It involves the detection of oxidation by potassium permanganate in an acid medium under hot conditions.
The method is to heat a sample in a boiling water-bath with a known amount of potassium permanganate and sulfuric acid for a fixed period time (10 min).
Part of the permanganate will be reduced by oxidizable material in the sample.
The method applies to waters having a chloride ion concentration of less than 300 mg/L.
The lower limit of the optimum range of the test is 0.5 mg/L.