The chromaticity of water is an index for quantitative measurement of natural water or various kinds of treated water.
Natural water often shows different colors such as light yellow, light brown or yellow-green. The reason for the color is due to humus, organic or inorganic substances dissolved in water. In addition, when the water body is polluted by industrial wastewater, it will also show different colors. These colors are divided into true colors and surface colors. True color is caused by soluble substances in water, that is, the color after removing suspended matter in water. The surface color is the color produced when the suspended matter in the water is not removed. The quantitative degree of these colors is chroma.
Chromaticity is determined by the platinum-cobalt standard colorimetric method, that is, potassium chloroplatinate (K2PtCl6) and cobalt chloride (CoCl2 • 6H2O) are formulated into a standard solution for colorimetric measurement. In the case of potassium platinum and 2.00 mg of cobalt chloride, the concentration of platinum (Pt) at 1 mg per liter is set to 1 degree (1.).
Water color often affects the quality of industrial products such as paper and textiles. Water for various purposes has certain requirements for chromaticity: for example, the chromaticity requirement for domestic water is less than 15. ; The chromaticity requirement of paper industry water is less than 15. ~ 30. ; The chromaticity requirement of the textile industry is less than 10. ~ 12. ; The chroma of dyeing water is required to be less than 5. .
Industrial wastewater may produce a variety of colors in water, but the presence of humus, suspended mud and insoluble minerals in the water can also make the water color. For example, clay can make the water yellowish, iron oxide can make the water brown, sulfide can make the water light blue, algae can make the water green, and spoiled organic matter can make the water dark brown.