The Hanna Instruments HI 3887 is a Test Kit that measures both Free Chlorine and pH,
complete with 2 color comparison cubes, 20 mL reagent 1, 15 mL reagent 2, and a 25 mL HI 3881-0 pH 6.0-8.5 reagent. Free
chlorine reacts with ammonium ions and organic compounds to form chlorine compounds resulting in diminished disinfecting
capabilities compared with free chlorine. These chlorine compounds together with chloramines form combined chlorine.
Combined chlorine and excess free chlorine together result in total chlorine. While free chlorine has a much higher
disinfectant potential, combined chlorine has a much higher stability and has a lesser volatility. There should be sufficient
levels of unreacted free chlorine for adequate disinfection, but not so much as to become harmful.