Abstract: There is described in the specification a mercury-free manganese primary dry battery wherein the cathode mixture contains boric acid or an alkali borate at a ratio of 0.04 to 0.4 parts by weight per 100 parts by weight of manganese dioxide as a boron conversion value or wherein the separator contains boric acid or an alkali borate at a ratio of 0.1 to 8.0 parts by weight per 100 parts by weight of a dry solid content in the pasting agent. Such battery has excellent discharge properties under light loading conditions.

Abstract: An electrolytic manganese dioxide having a composition of MnOx, wherein X is 1.90 to 1.96, an adhesive moisture content of not less than 1.5% by weight as measured according to the procedure specified in JIS, and a content of bound water, eliminative in the temperature range of 120.degree. to 400.degree. C., of not less than 3.0% by weight as measured by gravimetry, a process for preparing the same, and a manganese dry cell comprising a cathode mix comprised of a mixing of the electrolytic manganese dioxide with a conductive acetylene black, preferably a conductive acetylene black having a BET specific surface area of 70 to 2.50 m.sup.2 /g, and an electrolyte composed mainly of zinc chloride and/or ammonium chloride. In the process of preparing the electrolytic manganese dioxide, after electrolysis and during or after neutralization, the manganese dioxide is heated in an aqueous solution at 50.degree. to 100.degree. C. for 12 to 48 hours in the presence of an alkaline ammonium compound.