0 - 0.68 mg/L Cl? 0 - 3.4 mg/L Cl? Cl? 0 - 3.4 mg/L Cl? 1 - 10 mg/L Cl2 This color disc test kit uses powder DPD reagent that reacts with chlorine more quickly than tablet-form DPD, giving more accurate results. Powder DPD also has a considerable advantage over orthotolidine, a hazardous substance sometimes used as a free and total chlorine test reagent. Hach Chlorine Test Kits are manufactured by Hach to ensure compliance with stringent quality control standards. Kit contains 100 tests (50 free, 50 total). Quickly and accurately measures free and total chlorine levels in the field or in the lab Simple and fast color disc method Includes two reagents, color disc, color comparator box, tube, instruction sheet, and carrying case.