A solution of MnCl2⋅4H2O (200 g) in H2O (2 L) at 70 ◦C was gradually added during 10 min, with stirring, to a solution of KMnO4 (160 g) in H2O (2
L) at 60 ◦C in a hood. A vigorous reaction ensued with evolution of chlorine; the suspension was stirred for 2 h and kept overnight at rt. The
precipitate was filtered off, washed thoroughly with H2O (4 L) until pH 6.5–7 and the washing gave a negligible chloride test. The filter cake was
then dried at 120–130 ◦C for 18 h; this gave a chocolate-brown, amorphous powder; yield 195–200 g.
Manganese (II) sulphate monohydrate (140 g) was dissolved in 2.66 liters of water and heated to 60°C. Potassium permanganate (97.3 g) in 1.85 liter
of water was added over a period of 15 minutes and stirred at 60°C for 1 hour, until manganese dioxide precipitated out. The reaction mixture was
filtered and the residue was washed with deionised water until no sulphate ion was present. The solid was dried under suction for 2 hours followed by
drying at 70°C under vacuum to a constant weight (about 8 days) to give 115 g of a dark brown powder
In the span of 2h, to 250ml of 5% MnSO4 solution add 200ml of 5% KMnO4 solution while stiring at 50-60C. Filter out the precipitate and wash until the
absence of SO42- ions. Dry for 10h at 120C.
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