The HI775-26 are high-quality reagents that are pre-measured, allowing for users to achieve fast and accurate measurements with their Freshwater Alkalinity Checker® HC. These reagents follow the Colorimetric Method in which the reaction causes a distinctive range of colors from yellow to green to blue to develop. By simply adding one drop of the Chlorine Remover to remove the chlorine interference, and subsequently adding 1 mL of the Alkalinity Reagent to the sample, the reaction will take place and the HI775 will determine the concentration from the color that is produced. The results will be displayed in ppm of CaCO3 . These reagents are designed to be used with samples that have an expected range of 0 to 500 ppm CaCO3.