Hanna Instruments Laboratory Division has released three photometers for measuring free and total chlorine, the HI 95761, HI 95711 and HI 95724.
Total chlorine is given by the sum of free chlorine plus combined chlorine. Free chlorine combines with nitrogen to produce chloramine (combined chlorine ). Chloramine is harmful for aquatic life and damages water treatment plants that use membranes for water purification. It is therefore important to monitor the levels of free and/or total chlorine often. The chloramine concentration in water depends on pH, temperature, the initial ratio of chlorine versus amine, chlorine demand and the time of reaction. Both forms of chlorine (free and combined) can exist at the same time, though they need to be measured separately.
The HI 95711 has a wide range for free and total chlorine while the HI 95761 measures trace total chlorine for ionic-exchange membranes and resins. The HI 95724 has the same specifications as the HI 95711 but uses liquid reagents. Instrument validation is possible at any time with Cal Check standard cuvets.
The HI 95761, HI 95711 and HI 95724 are supplied complete with two measuring cuvets, a 9V battery and instructions. The HI 95761C , HI 95711C and HI 95724C kit includes the meter in a rugged carrying case, the Cal Check standard and accessories.