Hydrochloric acid is not one of those substances from which it is possible to prepare a solution of exact concentration based on weight. Therefore, an acid solution of approximate concentration is first prepared, and the exact concentration is established by titration with Na 2 CO 3 or Na 2 B 4 O 7.10H 2 O.

1. Preparation of the solution hydrochloric acid

According to the formula C(HCl) =

The mass of hydrogen chloride required to prepare 1 liter of acid solution with a molar concentration equivalent to 0.1 mol/l is calculated.

m(HCl) = C(HCl) . Me(HCl).V(solution),

where Me(HCl) = 36.5 g/mol;

m(HCl) = 0.1. 36.5. 1 = 3.65 g.

Since a solution of hydrochloric acid is prepared from concentrated acid, it is necessary to measure its density using a hydrometer and use a reference book to find what percentage the acid of such density corresponds to. For example, density (r) = 1.19 g/ml, w = 37%, then

m(size) = G;

V(solution) = m(solution)/r = 9.85/1.19 = 8 ml.

Thus, to prepare 1 liter of HCl solution, C(HCl) = 0.1 mol/l, measure about 8 ml of hydrochloric acid (r = 1.19 g/ml) using a cylinder (volume 10 - 25 ml) or a graduated test tube ), transfer it to a bottle with distilled water and bring the solution to the mark. The HCl solution prepared in this way has an approximate concentration (» 0.1 mol/l).

2. Preparation of standard sodium carbonate solution

The amount of sodium carbonate required to prepare 100.0 ml of a solution with a molar concentration equivalent to 0.1 mol/l is calculated.

m(Na 2 CO 3) = C e (Na 2 CO 3). Me(Na 2 CO 3).V(solution),

where Me(Na 2 CO 3) = M(Na 2 CO 3)/2 = 106/2 = 53 g/mol;

m(Na 2 CO 3) = 0.1.53.0.1 = 0.53 g.

First, 0.5–0.6 g of Na 2 CO 3 is weighed on a technical scale. Transfer the sample onto a watch glass, previously weighed on an analytical balance, and accurately weigh the glass with the sample. The sample is transferred through a funnel into a 100 ml volumetric flask, and distilled water is added to approximately 2/3 of the volume. The contents of the flask are mixed with careful rotational movements until the sample is completely dissolved, after which the solution is brought to the mark.

3.Standardization of hydrochloric acid solution

To establish the exact concentration of hydrochloric acid, a prepared Na 2 CO 3 solution of exact concentration is used. Due to hydrolysis, an aqueous solution of sodium carbonate has an alkaline reaction:

Na 2 CO 3 + 2H 2 O = 2NaOH + H 2 CO 3 (hydrolysis reaction);

2NaOH + 2HCl = 2NaCl + 2H 2 O;

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Na 2 CO 3 + 2HCl = 2NaCl + H 2 CO 3 (titration reaction).

From the summary equation it is clear that as a result of the reaction, weak carbonic acid accumulates in the solution, which determines the pH at the equivalence point:

pH = 1/2 pK 1 (H2CO3) – 1/2 logС (H2CO3) = 1/2 .6.35 – 1/2 log 0.1 = 3.675.

Methyl orange is best for titrations.

The burette is rinsed with the prepared HCl solution and filled almost to the top with a solution of hydrochloric acid. Then, placing a glass under the burette and slightly opening the clamp, fill the lower end of the burette so that there are no air bubbles left in it; the lower meniscus of the HCl solution in the burette should be at zero division. When reading along the burette (and pipette), the eye should be at the level of the meniscus.

Progress of determination. 10.00 ml of the prepared Na 2 CO 3 solution is taken into the titration flask with a pipette, 1-2 drops of methyl orange are added and titrated with HCl solution until the color changes from yellow to orange-pink. The experiment is repeated several times, the results obtained are entered into Table 4, the average volume of hydrochloric acid is found and its molar concentration of equivalent, titer and titer of the substance being determined are calculated.

