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See what “chlorine” is in other dictionaries. Diaphragm method with solid cathode

Chlorine

CHLORINE-A; m.[from Greek chlōros - pale green] Chemical element (Cl), an asphyxiating gas of greenish-yellow color with a pungent odor (used as a poisonous and disinfectant). Chlorine compounds. Chlorine poisoning.

Chlorine (see).

chlorine

(lat. Chlorum), chemical element Group VII periodic table, refers to halogens. The name comes from the Greek chlōros - yellow-green. Free chlorine consists of diatomic molecules (Cl 2); yellow-green gas with a pungent odor; density 3.214 g/l; t pl -101°C; t kip -33.97°C; at ordinary temperatures it easily liquefies under a pressure of 0.6 MPa. Chemically very active (oxidizing agent). The main minerals are halite ( rock salt), sylvine, bischofite; sea ​​water contains chlorides of sodium, potassium, magnesium and other elements. Used in the production of chlorine-containing organic compounds (60-75%), inorganic substances(10-20%), for bleaching cellulose and fabrics (5-15%), for sanitary needs and disinfection (chlorination) of water. Toxic.

CHLORINE

CHLORINE (lat. Chlorum), Cl (read “chlorine”), a chemical element with atomic number 17, atomic mass 35.453. In its free form it is a yellow-green heavy gas with a sharp suffocating odor (hence the name: Greek chloros - yellow-green).
Natural chlorine is a mixture of two nuclides (cm. NUCLIDE) with mass numbers of 35 (in a mixture of 75.77% by mass) and 37 (24.23%). Outer electron layer 3 configuration s 2 p 5 . In compounds it exhibits mainly oxidation states –1, +1, +3, +5 and +7 (valences I, III, V and VII). (cm. Located in the third period in group VIIA of Mendeleev’s periodic table of elements, belongs to the halogens.
HALOGEN) The radius of the neutral chlorine atom is 0.099 nm, the ionic radii are equal, respectively (values ​​are indicated in parentheses coordination number
): Cl - 0.167 nm (6), Cl 5+ 0.026 nm (3) and Clr 7+ 0.022 nm (3) and 0.041 nm (6). The sequential ionization energies of the neutral chlorine atom are, respectively, 12.97, 23.80, 35.9, 53.5, 67.8, 96.7 and 114.3 eV. Electron affinity 3.614 eV. According to the Pauling scale, the electronegativity of chlorine is 3.16.
History of discovery The most important chemical compound of chlorine is table salt ( NaCl, chemical name sodium chloride) has been known to man since ancient times. There is evidence that the extraction of table salt was carried out as early as 3-4 thousand years BC in Libya. It is possible that using table salt For various manipulations, alchemists also encountered chlorine gas. To dissolve the “king of metals” - gold - they used “aqua regia” - a mixture of hydrochloric and nitric acids, during the interaction of which chlorine is released.
For the first time, chlorine gas was obtained and described in detail Swedish chemist K. Scheele (cm. SCHEELE Karl Wilhelm) in 1774. He heated hydrochloric acid with the mineral pyrolusite (cm. PYROLUSITE) MnO 2 and observed the release of a yellow-green gas with a pungent odor. Since the theory of phlogiston dominated in those days (cm. PHLOGISTON), Scheele considered the new gas as “dephlogistonized hydrochloric acid,” i.e., as an oxide (oxide) of hydrochloric acid. A. Lavoisier (cm. LAVOISIER Antoine Laurent) considered the gas as an oxide of the element “muria” (hydrochloric acid was called muric acid, from the Latin muria - brine). The same point of view was first shared by the English scientist G. Davy (cm. DAVY Humphrey), who spent a lot of time breaking down “murium oxide” into simple substances. He failed, and by 1811 Davy came to the conclusion that this gas is a simple substance, and a chemical element corresponds to it. Davy was the first to suggest calling it chlorine in accordance with the yellow-green color of the gas. The name “chlorine” was given to the element in 1812 by the French chemist J. L. Gay-Lussac (cm. GAY LUSSAC Joseph Louis); it is accepted in all countries except Great Britain and the USA, where the name introduced by Davy has been preserved. It was suggested that this element should be called “halogen” (i.e., salt-producing), but over time it became common name all elements of group VIIA.
Being in nature
Chlorine content in earth's crust is 0.013% by weight, in a noticeable concentration it is present in the form of the Cl – ion in sea ​​water(average about 18.8 g/l). Chemically, chlorine is highly active and therefore does not occur in free form in nature. It is part of such minerals that form large deposits, such as table, or rock, salt (halite (cm. HALITE)) NaCl, carnallite (cm. CARNALLITE) KCl MgCl 2 6H 21 O, sylvine (cm. SYLVIN) KCl, sylvinite (Na, K)Cl, kainite (cm. KAINIT) KCl MgSO 4 3H 2 O, bischofite (cm. BISCHOFIT) MgCl 2 ·6H 2 O and many others. Chlorine can be found in a variety of rocks and soil.
Receipt
To obtain chlorine gas, use electrolysis of strong aqueous NaCl solution(sometimes KCl is used). Electrolysis is carried out using a cation exchange membrane separating the cathode and anode spaces. Moreover, due to the process
2NaCl + 2H 2 O = 2NaOH + H 2 + Cl 2
three valuable chemical products are obtained at once: chlorine at the anode, hydrogen at the cathode (cm. HYDROGEN), and alkali accumulates in the electrolyzer (1.13 tons of NaOH for every ton of chlorine produced). The production of chlorine by electrolysis requires large amounts of electricity: from 2.3 to 3.7 MW is consumed to produce 1 ton of chlorine.
To obtain chlorine in the laboratory, they use the reaction of concentrated hydrochloric acid with any strong oxidizing agent (potassium permanganate KMnO 4, potassium dichromate K 2 Cr 2 O 7, potassium chlorate KClO 3, bleach CaClOCl, manganese (IV) oxide MnO 2). It is most convenient to use potassium permanganate for these purposes: in this case, the reaction proceeds without heating:
2KMnO 4 + 16HCl = 2KСl + 2MnCl 2 + 5Cl 2 + 8H 2 O.
If necessary, chlorine in liquefied (under pressure) form is transported in railway tanks or in steel cylinders. Chlorine cylinders have a special marking, but even without it, a chlorine cylinder can be easily distinguished from cylinders with other non-toxic gases. The bottom of chlorine cylinders is shaped like a hemisphere, and a cylinder with liquid chlorine cannot be placed vertically without support.
Physical and Chemical properties

