AbstractManganese hydroxide was precipitated from MnSO4and NH4OH at controlled pH, partially oxidised by aeration and finally calcined at 573–623 K to yield manganese oxide with oxidation state between +3 and +4. When the calcined oxide was leached in dilute sulphuric acid, MnO2of high electrochemical activity was obtained. In order to improve the bulk or packing density of the product various oxidants were added during the aerial oxidation of the Mn(OH)2slurry and also during the leaching in dilute H2SO4. It was observed that the best results were obtained when active MnO2was added during the aerial oxidation of Mn(OH)2slurr