Characteristics of hydrochloric acid. Hydrochloric acid is one of the strongest acids, an extremely popular reagent

Hydrochloric acid is an inorganic substance, a monobasic acid, one of the strongest acids. Other names are also used: hydrogen chloride, hydrochloric acid, hydrochloric acid.

Properties

Acid in its pure form is a colorless and odorless liquid. Industrial acid usually contains impurities that give it a slightly yellowish tint. Hydrochloric acid is often called “fuming” because it emits hydrogen chloride vapors, which react with moisture in the air and form acid fog.

Very soluble in water. At room temperature, the maximum possible hydrogen chloride content by weight is 38%. An acid concentration greater than 24% is considered concentrated.

Hydrochloric acid actively reacts with metals, oxides, hydroxides, forming salts - chlorides. HCl reacts with salts of weaker acids; with strong oxidizing agents and ammonia.

To determine hydrochloric acid or chlorides, a reaction with silver nitrate AgNO3 is used, which results in the formation of a white cheesy precipitate.

Safety precautions

The substance is very caustic, corrodes skin, organic materials, metals and their oxides. When exposed to air, it releases hydrogen chloride vapors, which cause suffocation, burns to the skin, mucous membranes of the eyes and nose, damage the respiratory system, and destroy teeth. Hydrochloric acid belongs to substances of the 2nd degree of danger (highly dangerous), the maximum permissible concentration of the reagent in the air is 0.005 mg/l. You can work with hydrogen chloride only in filter gas masks and protective clothing, including rubber gloves, an apron, and safety shoes.

When acid spills, wash it off with plenty of water or neutralize it with alkaline solutions. Those affected by acid should be taken out of the danger area, rinse their skin and eyes with water or soda solution, and call a doctor.

The chemical reagent can be transported and stored in glass, plastic containers, as well as in metal containers coated on the inside with a rubber layer. The container must be hermetically sealed.

Receipt

On an industrial scale, hydrochloric acid is produced from hydrogen chloride (HCl) gas. Hydrogen chloride itself is produced in two main ways:
- exothermic reaction of chlorine and hydrogen - thus obtaining a high-purity reagent, for example, for the food industry and pharmaceuticals;
- from accompanying industrial gases - acid based on such HCl is called exhaust gas.

This is interesting

It was hydrochloric acid that nature “entrusted” with the process of breaking down food in the body. The concentration of acid in the stomach is only 0.4%, but this is enough to digest a razor blade in a week!

Acid is produced by the cells of the stomach itself, which is protected from this aggressive substance by the mucous membrane. However, its surface is renewed daily to restore damaged areas. In addition to participating in the process of digesting food, acid also performs a protective function, killing pathogens that enter the body through the stomach.

Application

- In medicine and pharmaceuticals - to restore the acidity of gastric juice in case of insufficiency; for anemia to improve the absorption of iron-containing drugs.
— In the food industry it is a food additive, acidity regulator E507, and also an ingredient in seltzer (soda) water. Used in the production of fructose, gelatin, citric acid.
- In the chemical industry - the basis for the production of chlorine, soda, monosodium glutamate, metal chlorides, for example zinc chloride, manganese chloride, ferric chloride; synthesis of organochlorine substances; catalyst in organic syntheses.
— Most of the hydrochloric acid produced in the world is consumed in metallurgy for cleaning workpieces from oxides. For these purposes, an inhibited industrial acid is used, which contains special reaction inhibitors (moderators), due to which the reagent dissolves oxides, but not the metal itself. Metals are also etched with hydrochloric acid; clean them before tinning, soldering, galvanizing.
— Treat the leather before tanning.
— In the mining industry it is in demand for cleaning boreholes from sediments, for processing ores and rock formations.
— In laboratory practice, hydrochloric acid is used as a popular reagent for analytical research and for cleaning vessels from difficult-to-remove contaminants.
— Used in the rubber, pulp and paper industries, and in ferrous metallurgy; for cleaning boilers, pipes, equipment from complex deposits, scale, rust; for cleaning ceramic and metal products.

