Fluctuations in aqueous methanol, ethanol, and propan-1-ol: amplitude and wavelength of fluctuation

Abstract

Density, heat capacity, and isentropic compressibility data for aqueous methanol, ethanol, and propan-1-ol by Benson's group were used to evaluate two kinds of fluctuations; mean-square fluctuation densities; and (mean-square) normalized fluctuations, respectively, in volume, entropy, and cross (entropy/volume) effect. The mean-square fluctuation densitiesprovide measures for the amplitude (intensity) of the fluctuation, while the normalized fluctuations contain information regarding the wavelength (extensity) of the fluctuation. Furthermore, their composition derivatives, the partial molar fluctuationsof alcohols were calculated. These quantities signify the effect of additional solute on the respective fluctuations. These data were interpreted in terms of mixing schemes learned earlier in this laboratory by using the data of excess partial molar enthalpy, entropy, and volume, and the respective alcohol-alcohol interaction functions, i.e., the composition derivatives of partial molar quantities.Key words: aqueous methanol, ethanol, and propan-1-ol;fluctuation density; normalized fluctuation; partial molar fluctuations of alcohol.