This part of ISO 7393 specifies a titrimetric method for the determination of free chlorine and total chlorine in water. Sea water and waters containing bromides and iodides comprise a group for which special procedures are required. The method is applicable to concentrations, in terms of chlorine (Cl2), from 0,0004 to 0,07 mmol/l (0,03 to 5 mg/l) total chlorine and at higher concentrations by dilution of samples. For concentrations above 0,07 mmol/l, ISO 7393-3 can also be used. In annex A a procedure is presented for the differentiation of combined chlorine of the monochloramine type, combined chlorine of the dichloramine type and combined chlorine in the form of nitrogen trichloride. Several compounds influence the determination specified in this part of ISO 7393. Interferences are noted in clauses 7 and 9.