Temperature of maximum density for aqueous mixtures of three pentanol isomers

Abstract

Densities of several aqueous mixtures of 2-pentanol, 3-pentanol, and 2-methyl-2-butanol in the diluted alcohol region were determined in the temperature interval (273.65–282.15) K at atmospheric pressure using the Anton Paar DSA48 vibrating tube densimeter. The variation of the temperature of maximum density with respect to that in pure water ΔT, its structural contribution ΔTstr, as well as the partial molar volume of the alcohol v2 and its excess magnitude v2E were calculated. It was found that ΔT decreases as the alcohol mole fraction x2 increases whereas ΔTstr increases. In both magnitudes, the values for the mixtures of 2-methyl-2-butanol were higher than those of 2-pentanol and 3-pentanol which were found very similar. The secondary or tertiary character of the alcohol seems to be the origin of such differences in complete agreement with previous findings. The slope of the v2-T curve was positive over the working mole fraction interval whereas that of the v2E-T curve was negative, in complete agreement with the tendencies observed for the ΔT-x2 and ΔTstr-x2 curves, respectively. The consistency check proposed by Armitage et al. was thus once fulfilled.