LaMotte 3308-01 Model SL-26 DPD Free, Total and Combined Chlorine Individual Test Kit, 0.2, 0.4, 0.6, 0.8, 1.0, 1.5, 2.0, 3.0ppm Cl Range

Free, Combined and Total Chlorine may be determined using DPD with either colorimetric or titrimetric methods. These determinations are generally limited to concentrations of 0–10 ppm, although the FAS titration can test higher concentrations by dilution or with the addition of more DPD indicator. Higher concentrations require the iodometric titration, whereby the sample is acidified and iodide is added, which is oxidized by chlorine to iodine and is titrated with a standard thiosulfate solution. Iodometric determinations will only test total chlorine.