The permanganate index (also referred to as oxidability) is a conventional parameter for the determination of the concentration of organic and oxidable inorganic matters in water. A water sample is mixed with a weight of potassium permanganate solution and heated up. A portion of the permanganate will be reduced by the oxidable matters contained in the sample. The consumption of permanganate is determined by the addition of a surplus of sodium oxalate solution and the subsequent titration using potassium permanganate. The procedure can be used for drinking water as well as swimming and bathing pool water. The lower application limit is 0.5 mg/l.