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The complex dielectric constant of liquid water was measured at 9.61 GHz down to −18 °C by means of a two resonant cavities apparatus. The static dielectric constant of bulk samples was also measured at 27.5 MHz down to −16.5 °C using a resonant circuit technique. From the analysis of the experimental results it follows that water in the metastable region has practically a single dielectric relaxation time τ. An analysis of the dynamic properties of water using our results and available data in literature, is presented. The main result is that self-diffusion DS, shear viscosity η, and τ below 0 °C are related to the same mechanism. For T≳0°C another mechanism affecting η rises.

We present here the first results of a systematic study of the dielectric properties of alcohols-water solutions. The complex dielectric constant i = t;' -it;" and the dielectric relaxation time T of MeOH, BtOH, 2-PrOH alcohols, and their aqueous solutions are reported for some values of the water mole fraction Xw in the range 0:::; x. :::; 0.5, at various temperatures (from 30·C down to -43 ·C for MeOH and its solutions). T has been measured by a two coaxial resonators spectrometer in a significant frequency range for the principal relaxation region of these liquids (0.47-4 GHz). Measurements of t;' at \3 MHz with a different experimental apparatus have also been made. Our data do not confirm previous determinations of T vs X. at 30 ·C. In all the investigated temperature range, T is a decreasing monotone function of Xw for the aqueous solutions of BtOH and 2-PrOH. On the contrary, the dielectric relaxation time of MeOH aqueous solution is practically constant up to X. = 0.1 at 30 ·C; at O· and -25 ·C, T increases at the beginning and a maximum is present; at lower temperature, T increases with x •. The observed behavior of T is discussed and a model for the dielectric relaxation in H-bond associated liquids is suggested.(1)

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