Chlorine

Occurrence and Uses

Chlorine does not occur in the elemental state because of its high reactivity. In nature the element occurs mainly as sodium chloride in seawater. Its abundance in seawater is 1.9% by weight. It also exists as chloride in many rocks and minerals such as carnallite (KMgCl3•6H2O) and sylvite (KCl).
Chlorine was discovered by Scheele in 1774 and named by Davy in 1810.Chlorine is extensively used in the production of paper products, dyestuffs, textiles, petroleum products, medicines, antiseptics, insecticides, food, solvents, paints, plastics, and many other consumer products. Chlorine is mainly used as a bleach in the manufacture of paper and cloth and to make a wide variety of products. Most of the chlorine produced is used in the manufacture of chlorinated compounds for sanitation, pulp bleaching, disinfectants, and textile processing. Further use is in the manufacture of chlorates, chloroform, and carbon tetrachloride and in the extraction of bromine. Organic chemistry demands much from chlorine, both as an oxidising agent and in substitution. In fact, chlorine was used as a war gas in 1915 as a choking (pulmonary) agent. Chlorine itself is not flammable, but it can react explosively or form explosive compounds with other chemicals such as turpentine and ammonia.
Chlorine gas is used to synthesise other chemicals and to make bleaches and disinfectants. Chlorine is a powerful disinfectant and in small quantities ensures clean drinking water. It is used in swimming pool water to kill harmful bacteria. Chlorine has a huge variety of uses, for instance, as a disinfectant and purifier, in plastics and polymers, solvents, agrochemicals, and pharmaceuticals, as well as an intermediate in manufacturing other substances where it is not contained in the final product. Also, a very large percentage of pharmaceuticals contain and are manufactured using chlorine. Thus, chlorine is essential in the manufacture of medicines to treat illnesses such as allergies, arthritis, and diabetes.

Physical Properties

Greenish-yellow gas; suffocating odor (odor threshold 3 ppm); gas density in the air 2.46 (air = 1); becomes a pale yellow liquid at –34.04°C; the color decreases with lowering temperature; becomes a pale yellow crystal at –101.5°C; critical temperature 143.8°C; critical pressure 76.89 atm; critical volume 123 cm3/mol; moderately soluble in water; solubility in water 0.061 mol Cl2/L at 20°C; bulk solubility in water (including all species formed) 0.091 mol/L.

Production

Chlorine is produced industrially by electrolysis of brine using either mercury cathode cells or, preferably, various commercially available membrane cells. Chlorine gas is liberated at the anode while sodium hydroxide and hydrogen are liberated at the cathode:
Na+ + Cl– + H2O → Na+ + OH– + ½Cl2 + ½H2
Also, Cl is made by electrolysis of fused sodium chloride, magnesium chloride salt, or hydrochloric acid. The electrolytic process has practically superseded the Weldon and Deacon processes employed earlier to produce chlorine. The Weldon process involves the action of HCl on manganese dioxide ores to produce chlorine and manganese chloride. The MnCl2 liquor obtained is first converted into calcium manganite (CaO•2MnO2) or “Weldon mud,” from which MnO2 is generated back for reuse. Deacon’s process involves catalytic oxidation of hydrogen chloride, catalyzed by copper:
2HCl + ½O2→Cl2 + H2O
The efficiency of Deacon’s process is improved by passing the HCl over CuO at 200°C. The product CuCl2 is oxidized at 300°C by treatment with oxygen:
2HCl + CuO→ CuCl2 + H2O
2CuCl2 + O2→2Cl2 + 2CuO
In the laboratory, chlorine may be prepared by oxidation of HCl with manganese dioxide:
4HCl + MnO2 → MnCl2 + Cl2 + 2H2O

Hazard

Chlorine is a pungent suffocating gas, exposure to which can cause irritation of the eyes, nose and throat; burning of mouth; coughing; choking; nausea, vomiting; dizziness and respiratory distress. Exposure to 15–20 ppm of chlorine in air can cause irritation and coughing. A 30 minute exposure to 500–800 ppm can be fatal to humans (Patnaik, P. 1999. A Comprehensive Guide to the Hazardous Properties of Chemical Substances, 2nd ed. New York: John Wiley & Sons).
Chlorine-hydrogen mixture can explode in the presence of sunlight, heat or a spark. Also, it can explode when mixed with acetylene or diborane at ordinary temperatures, and with ethylene, fluorine, and many hydrocarbons in the presence of heat, spark or catalysts.

