All about the chemical element chlorine. Chlorine: properties, application, production. Industrial chlorine applications

Chlorine - element of the 3rd period and VII of the A-group of the Periodic system, serial number 17. The electronic formula of the atom [10 Ne] 3s 2 Зр 5, the characteristic oxidation states are 0, -1, + 1, +5 and +7. The most stable state is Cl -1. Chlorine oxidation scale:

7 - Cl 2 O 7, ClO 4 -, HClO 4, KClO 4

5 - ClO 3 -, HClO 3, KClO 3

1 - Cl 2 O, ClO -, HClO, NaClO, Ca (ClO) 2

- 1 - Cl -, HCl, KCl, PCl 5

Chlorine has a high electronegativity (2.83) and exhibits non-metallic properties. It is a part of many substances - oxides, acids, salts, binary compounds.

In nature - twelfth in terms of chemical abundance, an element (fifth among non-metals). It is found only in chemically bound form. The third most abundant element in natural waters (after O and H), especially a lot of chlorine in seawater (up to 2% by weight). A vital element for all organisms.

Chlorine C1 2 ... Simple substance. Yellow-green gas with a pungent suffocating odor. The Сl 2 molecule is non-polar, contains the С1-С1 σ-bond. Thermally stable, non-flammable in air; a mixture with hydrogen explodes in the light (hydrogen burns out in chlorine):

Cl 2 + H 2 ⇌HCl

Let's well dissolve in water, undergo dismutation in it by 50% and completely in an alkaline solution:

Cl 2 0 + H 2 O ⇌HCl I O + HCl -I

Cl 2 + 2NaOH (cold) \u003d NaClO + NaCl + H 2 O

3Cl 2 + 6NaOH (hor) \u003d NaClO 3 + 5NaCl + H 2 O

A solution of chlorine in water is called chlorine water, in the light, the acid HClO decomposes into HCl and atomic oxygen O 0, therefore "chlorine water" must be stored in a dark bottle. The presence of HClO acid in "chlorine water" and the formation of atomic oxygen explain its strong oxidizing properties: for example, many dyes become discolored in wet chlorine.

Chlorine is a very strong oxidizing agent in relation to metals and non-metals:

Сl 2 + 2Nа \u003d 2NаСl 2

ЗСl 2 + 2Fе → 2FеСl 3 (200 ° C)

Сl 2 + Se \u003d SeCl 4

Сl 2 + Pb → PbCl 2 (300 °FROM)

5Cl 2 + 2P → 2PCl 5 (90 ° C)

2Cl 2 + Si → SiCl 4 (340 ° C)

Reactions with compounds of other halogens:

a) Cl 2 + 2KBg (P) \u003d 2KSl + Br 2 (boiling)

b) Сl 2 (weeks) + 2КI (р) \u003d 2КСl + I 2 ↓

ЗСl (ex.) + 3Н 2 O + КI \u003d 6HCl + КIO 3 (80 ° C)

Qualitative reaction - interaction of CL 2 deficiency with KI (see above) and the detection of iodine by blue coloration after adding a starch solution.

Receiving chlorine in industry:

2NаСl (melt) → 2Nа + Сl 2 (electrolysis)

2NaCl + 2H 2 O → H 2 + Сl 2 + 2NаОН (electrolysis)

and in laboratories:

4HCl (conc.) + МnO 2 \u003d Сl 2 + МnСl 2 + 2Н 2 O

(similarly with the participation of other oxidizing agents; for more details, see reactions for HCl and NaCl).

Chlorine belongs to the products of the main chemical industry, is used to obtain bromine and iodine, chlorides and oxygen-containing derivatives, for bleaching paper, as a disinfectant for drinking water. Poisonous.

Hydrogen chloride HC l ... Anoxic acid. Colorless gas with a pungent odor, heavier than air. The molecule contains a covalent σ-bond Н - Сl. It is thermally stable. Let's very well dissolve in water; diluted solutions are called hydrochloric acid, and a fuming concentrated solution (35-38%) - hydrochloric acid (the name was given by alchemists). Strong acid in solution, neutralized with alkalis and ammonia hydrate. A strong reducing agent in a concentrated solution (due to Cl - I), a weak oxidizing agent in a dilute solution (due to H I). An integral part of the "aqua regia".

A qualitative reaction to the Cl - ion is the formation of white precipitates of AgCl and Hg 2 Cl 2, which are not transferred into solution by the action of dilute nitric acid.

Hydrogen chloride serves as a raw material in the production of chlorides, organochlorine products, it is used (in the form of a solution) for etching metals, decomposition of minerals and ores. Equations of the most important reactions:

НСl (dil.) + NaOH (dil.) \u003d NaСl + Н 2 O

НСl (dil.) + NH 3 Н 2 O \u003d NH 4 Сl + Н 2 O

4HCl (conc., Hot.) + MO 2 \u003d МСl 2 + Сl 2 + 2Н 2 O (M \u003d Mn, Pb)

16HCl (conc., Horizontal) + 2KMnO 4 (s) \u003d 2MnCl 2 + 5Cl 2 + 8H 2 O + 2KCl

14HCl (conc.) + К 2 Сr 2 O 7 (t) \u003d 2СrСl 3 + ЗСl 2 + 7Н 2 O + 2КСl

6HCl (conc.) + KClO 3 (T) \u003d KCl + 3Cl 2 + 3H 2 O (50-80 ° C)

4HCl (conc.) + Ca (ClO) 2 (t) \u003d CaCl 2 + 2Cl 2 + 2H 2 O

2HCl (dil.) + M \u003d МСl 2 + H 2 (M \u003d Pe, 2p)

2HCl (dil.) + MCO 3 \u003d MCl 2 + CO 2 + H 2 O (M \u003d Ca, Ba)

НСl (dil.) + АgNO 3 \u003d НNO 3 + АgСl ↓

Obtaining HCl in industry - combustion of H 2 in Cl 2 (see), in the laboratory - displacement from chlorides with sulfuric acid:

NaCl (t) + H 2 SO4 (conc.) \u003d NaHSO 4 + NSl (50 ° C)

2NaСl (t) + Н 2 SO 4 (conc.) \u003d Na 2 SO 4 + 2HCl(120 ° C)

Chlorides

Sodium chloride Na Сl ... Oxygen-free salt. Household name salt... White, slightly hygroscopic. Melts and boils without decomposition. Moderately soluble in water, solubility depends little on temperature, the solution has a characteristic salty taste. Does not undergo hydrolysis. Weak reducing agent. It enters into ion exchange reactions. Electrolyzed in melt and solution.

It is used to produce hydrogen, sodium and chlorine, soda, caustic soda and hydrogen chloride, as a component of cooling mixtures, food and preservative.

In nature, the main part of rock salt deposits, or haliteand sylvinite (together with KCl), brine from salt lakes, mineral impurities of sea water (NaCl content \u003d 2.7%). In industry, they are obtained by evaporation of natural brines.

Equations of the most important reactions:

2NаСl (t) + 2Н 2 SO 4 (conc.) + МnO 2 (т) \u003d Сl 2 + МnSO 4 + 2Н 2 O + Na 2 SO 4 (100 ° C)

10NаСl (t) + 8Н 2 SO 4 (conc.) + 2КМnO 4 (т) \u003d 5Сl 2 + 2МnSO 4 + 8Н 2 О + 5Nа 2 SO 4 + К 2 SO 4 (100 ° C)

6NaСl (Т) + 7Н 2 SO 4 (conc.) + К 2 Сr 2 O 7 (т) \u003d 3Сl 2 + Сr 2 (SO 4) 3 + 7Н 2 O + ЗNа 2 SO 4 + К 2 SO 4 (100 ° C)

2NаСl (t) + 4Н 2 SO 4 (conc.) + PbO 2 (t) \u003d Сl 2 + Pb (НSO 4) 2 + 2Н 2 O + 2NaНSO 4 (50 ° C)

NaСl (dil.) + АgNO 3 \u003d NaNО 3 + АgСl ↓

NaCl (l) → 2Na + Cl 2 (850 ° C, electrolysis)

2NаСl + 2Н 2 O → Н 2 + Сl 2 + 2NаОН (electrolysis)

2NаСl (р, 20%) → Сl 2 + 2 Na (Hg) "amalgam"(electrolysis, onHg-cathode)

Potassium chloride KCl ... Oxygen-free salt. White, non-absorbent. Melts and boils without decomposition. We will moderately dissolve in water, the solution has a bitter taste, there is no hydrolysis. It enters into ion exchange reactions. It is used as a potash fertilizer to obtain K, KOH and Cl 2. In nature, the main constituent part (along with NaCl) of deposits sylvinite.

