Vergleichende Untersuchungen zum Nachweis von Chlor im Trink‐ und Badewasser auf der Basis von o‐Tolidin und Diäthyl‐p‐phenylendiamin (DPD)

The detection of free chlorine with the aid of o‐tolidine is connected with systematic errors within the range of concentration below 0.1 mg/l and above 0.7 mg/l, reproducibility being otherwise good. In the case of the simultaneous presence of free and bound active chlorine, especially in bathing water, this method determines 50 … 70% of varying shares of the bound chlorine in dependence on the reaction time. As detailed statistical investigations have shown, the determination of chlorine with the aid of diethyl‐p‐phenylenediamine (DPD) as to the prescription according to Palin is free of systematic errors and makes a correct determination of free and bound active chlorine possible with detection limits of 0.03 mg/l. Also low concentrations of free chlorine together with high concentrations of monochloro amine can be safely detected. Therefore, the DPD method is recommended as a standard method, and for the water‐works practice a battery‐operated chlorine photometer is developed for rapid determinations.