Хлор

Описание

Chlorine is a greenish-yellow, nonflammable gas with a distinctive, pungent odor. It is almost two and one-half times as heavy as air. The gas acts as a severe irritant if inhaled. Chlorine liquid has the color of clear amber and is about one and one-half times as heavy as water. It is shipped as a compressed liquefied gas having a vapor pressure of 86.767 psig at 70°F (598.26 kPa at 21.1°C). Chlorine is nonflammable in both gaseous and liquid states. However, like oxygen, it is capable of supporting the combustion of certain substances. Many organic chemicals react readily with chlorine, in some cases with explosive violence. Chlorine usually forms univalent compounds, but it can combine with a valence of 3, 4,5, or 7.
Chlorine is only slightly soluble in water. When it reacts with pure water, weak solutions of hydrochloric and hypochlorous acids are formed. Chlorine hydrate (Cl2·8H20) may crystallize below 49.3°F (9.61°C).

Химические свойства

Chlorine is a greenish-yellow gas. Pungent, irritating odor. Shipped as a liquefied compressed gas. It is the commonest of the four halogens which are among the most chemically reactive of all the elements. It is not flammable; but it is a strong oxidizer, and contact with other materials may cause fire.

Физические свойства

As a nonmetal, chlorine exists as a greenish-yellow gas that is corrosive and toxic at roomtemperatures. As a halogen, chlorine is not found in the elemental (atomic) state but formsdiatomic gas molecules (Cl₂). As a very active negative ion with the oxidation state of -₁,chlorine forms bonds with most metals found in groups I and II.
Chlorine is noncombustible but will support combustion. It is extremely electronegativeand a strong oxidizing agent. It is not as strong as fluorine, which is just above it in group 17,but is stronger than the other halogens.
As a gas, its specific gravity (density) is 3.214g/l or 0.003214g/cm³. As a liquid, it is aclear amber color with a density of 1.56g/cm³. Its melting point is –101.5°C, and its boilingpoint is –34.04°C.

Изотопы

There are a total of 25 isotopes of chlorine. Of these, only two are stable andcontribute to the natural abundance on Earth as follows: Cl-35 = 75.77% and Cl-37 =24.23%. All the other 23 isotopes are produced artificially, are radioactive, and have halflivesranging from 20 nanoseconds to 3.01×10⁺⁵ years.

Происхождение имени

From the Greek word khl?ros, meaning “greenish yellow.”

Вхождение

Chlorine is the 20th most abundant element on the Earth. It is not found as a free element(atoms) except as a diatomic gas escaping from very hot active volcanoes. It has been knownfor thousands of years as rock salt (halite). It is also found in sylvite and carnallite and as achloride in seawater. In nature, it is mostly found in dissolved salts in seawater and deposits insalt mines. Its best-known compound is sodium chloride (NaCl), which is common table salt.Chlorine is important for the chemical industry. Numerically, it is the 12th most producedchemical in the United States and ranks ninth in volume of chemicals produced in the UnitedStates.
Chlorine is produced commercially by the electrolysis of a liquid solution of sodium chloride(or seawater), through which process an electric current is passed though the solution(electrolyte).

Характеристики

Chlorine’s best-known characteristic is its smell. It can be detected when used as householdbleach or as an antiseptic in swimming pools. As an antiseptic, it is added to municipal drinkingwater supplies. Chlorine gas has a very pungent odor that is suffocating when inhaled. Ina more concentrated form, Cl₂ was also a deadly poisonous gas used in combat during WorldWar I. Because it combines with so many other elements, particularly metals, chlorine is fundamentalto many industries, particularly the plastics industry.
Laboratory amounts of chlorine (Cl₂) are produced by combining hydrochloric acid (HCl)with manganese dioxide (MnO₂). The HCl provides the Cl^-1 ion.

