Which compound is used as a color indicator in the DPD method for chlorine?

The DPD method, which stands for Diethyl-p-phenylenediamine, utilizes DPD Reagent as the color indicator for chlorine detection in water. When chlorine is present in the sample, it reacts with the DPD Reagent, forming a pink-colored compound. The intensity of this pink color is directly proportional to the concentration of chlorine in the water sample, allowing for accurate quantification.

Using DPD Reagent is crucial in this method as it specifically responds to free and total chlorine, making it invaluable for water quality analysis in drinking water laboratories. The DPD method is widely accepted and recognized for its effectiveness, reliability, and sensitivity in measuring chlorine levels, which are essential for ensuring safe drinking water. Other compounds listed, such as ferroin, phenolphthalein, and methyl orange, serve different purposes in acid-base titrations or other types of chemical analyses and do not indicate chlorine levels in water samples.