The HI713-25 are high-quality reagents that are pre-measured, allowing for users to achieve fast and accurate measurements with their Phosphate Low Range Checker® HC. These reagents follow the Ascorbic Acid Method in which the reaction between phosphate and reagent causes a blue tint in the sample. By simply adding the packet of HI713-25 reagent to the sample, the reaction will take place and the HI713 will determine the concentration from the color that is produced. The results will be displayed in ppm (mg/L) of phosphate. These reagents are designed to be used with samples that have an expected range of 0.00 to 2.50 ppm phosphate.