Hydrochloric acid

Chemical properties

Hydrochloric acid, hydrogen chloride or hydrochloric acid - solution HCl in water. According to Wikipedia, the substance belongs to the group of inorganic strong monobasic compounds. Full name of the compound in Latin: Hydrochloric acid.

Formula of Hydrochloric Acid in chemistry: HCl. In a molecule, hydrogen atoms combine with halogen atoms - Cl. If we consider the electronic configuration of these molecules, we can note that the compounds take part in the formation of molecular orbitals 1s-hydrogen orbitals and both 3s And 3p-atomic orbitals Cl. In the chemical formula of Hydrochloric Acid 1s-, 3s- And 3p-atomic orbitals overlap and form 1, 2, 3 orbitals. Wherein 3s-orbital is not bonding in nature. There is a shift in electron density towards the atom Cl and the polarity of the molecule decreases, but the binding energy of molecular orbitals increases (if we consider it along with other hydrogen halides ).

Physical properties of hydrogen chloride. It is a clear, colorless liquid that has the ability to smoke when exposed to air. Molar mass of chemical compound = 36.6 grams per mole. Under standard conditions, at an air temperature of 20 degrees Celsius, the maximum concentration of the substance is 38% by weight. The density of concentrated hydrochloric acid in this kind of solution is 1.19 g/cm³. In general, physical properties and characteristics such as density, molarity, viscosity, heat capacity, boiling point and pH, strongly depend on the concentration of the solution. These values ​​are discussed in more detail in the density table. For example, the density of Hydrochloric Acid is 10% = 1.048 kg per liter. When solidified, the substance forms crystal hydrates different compositions.

Chemical properties of Hydrochloric Acid. What does Hydrochloric Acid react with? The substance interacts with metals that are in the series of electrochemical potentials in front of hydrogen (iron, magnesium, zinc and others). In this case, salts are formed and gaseous gas is released. H. Lead, copper, gold, silver and other metals to the right of hydrogen do not react with Hydrochloric Acid. The substance reacts with metal oxides, forming water and soluble salt. Sodium hydroxide under the influence of sodium forms water. The neutralization reaction is characteristic of this compound.

Dilute Hydrochloric Acid reacts with metal salts, which are formed by weaker compounds. For example, propionic acid weaker than salt. The substance does not interact with stronger acids. And sodium carbonate will form after reaction with HCl chloride, carbon monoxide and water.

A chemical compound is characterized by reactions with strong oxidizing agents, with manganese dioxide , potassium permanganate : 2KMnO4 + 16HCl = 5Cl2 + 2MnCl2 + 2KCl + 8H2O. The substance reacts with ammonia , this produces thick white smoke, which consists of very small crystals of ammonium chloride. The mineral pyrolusite also reacts with Hydrochloric Acid, since it contains manganese dioxide : MnO2+4HCl=Cl2+MnO2+2H2O(oxidation reaction).

There is a qualitative reaction to hydrochloric acid and its salts. When a substance interacts with silver nitrate a white precipitate appears silver chloride and is formed nitrogen acid . Interaction reaction equation methylamine with hydrogen chloride looks like this: HCl + CH3NH2 = (CH3NH3)Cl.

The substance reacts with a weak base aniline . After aniline is dissolved in water, Hydrochloric Acid is added to the mixture. As a result, the base dissolves and forms aniline hydrochloride (phenylammonium chloride ): (C6H5NH3)Cl. The reaction of aluminum carbide with hydrochloric acid: Al4C3+12HCL=3CH4+4AlCl3. Reaction equation potassium carbonate with it looks like this: K2CO3 + 2HCl = 2KCl + H2O + CO2.

Obtaining hydrochloric acid

To obtain synthetic Hydrochloric Acid, hydrogen is burned in chlorine, and then the resulting hydrogen chloride gas is dissolved in water. It is also common to produce a reagent from exhaust gases, which are formed as by-products during the chlorination of hydrocarbons (exhaust Hydrochloric Acid). In the production of this chemical compound they use GOST 3118 77- for reagents and GOST 857 95– for technical synthetic hydrochloric acid.

