What color does DPD turn in the presence of chlorine?

In the presence of chlorine, DPD (N,N-diethyl-p-phenylenediamine) turns from a colorless solution to shades of pink and red. This reaction occurs because DPD acts as an indicator that reacts with free chlorine in the water sample. When free chlorine is present, it oxidizes the DPD, leading to the formation of a colored complex that varies from light pink to deep red, depending on the concentration of chlorine. This property makes DPD a widely used reagent for determining chlorine levels in water quality testing.

Other possible color changes, such as green to blue or brown to black, do not pertain to the DPD reaction with chlorine and are associated with different substances or indicators entirely. Hence, understanding the specific color response of DPD to chlorine is crucial for accurate water quality analysis.