What color does the DPD and chlorine reaction turn the water?

The reaction of DPD (N,N-diethyl-p-phenylenediamine) with chlorine is a key part of testing for chlorine levels in water, particularly in water treatment facilities. When DPD is added to a water sample that contains chlorine, it reacts to form a colorful compound. This compound typically turns the sample pink to red, indicating the presence and concentration of free chlorine.

This color change occurs because DPD reacts specifically with free chlorine in the water. The intensity of the pink to red color correlates with the concentration of chlorine; therefore, the shade can also provide a rough estimate of chlorine levels.

In practice, this method is widely used due to its reliability and simplicity, making it an essential skill for operators managing water systems. Recognizing the distinct pink to red coloration that results from this reaction is crucial for accurate water quality assessment and treatment decisions. This knowledge is fundamental for individuals preparing for the Texas Class D Water License, as it ensures they can effectively monitor and adjust chlorine levels in water.