Description

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).

Chemical Properties

Chlorine is a yellow-green gas that is heavier than air and has a strong irritating odor. Chlorine is used extensively in the production of paper products, dyestuffs, textiles, petroleum products, medicines, antiseptics, insecticides, food, solvents, paints, plastics, and many other consumer products. Chlorine is mainly used as a bleach in the manufacture of paper and cloth and to make a wide variety of products. Most of the chlorine produced is used in the manufacture of chlorinated compounds for sanitation, pulp bleaching, disinfectants, and textile processing. Further use is in the manufacture of chlorates, chloroform, carbon tetrachloride, and in the extraction of bromine. Organic chemistry demands much from chlorine, both as an oxidizing agent and in substitution. In fact, chlorine was used as a war gas in 1915 as a choking (pulmonary) agent. Chlorine itself is not flammable, but it can react explosively or form explosive compounds with other chemicals such as turpentine and ammonia. Chlorine is slightly soluble in water. It reacts with water to form hypochlorous acid and hydrochloric acid. Hypochlorous acid breaks down rapidly. Chlorine gas is used to synthesize other chemicals and to make bleaches and disinfectants. Chlorine is a powerful disinfectant, and in small quantities ensures clean drinking water. It is used in swimming pool water to kill harmful bacteria. Chlorine has a huge variety of uses, i.e., as a disinfectant and purifi er, in plastics and polymers, solvents, agrochemicals and pharmaceuticals, as well as an intermediate in manufacturing other substances where it is not contained in the fi nal product. Also, a large percentage of pharmaceuticals contain and are manufactured using chlorine. Thus, chlorine is essential in the manufacture of medicines to treat illnesses such as allergies, arthritis, and diabetes.

Chemical Properties

light greenish-yellow gas with an irritating odour

Chemical Properties

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.

Physical properties

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.

Isotopes

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.

Origin of Name

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

Occurrence

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).

Characteristics

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.

History

Chlorine was discovered in 1774 by Scheele, who thought it contained oxygen; named in 1810 by Davy, who insisted it was an element. In nature it is found in the combined state only, chiefly with sodium as common salt (NaCl), carnallite (KMgCl3 · 6H2O), and sylvite (KCl). It is a member of the halogen (salt-forming) group of elements and is obtained from chlorides by the action of oxidizing agents and more often by electrolysis; it is a greenish-yellow gas, combining directly with nearly all elements. At 10°C one volume of water dissolves 3.10 volumes of chlorine, at 30°C only 1.77 volumes. Chlorine is widely used in making many everyday products. It is used for producing safe drinking water the world over. Even the smallest water supplies are now usually chlorinated. It is also extensively used in the production of paper products, dyestuffs, textiles, petroleum products, medicines, antiseptics, insecticides, foodstuffs, solvents, paints, plastics, and many other consumer products. Most of the chlorine produced is used in the manufacture of chlorinat- The Elements 4-9 ed compounds for sanitation, pulp bleaching, disinfectants, and textile processing. Further use is in the manufacture of chlorates, chloroform, carbon tetrachloride, and in the extraction of bromine. Organic chemistry demands much from chlorine, both as an oxidizing agent and in substitution, since it often brings desired properties in an organic compound when substituted for hydrogen, as in one form of synthetic rubber. Chlorine is a respiratory irritant. The gas irritates the mucous membranes and the liquid burns the skin. As little as 3.5 ppm can be detected as an odor, and 1000 ppm is likely to be fatal after a few deep breaths. It was used as a war gas in 1915. Natural chlorine contains two isotopes. Twenty other isotopes and isomers are known.

Uses

In addition to the use of chlorine as an antiseptic for swimming pools and drinking water,large amounts are used during industrial processes that produce paper, plastics, textiles, dyes,medicines, insecticides, solvents, and some paints. Following are some of the more importantcompounds of chlorine used in industries: hydrochloric acid (HCl + H₂O), table salt (NaCl),chloroform (CHCL₃), carbon tetrachloride (CCl₄), magnesium chloride (MgCl₂), chlorinedioxide (ClO₂), potassium chloride (KCl), and lithium chloride (LiCl).
Chlorine is used to make plastics such as neoprene and polyvinyl chloride (vinyl). It is usedto make insecticides, fireworks, explosives, and paint pigments; pharmaceuticals, chloroform,and chlorofluorocarbons (ClFCs); and chlorohydrocarbons (ClHCs).

