A fixed volume of a KMnO4 solution is used to oxidise the same amount of a reductant, first in strongly acidic medium (to Mn^2+) and then in neutral medium (to MnO2), with the same reductant each time. The ratio of the volumes of the KMnO4 solution needed, V(acid) : V(neutral), is:

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A fixed volume of a $KMnO X_{4}$ solution is used to oxidise the same amount of a reductant, first in strongly acidic medium (to $Mn X^{2 +}$ ) and then in neutral medium (to $MnO X_{2}$ ), with the same reductant each time. The ratio of the volumes of the $KMnO X_{4}$ solution needed, V(acid) : V(neutral), is:

Equivalents of reductant are fixed, so

V \propto 1/ n

. The n-factors are 5 (acid) and 3 (neutral), so

V_{a c i d} : V_{n e u t r a l} = 3 : 5