CHLORINE (Cl) 35.45 Atomic weight
Chlorine, as a chloride is essential to all life. Chlorine constitutes about 0.013% 0f the earth’s crust. It makes up 1.9% of sea water by weight. Free chlorine is a minor constituent of volcanic gas. In plants, it aids in metabolism as it is required in the photosynthetic reaction of plants. Deficiency is not seen in the field due to its universal presence in nature. Chlorine is necessary for the growth of higher plants but other halides, such as bromine, may be a substitute at higher concentrations. The chloride ion is present in body fluids of higher animals and in the digestive secretions of the stomach.