Free and residual chlorine according to DIN EN ISO 7393-1
10/4/2017

Water drop bouncing off the water surface

Metrohm is pleased to present an Application Bulletin describing the determination of free and total chlorine by iodometric titration.

To disinfect water for human consumption, chlorine is added to the water in some countries. Because chlorine is highly toxic, organism like bacteria are killed and the onset of waterborne diseases like cholera is prevented. But chlorine is not only toxic to microorganism, it is toxic for humans as well. The main reason for its toxicity is the fact that chlorine may react with other organic compounds to form disinfection by-product (DBP) like trichloromethane and chloroacetic acid. Therefore the maximum permissible value is strictly controlled.

AB 249 shows the possibility to determine chlorine according to three different methods. These methods are modified a little bit in each case, by e. g., omitting the mercury chloride for stabilization or replacing the potassium dichromate by potassium permanganate.

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