In laboratory conditions, you can use an old method in which table salt is exposed to concentrated sulfuric acid. The product can also be obtained using a hydrolysis reaction aluminum chloride or magnesium . During the reaction may form oxychlorides variable composition. To determine the concentration of a substance, standard titers are used, which are produced in sealed ampoules, so that later it is possible to obtain a standard solution of known concentration and use it to determine the quality of another titrant.

The substance has a fairly wide range of applications:

• it is used in hydrometallurgy, pickling and pickling;
• when cleaning metals during tinning and soldering;
• as a reagent for obtaining manganese chloride , zinc, iron and other metals;
• in the preparation of mixtures with surfactants for cleaning metal and ceramic products from infection and dirt (inhibited hydrochloric acid is used);
• as an acidity regulator E507 in the food industry, as part of soda water;
• in medicine with insufficient acidity of gastric juice.

This chemical compound has a high hazard class - 2 (according to GOST 12L.005). When working with acid, special equipment is required. skin and eye protection. A fairly caustic substance that comes into contact with the skin or respiratory tract causes chemical burns. To neutralize it, alkali solutions are used, most often baking soda. Hydrogen chloride vapor forms a caustic mist with water molecules in the air, which irritates the respiratory tract and eyes. If the substance reacts with bleach, potassium permanganate and other oxidizing agents, a toxic gas is formed - chlorine. On the territory of the Russian Federation, the circulation of Hydrochloric Acid with a concentration of more than 15% is limited.

pharmachologic effect

Increases the acidity of gastric juice.

Pharmacodynamics and pharmacokinetics

What is gastric acidity? This is a characteristic of the concentration of Hydrochloric Acid in the stomach. Acidity is expressed in pH. Normally, gastric juice should produce acid and take an active part in the digestive process. Hydrochloric acid formula: HCl. It is produced by parietal cells located in the fundic glands, with the participation H+/K+ ATPases . These cells line the fundus and body of the stomach. The acidity of gastric juice itself is variable and depends on the number of parietal cells and the intensity of the processes of neutralization of the substance by the alkaline components of gastric juice. The concentration of the drug produced is stable and equal to 160 mmol/l. A healthy person should normally produce no more than 7 and no less than 5 mmol of the substance per hour.

With insufficient or excessive production of Hydrochloric Acid, diseases of the digestive tract occur, and the ability to absorb certain microelements, such as iron, deteriorates. The product stimulates the secretion of gastric juice, reduces pH. Activates pepsinogen , converts it into an active enzyme pepsin . The substance has a beneficial effect on the acid reflex of the stomach and slows down the transition of incompletely digested food into the intestines. The fermentation processes of the contents of the digestive tract slow down, pain and belching disappear, and iron is better absorbed.

After oral administration, the drug is partially metabolized by saliva and gastric mucus, the contents of the duodenum. The unbound substance penetrates the duodenum, where it is completely neutralized by its alkaline contents.

Indications for use

The substance is part of synthetic detergents, concentrate for rinsing the mouth and caring for contact lenses. Dilute Hydrochloric Acid is prescribed for stomach diseases accompanied by low acidity, with hypochromic anemia in combination with iron supplements.

Contraindications

The medicine should not be used if allergies on a synthetic substance, for diseases of the digestive tract associated with high acidity, with.

Side effects

Concentrated Hydrochloric Acid can cause severe burns if it comes into contact with the skin, eyes or respiratory tract. As part of various lek. drugs use a diluted substance; with long-term use of large dosages, deterioration of the condition of tooth enamel may occur.

Instructions for use (Method and dosage)

Hydrochloric acid is used in accordance with the instructions.

The medicine is prescribed orally, having previously been dissolved in water. Usually use 10-15 drops of the drug per half glass of liquid. The medicine is taken with meals, 2-4 times a day. The maximum single dosage is 2 ml (about 40 drops). Daily dose – 6 ml (120 drops).

Overdose

Cases of overdose have not been described. With uncontrolled ingestion of the substance in large quantities, ulcers and erosions occur in the digestive tract. You should seek help from a doctor.

