THE DEBYE-FALKENHAGEN EFFECT - EXPERIMENTAL FACT OR FICTION

Coulomb interactions produce spatial correlations between ions in solution. Debye-Falkenhagen (DF) suggested in 1929 that translational motion of any ion requires neighboring ions to readjust their relative positions. The readjustment process is time-dependent, and leads to a frequency-dependent conductivity, sigma(omega), and dielectric constant, epsilon(omega). Falkenhagen generated theoretical graphs showing a frequency dispersion of normalized conductance. Corresponding experimental data have never been reported. The present article considers the DF effect from an experimental standpoint. It is found that the predicted effect is extremely small in dilute electrolyte solutions. Impedance measurements on the water-p-dioxane and the methanol-toluene systems confirm this prediction. Both systems exhibit impedance dispersions entirely characterized by bulk dielectric constant and bulk conductance.