At normal conditions chlorine is a yellow-green gas, gas density at 25°C 3.214 g/dm 3 (about 2.5 times more density air). The melting point of solid chlorine is –100.98°C, the boiling point is –33.97°C. The standard electrode potential Cl 2 /Cl - in an aqueous solution is +1.3583 V.
In the free state, it exists in the form of diatomic Cl 2 molecules. The internuclear distance in this molecule is 0.1987 nm. The electron affinity of the Cl 2 molecule is 2.45 eV, ionization potential is 11.48 eV. The energy of dissociation of Cl 2 molecules into atoms is relatively low and amounts to 239.23 kJ/mol.
Chlorine is slightly soluble in water. At a temperature of 0°C, the solubility is 1.44 wt.%, at 20°C - 0.711°C wt.%, at 60°C - 0.323 wt. %. A solution of chlorine in water is called chlorine water. In chlorine water an equilibrium is established:
Сl 2 + H 2 O H + = Сl - + HOСl.
In order to shift this equilibrium to the left, i.e., reduce the solubility of chlorine in water, either sodium chloride NaCl or some non-volatile strong acid (for example, sulfuric) should be added to the water.
Chlorine is highly soluble in many non-polar liquids. Liquid chlorine itself serves as a solvent for substances such as BCl 3, SiCl 4, TiCl 4.
Due to the low dissociation energy of Cl 2 molecules into atoms and the high electron affinity of the chlorine atom, chemically chlorine is highly active. It reacts directly with most metals (including, for example, gold) and many non-metals. So, without heating, chlorine reacts with alkaline (cm. ALKALI METALS) and alkaline earth metals (cm. ALKALINE EARTH METALS), with antimony:
2Sb + 3Cl 2 = 2SbCl 3
When heated, chlorine reacts with aluminum:
3Сl 2 + 2Аl = 2А1Сl 3
and iron:
2Fe + 3Cl 2 = 2FeCl 3.
Chlorine reacts with hydrogen H2 either when ignited (chlorine burns quietly in a hydrogen atmosphere), or when a mixture of chlorine and hydrogen is irradiated with ultraviolet light. In this case, hydrogen chloride gas HCl appears:
H 2 + Cl 2 = 2HCl.
A solution of hydrogen chloride in water is called hydrochloric acid (cm. HYDROCHLORIC ACID)(hydrochloric) acid. The maximum mass concentration of hydrochloric acid is about 38%. Salts of hydrochloric acid - chlorides (cm. CHLORIDE), for example, ammonium chloride NH 4 Cl, calcium chloride CaCl 2, barium chloride BaCl 2 and others. Many chlorides are highly soluble in water. Silver chloride AgCl is practically insoluble in water and in acidic aqueous solutions. A qualitative reaction to the presence of chloride ions in a solution is the formation of a white AgCl precipitate with Ag + ions, practically insoluble in nitrogen. acidic environment:
CaCl 2 + 2AgNO 3 = Ca(NO 3) 2 + 2AgCl.
At room temperature, chlorine reacts with sulfur (the so-called sulfur monochloride S 2 Cl 2 is formed) and fluorine (the compounds ClF and ClF 3 are formed). When heated, chlorine interacts with phosphorus (forming, depending on the reaction conditions, compounds PCl 3 or PCl 5), arsenic, boron and other non-metals. Chlorine does not react directly with oxygen, nitrogen, or carbon (numerous chlorine compounds with these elements are formed indirect ways) and inert gases (recently scientists have found ways to activate such reactions and carry them out “directly”). With other halogens, chlorine forms interhalogen compounds, for example, very strong oxidizing agents - fluorides ClF, ClF 3, ClF 5. The oxidizing power of chlorine is higher than bromine, so chlorine displaces bromide ion from bromide solutions, for example:
Cl 2 + 2NaBr = Br 2 + 2NaCl
Chlorine undergoes substitution reactions with many organic compounds, for example, with methane CH 4 and benzene C 6 H 6:
CH 4 + Cl 2 = CH 3 Cl + HCl or C 6 H 6 + Cl 2 = C 6 H 5 Cl + HCl.
A chlorine molecule is capable of attaching via multiple bonds (double and triple) to organic compounds, for example, to ethylene C 2 H 4:
C 2 H 4 + Cl 2 = CH 2 Cl CH 2 Cl.
Chlorine interacts with aqueous solutions of alkalis. If the reaction occurs at room temperature, chloride (for example, potassium chloride KCl) and hypochlorite are formed (cm. HYPOCHLORITES)(for example, potassium hypochlorite KClO):
Cl 2 + 2KOH = KClO + KCl + H 2 O.
When chlorine interacts with a hot (temperature about 70-80°C) alkali solution, the corresponding chloride and chlorate are formed (cm. CHLORATES), For example:
3Cl 2 + 6KOH = 5KCl + KClO 3 + 3H 2 O.
When chlorine interacts with a wet slurry of calcium hydroxide Ca(OH) 2, bleach is formed (cm. BLEACHING POWDER)(“bleach”) CaClOCl.
