Detailed Study of Ice Clathrate Relaxation:  Evidence for the Existence of Clathrate Structures in Some Water−Alcohol Mixtures

Dielectric relaxation technique (10+6−10-3 Hz) and differential scanning calorimetry are used to study the existence of clathrate hydrates in aqueous solutions of a number of alcohols and non hydrogen-bonded liquids. The aqueous solutions studied are those of methanol, ethanol, 2-propanol, tert-butyl alcohol, acetone, and p-dioxane. The corresponding solid−liquid phase diagrams are also determined to support the dielectric results. Evidence for the existence of clathrate hydrates in 2-propanol and tert-butyl alcohol is provided. The clathrate hydrate of 2-propanol is metastable. No clathrate structure is found in methanol mixtures. The composition of the new clathrate found in 2-propanol and tert-butyl alcohol is suggested to be around A. 5H2O−A. 6H2O. The clathrate hydrate relaxation (including that of the two hydrates of ethanol) has been studied down to its kinetic freezing temperature Tg and is analyzed in terms of the Arrhenius equation. Also studied are the relaxation rates of the clathrate hydrates of acetone, tetrahydrofuran, and p-dioxane down to their respective Tgs. The nature of the dielectric relaxation is discussed.