The equations of the most important reactions are the same with those for NaCl.

Calcium chloride CaCl 2 ... Oxygen-free salt. White, melts without decomposition. Blurs in air due to vigorous absorption of moisture. Forms CaCl 2 6H 2 O crystalline hydrate with a dehydration temperature of 260 ° C. Let's well dissolve in water, no hydrolysis. It enters into ion exchange reactions. It is used for drying gases and liquids, preparing cooling mixtures. A component of natural waters, an integral part of their "constant" hardness.

Equations of the most important reactions:

CaCl 2 (T) + 2H 2 SO 4 (conc.) \u003d Ca (HSO 4) 2 + 2HCl (50 ° C)

CaCl 2 (T) + H 2 SO 4 (conc.) \u003d CaSO 4 ↓ + 2HCl (100 ° C)

CaCl 2 + 2NaOH (conc.) \u003d Ca (OH) 2 ↓ + 2NaCl

3CaCl 2 + 2Na 3 PO 4 \u003d Ca 3 (PO 4) 2 ↓ + 6NaCl

CaCl 2 + K 2 CO 3 \u003d CaCO 3 ↓ + 2KSl

CaCl 2 + 2NaF \u003d CaF 2 ↓ + 2NaCl

CaCl 2 (l) → Ca + Cl 2 (electrolysis, 800 ° C)

Receiving:

CaCO 3 + 2HCl \u003d CaCl 2 + CO 3 + H 2 O

Aluminum chloride AlCl 3 ... Oxygen-free salt. White, fusible, highly volatile. The pair consists of covalent monomers АlСl 3 (triangular structure, sp 2 hybridization, prevail at 440-800 ° С) and dimers Аl 2 Сl 6 (more precisely, Сl 2 АlСl 2 АlСl 2, structure - two tetrahedra with a common edge, sp 3 -hybridization, prevail at 183-440 ° C). It is hygroscopic, "smokes" in the air. Forms crystalline hydrate, which decomposes on heating. Let's well dissolve in water (with a strong exo-effect), completely dissociates into ions, creates a strongly acidic environment in solution due to hydrolysis. Reacts with alkalis, ammonia hydrate. Recovered by electrolysis of the melt. It enters into ion exchange reactions.

Qualitative reaction on the Al 3+ ion - the formation of a precipitate of AlPO 4, which is transferred into a solution with concentrated sulfuric acid.

It is used as a raw material in the production of aluminum, a catalyst in organic synthesis and in oil cracking, a carrier of chlorine in organic reactions. Equations of the most important reactions:

AlCl 3. 6Н 2 O → АlСl (ОН) 2 (100-200 ° C, -HCl, H 2 O) → Al 2 O 3 (250-450 ° C,-HCl, H2O)

AlCl 3 (t) + 2H 2 O (moisture) \u003d AlCl (OH) 2 (t) + 2HCl (White smoke")

АlCl 3 + ЗNаОН (dil.) \u003d Аl (OH) 3 (amorph.) ↓ + ЗNаСl

АlСl 3 + 4NаОН (conc.) \u003d Na [Аl (ОН) 4] + ЗNаСl

АlСl 3 + 3 (NH 3. Н 2 O) (conc.) \u003d Аl (ОН) 3 (amorphous) + ЗNН 4 Сl

АlCl 3 + 3 (NH 3 Н 2 O) (conc.) \u003d Аl (ОН) ↓ + ЗNН 4 Сl + Н 2 O (100 ° C)

2Аl 3+ + 3Н 2 O + ЗСО 2- 3 \u003d 2Аl (ОН) 3 ↓ + ЗСО 2 (80 ° C)

2Аl 3+ \u003d 6H 2 O + 3S 2- \u003d 2Аl (OH) 3 ↓ + 3H 2 S

Al 3+ + 2HPO 4 2- - AlPO 4 ↓ + H 2 PO 4 -

2АlСl 3 → 2Аl + 3Сl 2 (electrolysis, 800 ° C ,in the meltNaCl)

Receiving АlСl in industryand - chlorination of kaolin, alumina or bauxite in the presence of coke:

Al 2 O 3 + 3С (coke) + 3Сl 2 \u003d 2АlСl 3 + 3СО (900 ° C)

Ferric chloride ( II ) F eC l 2 ... Oxygen-free salt. White (blue-green hydrate), hygroscopic. Melts and boils without decomposition. At strong heating, volatile in the HCl flow. The Fe - Cl bonds are predominantly covalent; the pair consists of FeCl 2 monomers (linear structure, sp-hybridization) and Fe 2 Cl 4 dimers. Sensitive to atmospheric oxygen (darkens). Let's well dissolve in water (with a strong exo-effect), completely dissociates into ions, weakly hydrolyzes by cation. When boiled, the solution decomposes. Reacts with acids, alkalis, ammonia hydrate. Typical reducing agent. It enters into reactions of ion exchange and complexation.

It is used for the synthesis of FeCl and Fe 2 O 3, as a catalyst in organic synthesis, a component of drugs against anemia.

Equations of the most important reactions:

FeCl 2 4H 2 O \u003d FeCl 2 + 4H 2 O (220 ° С, in atm.N 2 )

FeCl 2 (conc.) + H 2 O \u003d FeCl (OH) ↓ + HCl (boiling)

FeCl 2 (t) + H 2 SO 4 (conc.) \u003d FeSO 4 + 2HCl (boiling)

FeCl 2 (t) + 4HNO 3 (conc.) \u003d Fe (NO 3) 3 + NO 2 + 2HCl + H 2 O

FеСl 2 + 2NаОН (dil.) \u003d Fе (ОН) 2 ↓ + 2NaСl (in atm.N 2 )

FeCl 2 + 2 (NH 3. H 2 O) (conc.) \u003d Fe (OH) 2 ↓ + 2NH 4 Cl (80 ° C)

FeCl 2 + H 2 \u003d 2HCl + Fe (extra pure, above 500 ° С)

4FеСl 2 + O 2 (air) → 2Fе (Сl) O + 2FеСl 3 (t)

2FеСl 2 (р) + Сl 2 (ex.) \u003d 2FеСl 3 (р)

5Fе 2+ + 8Н + + МnО - 4 \u003d 5Fе 3+ + Мn 2+ + 4Н 2 O

6Fе 2+ + 14Н + + Сr 2 O 7 2- \u003d 6Fе 3+ + 2Сr 3+ + 7Н 2 O

Fе 2+ + S 2- (split) \u003d FеS ↓

2Fе 2+ + H 2 O + 2CO 3 2- (dil.) \u003d Fe 2 CO 3 (OH) 2 ↓ + CO 2

FеСl 2 → Fe ↓ + Сl 2 (90 ° С, broken. НСl, electrolysis)

Receivinge: interaction of Fe with hydrochloric acid:

Fe + 2HCl \u003d FeCl 2+ H 2

(in industry use hydrogen chloride and conduct the process at 500 ° C).