Использование

The largest quantities of chlorine are used in manufacturing chemicals. These include:
• Solvents such as trichloroethylene, I, I, I-trichloroethane, perchloroethylene, and methylene chloride
• Pesticides, herbicides, and other agricultural products
• Plastics, rubbers, and fibers such as polyvinyl chloride and neoprene
• Refrigerants and propellants such as the halocarbons and methyl chloride
Chlorine is also an ingredient in bleach or sodium hypochlorite solutions. In addition, chlorine is used in bleaching pulp, paper, and textiles; for drinking and swimming water purification; in the sanitation of industrial and sewage wastes; and for the purification ofaluminum.

Методы производства

Chlorine is principally produced by electrolysis of NaCl or KCl brine in either diaphragm, mercury, or membrane cathode cells. In these processes, gaseous chlorine is released at the anode and caustic is a by-product. Chlorine may also be produced by electrolysis of hydrochloric acid (HCl) [7647- 01-0], by oxidation of HCl in the presence of nitrogen oxide as a catalyst (Kel-Chlor process), or as a coproduct from metal production.

Определение

chlorine: Symbol Cl. A halogen element;a.n. 17; r.a.m. 35.453; d. 3.214g dm^–3; m.p. –100.98°C; b.p. –34.6°C.It is a poisonous greenish-yellowgas and occurs widely in nature assodium chloride in seawater and ashalite (NaCl), carnallite (KCl.MgCl₂.6H₂O), and sylvite (KCl). It is manufacturedby the electrolysis of brineand also obtained in the Downsprocess for making sodium. It hasmany applications, including thechlorination of drinking water,bleaching, and the manufacture of alarge number of organic chemicals.
It reacts directly with many elementsand compounds and is astrong oxidizing agent. Chlorinecompounds contain the element inthe 1, 3, 5, and 7 oxidation states. Itwas discovered by Karl Scheele in1774 and Humphry Davy confirmedit as an element in 1810.

Реакции воздуха и воды

Water dissolves about twice its volume of Chlorine gas, forming a mixture of hydrochloric acid and hypochlorous acids. Will be corrosive due to acidity and oxidizing potential.

Опасность

A series of chlorofluorohydrocarbons that are used as refrigerants are being phased out ofmanufacture and use, because of their possible deleterious effects on the ozone layer of theatmosphere. (See the entry on oxygen for more on the ozone layer.)
From time to time, railroad tank cars are involved in accidents that will leak liquid orgaseous chlorine that, when escaping into the air, forms toxic chlorine compounds. This isextremely dangerous, both as a fire hazard and for human health. When water is used to flushaway the escaping chlorine, it may end up as hydrochloric acid, which can be hazardous tothe water supply and to aquatic life.
Concentrated chlorine gas and many chlorine compounds will oxidize powdered metals,hydrogen, and numerous organic materials and release enough heat to generate fires or explosions.Chlorine is constantly evaporating from the oceans and drifting into the atmospherewhere it causes a natural depletion of the ozone.
Warning: One should never mix, or use together, chlorine cleaners, such as Clorox, withother cleaning substances containing ammonia. It is a deadly mixture.

Угроза здоровью

Chlorine is a respiratory irritant. It causes irritation to the mucous membranes and the liquid burns the skin. The poisoning caused by chlorine depends on the amount of chlorine a person or an occupational worker is exposed to, and the length of exposure time. Prolonged exposures to high concentrations of chlorine cause poisoning with symptoms that include, but are not limited to, coughing, burning sensation in the nose, throat, and eyes, blurred vision, nausea, vomiting, pain, redness, and blisters on the skin, chest tightness, and pulmonary edema.

Пожароопасность

May ignite other combustible materials (wood, paper, oil, etc.). Mixture with fuels may cause explosion. Container may explode in heat of fire. Vapor explosion and poison hazard indoors, outdoors or in sewers. Hydrogen and Chlorine mixtures (5-95%) are exploded by almost any form of energy (heat, sunlight, sparks, etc.). May combine with water or steam to produce toxic and corrosive fumes of hydrochloric acid. Emits highly toxic fumes when heated. Avoid plastics and rubber. Avoid heat and contact with hydrogen gas or powdered metals.

Воспламеняемость и взрывоопасность

Chlorine is noncombustible but is a strong oxidizer and will support combustion of most flammable substances.

