On the Dielectric Constant of the Water in Wet Clay

Some recent experimental values of the variation of the dielectric constant of wet clay with moisture content cannot be explained on the assumption that the clay particles and water molecules form a simple mixture. The results can, however, be theoretically deduced by considering relatively dry clay to consist of closely packed water-coated clay particles in an air matrix and relatively wet clay to consist of clay particles uniformly distributed in a water matrix, the water associated with the clay having an effective dielectric constant which varies exponentially from that of `bound' water (about 3) to that of `free' water (about 80) as the percentage of water is gradually increased The conclusion follows that water films have a very low dielectric constant compared with that of water in bulk.