Ferric chloride ( III ) F eC l 3 ... Oxygen-free salt. Black-brown (dark red in transmitted light, green in reflected light), dark yellow hydrate. When melted, it turns into a red liquid. Very volatile, decomposes on strong heating. Fe - Cl bonds are predominantly covalent. The vapor consists of monomers FeCl 3 (triangular structure, sp 2 -hybridization, prevailing above 750 ° C) and dimers of Fe 2 Cl 6 (more precisely, Cl 2 FeCl 2 FeCl 2, structure - two tetrahedra with a common edge, sp 3 -hybridization, prevail at 316-750 ° C). Crystalline hydrate FeCl. 6Н 2 O has the structure Сl 2Н 2 O. Well soluble in water, the solution is yellow; strongly cationically hydrolyzed. Decomposes in hot water, reacts with alkalis. Weak oxidizing and reducing agent.

It is used as a chlorine agent, a catalyst in organic synthesis, a mordant for dyeing fabrics, a coagulant for purifying drinking water, an etchant for copper plates in electroforming, a component of hemostatic drugs.

Equations of the most important reactions:

FеСl 3 6Н 2 O \u003d Сl + 2Н 2 O (37 ° C)

2 (FeCl 8 6H 2 O) \u003d Fe 2 O 3 + 6HCl + 9H 2 O (above 250 ° C)

FeCl 3 (10%) + 4Н 2 O \u003d Сl - + + (yellow)

2FеСl3 (conc.) + 4Н 2 O \u003d + (yellow) + - (bts.)

FeCl 3 (dil., Conc.) + 2H 2 O → FeCl (OH) 2 ↓ + 2HCl (100 ° C)

FeCl 3 + 3NaOH (dil.) \u003d FeO (OH) ↓ + H 2 O + 3NaCl (50 ° C)

FeCl 3 + 3 (NH 3 H 2 O) (conc, hot) \u003d FeO (OH) ↓ + H 2 O + 3NH 4 Cl

4FеСl 3 + 3O 2 (air) \u003d 2Fе 2 O 3 + 3Сl 2 (350-500 ° C)

2FеСl 3 (р) + Сu → 2FеСl 2 + СuСl 2

Ammonium Chloride N H 4 Cl ... Oxygen-free salt, the technical name is ammonia. White, volatile, thermally unstable. Let's well dissolve in water (with a noticeable endo-effect, Q \u003d -16 kJ), hydrolyzed by cation. It decomposes with alkalis when the solution is boiled, transfers magnesium and magnesium hydroxide into solution. Enters into the reaction of conjugation with nitrates.

Qualitative reactionfor NH 4 + ion - the release of NH 3 when boiling with alkalis or when heated with slaked lime.

It is used in inorganic synthesis, in particular to create a weakly acidic environment, as a component of nitrogen fertilizers, dry galvanic cells, when brazing copper and tinning steel products.

Equations of the most important reactions:

NH 4 Cl (s) ⇌ NH 3 (g) + HCl (g) (above 337.8 ° C)

NH 4 Cl + NaOH (sat.) \u003d NaCl + NH 3 + H 2 O (100 ° C)

2NH 4 Cl (T) + Ca (OH) 2 (t) \u003d 2NH 3 + CaCl 2 + 2H 2 O (200 ° C)

2NН 4 Сl (conc.) + Mg \u003d Н 2 + МgСl 2 + 2NН 3 (80 ° C)

2NН 4 Сl (conc., Hot.) + Мg (ОН) 2 \u003d MgСl 2 + 2NН 3 + 2Н 2 O

NH + (sat.) + NO - 2 (sat.) \u003d N 2 + 2H 2 O (100 ° C)

NH 4 Cl + KNO 3 \u003d N 2 O + 2H 2 O + KCl (230-300 ° C)

Receiving: interaction of NH 3 with HCl in the gas phase or NH 3 H 2 O with HCl in solution.

Calcium hypochlorite Ca (C l O) 2 ... Hypochlorous acid salt HClO. White, decomposes on heating without melting. Let's well dissolve in cold water (colorless solution is formed), hydrolyzed by anion. Reactive, completely decomposed by hot water, acids. Strong oxidizing agent. When standing, the solution absorbs carbon dioxide from the air. Is an active component chlorine (bleaching) lime -mixtures of undefined composition with CaCl 2 and Ca (OH) 2. Equations of the most important reactions:

Ca (ClO) 2 \u003d CaCl 2 + O 2 (180 ° C)

Ca (ClO) 2 (t) + 4Hcl (conc.) \u003d CaCl + 2Cl 2 + 2H 2 O (80 ° C)

Ca (ClO) 2 + H 2 O + CO 2 \u003d CaCO 3 ↓ + 2HClO (in the cold)

Ca (ClO) 2 + 2H 2 O 2 (dil.) \u003d CaCl 2 + 2H 2 O + 2O 2

Receiving:

2Ca (OH) 2 (suspension) + 2Cl 2 (g) \u003d Ca (ClO) 2 + CaCl 2 + 2H 2 O

Potassium chlorate KS lO 3 ... Salt of chloric acid HClO 3, the best known salt of oxygenated chlorine acids. Technical name - berthollet's salt (named after its discoverer K.-L. Berthollet, 1786). White, melts without decomposition, decomposes upon further heating. Let's well dissolve in water (a colorless solution is formed), there is no hydrolysis. Decomposes with concentrated acids. Strong oxidizing agent when fusing.

It is used as a component of explosive and pyrotechnic mixtures, match heads, in the laboratory - a solid source of oxygen.

Equations of the most important reactions:

4KSlO 3 \u003d 3KSlO 4 + KCl (400 ° C)

2KSlO 3 \u003d 2KSl + 3O 2 (150-300 ° C, cat.MpO 2 )

KClO 3 (T) + 6HCl (conc.) \u003d KCl + 3Cl 2 + ЗН 2 O (50-80 ° C)

3КСlO 3 (Т) + 2Н 2 SO 4 (conc., Hot.) \u003d 2СlO 2 + КСlO 4 + Н 2 O + 2КНSO 4

(chlorine dioxide explodes in the light: 2ClO 2 (D) \u003d Сl 2 + 2O 2 )

2KClO 3 + E 2 (ex.) \u003d 2KEO 3 + Cl 2 (in part NNO 3 , E \u003d Br, I)

KClO 3 + H 2 O → H 2 + KClO 4 (Electrolysis)

Receiving KClO 3 in industry - electrolysis of a hot KCl solution (the KClO 3 product is released at the anode):

КСl + 3Н 2 O → Н 2 + КСlO 3 (40-60 ° C, Electrolysis)

Potassium bromide KB r ... Oxygen-free salt. White, non-hygroscopic, melts without decomposition. Let's well dissolve in water, no hydrolysis. Reducing agent (weaker than

Qualitative reaction for Br ion - displacement of bromine from KBr solution with chlorine and extraction of bromine into an organic solvent, for example, CCl 4 (as a result, the aqueous layer becomes discolored, the organic layer turns brown).

It is used as a component of etchants for metal engraving, a component of photographic emulsions, and a medicine.

Equations of the most important reactions:

2KBr (t) + 2H 2 SO 4 (CONC., Hor.) + MnO 2 (t) \u003d Br 2 + MnSO 4 + 2H 2 O + K 2 SO 4

5Вr - + 6Н + + ВrО 3 - \u003d 3Вr 2 + 3Н 2 O

Вr - + Аg + \u003d АgВr ↓

2KBr (p) + Cl 2 (G) \u003d 2KCl + Br 2 (p)

KBr + 3H 2 O → 3H 2 + KBrO 3 (60-80 ° C, electrolysis)

Receiving:

K 2 CO 3 + 2HBr \u003d 2KVr + CO 2 + H 2 O

Potassium iodide K I ... Oxygen-free salt. White, non-absorbent. It turns yellow when stored in light. Let's well dissolve in water, no hydrolysis. Typical reducing agent. An aqueous solution of KI dissolves I 2 well due to complexation.