Hydrochloric acid (H Cl)hazard class 3

(concentrated hydrochloric acid)

Colorless, transparent, aggressive, non-flammable liquid with a pungent odor of hydrogen chloride. Represents 36% ( concentrated) a solution of hydrogen chloride in water. Heavier than water. It boils at a temperature of +108.6 0 C, and hardens at a temperature of –114.2 0 C. It dissolves well in water in all proportions, “smoke” in air due to the formation of hydrogen chloride with water vapor and fog droplets. Interacts with many metals, metal oxides and hydroxides, phosphates and silicates. When interacting with metals, it releases a flammable gas (hydrogen); when mixed with other acids, it causes spontaneous combustion of some materials. Destroys paper, wood, fabrics. Causes burns upon contact with skin. Exposure to hydrochloric acid fog, which is formed as a result of the interaction of hydrogen chloride with water vapor in the air, causes poisoning.

Hydrochloric acid is used in chemical synthesis, for processing ores, pickling metals. It is obtained by dissolving hydrogen chloride in water. Technical hydrochloric acid is produced with a strength of 27.5-38% by weight.

Hydrochloric acid is transported and stored in rubberized (coated with a layer of rubber) metal railway and road tanks, containers, cylinders, which are its temporary storage. Typically, hydrochloric acid is stored in above-ground cylindrical vertical rubberized tanks (volume 50-5000 m3) at atmospheric pressure and temperature environment or in 20 liter glass bottles. Maximum storage volumes 370 tons.

Maximum permissible concentration (MPC) in the air inhabited items is 0.2 mg/m 3 in the air of the working area of ​​industrial premises 5 mg/m3. At a concentration of 15 mg/m3, the mucous membranes of the upper respiratory tract and eyes are affected, a sore throat, hoarseness, cough, runny nose, shortness of breath, and difficulty breathing appear. At concentrations of 50 mg/m3 and above, bubbling breathing occurs, sharp pains behind the sternum and in the stomach area, vomiting, spasm and swelling of the larynx, loss of consciousness. Concentrations of 50-75 mg/m 3 are difficult to tolerate. A concentration of 75-100 mg/m3 is intolerable. A concentration of 6400 mg/m 3 within 30 minutes is lethal. The maximum permissible concentration when using industrial and civil gas masks is 16,000 mg/m 3 .

When eliminating accidents, associated with a spill of hydrochloric acid, it is necessary to isolate the danger zone, remove people from it, stay to the windward side, and avoid low places. Directly at the accident site and in contamination zones with high concentrations at a distance of up to 50 m from the spill site, work is carried out in insulating gas masks IP-4M, IP-5 (using chemically bound oxygen) or breathing apparatus ASV-2, DASV (using compressed air ), KIP-8, KIP-9 (on compressed oxygen) and skin protection products (L-1, OZK, KIH-4, KIH-5). At a distance of more than 50 m from the source, where the concentration sharply decreases, skin protective equipment need not be used, and for respiratory protection, industrial gas masks with boxes of brands B, BKF, as well as civilian gas masks GP-5, GP-7, PDF-2D are used , PDF-2Sh complete with an additional cartridge DPG-3 or respirators RPG-67, RU-60M with a box of brand V.

Due to the fact that hydrochloric acid "smoke" in the air with the formation droplets of fog interacting hydrogen chloride with water vapor, the presence in the air is determined hydrogen chloride.

The presence of hydrogen chloride is determined:

In the air of an industrial zone with an OKA-T-N gas analyzer Cl , gas alarm IGS-98-N Cl , universal gas analyzer UG-2 with a measurement range of 0-100 mg/m 3 , gas detector of industrial chemical emissions GPHV-2 in the range of 5-500 mg/m 3 .

In open space – with SIP “CORSAR-X” devices.

