Mitsui Minings & Melting Co., Ltd.

Matsushita Electric Corp., Ltd.

Takuya Inoue

Hiroshi Sumida

Hajime Murakami

Yoshihiro Sakurai

Michiko Inui

Kiyoteru Enomoto

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.

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Takehara, Japan

Takuya Inoue