High qualitythe reaction to ion I is the displacement of iodine from the KI solution by a lack of chlorine and the extraction of iodine into an organic solvent, for example, CCl 4 (as a result, the aqueous layer becomes discolored, the organic layer turns violet).

Equations of the most important reactions:

10I - + 16H + + 2MnO 4 - \u003d 5I 2 ↓ + 2Mn 2+ + 8H 2 O

6I - + 14Н + + Сr 2 O 7 2- \u003d 3I 2 ↓ + 2Сr 3+ + 7Н 2 O

2I - + 2H + + H 2 O 2 (3%) \u003d I 2 ↓ + 2H 2 O

2I - + 4H + + 2NO 2 - \u003d I 2 ↓ + 2NO + 2H 2 O

5I - + 6H + + IO 3 - \u003d 3I 2 + 3H 2 O

I - + Аg + \u003d АgI (yellow.) ↓

2КI (р) + Сl 2 (р) (weeks) \u003d 2КСl + I 2 ↓

KI + 3H 2 O + 3Cl 2 (p) (ex) \u003d KIO 3 + 6HCl (80 ° C)

KI (P) + I 2 (t) \u003d K) (P) (short) ("Iodine water")

KI + 3H 2 O → 3H 2 + KIO 3 (electrolysis, 50-60 ° C)

Receiving:

K 2 CO 3 + 2HI \u003d 2 CI + CO 2 + H 2 O

Kuzbass State Technical University

Course work

BJD subject

Characterization of chlorine as an emergency chemically hazardous substance

Kemerovo-2009

Introduction

1. Characteristics of hazardous substances (according to the issued assignment)

2. Ways to prevent accidents, protection from hazardous chemicals

3. Task

4. Calculation of the chemical situation (according to the issued assignment)

Conclusion

Literature

Introduction

In total, there are 3,300 economic facilities in Russia with significant reserves of hazardous chemicals. More than 35% of them have choir reserves.

Chlorine (lat. Chlorum), Cl - chemical element VII of group of Mendeleev's periodic system, atomic number 17, atomic mass 35.453; belongs to the halogen family.

Chlorine is also used for chlorination some oto rykh ores for the purpose and attraction of titanium, niobium, zirconium and others.

Poisoning chlorine are possible in the chemical, pulp and paper, textile, pharmaceutical industries. Chlorine irritates the mucous membranes of the eyes and respiratory tract. A secondary infection usually joins the primary inflammatory changes. Acute poisoning develops almost immediately. When medium and low concentrations of chlorine are inhaled, chest tightness and pain, dry cough, rapid breathing, pain in the eyes, lacrimation, an increase in the content of leukocytes in the blood, body temperature, etc. are noted. Bronchopneumonia, toxic pulmonary edema, depressive conditions, convulsions are possible ... In mild cases, recovery occurs within 3 to 7 days. Catarrh of the upper respiratory tract, recurrent bronchitis, pneumosclerosis are observed as long-term consequences; possible activation of pulmonary tuberculosis. With prolonged inhalation of low concentrations of chlorine, similar, but slowly developing forms of the disease are observed. Prevention of poisoning, sealing of production facilities, equipment, effective ventilation, if necessary, use of a gas mask. The maximum permissible concentration of chlorine in the air of production facilities, premises is 1 mg / m 3. The production of chlorine, bleach and other chlorine-containing compounds belongs to industries with hazardous working conditions.

In the west of Flanders lies a tiny town. Nevertheless, its name is known to the whole world and will remain for a long time in the memory of mankind as a symbol of one of the greatest crimes against humanity. This town is Ypres. Kresi (at the Battle of Kresi in 1346, British troops used firearms for the first time in Europe.) - Ypres - Hiroshima - milestones on the way of turning the war into a gigantic destruction machine.

At the beginning of 1915, the so-called Ypres salient formed on the line of the western front. Allied Anglo-French forces northeast of Ypres wedged into the territory occupied by the German army. The German command decided to launch a counterattack and align the front line. On the morning of April 22, when the flat northeast was blowing, the Germans began unusual preparations for the offensive - they conducted the first gas attack in the history of war. On the Ypresky sector of the front, 6,000 chlorine cylinders were simultaneously opened. Within five minutes, a huge, 180 tonne, poisonous yellow-green cloud formed, which slowly moved towards the enemy trenches.

Nobody expected this. The troops of the French and British were preparing for an attack, for artillery fire, the soldiers dug in securely, but they were completely unarmed in front of the destructive chlorine cloud. The deadly gas penetrated into all cracks, into all shelters. The results of the first chemical attack (and the first violation of the 1907 Hague Convention on the Non-Use of Poisonous Substances!) Were overwhelming - chlorine struck about 15 thousand people, and about 5 thousand - to death. And all this - in order to align the front line 6 km long! Two months later, the Germans launched a chlorine attack on the eastern front. And two years later, Ypres increased his notoriety. During a heavy battle on July 12, 1917, a poisonous substance was first used in the area of \u200b\u200bthis city, later called mustard gas. Mustard gas is a chlorine derivative, dichlorodiethyl sulfide.

We recalled these episodes of history, connected with one small town and one chemical element, in order to show how dangerous element 17 can be in the hands of militant madmen. This is the darkest page in chlorine history.

But it would be completely wrong to see in chlorine only a toxic substance and raw material for the production of other toxic substances ...

Chlorine history

The history of elemental chlorine is relatively short; it dates back to 1774. The history of chlorine compounds is as old as the world. Suffice it to recall that sodium chloride is table salt. And, apparently, even in prehistoric times, the ability of salt to preserve meat and fish was noticed.

The most ancient archaeological finds - evidence of the use of salt by humans date back to about 3 ... 4 millennium BC. And the most ancient description of rock salt mining is found in the writings of the Greek historian Herodotus (5th century BC). Herodotus describes the mining of rock salt in Libya. The famous temple of the god Ammon-Ra was located in the Sinah oasis in the center of the Libyan desert. That is why Libya was called "Ammonia", and the first name for rock salt was "sal ammoniacum". Later, starting from about the XIII century. AD, this name was assigned to ammonium chloride.

Pliny the Elder's Natural History describes a method for separating gold from base metals by calcining with salt and clay. And one of the first descriptions of the purification of sodium chloride is found in the works of the great Arab physician and alchemist Jabir ibn-Hayyan (in the European spelling - Geber).

It is very likely that alchemists also encountered elemental chlorine, since in the countries of the East already in the IX, and in Europe in the XIII century. was known "royal vodka" - a mixture of hydrochloric and nitric acids. In the book "Hortus Medicinae" by the Dutchman Van Helmont, published in 1668, it is said that when ammonium chloride and nitric acid are heated together, a kind of gas is obtained. From the description, this gas is very similar to chlorine.

Chlorine was first described in detail by the Swedish chemist Scheele in his treatise on pyrolusite. Heating the pyrolusite mineral with hydrochloric acid, Scheele noticed a smell characteristic of aqua regia, collected and investigated the yellow-green gas that generated this smell, and studied its interaction with certain substances. Scheele was the first to discover the effect of chlorine on gold and cinnabar (in the latter case, mercuric chloride is formed) and the bleaching properties of chlorine.

Scheele did not consider the newly discovered gas a simple substance and called it "deflogistonized hydrochloric acid". In modern terms, Scheele, and after him other scientists of that time, believed that the new gas was hydrochloric acid oxide.

Somewhat later, Berthollet and Lavoisier proposed to consider this gas as an oxide of some new element "muria". For three and a half decades, chemists have tried unsuccessfully to isolate the unknown muri.