Indoors – SIP “VEGA-M”

Neutralizes hydrochloric acid and hydrogen chloride vapors the following alkaline solutions:

5% aqueous solution of caustic soda (for example, 50 kg of caustic soda per 950 liters of water);

5% aqueous solution of soda powder (for example, 50 kg of soda some powder for 950 liters of water);

5% aqueous solution of slaked lime (for example, 50 kg of slaked lime per 950 liters of water);

5% water solution of caustic soda (for example, 50 kg of caustic soda per 950 liters of water);

In the event of a hydrochloric acid spill and the absence of an embankment or pan, the spill site is fenced off with an earthen rampart, hydrogen chloride vapor is precipitated by placing a water curtain (water consumption is not standardized), the spilled acid is neutralized to safe concentrations with water (8 tons of water per 1 ton of acid) in compliance with all measures precautions or a 5% aqueous solution of alkali (3.5 tons of solution per 1 ton of acid) and neutralize 5% aqueous solution of alkali (7.4 tons of solution per 1 ton of acid).

To spray water or solutions, watering and fire trucks, auto-filling stations (ATs, PM-130, ARS-14, ARS-15), as well as hydrants and special systems available at chemically hazardous facilities are used.

To dispose of contaminated soil at the site of a hydrochloric acid spill, the surface layer of soil is cut off to the depth of contamination, collected and transported for disposal using earthmoving vehicles (bulldozers, scrapers, motor graders, dump trucks). The cut areas are covered with a fresh layer of soil and washed with water for control purposes.

Leader actions: isolate the danger zone within a radius of at least 50 meters, remove people from it, stay to the windward side, avoid low places. Enter the accident area only in full protective clothing.

Providing first aid:

In the contaminated area: rinse eyes and face generously with water, put on anti-vogaza, urgent withdrawal (removal) from the outbreak.

After evacuating a contaminated area: warming, rest, washing off the acid from exposed skin and clothing with water, washing the eyes abundantly with water, if breathing is difficult, apply heat to the neck area, subcutaneously - 1 ml. 0.1% atropine sulfate solution. Immediate evacuation to a medical facility.

HYDROCHLORIC ACID (hydrochloric acid) - a strong monobasic acid, a solution of hydrogen chloride HCl in water, is one of the most important components of gastric juice; in medicine it is used as a medicine for insufficiency of the secretory function of the stomach. S. to. is one of the most commonly used chemicals. reagents used in biochemical, sanitary and hygienic and clinical diagnostic laboratories. In dentistry, 10% S. solution is used for teeth whitening in case of fluorosis (see Teeth whitening). S. to. is used to produce alcohol, glucose, sugar, organic dyes, chlorides, gelatin and glue, in pharmaceuticals. industry, in tanning and dyeing leather, saponification of fats, in the production of activated carbon, dyeing fabrics, etching and soldering of metals, in hydrometallurgical processes for cleaning boreholes from deposits of carbonates, oxides and other sediments, in electroplating, etc.

S. to. for people who come into contact with it in the production process, represents a significant occupational hazard.

S. k. was known back in the 15th century. Its discovery is attributed to him. alchemist Valentin. For a long time it was believed that S. to. is an oxygen compound of a hypothetical chemical. element muria (hence one of its names - acidum muriaticum). Chem. the structure of the S. k. was finally established only in the first half of the 19th century. Davy (N. Davy) and J. Gay-Lussac.

In nature, free sodium chloride practically does not occur, but its salts sodium chloride (see Table salt), potassium chloride (see), magnesium chloride (see), calcium chloride (see), etc. are very widespread.

Hydrogen chloride HCl under normal conditions is a colorless gas with a specific pungent odor; when allocated to humid air it “smoke” strongly, forming tiny droplets of aerosol S. to. Hydrogen chloride is toxic. Weight (mass) of 1 liter of gas at 0° and 760 mm Hg. Art. equal to 1.6391 g, air density 1.268. Liquid hydrogen chloride boils at -84.8° (760 mmHg) and solidifies at -114.2°. Hydrogen chloride dissolves well in water, releasing heat and forming hydrogen chloride; its solubility in water (g/100 g H20): 82.3 (0°), 72.1 (20°), 67.3 (30°), 63.3 (40°), 59.6 (50° ), 56.1 (60°).

S. to. is a colorless transparent liquid with a pungent odor of hydrogen chloride; impurities of iron, chlorine or other substances color the soda yellowish-greenish.

