Product Technical Specification:
DPD (N,N-diethyl-p-phenylenediamine) is used in free chlorine colorimetric analysis since it reacts with Hypochlorous acid and Hypochlorite ions acquiring a pinkish color that can be quantitatively related to the concentraction of those substances if it's inside the working range, DPD-Method can't be used in very high concentrations of free chlorine.