Chlorine and Chloramines

Chlorine is used as bactericide for water treatment. This chapter summarizes some terms related to chlorine analysis. The terms include chlorine demand, total chlorine, combined chlorine and free chlorine. A part of the "total chlorine" reacts with ammonia and organic amines in the water to form chloramines, such as monochloroamine, NH₂Cl, dichloroamine, NHCl₂, and trichloroamine or nitrogen trichloride, NCl₃. There are several methods to analyze chlorine in water. They are either the colorimetric or titrimetric analyses. Among the titrimetric methods are the N,N-Diethyl-p-phenylenediamine (DPD) titration, iodometric titration, and the amperometric titration, all of which are highly accurate, though require adequate skill to perform such error-free titrations. The colorimetric methods for chlorine analysis include DPD colorimetric test, syringaldazine colorimetric test and orthotolidine colorimetric test. The titrimetric procedures for chlorine analysis include DPD titration method and iodometric back titration method.