ph of the manganese leachate is lower than the lower limit the recovery of manganese mn may be poor on the other hand a higher ph than the upper limit may cause the precipitation of impurities resulting in decreasing the purity of the final product the manganese precipitate may be in the form of manganese oxides such as mn oh 2 to obtain the manganese oxide precipitate solid liquid separation is conducted followed by washing this washing uses water at 60 to 90 u00b0 c in a non oxidative atmosphere through this washing other impurities are removed from the manganese oxide precipitate as well the washed manganese oxide is dissolved in sulfuric acid s 143 for this sulfuric acid is added in an amount 0 5 to 1 5 times the mole content of manganese in the manganese oxide to incur the reaction illustrated in the following chemical formula 4 mn 2 o 3 h 2 so 4 mnso 4 mno 2 h 2 o reaction formula 12 the sulfuric acid solution is neutralized with the manganese oxide obtained in step s 141 s 145 for this neutralization the manganese oxide is added to adjust the acidity of the sulfuric acid solution to a ph of 4 to 6 solid liquid separation is performed on the neutralized solution to give a fourth manganese leachate s 147 the fourth manganese leachate is vaporized in a vacuum to dryness to afford high purity manganese sulfate monohydrate as a crystal s 149 conditions for the vacuum vaporization are set to have a saturated vapor pressure of 0 57 u02dc 0 7 kgf cm 2 and.