The oxidation state of chlorine +1 corresponds to weak, unstable hypochlorous acid (cm. Hypochlorous acid) HClO. Its salts are hypochlorites, for example, NaClO - sodium hypochlorite. Hypochlorites are strong oxidizing agents and are widely used as bleaching and disinfecting agents. When hypochlorites, in particular bleach, interact with carbon dioxide CO 2 is formed among other products, volatile hypochlorous acid (cm. Hypochlorous acid), which can decompose to release chlorine oxide (I) Cl 2 O:
2HClO = Cl 2 O + H 2 O.
It is the smell of this gas, Cl 2 O, that is the characteristic smell of “bleach”.
The oxidation state of chlorine +3 corresponds to a low-stable acid medium strength HClO 2. This acid is called chloric acid, its salts are called chlorites (cm. CHLORITES (salts)), for example, NaClO 2 - sodium chlorite.
The oxidation state of chlorine +4 corresponds to only one compound - chlorine dioxide ClO 2.
The oxidation state of chlorine +5 corresponds to strong, stable only in aqueous solutions at concentrations below 40%, perchloric acid (cm. Hypochlorous acid) HClO 3. Its salts are chlorates, for example, potassium chlorate KClO 3.
The oxidation state of chlorine +6 corresponds to only one compound - chlorine trioxide ClO 3 (exists in the form of a dimer Cl 2 O 6).
The oxidation state of chlorine +7 corresponds to a very strong and fairly stable perchloric acid (cm. PERCHLORIC ACID) HClO 4. Its salts are perchlorates (cm. PERCHLORATES), for example, ammonium perchlorate NH 4 ClO 4 or potassium perchlorate KClO 4. It should be noted that perchlorates of heavy alkali metals - potassium, and especially rubidium and cesium - are slightly soluble in water. The oxide corresponding to the oxidation state of chlorine is +7 - Cl 2 O 7.
Among compounds containing chlorine in positive oxidation states, hypochlorites have the strongest oxidizing properties. For perchlorates oxidizing properties uncharacteristic.
Application
Chlorine is one of the essential products chemical industry. Its global production amounts to tens of millions of tons per year. Chlorine is used to produce disinfectants and bleaches (sodium hypochlorite, bleach and others), hydrochloric acid, chlorides of many metals and non-metals, many plastics (polyvinyl chloride (cm. POLYVINYL CHLORIDE) and others), chlorine-containing solvents (dichloroethane CH 2 ClCH 2 Cl, carbon tetrachloride CCl 4, etc.), for opening ores, separating and purifying metals, etc. Chlorine is used to disinfect water (chlorination (cm. CHLORINATION)) and for many other purposes.
Biological role
Chlorine is one of the most important biogenic elements (cm. BIOGENIC ELEMENTS) and is part of all living organisms. Some plants, the so-called halophytes, are not only able to grow on highly saline soils, but also accumulate in large quantities chlorides. Microorganisms (halobacteria, etc.) and animals are known that live in conditions of high salinity. Chlorine is one of the main elements of water-salt metabolism in animals and humans, determining physical and chemical processes in the tissues of the body. He is involved in maintaining acid-base balance in tissues, osmoregulation (cm. OSMOREGULATION)(chlorine is the main osmotically active substance blood, lymph and other body fluids), being mainly outside the cells. In plants, chlorine takes part in oxidative reactions and photosynthesis.
Human muscle tissue contains 0.20-0.52% chlorine, bone tissue - 0.09%; in the blood - 2.89 g/l. The average person's body (body weight 70 kg) contains 95 g of chlorine. Every day a person receives 3-6 g of chlorine from food, which more than covers the need for this element.
Features of working with chlorine
Chlorine is a poisonous asphyxiating gas; if it enters the lungs, it causes burns of lung tissue and suffocation. Irritant effect has an effect on the respiratory tract at a concentration in the air of about 0.006 mg/l. Chlorine was one of the first chemical poisons (cm. POISONIC SUBSTANCES), used by Germany in the First world war. When working with chlorine, you should use protective clothing, a gas mask, and gloves. For a short time, you can protect the respiratory organs from chlorine entering them with a cloth bandage moistened with a solution of sodium sulfite Na 2 SO 3 or sodium thiosulfate Na 2 S 2 O 3. Maximum concentration of chlorine in the air of working premises is 1 mg/m 3, in the air settlements 0.03 mg/m3.