At first, Davy was also a supporter of "muria oxide", who in 1807 electrically decomposed table salt into an alkali metal sodium and a yellow-green gas. However, three years later, after many fruitless attempts to obtain muria, Davy came to the conclusion that the gas discovered by Scheele was a simple substance, an element, and named it chloric gas or chlorine (from the Greek χλωροζ - yellow-green). And three years later, Gay-Lussac gave the new element a shorter name - chlorine. True, back in 1811 the German chemist Schweiger proposed another name for chlorine - "halogen" (literally it translates as soleod), but this name did not take root at first, but later became common for a whole group of elements, which includes chlorine.

Chlorine "personal card"

At least a dozen answers can be given to the question of what is chlorine. First, it is halogen; secondly, one of the strongest oxidizing agents; thirdly, an extremely poisonous gas; fourth, the most important product of the main chemical industry; fifth, raw materials for the production of plastics and pesticides, rubber and artificial fibers, dyes and medicines; sixth, the substance with which titanium and silicon, glycerin and fluoroplastic are obtained; seventh, a product for purifying drinking water and bleaching fabrics ...

This listing could be continued.

Under normal conditions, elemental chlorine is a rather heavy yellow-green gas with a pungent characteristic odor. The atomic weight of chlorine is 35.453, and the molecular weight is 70.906, because the chlorine molecule is diatomic. One liter of gaseous chlorine under normal conditions (temperature 0 ° C and pressure 760 mm Hg) weighs 3.214 g. When cooled to a temperature of -34.05 ° C, chlorine condenses into a yellow liquid (density 1.56 g / cm 3), and at a temperature of - 101.6 ° C it hardens. At elevated pressures, chlorine can be transformed into a liquid at higher temperatures up to + 144 ° C. Chlorine is readily soluble in dichloroethane and some other chlorine-containing organic solvents.

Element 17 is very active - it directly connects with almost all elements of the periodic table. Therefore, in nature, it is found only in the form of compounds. The most common minerals containing chlorine are halite NaCI, sylvinite KCl · NaCl, bischofite MgCl 2 · 6H 2 O, carnallite KCl · MgCl 2 · 6H 2 O, kainite KCl · MgSO 4 · 3H 2 O. These are primarily “wines "(Or" merit ") that the chlorine content in the earth's crust is 0.20% by weight. For non-ferrous metallurgy, some relatively rare chlorine-containing minerals are very important, for example, horny silver AgCl.

In terms of electrical conductivity, liquid chlorine ranks among the strongest insulators: it conducts current almost a billion times worse than distilled water, and 10 22 times worse than silver.

The speed of sound in chlorine is about one and a half times less than in air.

And finally - about chlorine isotopes.

Nine isotopes of this element are now known, but only two are found in nature - chlorine-35 and chlorine-37. The first is about three times more than the second.

The remaining seven isotopes are produced artificially. The shortest-lived of them - 32 Cl - has a half-life of 0.306 seconds, and the longest-lived - 36 Cl - 310 thousand years.

How chlorine is obtained

The first thing you pay attention to when you get to the chlorine plant is the numerous power lines. Chlorine production consumes a lot of electricity - it is needed in order to decompose natural chlorine compounds.

Naturally, the main raw material for chlorine is rock salt. If the chlorine plant is located near the river, then the salt is delivered not by rail, but by barges - this is more economical. Salt is an inexpensive product, but a lot of it is consumed: to get a ton of chlorine, you need about 1.7 ... 1.8 tons of salt.

Salt goes to warehouses. Three - six months' stocks of raw materials are stored here - chlorine production is usually large-scale.

Salt is crushed and dissolved in warm water. This brine is pumped through a pipeline to the cleaning shop, where in huge tanks the height of a three-story building, the brine is cleaned from impurities of calcium and magnesium salts and clarified (allowed to settle). A pure concentrated solution of sodium chloride is pumped to the main chlorine production shop - to the electrolysis shop.

In an aqueous solution, sodium chloride molecules are converted into Na + and Cl - ions. The Cl ion - differs from the chlorine atom only in that it has one extra electron. This means that in order to obtain elementary chlorine, it is necessary to tear off this extra electron. This happens in an electrolyzer on a positively charged electrode (anode). It is as if electrons are “sucked off” from it: 2Cl - → Cl 2 + 2ē. Anodes are made of graphite, because any metal (except platinum and its analogs), taking away excess electrons from chlorine ions, quickly corrodes and breaks down.

There are two types of technological design for chlorine production: diaphragm and mercury. In the first case, a perforated iron sheet serves as the cathode, and the cathode and anode spaces of the electrolyzer are separated by an asbestos diaphragm. At the iron cathode, a discharge of hydrogen ions occurs and an aqueous solution of sodium hydroxide is formed. If mercury is used as a cathode, then sodium ions are discharged on it and sodium amalgam is formed, which is then decomposed by water. Hydrogen and caustic soda are obtained. In this case, a diaphragm seal is not needed, and the alkali is more concentrated than in diaphragm cells.

So, the production of chlorine is at the same time the production of caustic soda and hydrogen.

Hydrogen is removed through metal pipes and chlorine through glass or ceramic pipes. Freshly prepared chlorine is saturated with water vapor and is therefore especially aggressive. Subsequently, it is first cooled with cold water in tall towers lined with ceramic tiles from the inside and filled with ceramic nozzles (the so-called Raschig rings), and then dried with concentrated sulfuric acid. It is the only chlorine desiccant and one of the few liquids that chlorine does not interact with.

Dry chlorine is no longer as aggressive, it does not destroy, for example, steel equipment.

Chlorine is usually transported in a liquid state in railway tanks or cylinders under pressure up to 10 atm.

In Russia, chlorine production was first organized back in 1880 at the Bondyuzhsky plant. Chlorine was then obtained in principle in the same way as Scheele obtained it in due time - by the interaction of hydrochloric acid with pyrolusite. All of the chlorine produced was used to obtain bleach. In 1900, for the first time in Russia, a chlorine electrolytic production shop was put into operation at the Donsoda plant. The capacity of this shop was only 6 thousand tons per year. In 1917, all chlorine plants in Russia produced 12 thousand tons of chlorine. And in 1965, the USSR produced about 1 million tons of chlorine ...

One of many

All the variety of practical uses of chlorine can be expressed without much straining in one phrase: chlorine is necessary for the production of chlorine products, i.e. substances containing "bound" chlorine. But speaking about these very chlorine products, you can't get off with one phrase. They are very different - both in properties and in purpose.

The limited volume of our article does not allow us to tell about all chlorine compounds, but without a story about at least some of the substances for which chlorine is needed, our "portrait" of element No. 17 would be incomplete and unconvincing.

Take, for example, organochlorine insecticides - substances that kill harmful insects, but are safe for plants. A significant part of the chlorine produced is consumed to obtain plant protection products.

One of the most important insecticides is hexachlorocyclohexane (often called hexachloran). This substance was first synthesized back in 1825 by Faraday, but found practical application only after more than 100 years - in the 30s of our century.

Now hexachlorane is obtained by chlorinating benzene. Like hydrogen, benzene reacts very slowly with chlorine in the dark (and in the absence of catalysts), but in bright light, the chlorination reaction of benzene (С 6 Н 6 + 3Сl 2 → С 6 Н 6 Сl 6) proceeds rather quickly.

Hexachloran, like many other insecticides, is used in the form of dusts with fillers (talc, kaolin), or in the form of suspensions and emulsions, or, finally, in the form of aerosols. Hexachloran is especially effective in seed dressing and pest control of vegetable and fruit crops. The consumption of hexachlorane is only 1 ... 3 kg per hectare, the economic effect of its use is 10 ... 15 times higher than the costs. Unfortunately, hexachloran is not harmless to humans ...

Polyvinyl chloride

If you ask any student to list the plastics known to him, he will be one of the first to name polyvinyl chloride (otherwise, vinyl plastic). From the point of view of a chemist, PVC (as polyvinyl chloride is often denoted in the literature) is a polymer in a molecule of which hydrogen and chlorine atoms are strung on a chain of carbon atoms:

There can be several thousand links in this chain.

