Measurement of the impedance on pressed electrodes from Ghanaian and Caucasian manganese dioxide

The capacity of Leclanche cells with bobbins pressed from ground Ghanaian MnO2 is in most cases .apprx.50% higher than with Caucasian ore. The Brunauer-Emmett-Teller surface of the latter is larger, however, than that of Ghanaian MnO. To explain this apparent contradiction the impedance of pressed MnO2 electrodes is measured first at i = 0, then under a cathodic load of i = 1 ma./0.5 cm.2, and finally again at i = 0 by use of a.c. polarization. These measurements in 4N(NH4)2SO4, at pH 4.7 and 22 Deg, indicate that the Ghanaian electrode has a larger electrochem. active surface than the Caucasian MnO2 electrode. This could be the explanation for the higher current efficiency of the pressed Ghanaian MnO2 electrode. [on SciFinder (R)]