Использование в материалах

At ordinary temperatures, dly chlorine, either liquid or gas, does not corrode steel. In the presence of moisture, however, highly corrosive conditions exist due to the formation of hydrochloric and hypochlorous acids. Thus precautions should be taken to keep chlorine and equipment free of moisture. Piping, valves, and containers should be closed or capped when not in use to keep atmospheric moisture out ofthe system.

Возможный контакт

Environmental danger. Chlorine is a toxic gas with corrosive properties. Gaseous chlorine is widely used as a bleaching agent in the paper, pulp, and textile industries for bleaching cellulose for artificial fibers. It is used in the manufacture of chlorinated lime; inorganic and organic compounds, such as metallic chlorides; chlorinated solvents; refrigerants, pesticides; and polymers, e.g., synthetic rubber and plastics; it is used as a disinfectant, particularly for water and refuse; and in detinning and dezincing iron. CL has been used as a warfare choking/pulmonary agent. Note: The lowest level at which humans can detect chlorine through smell and become alert to its irritant properties generally provides sufficient warning of exposure. However, chronic exposure to chlorine causes olfactory fatigue and tolerance to its irritant effects. Those with a history of prolonged exposure to chlorine, may eventually lose their ability to identify incidents of exposure.

Канцерогенность

In the chronic inhalation bioassay with rats and mice exposed to 0, 0.4, 1.0, or 2.5 ppm chlorine for 2 years, described above, incidence of neoplasia in the nasal passages was not increased by exposure, even though there were exposure-dependent lesions in the nasal tissues (199). Chlorine has not been identified as a carcinogen (IARC 1999).

хранилище

All work with chlorine should be conducted in a fume hood to prevent exposure by inhalation, and splash goggles and impermeable gloves should be worn at all times to prevent eye and skin contact. Cylinders of chlorine should be stored in locations appropriate for compressed gas storage and separated from incompatible compounds such as hydrogen, acetylene, ammonia, and flammable materials.

Перевозки

UN1017 Chlorine, Hazard Class: 2.3; Labels: 2.3-Poisonous gas, 5.1-Oxidizer, 8-Corrosive material, Inhalation Hazard Zone B. Cylinders must be transported in a secure upright position, in a well-ventilated truck. Protect cylinder and labels from physical damage. The owner of the compressed gas cylinder is the only entity allowed by federal law (49CFR) to transport and refill them. It is a violation of transportation regulations to refill compressed gas cylinders without the express written permission of the owner. Military driver shall be given full and complete information regarding shipment and conditions in case of emergency. AR 50-6 deals specifically with the shipment of chemical agents. Shipments of agent will be escorted in accordance with AR 740-32.

Методы очистки

Pass the gas in succession through aqueous KMnO4, dilute H2SO4, conc H2SO4, and a drying tower containing Mg(ClO4)2. Or bubble it through water, dry it over P2O5 and distil it from bulb to bulb in a vacuum line. One volume of water dissolves 4.6 volumes of Cl2 at 0o, 2.15 volumes at 20o, 1.22 volumes at 50o and 0.39 volumes at 90o. [Schmeisser in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol I p 272 1963.] HIGHLY TOXIC.

Несовместимости

A powerful oxidizer. Reacts explosively or forms explosive compounds with many organic compounds and common substances, such as acetylene, ether, turpentine, ammonia, fuel gas, hydrogen, and finely divided metals. Keep away from combustible substances and reducing agents. Corrosive to some plastic, rubber, and coating materials. Reacts with water to form hypochlorous acid. Corrosive to many metals in presence of water.

Утилизация отходов

Return refillable compressed gas cylinders to supplier. Introduce into large volume and solution of reducing agent (bisulfite, ferrous salts, or hypo), neutralize and flush to sewer with water. Recovery is an option to disposal for chlorine in the case of gases from aluminum chloride electrolysis and chlorine in waste waters. See also “Spill Handling.” Nonrefillable cylindersshould be disposed of in accordance with local, state, and federal regulations. Allow remaining gas to vent slowly into atmosphere in an unconfined area or exhaust hood. Refillable-type cylinders should be returned to original supplier with any valve caps and outlet plugs secured and valve protection caps in place.