Abstract: This specification is directed to a method of making a compound selected from the group consisting of birnessite compounds of the formula Bi.sub.x Mn.sub.y O.sub.2y+1.5x.zH.sub.2 O, wherein the y/x ratio is in a range of from about 7 to about 18 and the z/y ratio is in a range of from about 0.5 to about 0.6, Pb.sub.x Mn.sub.y O.sub.2y+x.zH.sub.2 O, wherein the y/x ratio is in a range of from about 6 to about 10 and the z/y ratio is in a range of from about 0.5 to about 0.6, and manganese oxide compounds containing both of these compounds. The method is characterized by the following steps. A solution is formed by mixing Mn(NO.sub.3).sub.2 with a nitrate of bismuth or lead or mixtures thereof. The solution is maintained at a relatively constant temperature and NaOH is added to the solution, whereby Mn(OH).sub.2 and a hydroxide of bismuth or lead or mixtures thereof form a suspension. While the suspension is being agitated, oxygen is passed through the suspension, whereby the Mn(OH).sub.