Uses

Chlorine is used as a disinfectant; for puri fying water; in the manufacture of bleachingpowder, chlorinated hydrocarbons, syntheticrubber, and plastics; and as a chlorinating andoxidizing agent. It was used as a poison gasin war under the name Bertholite.

Uses

A greenish yellow, poisonous gas, chlorine is one of the halogens used in silver halide photography. In its elemental form, chlorine was used in the daguerreotype process as an accelerator. See also the various chlorides listed under their compound names, such as Ammonium Chloride.

Uses

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.

Uses

manufacture of organic and inorganic chemicals. As oxidizing and bleaching agent in pulp and paper industry, and for textiles. As disinfectant for water purification, industrial waste, sewage, swimming pools. In the extraction and refining of metals. 36Cl for determining geological age of natural samples such as meteorites, surface rocks, polar ice and ground water. Has been used as a military poison gas under the name bertholite.

Definition

The 15th most abundant element in the earth’s crust, occurring only in the combined state, mainly in common salt. A strong corrosive acid.

Definition

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.

Production Methods

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.

Air & Water Reactions

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.

Reactivity Profile

Chlorine reacts explosively with or supports the burning of numerous common materials. Ignites steel at 100°C in the presence of soot, rust, carbon, or other catalysts. Ignites dry steel wool at 50°C. Reacts as either a liquid or gas with alcohols (explosion), molten aluminum (explosion), silane (explosion), bromine pentafluoride, carbon disulfide (explosion catalyzed by iron), 1-chloro-2-propyne (excess Chlorine causes an explosion), dibutyl phthalate (explosion at 118°C), diethyl ether (ignition), diethyl zinc (ignition), glycerol (explosion at 70-80°C), methane over yellow mercury oxide (explosion), acetylene (explosion initiated by sunlight or heating), ethylene over mercury, mercury(I) oxide, or silver(I) oxide (explosion initiated by heat or light), gasoline (exothermic reaction then detonation), naphtha-sodium hydroxide mixture (violent explosion), zinc chloride (exothermic reaction), wax (explosion), hydrogen (explosion initiated by light), Reacts as either a liquid or gas with carbides of iron, uranium and zirconium, with hydrides of potassium sodium and copper, with tin, aluminum powder, vanadium powder, aluminum foil, brass foil, copper foil, calcium powder, iron wire, manganese powder, potassium, antimony powder, bismuth, germanium, magnesium, sodium, and zinc. Causes ignition and a mild explosion when bubbled through cold methanol. Explodes or ignites if mixed in excess with ammonia and warmed. Causes ignition in contact with hydrazine, hydroxylamine, and calcium nitride. Forms explosive nitrogen trichloride from biuret contaminated with cyanuric acid. Readily forms an explosive N-chloro derivative with aziridine. Ignites or explodes with arsine, phosphine, silane, diborane, stibine, red phosphorus, white phosphorus, boron, active carbon, silicon, arsenic. Ignites sulfides at ambient temperature. Ignites (as a liquid) synthetic and natural rubber. Ignites trialkylboranes and tungsten dioxide.

Hazard

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.

Hazard

Moderately toxic; eye and upper respiratory tract irritant.

Health Hazard

Poisonous; may be fatal if inhaled. Contact may cause burns to skin and eyes. Bronchitis or chronic lung conditions.

Health Hazard

Chlorine is a severely irritating gas, caus ing irritation of the eyes, nose, andthroat. Exposure also causes burning ofthe mouth, coughing, choking, nausea,vomiting, headache, dizziness, pneumonia,muscle weakness, respiratory distress, andpulmonary edema. A 30-minute exposureto 500–800 ppm can be fatal to humans.Chronic exposure to concentrations around5 ppm have produced corrosion of theteeth, inflammation of the mucous mem branes, respiratory ailments, and increasedsusceptibility to tuberculosis among workers(Patty 1963)
Klonne and associates (1987) have repor ted a 1-year inhalation toxicity study of chlo rine in rhesus monkeys. Exposure to 2.3 ppmchlorine caused ocular irritation during thedaily exposures. Histopathological changeswere observed in the respiratory epitheliumof the nasal passages and trachea. Thesechanges, however, were mild at the forego ing level of exposures. Monkeys were lesssensitive to chlorine toxicity than were rats.
Zwart and Woutersen (1988) studied theacute inhalation toxicity of chlorine in ratsand mice and have proposed a time–concen tration–mortality relationship. The relation ship between any LC value, concentration,and time of exposure could be described bythe probit (P) equations, as follows
where C and T are concentration andtime, respectively. Zwart and Woutersen also observed that there was rapid shallow breath ing in animals after the exposure began.Some animals exhibited the formation of pul monary edema near the end of exposure.

