The properties of MnO_2 which are made from the thermal decomposition of MnCO_3 in air at 5 atm have been compared with those of MnO_2 made from several other methods. The following experiments were made to examine of the properties of MnO_2 : the specific surface area by BET method, the quantity of decomposition of oxalic acid, the quantity of decomposition of hydrazine hydrosulfate and discharge capacity of the Leclanche cell. From the results of the examinations, it was found that the depolarization activity of MnO_2 for dry cell were in order as follows : from electrolytic method＞from KMnO_4＋HNO_3＞from the other chemical processes and from the decomposition of MnCO_3 in the air at 5 atm＞from the decomposition of MnCO_3 in atmospheric air＞natural MnO_2.
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