This part of the standard specifies an iodometric titration method for the determination of total chlorine in water. The method is applicable for the measurement of concentrations in terms of chlorine (Cl2), from 0,01 mmol/l to 0,21 mmol/l (0,71 mg/l to 15 mg/l). Several substances interfere in the determination (see clause 10). In annex B a method for direct titration is specified. This is usually applied to the determination of chlorine concentrations above 7 µmol/l (0,5 mg/l) in treated drinking water.