Health Hazard

Chlorine is a severe irritant of the eyes, skin, and mucous membranes. Inhalation may cause coughing, choking, nausea, vomiting, headache, dizziness, difficulty breathing, and delayed pulmonary edema, which can be fatal. Exposure to -500 ppm for 30 min may be fatal, and 1000 ppm can be lethal after a few breaths. Chlorine is highly irritating to the eyes and skin; exposure to 3 to 8 ppm causes stinging and burning of the eyes, and contact with liquid chlorine or high concentrations of the vapor can cause severe burns. Chlorine can be detected by its odor below the permissible limit; however, because of olfactory fatigue, odor may not always provide adequate warning of the presence of harmful concentrations of this substance. Chronic exposures in animals up to 2.5 ppm for 2 years caused effects only in the upper respiratory tract, primarily the nose. Higher concentrations or repeated exposure has caused corrosion of the teeth. There is no evidence for carcinogenicity or reproductive or developmental toxicity of chlorine in humans.

Health Hazard

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.

Fire Hazard

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

Fire Hazard

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.

Flammability and Explosibility

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

Agricultural Uses

Chlorine (Cl) is a halogen, classified in Group 17 (formerly VII), Period 3 of the Periodic Table of elements. It is a greenish yellow gas and has an atomic weight of 35.5
Chlorine is one of the essential elements for plants, although it is not always listed as a micronutrient. It is absorbed in soil almost entirely as chloride ions ((Cl^-) which are very mobile, soluble and mostly non-reactive in soil. The role of chlorine in plants is believed to be biochemical, osmotic and in balancing cell cationic charges.
Plants responding to chloride are tomato, pea, lettuce, cabbage, carrot, sugar beet, barley, corn, berries, vine crops, potato, cotton, woody ornamental plants and fruit trees like coconut.
Chlorine is involved in the splitting of water molecules in photoreactionⅡ of photosynthesis. Several enzymes such as ATPase, alpha-amylase and asparagine synthetase require the chloride ion for activation. As the chloride ion is very mobile and is tolerated at high concentrations, it is ideal for maintaining the charge balance when cations (such as potassium) move across cell membranes. The chloride requirement of plants for biochemical functions is hardly more than 100mg/kg of dry plant matter. However, chloride is usually present at much higher concentrations (2000to 20,000mg/kg), suggesting its involvement in functions other than those of a biochemical nature.
The chloride content in plants ranges from 0.2 to 2.0% but in some salt tolerant plants it can be as high as 10%. Excessive chloride accumulation is harmful to plants, causing the leaves to thicken and roll, lowering the quality of potato tubers and the smoking quality of tobacco. If plants sensitive to chloride receive more than 1 to 2 % chloride ions (Cl') , yields are often reduced.
The environment entertains the chlorine cycle. Air, water and soil are at the receiving end of the cycle. For instance, air gets chloride from volcanoes and sea spray, whereas water receives chloride from sewage, food, water-softener wastes, industrial effluents and de-icing salts used on roads. Soil gets its chloride supply from animal manure, rainfall, irrigation waters and potassium chloride fertilizers.
Chlorine in soil follows water movements and is taken up by plants as the chloride (CT) anion. The greater the chloride concentration in a soil solution, the higher the plant uptake. It may also be taken up aerially as Cl- anion or chlorine gas. Chloride, highly mobile in plants, is required in the splitting of water (Hill reaction) during photosynthesis. It enhances oxygen synthesis and photophosphorylation. The accumulation of excessive chloride ions can be toxic. Foliar sprays with chloride- containing irrigation water, if left to dry on the leaves, may cause salt bum.
Since field plots do not display any chloride deficiency and most fertilizers have some chloride (as contaminant), not much is done for chloride rectification. More studies are required to find out the effect of large additions of chloride ions (30to 50kg/ha).
The symptoms of chloride deficiency are not easily identifiable. In nutrient cultures, it was shown that chlorine deficiency is associated with a reduced root growth. Chlorosis in younger leaves and an overall wilting of the plants are the two most common symptoms of chlorine deficiency. Necrosis in some plant parts and leaf bronzing may also be wimessed. Excessive chlorine can be harmful but crops vary widely in their tolerance. The principal effect of too much chlorine is to increase the osmotic pressure of soil water and thereby lower the availability of water to plants.
Chlorine in fertilizers suppresses many diseases. Adequate quantities of chloride-containing fertilizers can mitigate diseases like 'take all root rot', 'stripe rusts', 'leaf rust', 'tan spot of wheat', etc. A moderately excess quantity of chloride is employed to fight such diseases (many times above the nutritional needs). For example, chloride banding of 40kg/ha is recommended to reduce 'take all root rot' on winter wheat in western countries.
Potassium chloride, which contains large quantities of chloride, is a widely used fertilizer. Ammonium chloride, calcium chloride, magnesium chloride and sodium chloride are other sources of chlorine.

