The Dielectric Properties of Water in Solutions

Abstract

Results of dielectric constant and loss measurements at λ=9.22, 3.175, and 1.264 cm are given for a wide variety of aqueous solutions of ions and organic molecules. The water relaxation time is shortened by positive ions and lengthened by hydrogen bond-forming molecules. The properties of water are treated by a statistical method in which the numbers of molecules in four, three, two, one, and zero-bonded states are estimated from dielectric and latent heat data. Fair agreement with experiment is obtained in calculating the static dielectric constant of ice at 0° and water from 0–370°C, using Kirkwood's dielectric theory and Verwey's calculation of the dipole moment of a four-bonded water molecule. The effects of temperature and solutes on the water relaxation time are discussed in terms of this statistical method. The effective number of water molecules ``irrotationally bound,'' i.e., prevented from turning in the electric field by the ion or the organic molecule, is estimated from the depression of the low frequency dielectric constant, using a dielectric theory of mixtures. This number is zero for uncharged solute molecules but is finite for organic or inorganic ions.