0.1 N Potassium permanganate Solution
Preparation of 0.1 N Potassium Permanganate Solution
- Dissolve 3.2 g of Potassium Permanganate (KMnO4) in 100 mL of water and dilute the solution with water to 1 L.
Allow the solution to stand in the dark for two weeks and then filter through a fine-porosity sintered-glass crucible. Do not wash the filter. Store the solution in glass-stoppered, amber-colored glass bottles.
NOTE — Do not permit the filtered solution to come into contact with paper, rubber, or other organic material.
Standardization 0.1 N Potassium Permanganate Solution
- Transfer 2 g of primary standard sodium oxalate (Na2C2O4) to a platinum dish and dry at 105°C for 1 h. Cool in a desiccator.
- Weigh accurately 0.306 ± 0.01 g of the dried Na2C2O4 and transfer to a 500-ml glass container.
- Add 250 mL of sulfuric acid (H2SO4, 1 + 19) that was previously boiled for 10 to 15 min and then cooled to 27 ± 3°C, and stir until the sample is dissolved.
- Add 39 mL of the KMnO4 solution at a rate of 30 ± 5 mL/min, while stirring slowly, and let stand for about 45 s until the pink color disappears.
- Heat the solution to 60°C, and complete the titration by adding KMnO4 solution until a faint pink color persists for 30 s.
- Add the final 0.5 to 1.0 ml dropwise, and give the solution time to decolorize before adding the next drop.
- Carry out a blank determination on a second 250-ml portion of the H2SO4(1 + 19), and make sure that the pink color at the end point matches that of the standardization solution.
Correct the sample titration volume as shown to be necessary.
NOTE-1 — If the pink color of the solution persists more than 45 s after the addition of the first 39 mL of KMnO4 solution is complete, discard the solution and start over with a fresh solution of the Na2C 2O4, but add less of the KMnO4 solution.
NOTE-2 — The blank correction usually amounts to 0.03 to 0.05 ml.
Calculate the normality of the KMnO4 solution, as follows:
A = B / 0.06701 (C – D)
A = normality of the KMnO4 solution,
B = grams of Na2C2O4 used,
C = milliliters of KMnO4 solution required for titration of the solution, and
D = milliliters of KMnO4 solution required for blank titration.