About hydrochloric acid. Hydrochloric acid - physical properties Diluted hydrochloric acid

27.10.2023 Diseases

Hydrochloric acid (synonym: hydrochloric acid, acidum hydrochloricum; HCl) is a strong monobasic acid. Obtained by dissolving gaseous hydrogen chloride (HCl) in water. In aqueous solutions, hydrochloric acid dissociates into ions: HCl↔H + +Cl - . In its pure form, hydrochloric acid is a colorless liquid with a pungent odor. Technical hydrochloric acid, containing impurities of iron, arsenic and other substances, is colored yellowish-green. A saturated aqueous solution of HCl, containing about 42% hydrogen chloride, smokes strongly in air (fuming hydrochloric acid), since the released HCl forms tiny droplets of hydrochloric acid with water vapor in the air. Concentrated hydrochloric acid sold for sale contains about 38% HCl.

Hydrochloric acid dissolves many metals, metal oxides and hydroxides, resulting in the formation of hydrochloric acid salts (chlorides).

Human gastric juice normally contains about 0.2% hydrochloric acid, which promotes the transition of food masses from the stomach to the duodenum and neutralizes microbes that enter the stomach from the external environment. Hydrochloric acid activates pepsinogen, participates in the formation of secretin and some other hormones that stimulate the activity of the pancreas.

Hydrochloric acid is widely used in technology and laboratories. Tiny droplets of hydrochloric acid, as well as gaseous HCl, irritate the mucous membranes, causing coughing and suffocation. Chronic poisoning leads to tooth decay and gastrointestinal disorders. If it comes into contact with skin, hydrochloric acid causes burns.

First aid: inhalation with a 2% solution of bicarbonate (sodium bicarbonate). In case of a burn, the affected area is immediately washed with water, then with a solution of bicarbonate of soda and again with water.

The maximum permissible concentration of HCl in the air of working premises is 5 mg per 1 m 3.

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 stand 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 .

).
In the absence of hydrometers, density ρ(g/cm3) is calculated from the mass m(g) of a known volume of acid V(cm3), measured on an electronic scale: ρ = m/V.
It is convenient and safe to withdraw the acid into a polypropylene syringe with a 20 ml scale by smoothly moving the piston until it stops.
Volume V corresponds to the complete filling of the syringe. To determine this volume, place a dry syringe on a scale and reset the tare weight to zero (or write down the weight of the empty syringe). Fill the entire volume of the syringe with distilled water, avoiding any air bubbles, thoroughly wipe the surface of the syringe and re-weigh it.
Taking the value of water density ρв = 0.998 g/cm 3 (at 20 °C), determine the volume of the syringe
V = mв / 0.998, where mw is the mass of water (g).
Then completely fill the syringe with the available acid solution, measure the mass of the solution and calculate the density of the acid using the formula above. If the obtained density value is less than 1.174 g/cm 3, the concentrated acid does not meet the requirements of GOST 3118-78, or is diluted with water.

Example.

The acid is taken into a syringe, the total volume of which is V = 24.6 cm 3. The mass of acid, measured on an electronic scale, m = 29.175 g.
Therefore, the calculated density value ρ = 29.175 / 24.6 = 1.186 g/cm3.

2. Determination of the concentration of aqueous solutions of hydrochloric acid.

The concentration of hydrochloric acid solutions can be expressed as the percentage of HCL in the mass of the solution, as the volumetric ratio of the proportions of concentrated acid and water in the solution, and also as the number of moles of the substance per liter of solution.
The concentration of the solution is determined by density using the values given in the reference tables.

Example.

The mass of a solution of hydrochloric acid with a volume of 24.6 cm 3 is equal to 26.2 g. It is necessary to determine in what volumetric ratio the concentrated acid is mixed with water, the initial concentration, as well as the weight and molar concentration (normality) of the solution.
Based on the calculated density of the solution ρ = 26.2/24.6 = 1.065 g/cm3 using Table 3, determine the volume fractions of HCL and water (1:2) and the initial concentration of the acid from which the solution was prepared (36.5 wt.%).
Then, using table 4, find the molar concentration for a solution with a density of 1.065 g/cm3 by interpolating the values:

3.881 + (4.004 – 3.881)·(36.5 – 36.0) = 3.942 mol/l

Then, using Table 5, determine the weight concentration of the solution:

13.30 + (13.69 – 13.30)·(36.5 – 36.0) = 13.49% wt.

