DIN EN ISO 7393-2:2017-04

This document specifies a method for the determination of free chlorine and total chlorine in water, readily applicable to lab and field testing; it is based on measurement of the absorption the red DPD colour complex in a photometer or the colour intensity by visual comparison of the colour with a scale of standards that is regularly calibrated. Seawater and waters containing bromides and iodides comprise a group for which special procedures are required. This method is in practice applicable to concentrations, in terms of chlorine, from e. g. 0,000 4 mmol/l to 0,07 mmol/l (e. g. 0,03 mg/l to 5 mg/l) total chlorine. For higher concentrations, the test portion must be diluted.