The HI771-25 are high quality reagents that are pre-measured, allowing for users to achieve fast and accurate measurements with their Total Chlorine Ultra High Range Checker^® HC. These reagents follow the DPD Method in which the reaction between chlorine and reagent causes a pink tint in the sample. By simply adding the packet of HI771-25 reagent to the sample, the reaction will take place and the HI771 will determine the concentration from the color that is produced. The results will be displayed in ppm of total chlorine. These reagents are designed to be used with samples that have an expected range of 0 to 500 ppm total chlorine.