The HI-761-25 are high-quality reagents that are pre-measured, allowing for users to achieve fast and accurate measurements with their Total Chlorine Ultra Low 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 HI-761-25 reagent to the sample, the reaction will take place and the HI-761 will determine the concentration from the colour that is produced. The results will be displayed in ppb of total chlorine. These reagents are designed to be used with samples that have an expected range of 0 to 500 ppb total chlorine.