And from a consumer point of view, PVC is insulation for wires and raincoats, linoleum and phonograph records, protective varnishes and packaging materials, chemical equipment and foams, toys and device parts.

Polyvinyl chloride is formed during the polymerization of vinyl chloride, which is most often obtained by treating acetylene with hydrogen chloride: HC ≡ CH + HCl → CH 2 \u003d CHCl. There is another way to obtain vinyl chloride - thermal cracking of dichloroethane.

CH 2 Cl - CH 2 Cl → CH 2 \u003d CHCl + HCl. Of interest is the combination of these two methods, when in the production of vinyl chloride by the acetylene method, HCl is used, which is released during the cracking of dichloroethane.

Vinyl chloride is a colorless gas with a pleasant, somewhat heady, ethereal odor that polymerizes easily. To obtain a polymer, liquid vinyl chloride is injected under pressure into warm water, where it is crushed into tiny droplets. To prevent them from merging, a little gelatin or polyvinyl alcohol is added to the water, and in order to start the polymerization reaction, the initiator of polymerization, benzoyl peroxide, is also introduced there. After a few hours, the droplets solidify and a suspension of the polymer in water forms. The polymer powder is separated on a filter or centrifuge.

Polymerization usually takes place at a temperature of 40 to 60 ° C, and the lower the polymerization temperature, the longer the resulting polymer molecules ...

We talked about only two substances for which you need element number 17. Only about two out of many hundreds. There are a lot of similar examples. And they all say that chlorine is not only a poisonous and dangerous gas, but a very important, very useful element.

Elementary calculation

When chlorine is obtained by electrolysis of a solution of common salt, hydrogen and sodium hydroxide are simultaneously obtained: 2NACl + 2H 2 O \u003d H 2 + Cl 2 + 2NaOH. Of course, hydrogen is a very important chemical product, but there are cheaper and more convenient ways of producing this substance, for example, natural gas conversion ... But caustic soda is obtained almost exclusively by electrolysis of sodium chloride solutions - other methods account for less than 10%. Since the production of chlorine and NaOH is completely interconnected (as follows from the reaction equation, the production of one gram-molecule - 71 g of chlorine - is invariably accompanied by the production of two gram-molecules - 80 g of electrolytic alkali), knowing the productivity of the workshop (or plant, or the state) for alkali , you can easily calculate how much chlorine it produces. Each ton of NaOH is "accompanied" by 890 kg of chlorine.

What a lubricant!

Concentrated sulfuric acid is practically the only liquid that does not interact with chlorine. Therefore, for the compression and pumping of chlorine in factories, pumps are used in which sulfuric acid plays the role of a working fluid and at the same time a lubricant.

Friedrich Wöhler's pseudonym

Investigating the interaction of organic substances with chlorine, the French chemist of the 19th century. Jean Dumas made an amazing discovery: chlorine is able to replace hydrogen in the molecules of organic compounds. For example, in the chlorination of acetic acid, first one hydrogen of the methyl group is replaced by chlorine, then another, a third ... But the most striking thing was that in terms of chemical properties, chloroacetic acids differed little from acetic acid itself. The class of reactions discovered by Dumas was completely inexplicable by the electrochemical hypothesis and the theory of Berzelius' radicals that dominated at that time (in the words of the French chemist Laurent, the discovery of chloroacetic acid was like a meteor that destroyed the entire old school). Berzelius, his students and followers vigorously disputed the correctness of Dumas's work. In the German magazine "Annalen der Chemie und Pharmacie" there was a mocking letter from the famous German chemist Friedrich Wöhler under the pseudonym S.S.N. Windier (in German "Schwindler" means "liar", "deceiver"). It reported that the author was able to replace all carbon atoms in the cellulose (C 6 H 10 O 5). hydrogen and oxygen to chlorine, and the properties of fiber have not changed. And that now in London they make warm abdomens from cotton wool, consisting of ... pure chlorine.

Chlorine and water

Chlorine dissolves noticeably in water. At 20 ° C, 2.3 volumes of chlorine are dissolved in one volume of water. Aqueous solutions of chlorine (chlorine water) - yellow. But over time, especially when stored in the light, they gradually fade. This is explained by the fact that dissolved chlorine partially interacts with water, hydrochloric and hypochlorous acids are formed: Cl 2 + H 2 O → HCl + HOCl. The latter is unstable and gradually decomposes into HCl and oxygen. Therefore, the chlorine solution in water gradually turns into a hydrochloric acid solution.

But at low temperatures chlorine and water form a crystalline hydrate of an unusual composition - Cl 2 · 5 3/4 H 2 O. These greenish-yellow crystals (stable only at temperatures below 10 ° C) can be obtained by passing chlorine through ice water. The unusual formula is explained by the structure of the crystalline hydrate, and it is primarily determined by the structure of ice. In the crystal lattice of ice, H2O molecules can be located in such a way that regularly spaced voids appear between them. The unit cubic cell contains 46 water molecules, between which there are eight microscopic voids. Chlorine molecules settle in these voids. The exact formula of chlorine crystalline hydrate should therefore be written as follows: 8Cl 2 46H 2 O.

Chlorine poisoning

The presence of about 0.0001% chlorine in the air is irritating to the mucous membranes. Constant stay in such an atmosphere can lead to bronchial disease, dramatically impairs appetite, and gives a greenish tint to the skin. If the chlorine content in the air is 0.1 ° / o, then acute poisoning may occur, the first sign of which is attacks of severe coughing. In case of chlorine poisoning, absolute rest is necessary; it is useful to inhale oxygen, or ammonia (smelling ammonia), or a pair of alcohol with ether. According to the existing sanitary standards, the chlorine content in the air of industrial premises should not exceed 0.001 mg / l, i.e. 0.00003%.

Not just poison

"Everyone knows that wolves are greedy." That chlorine is poisonous too. However, in small doses, toxic chlorine can sometimes serve as an antidote. So, victims of hydrogen sulfide are given to sniff unstable bleach. By interacting, the two poisons are mutually neutralized.

Chlorine analysis

To determine the chlorine content, an air sample is passed through absorbers with an acidified solution of potassium iodide. (Chlorine displaces iodine, the amount of the latter is easily determined by titration with a solution of Na 2 S 2 O 3). To determine the trace amounts of chlorine in the air, a colorimetric method is often used, based on a sharp change in the color of some compounds (benzidine, orthotoluidine, methyl orange) during their oxidation with chlorine. For example, a colorless acidified solution of benzidine becomes yellow, and neutral - blue. The color intensity is proportional to the amount of chlorine.

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At present, anodes made of titanium dioxide modified with platinum metal oxides, primarily with ruthenium dioxide RuO 2, are considered the "gold standard" of anodes for chlorine production. Ruthenium-titanium oxide anodes (ORTA) are known in the English literature under the names MMO (mixed metal oxide) or DSA (dimensionally stable anode). A doped titanium dioxide film is produced directly on the surface of a titanium metal substrate. Despite the high cost, ORTA has undeniable advantages over graphite anodes:

Several times higher permissible current density makes it possible to reduce the size of the equipment;
- there are practically no products of corrosion of the anode, which greatly simplifies the cleaning of the electrolyte;
- anodes have excellent corrosion resistance, are able to operate in industrial conditions for more than a year without replacement (repair).

For the manufacture of chlorine production anodes, perspectives and other materials. However, this is a topic for a separate (and large) publication. - Ed.

Due to the toxicity and high cost of mercury, the third variant of electrolyzers is actively developing - membrane electrolysers, which is currently the main one in developed countries. In this version, the cathode and anode spaces are separated by an ion-exchange membrane, which is permeable to sodium ions, but does not allow anions to pass through. At the same time, as in the mercury process, chloride contamination of the alkaline catholyte is excluded.