In nature, chlorine occurs in gaseous state and only in the form of compounds with other gases. In conditions close to normal, it is a poisonous, caustic gas of a greenish color. Has more weight than air. Has a sweet smell. A chlorine molecule contains two atoms. In a calm state it does not burn, but at high temperatures it interacts with hydrogen, after which an explosion is possible. As a result, phosgene gas is released. Very poisonous. Thus, even at low concentrations in the air (0.001 mg per 1 dm 3) it can cause death. chlorine states that it is heavier than air, therefore, it will always be located near the floor in the form of a yellowish-green haze.

Historical facts

For the first time in practice, this substance was obtained by K. Scheeley in 1774 by combining hydrochloric acid and pyrolusite. However, only in 1810 P. Davy was able to characterize chlorine and establish that it is a separate chemical element.

It is worth noting that in 1772 he was able to obtain hydrogen chloride, a compound of chlorine and hydrogen, but the chemist was unable to separate these two elements.

Chemical characteristics of chlorine

Chlorine is a chemical element of the main subgroup of group VII of the periodic table. It is in the third period and has atomic number 17 (17 protons in the atomic nucleus). Chemically active non-metal. Denoted by the letters Cl.

It is a typical representative of gases that have no color, but have a pungent, pungent odor. Typically toxic. All halogens are well diluted in water. When exposed to humid air, they begin to smoke.

External electronic configuration atom Cl 3s2Зр5. Therefore, in compounds, a chemical element exhibits oxidation levels of -1, +1, +3, +4, +5, +6 and +7. The covalent radius of the atom is 0.96 Å, the ionic radius of Cl- is 1.83 Å, the atomic electron affinity is 3.65 eV, the ionization level is 12.87 eV.

As stated above, chlorine is a fairly active non-metal, which makes it possible to create compounds with almost any metals (in some cases using heat or moisture, displacing bromine) and non-metals. In powder form, it reacts with metals only when exposed to high temperatures.

The maximum combustion temperature is 2250 °C. With oxygen it can form oxides, hypochlorites, chlorites and chlorates. All compounds containing oxygen become explosive when interacting with oxidizing substances. It is worth noting that they can explode arbitrarily, while chlorates explode only when exposed to any initiators.

Characteristics of chlorine by position in the periodic table:

Simple substance;
. element of the seventeenth group periodic table;
. third period of the third row;
. seventh group main subgroup;
. atomic number 17;
. denoted by the symbol Cl;
. reactive non-metal;
. is in the halogen group;
. in conditions close to normal, it is a poisonous gas of a yellowish-green color with a pungent odor;
. a chlorine molecule has 2 atoms (formula Cl 2).

Physical properties of chlorine:

Boiling point: -34.04 °C;
. melting point: -101.5 °C;
. density in the gaseous state - 3.214 g/l;
. density of liquid chlorine (during the boiling period) - 1.537 g/cm3;
. density of solid chlorine - 1.9 g/cm 3 ;
. specific volume - 1.745 x 10 -3 l/g.

Chlorine: characteristics of temperature changes

In the gaseous state it tends to liquefy easily. At a pressure of 8 atmospheres and a temperature of 20 ° C, it looks like a greenish-yellow liquid. Has very high corrosive properties. As practice shows, this chemical element can remain liquid up to critical temperature(143 °C), subject to increasing pressure.

If it is cooled to a temperature of -32 ° C, it will change to liquid regardless of atmospheric pressure. With a further decrease in temperature, crystallization occurs (at -101 ° C).

Chlorine in nature

The earth's crust contains only 0.017% chlorine. The bulk is in volcanic gases. As stated above, the substance has great chemical activity, as a result of which it is found in nature in compounds with other elements. However, many minerals contain chlorine. The characteristics of the element allow the formation of about a hundred different minerals. As a rule, these are metal chlorides.

Also, a large amount of it is found in the World Ocean - almost 2%. This is due to the fact that chlorides dissolve very actively and are carried by rivers and seas. The reverse process is also possible. The chlorine washes back onto the shore, and then the wind carries it around the surrounding area. That is why its greatest concentration is observed in coastal zones. In the arid regions of the planet, the gas we are considering is formed through the evaporation of water, as a result of which salt marshes appear. About 100 million tons are mined annually in the world of this substance. Which, however, is not surprising, because there are many deposits containing chlorine. Its characteristics, however, largely depend on its geographical location.

Methods for producing chlorine

Today there are a number of methods for producing chlorine, of which the most common are the following:

1. Diaphragm. It is the simplest and least expensive. The brine solution in diaphragm electrolysis enters the anode space. Then it flows through the steel cathode grid into the diaphragm. It contains a small amount of polymer fibers. Important feature This device is countercurrent. It is directed from the anode space to the cathode space, which makes it possible to obtain chlorine and alkalis separately.

2. Membrane. The most energy efficient, but difficult to implement in an organization. Similar to diaphragm. The difference is that the anode and cathode spaces are completely separated by a membrane. Therefore, the output is two separate streams.

It is worth noting that the characteristics of the chemical element (chlorine) obtained by these methods will be different. The membrane method is considered to be more “clean”.

3. Mercury method with liquid cathode. Compared to other technologies, this option allows you to obtain the purest chlorine.

The basic diagram of the installation consists of an electrolyzer and an interconnected pump and amalgam decomposer. The mercury pumped along with a solution of table salt serves as the cathode, and carbon or graphite electrodes serve as the anode. The operating principle of the installation is as follows: chlorine is released from the electrolyte, which is removed from the electrolyzer along with the anolyte. Impurities and residual chlorine are removed from the latter, re-saturated with halite and returned for electrolysis.

Industrial safety requirements and unprofitable production led to the replacement of the liquid cathode with a solid one.

Use of chlorine for industrial purposes

The properties of chlorine allow it to be actively used in industry. Using this chemical element, various (vinyl chloride, chlorine rubber, etc.) are obtained. medications, disinfectants. But the largest niche occupied in the industry is the production of hydrochloric acid and lime.

