Soap solution formula. Chemistry of soap and detergents. The effect of soap composition on the skin

06.10.2023

The structure of soap (chemistry of soap)

Soaps are sodium or potassium salts of higher fatty acids (Scheme 1), which hydrolyze in an aqueous solution to form acid and alkali.

General formula of solid soap:

Salts formed by strong alkali metal bases and weak carboxylic acids undergo hydrolysis:

The resulting alkali emulsifies, partially decomposes fats and thus releases dirt stuck to the fabric. Carboxylic acids form foam with water, which captures dirt particles. Potassium salts are more soluble in water than sodium salts and therefore have stronger cleaning properties.

The hydrophobic portion of the soap penetrates the hydrophobic contaminant, resulting in the surface of each contaminant particle being surrounded by a shell of hydrophilic groups. They interact with polar water molecules. Due to this, the ions of the detergent, along with the contamination, are torn off from the surface of the fabric and pass into the aqueous environment. This is how the contaminated surface is cleaned with a detergent.

Soap production consists of two stages: chemical and mechanical. At the first stage (soap cooking), an aqueous solution of sodium (less often potassium) salts, fatty acids or their substitutes is obtained.

Production of higher carboxylic acids during cracking and oxidation of petroleum products:

Preparation of sodium salts:

СnHmCOOH + NaOH = СnHmCOONa + H2O.

Soap cooking is completed by treating the soap solution (soap glue) with excess alkali or sodium chloride solution. As a result, a concentrated layer of soap, called a core, floats to the surface of the solution. The resulting soap is called sound soap, and the process of separating it from the solution is called salting or salting out.

Mechanical processing consists of cooling and drying, grinding, finishing and packaging of finished products.

As a result of the soap-making process, we obtain a wide variety of products that you can familiarize yourself with.

The production of laundry soap is completed at the salting out stage, during which the soap is cleaned from protein, coloring and mechanical impurities. The production of toilet soap goes through all stages of mechanical processing. The most important of these is grinding, i.e. transferring sound soap into a solution by boiling with hot water and salting out again. In this case, the soap turns out to be especially clean and light.

Washing powders can:

* irritate the respiratory tract;
* stimulate the penetration of toxic substances into the skin;
* cause allergies and skin dermatitis.

In all these cases, you need to switch to using soap, the only drawback of which is that it dries the skin.

If the soap was made from animal or vegetable fats, then glycerin, which is formed during saponification, is separated from the solution after separating the kernel, which is widely used: in the production of explosives and polymer resins, as a fabric and leather softener, in the manufacture of perfumes, cosmetics and medicines, in production of confectionery products.

In the production of soap, naphthenic acids are used, released during the purification of petroleum products (gasoline, kerosene). For this purpose, petroleum products are treated with a solution of sodium hydroxide and an aqueous solution of sodium salts of naphthenic acids is obtained. This solution is evaporated and treated with table salt, as a result of which a dark-colored ointment-like mass - soap naphtha - floats to the surface of the solution. To clean soaponaft, it is treated with sulfuric acid. This water-insoluble product is called asidol or asidol-mylonaft. Soap is made directly from asidol.

Soap raw materials

General information on the raw materials from which soap is made.

Animal fats are an ancient and valuable raw material for soap making. They contain up to 40% saturated fatty acids. Artificial, that is, synthetic, fatty acids are obtained from petroleum paraffin by catalytic oxidation with atmospheric oxygen. During oxidation, the paraffin molecule is broken in different places, and a mixture of acids is obtained, which are then separated into fractions. In soap production, mainly two fractions are used: C10-C16 and C17-C20. Synthetic acids are introduced into laundry soap in an amount of 35-40%.

Naphthenic acids, released during the purification of petroleum products (gasoline, kerosene, etc.), are also used to produce soap. For this purpose, petroleum products are treated with a solution of sodium hydroxide and an aqueous solution of sodium salts of naphthenic acids (monocarboxylic acids of the cyclopentane and cyclohexane series) is obtained. This solution is evaporated and treated with table salt, as a result of which a dark-colored ointment-like mass - soap naphtha - floats to the surface of the solution. To purify soap naphtha, it is treated with sulfuric acid, that is, the naphthenic acids themselves are displaced from the salts. This water-insoluble product is called asidol, or asidolmylonaft. Only liquid or soft soap can be made directly from asidol. It has a petroleum smell, but has bactericidal properties.

In the production of soap, rosin has long been used, which is obtained by processing the resin of coniferous trees. Rosin consists of a mixture of resin acids containing about 20 carbon atoms in the carbon chain. 12-15% of rosin by weight of fatty acids is usually added to laundry soap, and no more than 10% to the formulation of toilet soaps. The introduction of rosin in large quantities makes the soap soft and sticky.

Of course, today it is important to use a variety of vegetable fats; there is a separate article about them in the section.