The material for the manufacture of membranes for chlorine production is Nafion, an ionomer based on polytetrafluoroethylene with grafted groups of perfluorovinylsulfonic ether. Developed in the 1960s by DuPont, this material has excellent chemical, thermal and mechanical resistance and satisfactory conductivity. Until now, it remains the material of choice in the construction of many electrochemical installations. - Ed.

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

How this item was discovered

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

After 2 years, his Swedish colleague Karl Scheele was able to describe a method for the isolation of Cl using a reaction between hydrochloric acid and manganese dioxide. However, this chemist did not understand that a new chemical element was synthesized as a result.

It took scientists almost 40 years to learn how to extract chlorine in practice. This was first done by the Briton Humphrey Davy in 1811. In doing so, he used a different reaction than his theoretical predecessors. Davy, using electrolysis, decomposed NaCl (known to most as kitchen salt).

Having studied the resulting substance, the British chemist realized that it was elementary. After this discovery, Davy not only called 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 \u200b\u200btoday. In English to this day the name "chlorin" is used, and in Italian and Spanish "chloro".

The element under consideration 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 the Greek word χλωρός (green). It was given because of the yellowish-greenish color of this substance.

Chlorine independently exists as a diatomic gas Cl 2, but it practically does not occur in this form in nature. More often it appears in various compounds.

In addition to its distinctive shade, chlorine has a sweetish acrid odor. It is a very toxic substance, therefore, if it enters the air and inhales it by humans or animals, it can lead to their death within a few minutes (depends on the concentration of Cl).

Since chlorine is almost 2.5 times heavier than air, it will always be below it, that is, at the very 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 other toxic substances, chlorine-containing substances have a characteristic color, which can allow them to be visually identified and taken action. Most standard gas masks help protect the respiratory system and mucous membranes from Cl damage. However, for complete safety, you need to take more serious measures, up to the neutralization of the poisonous substance.

It should be noted that it was with the use of chlorine by the Germans as a poisonous gas in 1915 that chemical weapons began their history. 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 produced annually in millions of tons? It's all about its special properties, and in order to understand them, it is worth considering the characteristics of chlorine. The easiest way to do this is using the periodic table.

Chlorine characteristics in the periodic system

Chlorine as halogen

In addition to extreme toxicity and a pungent odor (typical for all representatives of this group), Cl is highly soluble in water. A practical confirmation of this is the addition of chlorine-based detergents to pool water.

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

Cl properties as a non-metal

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 the reactions. This role can be played by H 2 O.

Reactions with Cl are often endothermic (they absorb heat).

It should be noted that in crystalline form (in the form of a powder) 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, oxides that are extremely unstable and prone to decomposition are formed. In them, the Cl oxidation state can manifest itself from +1 to +7.

When interacting with F, fluorides are formed. Their oxidation state can be different.

Chlorine: characterization of a substance in terms of its physical properties

In addition to chemical properties, the element under consideration also has physical ones.

Influence of temperature on the state of aggregation Cl

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

Cl is normally a highly corrosive gas. However, it can liquefy with ease. This is influenced 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. It is able to maintain this state of aggregation up to +143 degrees, if the pressure also continues to rise.

Upon reaching -32 ° С, the state of chlorine ceases to depend on pressure, and it continues to remain liquid.

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

Where Cl exists in nature

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

Due to its high reactivity, it is almost never found in its pure form (therefore, at the beginning of the study of this element by scientists, it took years to learn how to synthesize it). Cl is usually found in compounds in various minerals: halite, sylvite, cainite, 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. At the same time, the atoms of a 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 better than others through cell membranes (therefore, more than 80% of all chlorine in the human body is 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 whole organisms. However, in controlled doses and with short-term exposure, it does not have time to cause damage.

Any swimming pool is a prime example of this last statement. As you know, water in such institutions is disinfected with Cl. Moreover, if a person rarely visits such an institution (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 stay in the water almost all day (lifeguards, instructors) often suffer from skin diseases or have weakened immunity.

In this regard, after visiting the pools, you must definitely take a shower - in order to wash off possible chlorine residues from the skin and hair.

Human use of Cl

Keeping in mind from the characteristics of chlorine that it is a "capricious" element (when it comes to interactions with other substances), it will be interesting to know that it is very 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 to 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 to extract some 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 medicines (chlorhexidine).

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

How chlorine is obtained

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 produced by a chemical reaction. However, in practice, they are very costly and inefficient.

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

Chlorine (lat. Chlorum), Cl, chemical element VII of group of the periodic system of Mendeleev, atomic number 17, atomic mass 35.453; belongs to the halogen family. Under normal conditions (0 ° C, 0.1 MN / m 2, or 1 kgf / cm 2) a yellow-green gas with a sharp irritating odor. Natural Chlorine consists of two stable isotopes: 35 Cl (75.77%) and 37 Cl (24.23%). Radioactive isotopes with mass numbers 31-47 have been artificially obtained, in particular: 32, 33, 34, 36, 38, 39, 40 with half-lives (T ½), respectively, 0.31; 2.5; 1.56 sec; 3.1 · 10 5 years; 37.3, 55.5 and 1.4 minutes. 36 Cl and 38 Cl are used as isotopic indicators.

Historical reference. Chlorine was first obtained in 1774 by K. Scheele by the interaction of hydrochloric acid with pyrolusite MnO 2. However, only in 1810 G. Davy established that chlorine is an element and named it chlorine (from the Greek chloros - yellow-green). In 1813 J.L. Gay-Lussac proposed the name Chlorine for this element.

Distribution of Chlorine in nature. Chlorine is found in nature only in the form of compounds. The average content of Chlorine in the earth's crust (clarke) is 1.7 · 10 -2% by weight, in acid igneous rocks - granites and others 2.4 · 10 -2, in basic and ultrabasic 5 · 10 -3. Water migration plays a major role in the history of Chlorine in the earth's crust. In the form of the Cl ion, it is contained in the World Ocean (1.93%), underground brines and salt lakes. The number of its own minerals (mainly natural chlorides) is 97, the main of which is halite NaCl (rock salt). Large deposits of potassium and magnesium chlorides and mixed chlorides are also known: sylvinite KCl, sylvinite (Na, K) Cl, carnalite KCl MgCl 2 6H 2 O, kainite KCl MgSO 4 3H 2 O, bischofite MgCl 2 6H 2 O In the history of the Earth, the influx of HCl contained in volcanic gases into the upper parts of the earth's crust was of great importance.

Physical properties of Chlorine. Chlorine has a boiling point of -34.05 ° C, a melting point of -101 ° C. Density of gaseous Chlorine under normal conditions is 3.214 g / l; saturated steam at 0 ° C 12.21 g / l; liquid Chlorine at a boiling point of 1.557 g / cm 3; solid Chlorine at - 102 ° C 1.9 g / cm 3. The vapor pressure of Chlorine at 0 ° C is 0.369; at 25 ° C 0.772; at 100 ° C 3.814 MN / m 2 or 3.69, respectively; 7.72; 38.14 kgf / cm 2. Heat of fusion 90.3 kJ / kg (21.5 cal / g); heat of vaporization 288 kJ / kg (68.8 cal / g); the heat capacity of the gas at a constant pressure of 0.48 kJ / (kg · K). Chlorine critical constants: temperature 144 ° C, pressure 7.72 MN / m 2 (77.2 kgf / cm 2), density 573 g / l, specific volume 1.745 · 10 -3 l / g. Solubility (in g / l) of Chlorine at a partial pressure of 0.1 MN / m 2, or 1 kgf / cm 2, in water 14.8 (0 ° C), 5.8 (30 ° C), 2.8 ( 70 ° C); in a solution of 300 g / l NaCl 1.42 (30 ° C), 0.64 (70 ° C). Below 9.6 ° C, chlorine hydrates of variable composition Cl 2 · nH 2 O (where n \u003d 6-8) are formed in aqueous solutions; these are yellow crystals of a cubic system, decomposing with increasing temperature into Chlorine and water. Chlorine is readily soluble in TiCl 4, SiCl 4, SnCl 4 and some organic solvents (especially in hexane C 6 H 14 and carbon tetrachloride CCl 4). Chlorine molecule is diatomic (Cl 2). The degree of thermal dissociation Cl 2 + 243 kJ \u003d 2Cl at 1000 K is 2.07 10 -4%, at 2500 K 0.909%.