Cleansing methods are widely used drinking water. Today they are trying to move away from this method, replacing it with ozonation, since the substance we are considering negatively affects the human body, and chlorinated water destroys pipelines. This is due to the fact that in the free state Cl has a detrimental effect on pipes made from polyolefins. However, most countries prefer the chlorination method.

Chlorine is also used in metallurgy. With its help, a number of rare metals (niobium, tantalum, titanium) are obtained. In the chemical industry, various organochlorine compounds are actively used to control weeds and for other agricultural purposes; the element is also used as a bleach.

Thanks to its chemical structure Chlorine destroys most organic and inorganic dyes. This is achieved by completely bleaching them. This result is possible only in the presence of water, because the process of discoloration occurs due to which it is formed after the breakdown of chlorine: Cl 2 + H 2 O → HCl + HClO → 2HCl + O. This method found application a couple of centuries ago and is still popular today.

The use of this substance for the production of organochlorine insecticides is very popular. These agricultural products kill harmful organisms while leaving the plants intact. A significant portion of all chlorine produced on the planet is used for agricultural needs.

It is also used in the production of plastic compounds and rubber. They are used to make wire insulation, office supplies, equipment, housings for household appliances, etc. There is an opinion that rubbers obtained in this way are harmful to humans, but this has not been confirmed by science.

It is worth noting that chlorine (the characteristics of the substance were described in detail by us earlier) and its derivatives, such as mustard gas and phosgene, are also used for military purposes to produce chemical warfare agents.

Chlorine as a prominent representative of non-metals

Nonmetals are simple substances that include gases and liquids. In most cases they perform worse electricity than metals, and have significant differences in physical and mechanical characteristics. With help high level ionization are capable of forming covalent chemical compounds. Below we will give a description of a non-metal using chlorine as an example.

As mentioned above, this chemical element is a gas. IN normal conditions it completely lacks properties similar to those of metals. Without outside help, it cannot interact with oxygen, nitrogen, carbon, etc. It exhibits its oxidizing properties in connections with simple substances and some complex ones. It is a halogen, which is clearly reflected in its chemical properties. In combination with other representatives of halogens (bromine, astatine, iodine), it displaces them. In the gaseous state, chlorine (its characteristics are direct confirmation of this) is highly soluble. Is an excellent disinfectant. Kills only living organisms, which makes it indispensable in agriculture and medicine.

Use as a poisonous substance

The characteristics of the chlorine atom make it possible to use it as a poisonous agent. Gas was first used by Germany on April 22, 1915, during the First World War, as a result of which about 15 thousand people died. On this moment as it does not apply.

Let us give a brief description of the chemical element as an asphyxiant. Affects the human body through suffocation. First it irritates the upper respiratory tract and the mucous membrane of the eyes. A severe cough begins with attacks of suffocation. Further, penetrating into the lungs, the gas corrodes the lung tissue, which leads to edema. Important! Chlorine is a fast-acting substance.

Depending on the concentration in the air, symptoms vary. At low levels, a person experiences redness of the mucous membrane of the eyes and mild shortness of breath. A content of 1.5-2 g/m 3 in the atmosphere causes heaviness and sharp sensations in the chest, sharp pain in the upper respiratory tract. The condition may also be accompanied by severe lacrimation. After 10-15 minutes of being in a room with such a concentration of chlorine, severe burn lungs and death. At denser concentrations, death is possible within a minute from paralysis of the upper respiratory tract.

Chlorine in the life of organisms and plants

Chlorine is found in almost all living organisms. The peculiarity is that it is not present in pure form, but in the form of connections.

In animal and human organisms, chlorine ions maintain osmotic equality. This is due to the fact that they have the most suitable radius for penetration into membrane cells. Along with potassium ions, Cl regulates the water-salt balance. In the intestines, chlorine ions create favorable environment for action proteolytic enzymes gastric juice. Chlorine channels are found in many cells in our body. Through them, intercellular exchange of fluids occurs and the pH of the cell is maintained. About 85% of the total volume of this element in the body resides in the intercellular space. It is eliminated from the body through the urethra. Produced by the female body during breastfeeding.

On at this stage development, it is difficult to say unequivocally which diseases are provoked by chlorine and its compounds. This is due to the lack of research in this area.

Chlorine ions are also present in plant cells. He actively participates in energy metabolism. Without this element, the process of photosynthesis is impossible. With its help, the roots actively absorb the necessary substances. But a high concentration of chlorine in plants can have a detrimental effect (slowing down the process of photosynthesis, stopping development and growth).

However, there are representatives of the flora who were able to “make friends” or at least get along with this element. The characteristics of a non-metal (chlorine) contain such an item as the ability of a substance to oxidize soils. In the process of evolution, the above-mentioned plants, called halophytes, occupied empty salt marshes, which were empty due to an overabundance of this element. They absorb chlorine ions, and then get rid of them with the help of leaf fall.

Transportation and storage of chlorine

There are several ways to move and store chlorine. The characteristics of the element suggest the need for special cylinders with high pressure. Such containers have an identification marking - a vertical green line. Cylinders must be thoroughly washed monthly. When chlorine is stored for a long time, a very explosive precipitate is formed - nitrogen trichloride. Failure to comply with all safety rules may result in spontaneous ignition and explosion.

Chlorine study

Future chemists should know the characteristics of chlorine. According to the plan, 9th graders can even put laboratory experiments with this substance based basic knowledge by discipline. Naturally, the teacher is obliged to provide safety instructions.

