To Prepare a 1 N Solution of Potassium Permanganate (KMnO4) Solution

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.

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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  =  V_b  N_b
 
Where Va and Na are the volumes taken in ml and normality of oxalic acid solution respectively, V_b is the volume of KMnO₄ solution in ml and N_b is the (unknown) normality of KmnO₄ solution.
 
Strength of original KMnO₄ solution.   = 10 x 10 x 0.1     =     10
                                                                             V_b                   V_b

_{Preparation and Standardization of 0.1 M Ammonium Thiocyanate}