THE STRUCTURE OF WATER AND METHANOL IN P-DIOXANE AS DETERMINED BY MICROWAVE DIELECTRIC-SPECTROSCOPY

Dielectric measurements were performed on water-p-dioxane and methanol-p-dioxane mixtures using time domain reflectometry over the frequency range 0.1-10 GHz. In the case of water-p-dioxane mixtures, the relaxation strength normalized by the number of water molecules per unit volume is independent of the molar fraction of water x(w) if x(w) < 0.83. There are no ordered micellelike clusters in the mixture. On the other hand, if x(w) is larger than 0.83, the normalized strength increases linearly with x(w). The clusters of pure water which appear in this region are cyclic and consist of six molecules. In the case of methanol-p-dioxane, the normalized strength is independent of x(M) for x(M) < 0.66 and increases linearly with x(M) for x(M) > 0.66. However, the relaxation time of pure methanol is too large for clusters consisting of three molecules. It is suggested that the chainlike clusters form network structures.