The work procedure is as follows: you need to take a flask with chlorine and pour small metal shavings into it. In flight, the shavings will flare up with bright light sparks and at the same time light white SbCl 3 smoke will form. When tin foil is immersed in a vessel with chlorine, it will also spontaneously ignite, and fiery snowflakes will slowly fall to the bottom of the flask. During this reaction, a smoky liquid is formed - SnCl 4. When iron filings are placed in a vessel, red “drops” will form and red FeCl 3 smoke will appear.

Along with practical work, theory is repeated. In particular, such a question as the characteristics of chlorine by position in the periodic table (described at the beginning of the article).

As a result of experiments, it turns out that the element actively reacts to organic compounds. If you place cotton wool, previously soaked in turpentine, in a jar of chlorine, it will instantly ignite and soot will suddenly fall out of the flask. Sodium smolders spectacularly with a yellowish flame, and salt crystals appear on the walls of the chemical container. Students will be interested to know that, while still a young chemist, N. N. Semenov (later laureate Nobel Prize), having carried out such an experiment, collected salt from the walls of the flask and, sprinkled it on the bread, ate it. Chemistry turned out to be right and did not let the scientist down. As a result of the experiment carried out by the chemist, ordinary table salt actually turned out!

No matter how negatively we view public restrooms, nature dictates its own rules, and we have to visit them. In addition to natural (for a given place) odors, another common aroma is bleach used to disinfect the room. It got its name because of the main active substance in it - Cl. Let us learn about this chemical element and its properties, and also characterize chlorine by position in the periodic table.

How was this element discovered?

The first chlorine-containing compound (HCl) was synthesized in 1772 by the British priest Joseph Priestley.

Two years later, his Swedish colleague Karl Scheele was able to describe a method for isolating Cl using the reaction between hydrochloric acid and manganese dioxide. However, this chemist did not understand that as a result a new chemical element was synthesized.

It took scientists almost 40 years to learn how to produce chlorine in practice. This was first done by the British Humphry Davy in 1811. At the same time, he used a different reaction than his theoretic predecessors. Davy used electrolysis to break down NaCl (known to most as table salt) into its components.

After studying the resulting substance, the British chemist realized that it was elemental. After this discovery, Davy not only named it chlorine, but was also able to characterize chlorine, although it was very primitive.

Chlorine turned into chlorine (chlore) thanks to Joseph Gay-Lussac and in this form exists in French, German, Russian, Belarusian, Ukrainian, Czech, Bulgarian and some other languages ​​today. In English the name "chlorine" is still used, and in Italian and Spanish "chloro".

The element in question was described in more detail by Jens Berzelius in 1826. It was he who was able to determine its atomic mass.

What is chlorine (Cl)

Having considered the history of the discovery of this chemical element, it is worth learning more about it.

The name chlorine was derived from Greek wordχλωρός (“green”). It was given because of the yellowish-greenish color of this substance

Chlorine itself exists as a diatomic gas, Cl2, but it is practically never found in nature in this form. More often it appears in various compounds.

In addition to its distinctive hue, chlorine is characterized by a sweetish-acrid odor. It is a very toxic substance, therefore, when released into the air and inhaled by a person or animal, it can lead to their death within a few minutes (depending on the concentration of Cl).

Since chlorine is almost 2.5 times heavier than air, it will always be located below it, that is, near the ground. For this reason, if you suspect the presence of Cl, you should climb as high as possible, since there will be a lower concentration of this gas.

Also, unlike some others toxic substances, chlorine-containing substances have a characteristic color, which can make it possible to visually identify them and take action. Most standard gas masks help protect the respiratory system and mucous membranes from Cl. However, for complete safety, more serious measures must be taken, including neutralizing the toxic substance.

It is worth noting that it was with the use of chlorine as a poisonous gas by the Germans in 1915 that its history began. chemical weapon. As a result of the use of almost 200 tons of the substance, 15 thousand people were poisoned in a few minutes. A third of them died almost instantly, a third received permanent damage, and only 5 thousand managed to escape.

Why is such a dangerous substance still not banned and is mined annually in millions of tons? It's all about him special properties oh, and to understand them, it’s worth considering the characteristics of chlorine. The easiest way to do this is using the periodic table.

Characteristics of chlorine in the periodic system


Chlorine as a halogen

In addition to its extreme toxicity and pungent odor (characteristic of all representatives of this group), Cl is highly soluble in water. Practical confirmation of this is the addition of chlorine-containing detergents to pool water.

Upon contact with moist air, the substance in question begins to smoke.

Properties of Cl as a non-metal

When considering the chemical characteristics of chlorine, it is worth paying attention to its non-metallic properties.

It has the ability to form compounds with almost all metals and non-metals. An example is the reaction with iron atoms: 2Fe + 3Cl 2 → 2FeCl 3.

It is often necessary to use catalysts to carry out reactions. H2O can play this role.

Often reactions with Cl are endothermic (they absorb heat).

It is worth noting that in crystalline form (in powder form), chlorine interacts with metals only when heated to high temperatures.

Reacting with other non-metals (except O 2, N, F, C and inert gases), Cl forms compounds - chlorides.

When reacting with O 2, extremely unstable oxides are formed that are prone to decomposition. In them, the oxidation state of Cl can manifest itself from +1 to +7.

When interacting with F, fluorides are formed. Their degree of oxidation may be different.

Chlorine: characteristics of the substance in terms of its physical properties

In addition to chemical properties, the element in question also has physical properties.


Effect of temperature on the state of aggregation of Cl

Having considered physical characteristics element of chlorine, we understand that it is capable of transforming into different states of aggregation. It all depends on the temperature.

