The factors governing the electrochemical behavior of manganese dioxide in dry cells have never been adequately correlated with the usual physical and chemical properties of this material. Two tests are described, (a) determination of the pH‐potential relation in zinc and ammonium chloride electrolyte and (b) determination of the “utilization factor”, i.e., the extent of cathodic reduction in a continuous stream of fresh electrolyte. In combination, these give valuable information regarding the general suitability of a sample for dry cell use and afford a partial measure of intrinsic depolarizer capacity, heretofore not obtainable by other than actual battery tests.