This reduction is most rapid in acid and slowest in alkaline solutions.
III
The rate of reduction is greatly increased by increasing the proportion of manganese dioxide.
IV
In concentrated solutions of potassium permanganate, the reduction by manganese dioxide is relatively more rapid than in dilute.
V
Manganese oxide, prepared in the wet way i.e. by the addition of manganese sulphate to a hot solution containing an excess of permanganate, has the composition MnO₂ as regards the ratio of manganese to available oxygen.
VI
This oxide is unstable. It loses oxygen spontaneously even at ordinary temperatures.
VII