IN in good condition Cl is a gas with highly corrosive properties. However, it can easily liquefy. This is affected by temperature and pressure. For example, if it is 8 atmospheres and the temperature is +20 degrees Celsius, Cl 2 is an acid-yellow liquid. Given state of aggregation it is capable of maintaining up to +143 degrees if the pressure also continues to rise.

When it reaches -32 °C, the state of chlorine ceases to depend on pressure, and it continues to remain liquid.

Crystallization of matter ( solid state) occurs at -101 degrees.

Where does Cl exist in nature?

Having considered the general characteristics of chlorine, it is worth finding out where such a complex element can be found in nature.

Due to its high reactivity, it is almost never found in its pure form (which is why it took scientists years to learn how to synthesize it when they first studied this element). Typically, Cl is found in compounds in various minerals: halite, sylvite, kainite, bischofite, etc.

Most of all, it is found in salts extracted from sea or ocean water.

Effect on the body

When considering the characteristics of chlorine, it has already been said more than once that it is extremely toxic. Moreover, atoms of the substance are contained not only in minerals, but also in almost all organisms, from plants to humans.

Due to their special properties, Cl ions penetrate cell membranes better than others (therefore, more than 80% of all chlorine in the human body is located in the intercellular space).

Together with K, Cl is responsible for the regulation of water-salt balance and, as a consequence, for osmotic equality.

Despite such an important role in the body, in its pure form Cl 2 kills all living things - from cells to entire organisms. However, in controlled doses and with short-term exposure, it does not have time to cause damage.

A striking example of the latter statement is any swimming pool. As you know, water in such institutions is disinfected with Cl. Moreover, if a person rarely visits such an establishment (once a week or a month), it is unlikely that he will suffer from the presence of this substance in the water. However, employees of such institutions, especially those who spend almost the entire day in the water (rescuers, instructors), often suffer skin diseases or have a weakened immune system.

In connection with all this, after visiting the pools, you should definitely take a shower - to wash off possible chlorine residues from your skin and hair.

Human uses of Cl

Remembering from the characteristics of chlorine that it is a “capricious” element (when it comes to interaction with other substances), it will be interesting to know that it is quite often used in industry.

First of all, it is used to disinfect many substances.

Cl is also used in the manufacture of certain types of pesticides, which helps save crops from pests.

The ability of this substance to interact with almost all elements of the periodic table (characteristic of chlorine as a non-metal) helps with its help to extract certain types of metals (Ti, Ta and Nb), as well as lime and hydrochloric acid.

In addition to all of the above, Cl is used in the production of industrial substances (polyvinyl chloride) and medications (chlorhexidine).

It is worth mentioning that today a more effective and safe disinfectant has been found - ozone (O 3). However, it is more expensive to produce than chlorine, and the gas is even more unstable than chlorine ( a brief description of physical properties in 6-7 points). Therefore, few people can afford to use ozonation instead of chlorination.

How is chlorine produced?

Today, many methods are known for the synthesis of this substance. They all fall into two categories:

  • Chemical.
  • Electrochemical.

In the first case, Cl is obtained due to a chemical reaction. However, in practice they are very costly and ineffective.

Therefore, industry prefers electrochemical methods (electrolysis). There are three of them: diaphragm, membrane and mercury electrolysis.

Chlorine was first obtained in 1772 by Scheele, who described its release during the interaction of pyrolusite with hydrochloric acid in his treatise on pyrolusite: 4HCl + MnO 2 = Cl 2 + MnCl 2 + 2H 2 O
Scheele noted the odor of chlorine, similar to that of aqua regia, its ability to react with gold and cinnabar, and its bleaching properties. However, Scheele, in accordance with the phlogiston theory that was dominant in chemistry at that time, suggested that chlorine is dephlogisticated hydrochloric acid, that is, the oxide of hydrochloric acid.
Berthollet and Lavoisier suggested that chlorine is an oxide of the element muria, but attempts to isolate it remained unsuccessful until the work of Davy, who managed to decompose table salt into sodium and chlorine by electrolysis.
The name of the element comes from the Greek clwroz- "green".

Being in nature, receiving:

Natural chlorine is a mixture of two isotopes 35 Cl and 37 Cl. In the earth's crust, chlorine is the most common halogen. Since chlorine is very active, in nature it occurs only in the form of compounds in the minerals: halite NaCl, sylvite KCl, sylvinite KCl NaCl, bischofite MgCl 2 6H 2 O, carnallite KCl MgCl 2 6H 2 O, kainite KCl MgSO 4 ·3H 2 O. The largest reserves of chlorine are contained in the salts of the waters of the seas and oceans.
On an industrial scale, chlorine is produced together with sodium hydroxide and hydrogen by electrolysis of a solution of table salt:
2NaCl + 2H 2 O => H 2 + Cl 2 + 2NaOH
To recover chlorine from hydrogen chloride, which is a by-product during the industrial chlorination of organic compounds, the Deacon process is used (catalytic oxidation of hydrogen chloride with atmospheric oxygen):
4HCl + O 2 = 2H 2 O + 2Cl 2
Processes usually used in laboratories are based on the oxidation of hydrogen chloride with strong oxidizing agents (for example, manganese (IV) oxide, potassium permanganate, potassium dichromate):
2KMnO 4 + 16HCl = 5Cl 2 + 2MnCl 2 + 2KCl +8H 2 O
K 2 Cr 2 O 7 + 14HCl = 3Cl 2 + 2CrCl 3 + 2KCl + 7H 2 O

Physical properties:

Under normal conditions, chlorine is a yellow-green gas with a suffocating odor. Chlorine is noticeably soluble in water ("chlorine water"). At 20°C, 2.3 volumes of chlorine dissolve in one volume of water. Boiling point = -34°C; melting point = -101°C, density (gas, n.s.) = 3.214 g/l.

