The Reduction of
Neutral Potassium Permanganate
by Manganese Oxide at
Ordinary Temperature.
In these experiments, the manganese oxide used was prepared in the same manner as that in which the proportion of manganese to available oxygen was found immediately after its preparation to be
1.018 : 1.000
It was dried for several days at 65°C., but for almost a month after its preparation was not used. Hence, what the ratio of the manganese to the oxygen at the time when the permanganate was treated with it, is quite uncertain. It however appears probable from the subsequent experiments on the instability of manganese dioxide at 65°C. that the ratio of manganese to available oxygen must have been at about 1.05: 1.00 corresponding to a formula MnO·20MnO₂.
Two solutions of permanganate were made, filtered through glass wool and standardized.
Solution A.
A cubic centimetre of this was found to be equivalent to 5.278 m.g. iron in the ferrous condition.
Solution B.
A cubic centimetre of this was found to be equivalent to 14.379 m.g. iron in the ferrous condition.
Three 250 c.c. portions of each of the solutions A and B were placed in clean glass-stoppered bottles. These bottles were labelled “a”, “a′ ” and “a″ ” “b”, “b′ ” and “b″ ”.