ds. Chlorine is stored and transported in liquid form in tanks, cylinders, railroad tank cars, or specially equipped ships. The following consumption of chlorine is characteristic of industrial countries: 60–75 percent is used for the production of chlorine-containing organic compounds, 10–20 percent for the production of chlorine-containing inorganic compounds, 5–15 percent for the bleaching of pulp and fabrics, and 2–6 percent for sanitary purposes and water chlorination.
Chlorine is also used for the chlorination of some ores in order to extract titanium, niobium, and zirconium.
Various chlorine-containing organic and inorganic compounds are discussed in separate articles (see Index).
L. M. IAKIMENKO
Chlorine in organisms. Chlorine is a biogenic element and a component of plant and animal tissues. The content of chlorine in plants ranges from thousandths of 1 percent to several percent (halophytes contain large amounts of chlorine), while the chlorine content in animals ranges from hundredths to tenths of 1 percent. The daily chlorine requirement of an adult human is 2–4 g and is met simply with the ingestion of food. In food, chlorine is usually present in excess in the form of sodium chloride and potassium chloride. Bread, meat, and milk products are especially rich in chlorine.
In animal organisms, chlorine is a major osmotically active substance of blood plasma, lymph, spinal fluid, and some tissues. It is important in water-salt metabolism, facilitating the retention of water by tissues. The regulation of the acid-base equilibrium in tissues is accomplished, in addition to other processes, by a change in the chlorine distribution between blood and other tissues.
In plants, chlorine participates in energy exchange, activating both oxidative phosphorylation and photophosphorylation. It also affects the absorption of oxygen by roots and is necessary for the formation of oxygen in photosynthesis by isolated chloroplasts. Chlorine is not included in the composition of most nutritive media for artificial plant cultivation. It is possible that very low concentrations of chlorine are sufficient for the development of plants.
M. IA. SHKOL’NIK
Poisoning. Chlorine poisoning is possible in the chemical, pulp-and-paper, textile, and pharmaceutical industries. Chlorine irritates the mucous membranes of the eyes and respiratory tract. Secondary infections usually follow the primary inflammatory changes. Acute poisoning develops almost immediately. Among the symptoms noted upon the inhalation of medium and low concentrations of chlorine are tightening and pain in the chest, dry cough, rapid breathing, burning sensation in the eyes and tearing, increased content of leukocytes in the blood, and increased body temperature. Bronchial pneumonia, toxic pulmonary edema, depression, and convulsions are possible. In light cases, recovery occurs after three to seven days. Catarrh of the upper respiratory tract and recurring bronchitis and pneumosclerosis are long-term sequellae; the activation of pulmonary tuberculosis is also possible. Upon prolonged breathing of low concentrations of chlorine, similar but slowly developing disorders are observed.
Safety measures to prevent chlorine poisoning include the hermetic sealing of production equipment, good ventilation, and, when necessary, the use of gas masks. The maximum allowable concentration of chlorine in the air at production sites is 1 mg/m3. The production of chlorine, chlorinated lime, and other chlorine-containing compounds is considered potentially harmful and consequently Soviet law restricts the use of female and juvenile labor.
A. A. KASPAROV
REFERENCESIakimenko, L. M. Proizvodstvo khlora, kausticheskoi sody i neorganicheskikh khlorproduktov. Moscow, 1974. Nekrasov, B. V. Osnovy obshchei khimii, 3rd ed. [vol.] 1. Moscow, 1973.
Vrednye veshchestva v promyshlennosti, 6th ed., vol. 2. Edited by N. V. Lazarev. Leningrad, 1971.
Comprehensive Inorganic Chemistry, vols. 1–5. Edited by J. C. Bailar et al. Oxford, 1973.