3. Preparation of aqueous solutions of hydrochloric acid in a given volume ratio.

To prepare solutions, it is necessary to use hydrochloric acid in accordance with GOST 3118-78 with a weight concentration of 35 to 38% wt. (Table 1).
If the acid concentration is not known, determine it by density.
The solution must be prepared by adding a volume of concentrated acid to a given volume of distilled water, observing safety requirements. Use an appropriate container to prepare the solution. Work under a hood.

Example.

To prepare 500 ml of a solution in a volume ratio of 1:4, carefully pour 100 ml of concentrated acid into 400 ml of distilled water, mix thoroughly and pour the solution into a dark glass container with a sealed lid.

4. Preparation of aqueous solutions of hydrochloric acid of the required weight concentration.

To prepare the solution, it is necessary to mix the calculated amounts of acid of known concentration and distilled water.

Example.

It is necessary to prepare 1 liter of HCL solution with a concentration of 6% wt. from hydrochloric acid with a concentration of 36% wt. (this solution is used in KM carbonatometers produced by NPP Geosphere LLC).
Using Table 2, determine the molar concentration of the acid with a weight fraction of 6% wt. (1.692 mol/l) and 36% wt. (11.643 mol/l).
Calculate the volume of concentrated acid containing the same amount of HCl (1.692 g-eq.) as in the prepared solution:

1.692 / 11.643 = 0.1453 l.

Therefore, adding 145 ml of acid (36% wt.) to 853 ml of distilled water will obtain a solution of the given weight concentration.

5. Preparation of aqueous solutions of hydrochloric acid of a given molar concentration.

To prepare a solution with the required molar concentration (Mp), it is necessary to pour one volume of concentrated acid (V) into the volume (Vв) of distilled water, calculated according to the ratio

Vв = V(M/Mp – 1)

Where M is the molar concentration of the starting acid.
If the acid concentration is not known, determine it by density using Table 2.

Example.

The weight concentration of the acid used is 36.3% wt. It is necessary to prepare 1 liter of an aqueous solution of HCL with a molar concentration of 2.35 mol/l.
Using Table 1, find by interpolating the values of 12.011 mol/l and 11.643 mol/l the molar concentration of the acid used:

11.643 + (12.011 – 11.643)·(36.3 – 36.0) = 11.753 mol/l

Using the above formula, calculate the volume of water:

Vв = V (11.753 / 2.35 – 1) = 4 V

Taking Vв + V = 1 l, obtain the volume values: Vв = 0.2 l and V = 0.8 l.

Therefore, to prepare a solution with a molar concentration of 2.35 mol/L, you need to pour 200 ml of HCL (36.3% wt.) into 800 ml of distilled water.

6. Consumption of hydrochloric acid to determine the carbonate content of rock samples.

The amount of concentrated acid spent on the study of the sample is calculated from the following reactions of interaction of carbonate substances, taking into account molecular weights (Table 6) and molar concentration of the acid (Table 2):

for calcite:

CaCO3 + 2HCL = CaCL2 + H2O + CO2

for dolomite:

CaMg(CO3)2 + 4HCL = CaCL2 + MgCL2 + 2H2O + 2CO2

for siderite:

FeCO3 + 2HCL = FeCL2 + H2O + CO2

The largest amount of acid is spent on the decomposition of dolomite, because 1 g of CaMg(CO3)2 contains 21.691 mEq., 1 g of CaCO3 – 19.982 mEq., and 1 g of FeCO3 – 17.262 mEq. For complete decomposition of carbonates, it is necessary to consume the same amount of mEq. HCL.

1 ml of concentrated hydrochloric acid (35...38% wt.) contains 11.267...12.381 mEq. (Table 1). Therefore, the decomposition of 1 g of dolomite theoretically requires from 21.691 / 12.381 = 1.75 ml to 21.691 / 11.267 = 1.92 ml of concentrated acid (Table 7).

When conducting studies of rock samples, the consumption of concentrated acid should be at least 2 ml per 1 g of carbonate substances. Excess acid is necessary for the normal occurrence of a chemical reaction.
The calculated values of the volume of acid solutions required for the interaction of 1 g of carbonates with acid are given in Table 8.
The consumption of aqueous solutions containing the optimal excess of hydrochloric acid for the complete decomposition of 1 g of carbonate rocks is given in Table 9.
The actual volume of acid solution consumed to study one sample is determined by the carbonatometer manufacturer.

