Water quality - Determination of permanganate index

The principle of the method specified is heating a sample in a boiling water-bath with a known amount of potassium permanganate und sulfuric acid for a fixed period time (10 min), reducing part of the permanganate by oxidizable material in the sample and determining the consumed permanganate by addition of an excess of oxalate solution, followed by titration with permanganate. Applies to waters having a cloride ion concentration of less than 300 mg/l. Samples having a permanganate index over 10 mg/l should be diluted before analysis. The lower limit of the optimum range of the test is 0,5 mg/l.