Interaction

The substance is often used in combination with pepsin and other medications. drugs. A chemical compound in the digestive tract interacts with bases and certain substances (see chemical properties).

special instructions

When treating with Hydrochloric Acid preparations, you must strictly adhere to the recommendations in the instructions.

Drugs containing (Analogs)

Level 4 ATX code matches:

For industrial purposes, inhibited hydrochloric acid (22-25%) is used. For medical purposes the solution is used: Hydrochloric acid diluted . The substance is also contained in a concentrate for rinsing the mouth. Parontal , in solution for the care of soft contact lenses Biotra .

Like acids. The education program requires students to memorize the names and formulas of six representatives of this group. And, looking through the table provided by the textbook, you notice in the list of acids the one that comes first and interested you in the first place - hydrochloric acid. Alas, neither properties nor any other information about it is studied in school classes. Therefore, those who are eager to gain knowledge outside the school curriculum are looking for additional information in all sorts of sources. But often many people do not find the information they need. And therefore, the topic of today’s article is devoted to this particular acid.

Definition

Hydrochloric acid is a strong monobasic acid. In some sources it may be called hydrochloric and hydrochloric acid, as well as hydrogen chloride.

It is a colorless, caustic liquid that fumes in air (photo on the right). However, industrial acid, due to the presence of iron, chlorine and other additives in it, has a yellowish color. Its highest concentration at a temperature of 20 o C is 38%. The density of hydrochloric acid with these parameters is 1.19 g/cm 3 . But this compound has completely different data in different degrees of saturation. As the concentration decreases, the numerical value of molarity, viscosity and melting point decreases, but the specific heat capacity and boiling point increase. Solidification of hydrochloric acid of any concentration gives various crystalline hydrates.

Chemical properties

All metals that come before hydrogen in the electrochemical series of their voltage can react with this compound, forming salts and releasing hydrogen gas. If they are replaced by metal oxides, the reaction products will be soluble salt and water. The same effect will occur when hydrochloric acid reacts with hydroxides. If you add any metal salt (for example, sodium carbonate), the remainder of which was taken from a weaker acid (carbonic acid), then the chloride of this metal (sodium), water and a gas corresponding to the acidic residue (in this case, carbon dioxide) are formed. .

Receipt

The compound now discussed is formed when hydrogen chloride gas, which can be produced by burning hydrogen in chlorine, is dissolved in water. Hydrochloric acid obtained using this method is called synthetic. Exhaust gases can also serve as a source for the extraction of this substance. And such hydrochloric acid will be called abgasic. Recently, the level of production of hydrochloric acid using this method is much higher than its production by the synthetic method, although the latter produces the compound in a purer form. These are all the ways of its production in industry. However, in laboratories, hydrochloric acid is produced in three ways (the first two differ only in temperature and reaction products) using various types of interaction of chemical substances, such as:

1. The effect of saturated sulfuric acid on sodium chloride at a temperature of 150 o C.
2. Interaction of the above substances under conditions with a temperature of 550 o C and above.
3. Hydrolysis of aluminum or magnesium chlorides.

Hydrometallurgy and electroplating cannot do without the use of hydrochloric acid, where it is needed to clean the surface of metals during tinning and soldering and to obtain chlorides of manganese, iron, zinc and other metals. In the food industry, this compound is known as food additive E507 - there it is an acidity regulator necessary to make seltzer (soda) water. Concentrated hydrochloric acid is also found in the gastric juice of any person and helps digest food. During this process, its degree of saturation decreases, because this composition is diluted with food. However, with prolonged fasting, the concentration of hydrochloric acid in the stomach gradually increases. And since this compound is very caustic, it can lead to stomach ulcers.

Conclusion

Hydrochloric acid can be both beneficial and harmful to humans. Contact with the skin results in severe chemical burns, and the vapors of this compound irritate the respiratory tract and eyes. But if you handle this substance carefully, it can come in handy more than once.

In water it is called hydrochloric acid ( HCl).

Physical properties of hydrochloric acid

Under ordinary conditions, hydrochloric acid is a clear, colorless liquid with a strong, unpleasant odor.

