Hydration of alcohols in aqueous methanol solutions from ultrasonic velocity measurements

Ultrasonic velocity maxima, as a function of alcohol concentration in aqueous methanol solution, have been determined for solutions of a number of mono- and polyhydroxyalcohols. The location of the maximum relative to that in the water-methanol system alone was related to the hydration of the solute molecule. Calculated hydration numbers are linearly correlated with the number of hydroxyl groups in the case of polyhydroxyalcohols, and with the surface area of the non-polar regions in the case of monohydroxyalcohols.