The approximate value of S. concentration as a percentage can be found if the beat. reduce the weight of the S. by one and multiply the resulting number by 200; for example, if ud. S.'s weight is 1.1341, then its concentration is 26.8%, i.e. (1.1341 - 1) 200.

S. K. is chemically very active. It dissolves with the release of hydrogen all metals that have a negative normal potential (see Physical and chemical potentials), converts many metal oxides and hydroxides into chlorides and releases free compounds from salts such as phosphates, silicates, borates, etc.

In a mixture with nitrogen (3:1), the so-called. aqua regia, S. reacts with gold, platinum and other chemically inert metals, forming complex ions (AuCl4, PtCl6, etc.). Under the influence of oxidizing agents, S. is oxidized to chlorine (see).

S. to. reacts with many organic substances, for example, proteins, carbohydrates, etc. Certain aromatic amines, natural and synthetic alkaloids and other organic compounds of a basic nature form salts with S. to. hydrochlorides. Paper, cotton, linen, and many artificial fibers are destroyed under the influence of synthetic acid.

The main method of producing hydrogen chloride is synthesis from chlorine and hydrogen. The synthesis of hydrogen chloride proceeds in accordance with the reaction H2 + 2C1-^2HCl + 44.126 kcal. Other methods for producing hydrogen chloride are the chlorination of organic compounds, dehydrochlorination of organic chlorine derivatives and the hydrolysis of certain inorganic compounds with the elimination of hydrogen chloride. Less often, in the lab. In practice, they use the old method of producing hydrogen chloride by reacting table salt with sulfuric acid.

A characteristic reaction to S. and its salts is the formation of a white cheesy precipitate of silver chloride AgCl, soluble in excess water solution ammonia:

HCl + AgN03 - AgCl + HN03; AgCl + 2NH4OH - [Ag (NHs)2] Cl + + 2H20.

Store S. to. in glass containers with ground-in stoppers in a cool room.

In 1897, I.P. Pavlov established that the parietal cells of the gastric glands of humans and other mammals secrete S. to a constant concentration. It is assumed that the mechanism of S.'s secretion consists of the transfer of H+ ions by a specific carrier to the outer surface of the apical membrane of the intracellular tubules of the parietal cells and their entry after additional conversion into gastric juice (see). C1~ ions from the blood penetrate into the parietal cell while simultaneously transporting the bicarbonate ion HCO in the opposite direction. Due to this, C1~ ions enter the parietal cell against the concentration gradient and from it into the gastric juice. Parietal cells secrete solution

S. to., the concentration of which is approx. 160 mmol!l.

Bibliography: Volfkovich S.I., Egorov A.P. and Epstein D.A. General chemical technology, vol. 1, p. 491 and others, M.-L., 1952; Harmful substances in industry, ed. N.V. Lazarev and I.D. Gadaskina, vol. 3, p. 41, L., 1977; Nekrasov B.V. Fundamentals of general chemistry, vol. 1 - 2, M., 1973; Emergency care for acute poisoning, Handbook of toxicology, ed. S. N. Golikova, p. 197, M., 1977; Fundamentals of Forensic Medicine, ed. N.V. Popova, p. 380, M.-L., 1938; Radbil O. S. Pharmacological basis for the treatment of diseases of the digestive system, p. 232, M., 1976; Rehm and G. Kurs inorganic chemistry, trans. with German, vol. 1, p. 844, M., 1963; Guide to forensic medical examination of poisonings, ed. R.V. Berezhny et al., p. 63, M., 1980.

