Calcium Hardness Portable Photometer-Kit - HI97720 - HI97720C

Water, with exception of distilled water, contains dissolved salts (magnesium and calcium carbonates). The concentration of these salts determines the water hardness, which can be expressed in calcium carbonate or magnesium carbonate. The sum of these two represents the total hardness level. In addition, water hardness is also related to the phenomenon of pipe rusting in water heating and cooling systems, reverse osmosis, and demineralization plants.

The HI97720 uses an adaptation of the Standard Methods for the Examination of Water and Wastewater, 23rd Edition, calmagite method to measure calcium hardness concentrations of up to 2.70 mg/L (ppm). When the reagent is added to samples containing calcium salts, the sample will turn a red hue; the greater the concentration, the deeper the color. The associated color change is then colorimetrically analyzed according to the Beer-Lambert Law. This principle states that light is absorbed by a complementary color, and the emitted radiation is dependent upon concentration. For calcium hardness determination, a narrow band interference filter at 525 nm allows only green light to be detected by the silicon photodetector and omits all other visible light emitted from the LED lamp. As the change in color of the reacted sample increases, absorbance of the specific wavelength of light also increases, while transmittance decreases.