Chlorine chemical properties. The outer electronic configuration of the atom is Cl 3s 2 3p 5. In accordance with this, Chlorine in compounds exhibits oxidation states -1, + 1, +3, +4, +5, +6 and +7. The covalent radius of the atom is 0.99 Å, the ionic radius of Cl is 1.82 Å, the affinity of the Chlorine atom to the electron is 3.65 eV, and the ionization energy is 12.97 eV.

Chemically, Chlorine is very active, it combines directly with almost all metals (with some only in the presence of moisture or when heated) and with non-metals (except carbon, nitrogen, oxygen, inert gases), forming the corresponding chlorides, reacts with many compounds, replaces hydrogen in saturated hydrocarbons and attaches to unsaturated compounds. Chlorine displaces bromine and iodine from their compounds with hydrogen and metals; it is displaced by fluorine from chlorine compounds with these elements. Alkali metals, in the presence of traces of moisture, interact with Chlorine with inflammation, most metals react with dry Chlorine only when heated. Steel, as well as some metals, are resistant in an atmosphere of dry Chlorine at low temperatures, therefore they are used for the manufacture of equipment and storage facilities for dry Chlorine. Phosphorus ignites in an atmosphere of Chlorine, forming РCl 3, and upon further chlorination - РСl 5; sulfur with Chlorine when heated gives S 2 Cl 2, SCl 2 and other S n Cl m. Arsenic, antimony, bismuth, strontium, tellurium interact vigorously with Chlorine. A mixture of Chlorine with hydrogen burns with a colorless or yellow-green flame with the formation of hydrogen chloride (this is a chain reaction).

The maximum temperature of the hydrogen-chlorine flame is 2200 ° C. Chlorine-hydrogen mixtures containing from 5.8 to 88.5% H 2 are explosive.

Chlorine forms oxides with oxygen: Cl 2 O, ClO 2, Cl 2 O 6, Cl 2 O 7, Cl 2 O 8, as well as hypochlorites (salts of hypochlorous acid), chlorites, chlorates and perchlorates. All oxygenated chlorine compounds form explosive mixtures with easily oxidizable substances. Chlorine oxides are unstable and can explode spontaneously, hypochlorites decompose slowly during storage, chlorates and perchlorates can explode under the influence of initiators.

Chlorine in water is hydrolyzed, forming hypochlorous and hydrochloric acids: Cl 2 + H 2 O \u003d HClO + HCl. When chlorinating aqueous solutions of alkalis in the cold, hypochlorites and chlorides are formed: 2NaOH + Cl 2 \u003d NaClO + NaCl + H 2 O, and when heated, chlorates. Chlorinating dry calcium hydroxide produces bleach.

When ammonia interacts with Chlorine, nitrogen trichloride is formed. In the chlorination of organic compounds, Chlorine either replaces hydrogen, or binds at multiple bonds, forming various chlorine-containing organic compounds.

Chlorine forms interhalogen compounds with other halogens. Fluorides ClF, ClF 3, ClF 3 are very reactive; for example, glass wool ignites spontaneously in a ClF 3 atmosphere. Known compounds of chlorine with oxygen and fluorine - Chlorine oxyfluorides: ClO 3 F, ClO 2 F 3, ClOF, ClOF 3 and fluorine perchlorate FClO 4.

Chlorine production. Chlorine began to be produced commercially in 1785 by the interaction of hydrochloric acid with manganese (II) oxide or pyrolusite. In 1867, the English chemist G. Deacon developed a method for producing Chlorine by oxidizing HCl with atmospheric oxygen in the presence of a catalyst. Since the late 19th - early 20th century, Chlorine is produced by electrolysis of aqueous solutions of alkali metal chlorides. These methods produce 90-95% of the world's Chlorine. Small amounts of Chlorine are produced along the way in the production of magnesium, calcium, sodium and lithium by electrolysis of molten chlorides. There are two main methods of electrolysis of aqueous NaCl solutions: 1) in electrolyzers with a solid cathode and a porous filtering diaphragm; 2) in electrolyzers with a mercury cathode. Both methods produce chlorine gas at the graphite or titanium-ruthenium oxide anode. According to the first method, hydrogen is released at the cathode and a solution of NaOH and NaCl is formed, from which commercial caustic soda is isolated by subsequent processing. According to the second method, sodium amalgam is formed at the cathode, when it is decomposed with pure water in a separate apparatus, a NaOH solution, hydrogen and pure mercury are obtained, which again goes into production. Both methods give 1.125 tons of NaOH per ton of Chlorine.

Diaphragm electrolysis requires less capital investment for the organization of Chlorine production, gives cheaper NaOH. The mercury cathode method produces very pure NaOH, but the loss of mercury pollutes the environment.

Chlorine application. One of the important branches of the chemical industry is the chlorine industry. The main quantities of Chlorine are processed at the site of its production into chlorine-containing compounds. Chlorine is stored and transported in liquid form in cylinders, barrels, railway tanks or in specially equipped vessels. The following approximate consumption of Chlorine is typical for industrialized countries: for the production of chlorine-containing organic compounds - 60-75%; inorganic compounds containing Chlorine, -10-20%; for bleaching of cellulose and fabrics - 5-15%; for sanitary needs and water chlorination - 2-6% of the total output.

Chlorine is also used for the chlorination of some ores in order to extract titanium, niobium, zirconium and others.

Chlorine in the body. Chlorine is one of the biogenic elements, a constant component of plant and animal tissues. Chlorine content in plants (a lot of Chlorine in halophytes) is from thousandths of a percent to whole percent, in animals - tenths and hundredths of a percent. The daily requirement of an adult for Chlorine (2-4 g) is covered by food. Chlorine is usually supplied with food in excess in the form of sodium chloride and potassium chloride. Bread, meat and dairy products are especially rich in Chlorine. In animals, chlorine is the main osmotically active substance in blood plasma, lymph, cerebrospinal fluid and some tissues. Plays a role in water-salt metabolism, contributing to the retention of water by tissues. Regulation of acid-base balance in tissues is carried out along with other processes by changing the distribution of Chlorine between blood and other tissues. Chlorine is involved in energy metabolism in plants, activating both oxidative phosphorylation and photophosphorylation. Chlorine has a positive effect on oxygen uptake by the roots. Chlorine is required for the formation of oxygen by isolated chloroplasts during photosynthesis. Chlorine is not a part of most nutrient media for artificial cultivation of plants. It is possible that very low concentrations of Chlorine are sufficient for the development of plants.

Chlorine poisoning is possible in the chemical, pulp and paper, textile, pharmaceutical industries and others. Chlorine irritates the mucous membranes of the eyes and respiratory tract. A secondary infection usually joins the primary inflammatory changes. Acute poisoning develops almost immediately. When inhaling medium and low concentrations of Chlorine, chest tightness and pain, dry cough, rapid breathing, pain in the eyes, lacrimation, increased white blood cell count, body temperature, etc. are noted. Bronchopneumonia, toxic pulmonary edema, depression, convulsions are possible ... In mild cases, recovery occurs within 3-7 days. Catarrh of the upper respiratory tract, recurrent bronchitis, pneumosclerosis and others are observed as long-term consequences; possible activation of pulmonary tuberculosis. With prolonged inhalation of small concentrations of Chlorine, similar, but slowly developing forms of the disease are observed. Prevention of poisoning: sealing of industries, equipment, effective ventilation, if necessary, the use of a gas mask. The production of Chlorine, bleach and other chlorine-containing compounds refers to industries with hazardous working conditions.