N. G. Budkovskaya; N. V. Korobov (pharm.), A. F. Rubtsov (judgment).

Hydrogen chloride is a gas approximately 1.3 times heavier than air. It is colorless, but has a sharp, suffocating and characteristic odor. At a temperature of minus 84C, hydrogen chloride passes from a gaseous to a liquid state, and at minus 112C it solidifies. Hydrogen chloride dissolves in water. One liter of H2O can absorb up to 500 ml of gas. Its solution is called hydrochloric or hydrochloric acid. Concentrated hydrochloric acid at 20C is characterized by the maximum possible basic substance equal to 38%. The solution is a strong monobasic acid (it “smoke” in the air, and in the presence of moisture it forms an acid mist), it also has other names: hydrochloric acid, and according to the Ukrainian nomenclature - chloric acid. The chemical formula can be presented as follows: HCl. The molar mass is 36.5 g/mol. The density of concentrated hydrochloric acid at 20C is 1.19 g/cm³. This is a harmful substance that belongs to the second hazard class.

In its “dry” form, hydrogen chloride cannot react even with active metals, but in the presence of moisture the reaction proceeds quite vigorously. This strong hydrochloric acid is capable of reacting with all metals that are to the left of hydrogen in the voltage series. In addition, it interacts with basic and amphoteric oxides, bases, as well as salts:

• Fe + 2HCl → FeCl2 + H2;
• 2HCl + CuO → CuCl2 + H2O;
• 3HCl + Fe(OH)3 → FeCl3 + 3H2O;
• 2HCl + Na2CO3 → 2NaCl + H2O + CO2;
• HCl + AgNO3 → AgCl↓ + HNO3.

Except general properties, characteristic of each strong acid, hydrochloric acid has reducing properties: in concentrated form it reacts with various oxidizing agents, releasing free chlorine. Salts of this acid are called chlorides. Almost all of them are highly soluble in water and completely dissociate into ions. Slightly soluble are: lead chloride PbCl2, silver chloride AgCl, monovalent mercury chloride Hg2Cl2 (calomel) and cuprous chloride CuCl. Hydrogen chloride is capable of reacting with a double or triple bond, resulting in the formation of chlorinated organic compounds.

In laboratory conditions, hydrogen chloride is produced by exposure to dry concentrated sulfuric acid. Reaction in different conditions may occur with the formation of sodium salts (acidic or moderate):

• H2SO4 + NaCl → NaHSO4 + HCl
• H2SO4 + 2NaCl → Na2SO4 + 2HCl.

The first reaction goes to completion with low heating, the second - with more high temperatures. Therefore, in the laboratory, it is better to obtain hydrogen chloride using the first method, for which it is recommended to take the amount of sulfuric acid based on the production sour salt NaHSO4. Then, by dissolving hydrogen chloride in water, hydrochloric acid is obtained. In industry, it is obtained by burning hydrogen in an atmosphere of chlorine or by treating dry sodium chloride (only the second with concentrated sulfuric acid. Hydrogen chloride is also obtained as a by-product during the chlorination of saturated organic compounds. In industry, hydrogen chloride obtained by one of the above methods is dissolved in special towers in which liquid is passed from top to bottom, and gas is supplied from bottom to top, that is, according to the counterflow principle.

Hydrochloric acid is transported in special rubberized tanks or containers, as well as in polyethylene barrels with a capacity of 50 liters or glass bottles with a capacity of 20 liters. There is a risk of formation of explosive hydrogen-air mixtures. Therefore, contact of the hydrogen formed as a result of the reaction with air must be completely excluded, as well as (with the help of anti-corrosion coatings) contact of the acid with metals. Before removing the apparatus and pipelines where it was stored or transported for repairs, it is necessary to carry out nitrogen purging and monitor the state of the gas phase.

Hydrogen chloride is widely used in industrial production and in laboratory practice. It is used to obtain salts and as a reagent in analytical studies. Technical hydrochloric acid is produced in accordance with GOST 857-95 (the text is identical to the international standard ISO 905-78), the reagent is produced in accordance with GOST 3118-77. The concentration of the technical product depends on the brand and variety and can be 31.5%, 33% or 35%, and externally the product is yellowish in color due to the content of iron, chlorine and other impurities chemicals. The reactive acid should be a colorless and transparent liquid with a mass fraction of 35 to 38%.