Concentrated hydrochloric acid contains 37% hydrogen chloride. This acid “smoke” in air. Hydrogen chloride is released from it, which, with water vapor in the air, forms a “fog” consisting of small droplets of hydrochloric acid. Hydrochloric acid is slightly heavier than water (the specific gravity of 37 percent hydrochloric acid is 1.19).

In school laboratories, most diluted hydrochloric acid is used.

Chemical properties of hydrochloric acid

Hydrochloric acid solution has a sour taste. Litmus in this solution is red, but phenolphthalein remains colorless.

Substances whose color changes due to the action of alkalis and acids are called indicators.

Litmus, phenolphthalein - indicators for acids and alkalis. Using indicators, you can determine whether there is an acid or alkali in a solution.

Hydrochloric acid reacts with many metals. The interaction of hydrochloric acid with sodium occurs especially rapidly. This can be easily verified by experiment, which can be carried out in the device.

Concentrated hydrochloric acid is poured into a test tube to approximately 1/4 of its volume, secured in a stand and a small piece of sodium (the size of a pea) is dropped into it. Hydrogen is released from the test tube, which can be set on fire, and small crystals of table salt settle to the bottom of the test tube.

From this experiment it follows that sodium displaces hydrogen from the acid and combines with the rest of its molecule:

2Na + 2HCl = 2NaCl + H2?

When hydrochloric acid acts on zinc, hydrogen is released, and the substance zinc chloride ZnCl 2 remains in the solution.

Since zinc is divalent, each zinc atom replaces two hydrogen atoms in two molecules of hydrochloric acid:

Zn + 2HCl = ZnCl 2 + H 2?

Hydrochloric acid also acts on iron, aluminum and many other metals.

As a result of these reactions, hydrogen is released, and chloride metals remain in solutions: ferric chloride FeCl 2, aluminum chloride AlCl 3, etc.

These metal chlorides are products of the replacement of hydrogen in hydrochloric acid with metals.

Complex substances that can be considered as products of the substitution of a metal for the hydrogen of an acid are called salts.

Metal chlorides are salts of hydrochloric acid.

Neutralization reaction (equation)

A very important chemical property of hydrochloric acid is its interaction with bases. Let us first consider its interaction with alkalis, for example with caustic soda.

For this purpose, pour into a glass cup not a large number of dilute sodium hydroxide solution and add a few drops of litmus solution to it.

The liquid will turn blue. Then we will pour in small portions into the same glass a solution of hydrochloric acid from a graduated tube (burette) until the color of the liquid in the glass turns purple. The violet color of litmus indicates that the solution contains neither acid nor alkali.

This solution is called neutral. After boiling the water from it, table salt NaCl will remain. Based on this experience, we can conclude that when solutions of sodium hydroxide and hydrochloric acid are combined, water and sodium chloride are obtained. Water molecules are formed from the combination of hydrogen atoms (from acid molecules) with hydroxyl groups (from alkali molecules). Molecules of sodium chloride were formed from sodium atoms (from alkali molecules) and chlorine atoms - acid residues. The equation for this reaction can be written as follows:

Na |OH + H| Cl = NaCl + H2O

Other alkalis also react with hydrochloric acid - caustic potassium, caustic calcium.

Let's get acquainted with how hydrochloric acid reacts with insoluble bases, for example, copper oxide hydrate. For this purpose, we will place a certain amount of this base in a glass and carefully pour hydrochloric acid into it until the copper oxide hydrate is completely dissolved.

After evaporation of the blue solution thus obtained, crystals of copper chloride CuCl 2 are obtained. Based on this, we can write the following equation:

And in this case, a reaction similar to the interaction of this acid with alkalis occurred: hydrogen atoms from acid molecules combined with hydroxyl groups from base molecules, and water molecules were formed. Copper atoms combined with chlorine atoms (residues from acid molecules) and formed salt molecules - copper chloride.

Hydrochloric acid reacts in the same way with other insoluble bases, for example with iron oxide hydrate:

Fe(OH) 3 + 3HCl = 3H 2 O + FeCl 3

The reaction of an acid with a base to produce salt and water is called neutralization.