Materials Uses

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.

Safety Profile

Moderately toxic to humans by inhalation. Very irritating by inhalation. Human mutation data reported. Human respiratory system effects by inhalation: changes in the trachea or bronchi, emphysema, chronic pulmonary edema or congestion, A strong irritant to eyes and mucous membranes. Questionable carcinogen. Chlorine is extremely irritating to the mucous membranes of the eyes and the respiratory tract at 3 ppm. Combines with moisture to form HCl. Both these substances, if present in quantity, cause inflammation of the tissues with which they come in contact. A concentration of 3.5 ppm produces a detectable odor; 15 ppm causes immediate irritation of the throat. Concentrations of 50 pprn are dangerous for even short exposures; 1000 pprn may be fatal, even when exposure is brief. Because of its intensely irritating properties, severe industrial exposure seldom occurs, as the worker is forced to leave the exposure area before he can be seriously affected. In cases where this is impossible, the initial irritation of the eyes and mucous membranes of the nose and throat is followed by coughing, a feeling of suffocation, and, later, pain and a feeling of constriction in the chest. If exposure has been severe, pulmonary edemamay follow, with rales being heard over the chest. It is a common air contaminant. or UV light, air + ethylene, molten aluminum, ammonia, amidosulfuric acid, antimony trichloride + tetramethyl silane (at loo'), benzene + light, biuret, bromine pentafluoride + heat, tert-butanol, butyl rubber + naphtha, carbon disulfide + iron catalyst, chlorinated pyridine + iron powder, 3-chloropropyne, cobalt(Ⅱ) chloride + methanol, dborane, dbutyl phthalate (at 1 18'), dchloro(methy1)arsine (in a sealed container), diethyl ether, dimethyl phosphoramidiate, dioxygen difluoride, dsilyl oxide, 4,4'-dithiodimorpholine, ethane over activated carbon (at 350'), fluorine + sparks, gasoline, glycerol (above 70' in a sealed container), hexachlorodisilane (above 300'), hydrocarbon oils or waxes, iron(IⅡ) chloride + monomers (e.g., styrene), methane over mercury oxide, methanol, methanol + tetrapyridme cobalt(Ⅱ) chloride, naphtha + sodium hydroxide, nitrogen triiodide, oxygen difluoride, whte phosphorus (in liquid Cl2), phosphorus compounds, polypropylene + zinc oxide, propane (at 300°), shcones when heated in a sealed container [e.g., polydimethyl siloxane (above 88'), polymethyl trifluoropropylsiloxane (above 68')], stibine, synthetic rubber (in liquid Cl2), tetraselenium tetranitride, trimethyl thionophosphate. Explosive products are formed on reaction with alkylthiouronium salts, amidosulfuric acid, acidc ammonium chloride solutions, aziridine, bis(2,4-dinitrophenyl)disulfide, cyanuric acid, phenyl magnesium bromide. Mixtures with ethylene are explosives initiated by light, heat, or by the presence of mercury, mercury oxide, silver oxide, lead oxide (at 100°). Mxtures with hydrogen are explosives initiated by sparks, light, heating to over 280°, or the presence of yellow mercuric oxide or nitrogen trichloride. Murtures with hydrogen and other gases (e.g., air, hydrogen chloride, oxygen) are also explosive. Iption or explosive reaction with metals (e.g., aluminum, antimony powder, bismuth powder, brass, calcium powder, copper, germanium, iron, manganese, potassium, tin, vanadium powder). Reaction with some metals requires moist Cl2 or heat. Ignites with diethyl zinc (on contact), polyisobutylene (at 130'), metal acetylides, metal carbides, metal hydrides (e.g., potassium hydride, sodium hydride, copper hydride), metal phosphtdes (e.g., copper(Ⅱ) phosphide), methane + oxygen, hydrazine, hydroxylamine, calcium nitride, nonmetals (e.g., boron, active carbon, silicon, phosphorus), nonmetal hydrides (e.g., arsine, phosphine, silane), steel (above 200' or as low as 50℃ when impurities are present), sulfides (e.g., arsenic disulfide, boron trisulfide, mercuric sulfide), trialkyl boranes. Violent reaction with alcohols, N-aryl sulfinamides, dimethyl formamide, polychlorobiphenyl, sodium hydroxide, hydrochloric acid + dinitroanilines. Incandescent reaction when warmed with cesium oxide (above 1 50°), tellurium, arsenic, tungsten dioxide. Potentially dangerous reaction with hydrocarbons + Lewis acids releases toxic and reactive HCl gas. Can react to cause fires or explosions upon contact with turpentine, illuminating gas, polypropylene, rubber, sulfamic acid, As2(CH3)4, UC2, acetaldehyde, alcohols, alkylisothiourea salts, alkyl phosphtnes, Al, Sb, As, AsS2, AsH3, Ba3P2, C6H6, Bi, B, BPI2, B2S3, brass, BrF5, Ca, (CaC2 + KOH), Ca(ClO2)2, Ca3N2, Ca3P, C, CS2, Cs, CsHC2, CO20, Cs3N, (C + Cr(OCl)2), CuH2, CuC2, dialklyl phosphines, diborane, dibutyl phthalate, Zn(C2H5)2, C2H6, C2H4, ethylene imine, C2H5PH2, F2, Ge, glycerol, (NH2)2, (H20 + KOH), I2, hydroxylamine, Fe, FeC2, Li, Li2C2, Li6c2, Mg, Mg2P3, Mn, Mn3P2, HgO, HgS, Hg, Hg3P2, CH4,Nb,NI3, OF2, H2SiO, (OF2 + Cu), PH3, P, P(SNC)3, P203, PCB's, K, KHC2, KH, Ru, RuHC2, Si, SiH2, Ag2O, Na, NaHC2, Na2C2, SnF2, SbH3, Sr3P, Te, Th, Sn, WO2, U, V, Zn, ZrC2.

