The HI-729-26 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 colourless complex in the sample. By simply adding 2 mL of SPADNS reagent to two cuvettes, and subsequently 8 mL of deionised water to one and 8 mL of sample in the other, the reaction will take place and the HI-729 will determine the concentration from the colour 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.