Chlorine [Cl, 17]

Chlorine is a common element of the halogen group 17 in the periodic table of elements. Its total content in the upper Earth’s crust is estimated at 640 mg/kg. Chlorine is a lithophilic and a very mobile element; it may be a minor constituent of several minerals, mainly amphiboles, apatite, and micaceous and clay minerals. Chlorine is a component of some pesticides and various chlorinated organic compounds. Chlorine dioxide load of various environmental compartments may infiltrate the food chain and is of a health concern. Chlorine is easily transported along with stream and river water to all water basins. Chlorine is produced in large amounts and widely used, both industrially and domestically, as an important disinfectant and bleach. Chlorine stimulates activity of some enzymes, such as cytochromeoxidase and phosphorylase, and plays a role in the osmotic system of plants. Chlorine provides the acid medium for the activation of the gastric enzymes and digestion in the stomach.