The HI770-25 are high-quality reagents that are pre-measured, allowing for users to achieve fast and accurate measurements with their Silica High-Range Checker® HC. These reagents follow the Standard Method 4500-SiO2 C in which the reaction between silica and reagents causes a yellow tint in the sample. By simply adding the packet of HI770-25 reagent to the sample, the reaction will take place and the HI770 will determine the concentration from the color that is produced. The results will be displayed in ppm of silica. These reagents are designed to be used with samples that have an expected range of 0 to 200 ppm silica.