Take 1 litre of distilled water in a 2-lit glass beaker. Weigh out 32.0-32.5gms. Add potassium Permanganate (KMnO4 ) in a watch glass to the distilled water in the beaker. Heat the beaker on a hot plate and gently boil its content for 15-30 minutes till it dissolves in water.
Cool the solution to room temperature. Filter through glass wool or sintered glass crucible and store in a stoppered dark brown bottle. This is approx. 1(N) KMnO4 solution.
Standardization of Potassium Permanganate (KMnO4) Solution
Take 10 ml of the above KMnO4 solution in a 100-ml volumetric flask with a pipette and make up the volume to the mark with distilled water. Transfer 10 ml standard 0.1 (N) oxalic acid solution by a volumetric pipette to a conical flask. Add 60 ml 2(N) H2SO4 solution & titrate rapidly with the diluted KMnO4 solution taken in a burette until the first pink colour appears throughout the solution. Allow standing for some time. If the solution becomes colorless, warm it to 50-60 oC and continue the titration to a permanent faint pink color. Successive titrations should agree within 0.1 ml
Normality is readily computed from the relation, Va Na = Vb Nb
Where Va and Na are the volumes taken in ml and normality of oxalic acid solution respectively, Vb is the volume of KMnO4 solution in ml and Nb is the (unknown) normality of KmnO4 solution.
Strength of original KMnO4 solution. = 10 x 10 x 0.1 = 10
Vb Vb