The HI729-26 are high-quality reagents that are pre-measured, allowing for users to achieve fast and accurate measurements with their Fluoride Low-Range Checker® HC. These reagents follow the SPADNS Method in which the reaction between fluoride and the reagent causes a colorless complex in the sample. By simply adding 2 mL of SPADNS reagent to two cuvettes, and subsequently 8 mL of deionized water to one and 8 mL of sample in the other, the reaction will take place and the HI729 will determine the concentration from the color that is produced. The results will be displayed in ppm of fluoride. These reagents are designed to be used with samples that have an expected range of 0.00 to 2.00 ppm (mg/L) fluoride.