For carbonatometers of the KM series produced by NPP Geosphere LLC, the consumption of concentrated hydrochloric acid per sample is no more than 2.35 ml.

7. Sample preparation

To determine the carbonate content of a rock, a weighed portion of a crushed sample weighing from 500 mg to 1000 mg is required.

Weighing a larger mass makes it possible to more reliably determine the content of calcite and dolomite, especially in low-carbonate samples.

To obtain a sample weighing 1000 mg, you need to select and grind at least 3 g of dry core flagments or washed and dried particles of base rock mud.

After grinding the sample, it is necessary to sift the powder through a sieve with a mesh size of 0.056 mm or 0.063 mm.

For extraction, the sifted powder must be poured in a heap onto a piece of filter paper and, using a pipette, apply 30...40 drops of solvent onto it under hood. After the solvent has evaporated from the sample, a sample must be taken for weighing.

Weighing should be carried out on electronic scales of at least class 3 accuracy, with a readout resolution of at least 1 mg.

It is recommended to pour the weighed sample onto a substrate of thick coated paper (for ease of subsequent filling into the container of the carbonatomer reaction chamber).

It should be taken into account that inaccurate weighing of the sample increases the error in determining carbonate content. For example, with a weighing error of ± 10 mg, the additional error in determining the carbonate content of a sample weighing 500 mg is ± 2%.

8. Neutralization of hydrochloric acid residues
After the end of the reaction between carbonate substances and acid, a certain amount of HCl remains in the solution, depending on the carbonate content of the studied rock sample.

When the carbonate content in the sample is 100% wt. this amount corresponds to the excess volume of HCl introduced into the solution in excess of the calculated amount of acid required for the decomposition of 1 g of carbonate substances (Table 7.8). If the carbonate content of the sample is less than 100 wt.%, the excess HCl in the solution increases by the amount of unreacted acid.

To neutralize residual HCl, an equal amount of mEq must be added to the solution. one of the substances that reacts with hydrochloric acid (for example, sodium bicarbonate NaHCO3, potassium bicarbonate KHCO3, sodium carbonate Na2CO3, potassium carbonate K2CO3, sodium hydroxide NaOH or potassium hydroxide KOH).

The estimated amount of anhydrous substances spent on neutralizing the acid contained in 1 ml of aqueous HCl solutions of different concentrations is given in Table 10.

Example.

The amount of substance used to neutralize residual HCl after examining a 1 g rock sample can be determined based on the volume of acid solution not consumed in the reaction.

When studying a rock sample weighing 1 g, containing 85% calcite, 15 ml of an aqueous solution of HCl (1:6), prepared from acid with a concentration of 38 wt.%, was consumed. It is necessary to determine the amount of NaHCO3 to neutralize the remaining HCl after the reaction.

The calculated volume of the acid solution for the decomposition of 1 g of CaCO3 is 11.3 ml (Table 8). The excess HCl solution is

15.0 – 11.3 = 3.7 ml. The estimated amount of unreacted acid is Therefore, it is necessary to neutralize the acid in a solution with a volume of 3.7 + 1.7 = 5.4 ml.

Approximate solutions. In most cases, the laboratory has to use hydrochloric, sulfuric and nitric acids. Acids are commercially available in the form of concentrated solutions, the percentage of which is determined by their density.

Acids used in the laboratory are technical and pure. Technical acids contain impurities, and therefore are not used in analytical work.

Concentrated hydrochloric acid smokes in air, so you need to work with it in a fume hood. The most concentrated hydrochloric acid has a density of 1.2 g/cm3 and contains 39.11% hydrogen chloride.

The dilution of the acid is carried out according to the calculation described above.

Example. You need to prepare 1 liter of a 5% solution of hydrochloric acid, using a solution with a density of 1.19 g/cm3. From the reference book we find out that a 5% solution has a density of 1.024 g/cm3; therefore, 1 liter of it will weigh 1.024 * 1000 = 1024 g. This amount should contain pure hydrogen chloride:

An acid with a density of 1.19 g/cm3 contains 37.23% HCl (we also find it from the reference book). To find out how much of this acid should be taken, make up the proportion:

or 137.5/1.19 = 115.5 acid with a density of 1.19 g/cm3. Having measured out 116 ml of acid solution, bring its volume to 1 liter.

