THE DEBYE-FALKENHAGEN EFFECT - EXPERIMENTAL FACT OR FICTION

Coulomb interactions produce spatial correlations between ions in solu tion. Debye-Falkenhagen (DF) suggested in 1929 that translational moti on of any ion requires neighboring ions to readjust their relative pos itions. The readjustment process is time-dependent, and leads to a fre quency-dependent conductivity, sigma(omega), and dielectric constant, epsilon(omega). Falkenhagen generated theoretical graphs showing a fre quency dispersion of normalized conductance. Corresponding experimenta l 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 c onfirm this prediction. Both systems exhibit impedance dispersions ent irely characterized by bulk dielectric constant and bulk conductance.