Hydrochloric acid is found in small quantities in the gastric juice of humans and animals and plays an important role in digestion.

Hydrochloric acid is used to neutralize alkalis and produce chloride salts. It also finds application in the production of certain plastics and medicines.

Application of hydrochloric acid

Hydrochloric acid is widely used in the national economy, and you will often encounter it when studying chemistry.

Large quantities of hydrochloric acid are used to pickle steel. Nickel-plated, galvanized, tin-plated (tin-plated), and chrome-plated products are widely used in everyday life. To coat steel products and sheet iron with a layer of protective metal, you must first remove the film of iron oxides from the surface, otherwise the metal will not stick to it. Removal of oxides is achieved by etching the product with hydrochloric or sulfuric acid. The disadvantage of etching is that the acid reacts not only with the oxide, but also with the metal. To avoid this, a small amount of inhibitor is added to the acid. Inhibitors are substances that slow down an unwanted reaction. Inhibited hydrochloric acid can be stored in steel containers and transported in steel tanks.

A solution of hydrochloric acid can also be bought at a pharmacy. Doctors prescribe a diluted solution to patients with low acidity of gastric juice.

1.2679; G crit 51.4°C, p crit 8.258 MPa, d crit 0.42 g/cm 3 ; -92.31 kJ/, DH pl 1.9924 kJ/ (-114.22°C), DH isp 16.1421 kJ/ (-8.05°C); 186.79 J/(mol K); (Pa): 133.32 10 -6 (-200.7 °C), 2.775 10 3 (-130.15 °C), 10.0 10 4 (-85.1 °C), 74, 0 10 4 (-40°C), 24.95 10 5 (O °C), 76.9 10 5 (50 °C); level of temperature dependence logp(kPa) = -905.53/T+ 1.75lgT- -500.77·10 -5 T+3.78229 (160-260 K); coefficient 0.00787; g 23 mN/cm (-155°C); r 0.29 10 7 Ohm m (-85°C), 0.59 10 7 (-114.22°C). See also table. 1.

R-value of HC1 at 25 °C and 0.1 MPa (mol %): in pentane - 0.47, hexane - 1.12, heptane - 1.47, octane - 1.63. The P-rhythm of HC1 in alkyl and aryl halides is low, for example. 0.07 / for C 4 H 9 C1. The pH value in the range from -20 to 60° C decreases in the series dichloroethane-tri-chloroethane-tetrachloroethane-trichlorethylene. The pH value at 10°C in a series is approximately 1/, in carbon ethers it is 0.6/, in carbonic compounds it is 0.2/. Stable R 2 O · HCl are formed. The P-rhythm of HC1 in obeys and is for KCl 2.51·10 -4 (800°С), 1.75·10 -4 / (900°С), for NaCl 1.90·10 -4 / (900° WITH).

Salt room. HCl in water is highly exothermic. process, for endless dilution. aqueous solution D H 0 HCl -69.9 kJ/, Cl -- 167.080 kJ/; HC1 is completely ionized. The pH value of HC1 depends on the temperature (Table 2) and the partial HC1 in the gas mixture. Density of salt decomposition. and h at 20 °C are presented in table. 3 and 4. As the temperature increases, h hydrochloric acid decreases, for example: for 23.05% hydrochloric acid at 25 °C h 1364 mPa s, at 35 °C 1.170 mPa s hydrochloric acid containing h per 1 HC1, is [kJ/(kg K)]: 3.136 (n = 10), 3.580 (n = 20), 3.902 (n = 50), 4.036 (n = 100), 4.061 (n = 200).

HCl forms c (Table 5). In the HCl-water system there are three eutectics. points: - 74.7 °C (23.0% by weight HCl); -73.0°C (26.5% HCl); -87.5°C (24.8% HC1, metastable phase). Known HCl nH 2 O, where n = 8. 6 (mp. -40 ° C), 4. 3 (mp. -24.4 ° C), 2 (mp. -17.7 °C) and 1 (mp -15.35°C). crystallizes from 10% hydrochloric acid at -20, from 15% at -30, from 20% at -60 and from 24% at -80°C. The P-value of halides decreases with increasing HCl in hydrochloric acid, which is used for their.

