Volumetric Properties of Aqueous Solutions of Ethylene Glycols in the Temperature Range of 293.15–318.15 K

Abstract

Densities of aqueous solutions of Ethylene glycol (EG), diethylene glycol (DEG), and triethylene glycol (TEG) were measured at temperatures from 293.15 to 318.15 K and molalities ranging from 0.0488 to 0.5288 mol·kg −1 . Volumes of all investigated solutions at a definite temperature were linearly dependent on the solute molality; from this dependence the partial molar volumes at infinite dilution were determined for all solutes. It was found that the partial molar volumes at infinite dilution V - 2,0 were concentration independent and slightly increase with increasing temperature. The partial molar volumes at infinite dilution V - 2,0 or the limiting apparent molar volumes of ethylene glycols were fitted to a linear equation with the number of oxyethylene groups ( n ) in the solute molecule. From this equation a constant contribution of the terminal ( O H ) and the ( C H 2 C H 2 O ) groups to the volumetric properties was obtained. The thermal expansion coefficient ( α 1,2 ) for all investigated solutions was calculated at temperatures from 293.15 to 318.15 K. The thermal expansion coefficients for all solutes increase with increasing temperature and molality. Values of ( α 1,2 ) were higher than the value of the thermal expansion coefficient of the pure water.