Potential Exposure

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.

Physiological effects

Chlorine gas is primarily a respiratory irritant. In sufficient concentration, the gas irritates the mucous membranes, the respiratory tract and the eyes. In extreme cases difficulty in breathing may increase to the point where death can occur from respiratory collapse or lung failure. The characteristic, penetrating odor of chlorine gas usually gives warning of its presence in the air. Also, at high concentrations, it is visible as a greenish yellow gas. Liquid chlorine in contact with skin or eyes will cause chemical bums or frostbite.
ACGIH recommends a Threshold Limit Value-Time-Weighted Average (TLV-TWA) of 0.5 ppm (1.5 mg/m3 ) for chlorine. The TLVTWA is the time-weighted average concentration for a normal 8-hour workday and a 40-hour workweek, to which nearly all workers may be repeatedly exposed, day after day, without adverse effect.

First aid

If this chemical gets into the eyes, remove anycontact lenses at once and irrigate immediately for at least30 min, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts theskin, remove contaminated clothing and wash immediatelywith soap and water. Seek medical attention immediately. Ifthis chemical has been inhaled, remove from exposure,begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR ifheart action has stopped. Transfer promptly to a medicalfacility. When this chemical has been swallowed, get medical attention. Give large quantities of water and inducevomiting. Do not make an unconscious person vomit.Medical observation is recommended for 24-48 h afterbreathing overexposure, as pulmonary edema may bedelayed. As first aid for pulmonary edema, a doctor orauthorized paramedic may consider administering a corticosteroid spray.
If frostbite has occurred, seek medical attention immediately; do NOT rub the affected areas or flush them withwater. In order to prevent further tissue damage, do NOTattempt to remove frozen clothing from frostbitten areas. Iffrostbite has NOT occurred, immediately and thoroughlywash contaminated skin with soap and water.

Carcinogenicity

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).

storage

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.

Shipping

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.

Purification Methods

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.

Incompatibilities

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.

Waste Disposal

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.

GRADES AVAILABLE

Chlorine for commercial and industrial use has much the same quality from all producers. High purity grades (99.9 percent) are available from specialty gas suppliers.