The HI93703-53 are high quality reagents that are pre-measured, allowing for users to achieve fast and accurate colorimetric measurements. These reagents are used to remove the chlorine interference which would interfere with measuring the sample. To eliminate Cl₂ interference add to the 10 mL unreacted sample, 1 drop of the HI93703-53 Chlorine Remover, for each 2 mg/L of chlorine.These reagents are optional and should only be used when chlorine is present in the sample.