Sulfuric acid is also diluted. When diluting it, remember that you need to add acid to water, and not vice versa. When diluted, strong heating occurs, and if you add water to the acid, it may splash, which is dangerous, since sulfuric acid causes severe burns. If acid gets on clothes or shoes, you should quickly wash the doused area with plenty of water, and then neutralize the acid with sodium carbonate or ammonia solution. In case of contact with the skin of your hands or face, immediately wash the area with plenty of water.

Particular care is required when handling oleum, which is a sulfuric acid monohydrate saturated with sulfuric anhydride SO3. According to the content of the latter, oleum comes in several concentrations.

It should be remembered that with slight cooling, oleum crystallizes and is in a liquid state only at room temperature. In air, it smokes, releasing SO3, which forms sulfuric acid vapor when interacting with air moisture.

It is very difficult to transfer oleum from large to small containers. This operation should be carried out either under draft or in air, but where the resulting sulfuric acid and SO3 cannot have any harmful effect on people and surrounding objects.

If the oleum has hardened, it should first be heated by placing the container with it in a warm room. When the oleum melts and turns into an oily liquid, it must be taken out into the air and then poured into a smaller container, using the method of squeezing with air (dry) or an inert gas (nitrogen).

When nitric acid is mixed with water, heating also occurs (though not as strong as in the case of sulfuric acid), and therefore precautions must be taken when working with it.

Solid organic acids are used in laboratory practice. Handling them is much simpler and more convenient than liquid ones. In this case, care should only be taken to ensure that the acids are not contaminated with anything foreign. If necessary, solid organic acids are purified by recrystallization (see Chapter 15 “Crystallization”),

Precise solutions. Precise acid solutions They are prepared in the same way as approximate ones, with the only difference that at first they strive to obtain a solution of a slightly higher concentration, so that later it can be diluted exactly, according to calculations. For precise solutions, only chemically pure preparations are used.

The required amount of concentrated acids is usually taken by volume, calculated based on density.

Example. You need to prepare 0.1 and. H2SO4 solution. This means that 1 liter of solution should contain:

An acid with a density of 1.84 g/cmg contains 95.6% H2SO4 n to prepare 1 liter of 0.1 n. of the solution you need to take the following amount (x) of it (in g):

The corresponding volume of acid will be:

Having measured exactly 2.8 ml of acid from the burette, dilute it to 1 liter in a volumetric flask and then titrate with an alkali solution to establish the normality of the resulting solution. If the solution turns out to be more concentrated), the calculated amount of water is added to it from a burette. For example, during titration it was found that 1 ml of 6.1 N. H2SO4 solution contains not 0.0049 g of H2SO4, but 0.0051 g. To calculate the amount of water needed to prepare exactly 0.1 N. solution, make up the proportion:

Calculation shows that this volume is 1041 ml; the solution needs to be added 1041 - 1000 = 41 ml of water. You should also take into account the amount of solution taken for titration. Let 20 ml be taken, which is 20/1000 = 0.02 of the available volume. Therefore, you need to add not 41 ml of water, but less: 41 - (41*0.02) = = 41 -0.8 = 40.2 ml.

* To measure the acid, use a thoroughly dried burette with a ground stopcock. .

The corrected solution should be checked again for the content of the substance taken for dissolution. Accurate solutions of hydrochloric acid are also prepared using the ion exchange method, based on an accurately calculated sample of sodium chloride. The sample calculated and weighed on an analytical balance is dissolved in distilled or demineralized water, and the resulting solution is passed through a chromatographic column filled with a cation exchanger in the H-form. The solution flowing from the column will contain an equivalent amount of HCl.

As a rule, accurate (or titrated) solutions should be stored in tightly closed flasks. A calcium chloride tube must be inserted into the stopper of the vessel, filled with soda lime or ascarite in the case of an alkali solution, and with calcium chloride or simply cotton wool in the case of an acid.

To check the normality of acids, calcined sodium carbonate Na2COs is often used. However, it is hygroscopic and therefore does not fully satisfy the requirements of analysts. It is much more convenient to use acidic potassium carbonate KHCO3 for these purposes, dried in a desiccator over CaCl2.

When titrating, it is useful to use a “witness”, for the preparation of which one drop of acid (if an alkali is being titrated) or alkali (if an acid is being titrated) and as many drops of an indicator solution as added to the titrated solution are added to distilled or demineralized water.

The preparation of empirical, according to the substance being determined, and standard solutions of acids is carried out by calculation using the formulas given for these and the cases described above.