 1.00 MPa. The g-factors were given by two liner functions crossed around 0.6 for the mole fraction of DME. Considering an atomic composition (C2H6O), the molecular sizes are not so different for DME and ethanol. Then, the solution structure was thought to be microscopically changed around 0.6 for the mole fraction of DME. The mole fraction will be utilized to switch the solubility for an extraction of amphipathic compounds.