Chemical properties:

Chlorine is very active - it directly combines with almost all elements of the periodic table, metals and non-metals (except carbon, nitrogen, oxygen and inert gases). Chlorine is a very strong oxidizing agent, displacing less active non-metals (bromine, iodine) from their compounds with hydrogen and metals:
Cl 2 + 2HBr = Br 2 + 2HCl; Cl 2 + 2NaI = I 2 + 2NaCl
When dissolved in water or alkalis, chlorine dismutates, forming hypochlorous (and when heated, perchloric) and hydrochloric acids, or their salts.
Cl 2 + H 2 O HClO + HCl;
Chlorine interacts with many organic compounds, entering into substitution or addition reactions:
CH 3 -CH 3 + xCl 2 => C 2 H 6-x Cl x + xHCl
CH 2 =CH 2 + Cl 2 => Cl-CH 2 -CH 2 -Cl
C 6 H 6 + Cl 2 => C 6 H 6 Cl + HCl
Chlorine has seven oxidation states: -1, 0, +1, +3, +4, +5, +7.

The most important connections:

Hydrogen chloride HCl- a colorless gas that smokes in air due to the formation of fog droplets with water vapor. It has a pungent odor and severely irritates the respiratory tract. Contained in volcanic gases and waters, in gastric juice. Chemical properties depend on what state it is in (it can be gaseous, liquid state or in solution). The HCl solution is called hydrochloric acid. It is a strong acid and displaces more weak acids from their salts. Salts - chlorides- hard crystalline substances With high temperatures melting.
Covalent chlorides- chlorine compounds with non-metals, gases, liquids or fusible ones solids, having characteristic acid properties, as a rule, easily hydrolyzed by water to form hydrochloric acid:
PCl 5 + 4H 2 O = H 3 PO 4 + 5HCl;
Chlorine(I) oxide Cl 2 O., a gas of brownish-yellow color with a pungent odor. Affects the respiratory organs. Easily dissolves in water, forming hypochlorous acid.
Hypochlorous acid HClO. Exists only in solutions. It is a weak and unstable acid. Easily decomposes into hydrochloric acid and oxygen. Strong oxidizing agent. Formed when chlorine dissolves in water. Salts - hypochlorites, low stability (NaClO*H 2 O decomposes explosively at 70 °C), strong oxidizing agents. Widely used for whitening and disinfection bleaching powder, mixed salt Ca(Cl)OCl
Chlorous acid HClO 2, in its free form is unstable, even in a dilute aqueous solution it quickly decomposes. Medium strength acid, salts - chlorites, as a rule, are colorless and highly soluble in water. Unlike hypochlorites, chlorites exhibit pronounced oxidizing properties only in an acidic environment. The greatest use (for bleaching fabrics and paper pulp) is sodium chlorite NaClO 2.
Chlorine(IV) oxide ClO 2, is a greenish-yellow gas with an unpleasant (pungent) odor, ...
Chloric acid, HClO 3 - in its free form is unstable: it disproportionates into ClO 2 and HClO 4. Salts - chlorates; of them highest value have sodium, potassium, calcium and magnesium chlorates. These are strong oxidizing agents and are explosive when mixed with reducing agents. Potassium chlorate ( Berthollet's salt) - KClO 3, was used to produce oxygen in the laboratory, but due to its high danger it was no longer used. Solutions of potassium chlorate were used as a weak antiseptic, external medicine for gargling.
Perchloric acid HClO 4, in aqueous solutions, perchloric acid is the most stable of all oxygen-containing chlorine acids. Anhydrous perchloric acid, which is obtained using concentrated sulfuric acid from 72% HClO 4, is not very stable. It is the strongest monoprotic acid (in aqueous solution). Salts - perchlorates, are used as oxidizers (solid propellant rocket engines).

Application:

Chlorine is used in many industries, science and household needs:
- In the production of polyvinyl chloride, plastic compounds, synthetic rubber;
- For bleaching fabric and paper;
- Production of organochlorine insecticides - substances that kill insects harmful to crops, but are safe for plants;
- For water disinfection - “chlorination”;
- IN Food Industry registered as a food additive E925;
- IN chemical production hydrochloric acid, bleach, bertholet salt, metal chlorides, poisons, drugs, fertilizers;
- In metallurgy for production pure metals: titanium, tin, tantalum, niobium.

Biological role and toxicity:

Chlorine is one of the most important biogenic elements and is part of all living organisms. In animals and humans, chlorine ions are involved in maintaining osmotic balance; the chloride ion has an optimal radius for penetration through the cell membrane. Chlorine ions are vital for plants, participating in energy metabolism in plants, activating oxidative phosphorylation.
Chlorine in the form simple substance poisonous, causes a burn if it gets into the lungs lung tissue, suffocation. It has an irritating effect on the respiratory tract at a concentration in the air of about 0.006 mg/l (i.e., twice the threshold for the perception of the smell of chlorine). Chlorine was one of the first chemical agents used by Germany in World War I.

Korotkova Yu., Shvetsova I.
HF Tyumen State University, 571 group.

Sources: Wikipedia: http://ru.wikipedia.org/wiki/Cl, etc.,
Website of the Russian Chemical Technical University named after. D.I. Mendeleev: