Dielectric Behavior of an Aqueous Cation Exchange

High-frequency dielectric constant and loss measurements for suspensions of an aqueous cation exchange resin (Biogel CM 30) in deionizedwater were predicted by the Debye models for pure polar solvents, as modified for water binding and conductivity effects of the ionizable particle suspensions. Predictions, basedonfree sodium equivalents without colloidal swface charge effects, agreed very closely with standing wave measurements at a 3 GHz and 25°C. Measurements from 50 to 200 KHz also suggested regions of dispersion similar to those of mammalian red blood cells. These results are consistent with the concepts of the Donnan equilibrium and Stern-Gouy double layer as a basis for the “suspension effect” observed by many researchers in aqueous suspensions of acid soil samples. The results also suggest that colloidal swface charge effects on cell walls and membranes of foods are negligible in predicting food dielectric properties, as compared with the dipole rotation of free water and the conductive migration ofdissolved ions at microwave frequencies.