The HI93735-02 are high quality reagents that are pre-measured, allowing for users to achieve fast and accurate colorimetric measurements. These reagents follow an adaptation of the EPA recommended method 130.1 in which the reaction between calcium, magnesium, and the reagents causes a red-violet tint in the sample. By simply adding liquid reagent A, two drops of reagent B, and the packet of reagent C to the sample, the reaction between calcium and magnesium and the reagents causes a color change dependent upon concentration. The intensity of color is determined by the compatible HI96735 photometer and the concentration will be displayed. The results will be displayed in mg/L (ppm) as CaCO3. These reagents are designed to be used with samples that have an expected range of 400 to 750 mg/L (ppm) CaCO3 total hardness.