DETERMINATION OF Fe2+ WITH PERMANGANATE
ANALYSIS OF SAMPLE1
First, weigh accurately about 0.1 g of your unknown. Dissolve the unknown into about 500 mL of DI water, add 1-2 mL of con. sulfuric acid, and then dilute accurately to 1L. Transfer this solution to your 1 liter polyethylene flask for storage until the next experiment.
Weigh a sample of approximately 1.5 grams into a 500 mL conical flask. Based on the results of this titration, be sure to choose sample sizes that will require between 30 and 50 mL of titrant for the rest of the samples. Add 200 mL of 5% sulfuric acid, stir, and titrate with 0.02 M potassium permanganate solution.
DISPOSAL OF POTASSIUM PERMANGANATE2
2MnO4- + 5HSO3- + H+ 2Mn2+ + 5SO42- + 3H2O
For each 200 mL of your permanganate solution add 1 mL of 1M sulfuric acid. IN THE FUME HOOD, slowly and with stirring, add 10% sodium bisulfite solution until the permanganate color is discharged and the initial brown precipitate of manganese dioxide dissolves. About 13 mL of the bisulfite solution is required for each 200 mL of the permanganate solution. Neutralize the resulting solution by adding, with stirring, solid sodium carbonate, and wash the colorless solution into the drain with water.
2. Armour, M.A. J. Chem. Educ. 1988, 65, A66