Chemical properties. Pure dry HCl begins to dissociate above 1500°C and is chemically passive. Mn. , C, S, P do not interact. even with liquid HCl. C, reacts above 650 °C, with Si, Ge and B-c present. AlCl 3, with transition metals - at 300 °C and above. It is oxidized by O 2 and HNO 3 to Cl 2, with SO 3 it gives C1SO 3 H. About the solutions with org. connections see .

WITH Olina is chemically very active. Dissolves with the release of H 2 everything that has a negative. ,with me. and forms, releases free. who are you from people like , etc.

Receipt. In the HCl industry, the following is obtained. methods - sulfate, synthetic. and from exhaust gases (by-products) of a number of processes. The first two methods lose their meaning. Thus, in the USA in 1965 the share of waste hydrochloric acid was 77.6% of the total production volume, and in 1982 - 94%.

The production of hydrochloric acid (reactive, obtained by the sulfate method, synthetic, waste gas) is to obtain HCl from the last. his . Depending on the method of heat removal (reaches 72.8 kJ/), processes are divided into isothermal, adiabatic. and combined.

The sulfate method is based on interaction. NaCl with conc. H 2 SO 4 at 500-550 ° C. Reaction contain from 50-65% HCl (muffle) to 5% HCl (reactor with). It is proposed to replace H 2 SO 4 with a mixture of SO 2 and O 2 (process temperature approx. 540 °C, cat. Fe 2 O 3).

The direct synthesis of HCl is based on a chain reaction: H 2 + Cl 2 2HCl + 184.7 kJ K p is calculated by the equation: logK p = 9554/T- 0.5331g T+ 2.42.

The reaction is initiated by light, moisture, solid porous (, porous Pt) and certain minerals. in-you ( , ). Synthesis is carried out with an excess of H 2 (5-10%) in combustion chambers made of steel and refractory bricks. Naib. modern material that prevents HCl contamination - graphite, impregnated phenol-formal. resins. To prevent explosiveness, mix directly in the burner flame. To the top. the combustion chamber area is installed to cool the reaction. up to 150-160°C. Power modern graphite reaches 65 tons/day (in terms of 35% salt). In case of H2 deficiency, dil. is used. process modifications; for example, pass a mixture of Cl 2 and water through a layer of porous hot water:

2Cl 2 + 2H 2 O + C: 4HCl + CO 2 + 288.9 kJ

The temperature of the process (1000-1600 °C) depends on the type and presence of impurities in it, which are (for example, Fe 2 O 3). It is promising to use a mixture of CO with:

CO + H 2 O + Cl 2: 2HCl + CO 2

More than 90% of hydrochloric acid in developed countries is obtained from waste HCl, formed during dehydrochlorination of org. compounds, chlororg. waste, obtaining non-chlorinated potash. etc. Abgases contain various. quantity of HC1, inert impurities (N 2, H 2, CH 4), poorly soluble in org. substances (,), water-soluble substances (acetic acid), acidic impurities (Cl 2, HF, O 2) and. Application of isothermal advisable when the content of HC1 in exhaust gases is low (but when the content of inert impurities is less than 40%). Naib. Film ones are promising, making it possible to extract from 65 to 85% HCl from the initial exhaust gas.

Naib. Adiabatic schemes are widely used. . Abgases are introduced into the lower part, and (or diluted salt) - countercurrent to the upper one. The salt water is heated to temperature due to the heat of HCl. The change in temperature and HCl is shown in Fig. 1. The temperature is determined by the temperature corresponding to the temperature (max. boiling point of the azeotropic mixture - approx. 110°C).

In Fig. 2 shows a typical adiabatic circuit. HCl from exhaust gases formed during (eg, production). HCl is absorbed in 1, and the residues are poorly soluble in org. the substances are separated from the after in apparatus 2, further purified in the tail column 4 and separators 3, 5 and commercial salt is obtained.

Rice. 1. T-p distribution diagram (curve 1) and