Structural formula

True, empirical, or gross formula: HCl

Chemical composition of hydrochloric acid

Molecular weight: 36.461

Hydrochloric acid(also hydrochloric acid, hydrochloric acid, hydrogen chloride) - a solution of hydrogen chloride (HCl) in water, a strong monobasic acid. Colorless, transparent, caustic liquid, “smoking” in air (technical hydrochloric acid is yellowish in color due to impurities of iron, chlorine, etc.). It is present in a concentration of about 0.5% in the human stomach. The maximum concentration at 20 °C is 38% by weight, the density of such a solution is 1.19 g/cm³. Molar mass 36.46 g/mol. Salts of hydrochloric acid are called chlorides.

Physical properties

The physical properties of hydrochloric acid strongly depend on the concentration of dissolved hydrogen chloride. When solidified, it gives crystal hydrates of the compositions HCl H 2 O, HCl 2H 2 O, HCl 3H 2 O, HCl 6H 2 O.

Chemical properties

• Interaction with metals in the series of electrochemical potentials up to hydrogen, with the formation of salt and the release of hydrogen gas.
• Interaction with metal oxides to form soluble salt and water.
• Interaction with metal hydroxides to form soluble salt and water (neutralization reaction).
• Interaction with metal salts formed by weaker acids, such as carbonic acid.
• Interaction with strong oxidizing agents (potassium permanganate, manganese dioxide) with the release of chlorine gas.
• Reaction with ammonia to form thick white smoke consisting of tiny crystals of ammonium chloride.
• A qualitative reaction to hydrochloric acid and its salts is its interaction with silver nitrate, which forms a cheesy precipitate of silver chloride, insoluble in nitric acid.

Receipt

Hydrochloric acid is prepared by dissolving hydrogen chloride gas in water. Hydrogen chloride is produced by burning hydrogen in chlorine; the acid obtained in this way is called synthetic. Hydrochloric acid is also obtained from exhaust gases - by-product gases formed during various processes, for example, during the chlorination of hydrocarbons. The hydrogen chloride contained in these gases is called free gas, and the acid thus obtained is called free gas. IN last decades The share of gas-free hydrochloric acid in production volume is gradually increasing, displacing acid obtained by burning hydrogen in chlorine. But hydrochloric acid obtained by burning hydrogen in chlorine contains fewer impurities and is used when high purity is required. In laboratory conditions, a method developed by alchemists is used, which consists of the action of concentrated sulfuric acid on table salt. At temperatures above 550 °C and excess table salt, interaction is possible. It is possible to obtain by hydrolysis of magnesium and aluminum chlorides (hydrated salt is heated). These reactions may not proceed to completion with the formation of basic chlorides (oxychlorides) of variable composition, for example. Hydrogen chloride is highly soluble in water. Thus, at 0 °C, 1 volume of water can absorb 507 volumes of HCl, which corresponds to an acid concentration of 45%. However, when room temperature The solubility of HCl is lower, so in practice 36% hydrochloric acid is usually used.

Application

Industry

• It is used in hydrometallurgy and electroplating (pickling, pickling), for cleaning the surface of metals during soldering and tinning, for producing chlorides of zinc, manganese, iron and other metals. In a mixture with surfactants, it is used to clean ceramic and metal products (inhibited acid is required here) from contamination and disinfection.
• IN food industry registered as an acidity regulator (food additive E507). Used to make seltzer (soda) water.

Medicine

• A natural constituent of human gastric juice. In a concentration of 0.3-0.5%, usually mixed with the enzyme pepsin, it is administered orally in case of insufficient acidity.

Features of treatment

Highly concentrated hydrochloric acid is a caustic substance that causes severe chemical burns if it comes into contact with the skin. Contact with eyes is especially dangerous. To neutralize burns, use a weak alkali solution, usually baking soda. When opening vessels with concentrated hydrochloric acid, hydrogen chloride vapors, attracting air moisture, form a fog that irritates the eyes and respiratory tract of humans. Reacting with strong oxidizing agents (bleach, manganese dioxide, potassium permanganate) forms toxic chlorine gas. In the Russian Federation, the circulation of hydrochloric acid with a concentration of 15% or more is limited.