Abstract
The electrical conductances of aqueous solutions of magnesium and manganese (H) oxalates and diothionates, barium dithionate and of acetic acid have been measured at various frequencies in the range 1 KHz to 50 Mz, using a conventional audio-frequency Wheatstone bridge and two radio-frequency transformer ratio-arm bridges. The measurements of the radio-frequency conductances were determined with respect to potassium chloride which is taken as the reference electrolyte. The evaluation of the conductance data was carried out by extrapolation and minimisation techniques using the following theoretical conductance equations: the complete and modified forms of Pitts (8,29) and Fuoss-Hsia(19,30) and those of Falkenhagen-Leist-Kelbg(5) D'Aprano(20). and Murphy-Cohen(25). Quantitative results showed that magnesium, manganese and barium dithionates could be only treated as essentially fully dissociated electrolytes which exhibit ion pairing. All the oxalate and dithionate salts showed an increase in their conductances in a high-frequency field (normal Falkenhagen effect). This could be explained in terms of two effects: the ion atmosphere relaxation(5), and the relaxation of ion-pair equilibrium as calculated by Gilkerson(50). The above-mentioned electrolytes exhibited variations in the values of their association constants (second Falkenhagen effect) with frequency. Estimation has been made for the rate constants of the ion-pair dissociation rate by using Gilkerson theory. The results indicate that acetic acid does not exhibit any effect other than relaxation Of the ionic atmosphere, corresponding to the frequency of the alternating field. It is concluded that this electrolyte is present in neutral molecules which can not be dissociated by the alternating field.