In addition to using soap as a detergent, it is used in bleaching fabrics, in the production of cosmetics, and for the manufacture of polishing compounds for water-based paints.

In everyday life, various items and objects are subjected to the washing process. Pollutants come in a wide variety of forms, but most often they are poorly soluble or insoluble in water. Such substances, as a rule, are hydrophobic, since they are not wetted by water and do not interact with water. Therefore, various detergents are needed.

Washing can be called cleaning a contaminated surface with a liquid containing a detergent or a system of detergents. Water is mainly used as a liquid in everyday life. A good cleaning system should perform a dual function: remove dirt from the surface being cleaned and transfer it into an aqueous solution. This means that the detergent must also have a dual function: the ability to interact with the pollutant and the ability to transfer it into water or an aqueous solution.

Therefore, a detergent molecule must have hydrophobic and hydrophilic parts. "Phobos" in Greek means fear. Fear. So, hydrophobic means “afraid of, avoiding water.” “Phileo” in Greek means “love”, hydrophilic means loving. Water retaining.

The hydrophobic part of the detergent molecule has the ability to interact with the surface of the hydrophobic contaminant. The hydrophilic portion of the detergent interacts with the water, penetrates the water, and carries with it the contaminant particle attached to the hydrophobic end.

Detergents must have the ability to be adsorbed on the boundary surface, that is, they must have surfactants.

Salts of heavy carboxylic acids, for example CH3(CH2)14COONa, are typical surfactants. They contain a hydrophilic part (in this case, a carboxyl group) and a hydrophobic part (hydrocarbon radical).

Properties of soaps. What is soap?

Soaps are salts of high molecular fatty acids. In technology, soaps are sodium or potassium salts of higher fatty acids, the molecules of which contain at least 8 and no more than 20 carbon atoms, as well as similar naphthenic and resin acids (rosin); aqueous solutions of such salts have surface-active and detergent properties. Salts of alkaline earth and heavy metals are conventionally called metal soaps; most of them are insoluble in water.

In an anhydrous state, sodium and potassium salts of fatty acids are solid crystalline substances with melt. 220o-270o. Anhydrous soaps, especially potassium soaps, are hygroscopic; Moreover, salts of unsaturated fatty acids are more hygroscopic than saturated salts.

In hot water at a temperature close to the boiling point, soaps dissolve in all respects; at average room temperatures, their solubility is limited and depends on the nature and composition of acids and alkalis.

Soaps, which contain large amounts of salts of high molecular weight solid fatty acids, do not foam well in cold water and have low cleaning power, while soaps made from liquid oils, as well as from low molecular weight solid fatty acids, such as coconut oil, wash well at room temperature . Soaps, being salts of alkali metals and weak organic acids, when dissolved in water undergo hydrolysis with the formation of free alkali and acids, as well as acid salts, which for most fatty acids are poorly soluble precipitates that impart turbidity to solutions. For salts of various fatty acids, hydrolysis increases with increasing molecular weight, decreasing soap concentration, and increasing solution temperature. Due to hydrolysis, aqueous solutions of even neutral soaps have an alkaline reaction. Alcohol inhibits the hydrolysis of soaps.

Soaps in aqueous solutions are partly in a true solution state, partly in a colloidal polydisperse state, forming a complex system consisting of molecules and micelles of neutral soap, its ions and other hydrolysis products.

With decreasing polarity of the solvent, i.e. with the transition from water to organic liquids, such as alcohol, the colloidal properties of soap solutions decrease. The solubility of soaps in methyl and ethyl alcohol is much higher than in water, and in anhydrous alcohols soap is in a state of true solution. Concentrated solutions of solid fatty acid soaps in ethyl alcohol, prepared by heating, give solid gels when cooled, which is used in technology to prepare the so-called solid alcohol.

Soaps are almost insoluble in anhydrous ether and gasoline. The solubility of acidic soaps in gasoline and other hydrocarbon liquids is much higher than neutral ones. Alkaline earth metal salts of higher fatty acids, as well as heavy metal salts, are insoluble in water. Metal soaps dissolve in fats, which is used in the production of drying oils, where these soaps act as catalysts to accelerate the drying process of fatty oils. The solubility of soaps in mineral oils is used in technology in the production of greases (solid oils).

The widespread use of soaps as detergents, wetting agents, emulsifiers, peptizers, lubricants and active hardness reducers, for example, when cutting metals, is explained by the specific structure of their molecules. Soaps are typical surfactants.

soap sodium salt potash

How to prepare caustic soda and potash

Purity of soda

The higher the percentage, the purer the soda. Chda is not a manufacturer, but a qualification. There is also ch - pure, khch - chemically pure and special purity - the highest purification.

GOST reagent grade is 4328-77 (the final numbers are the year the GOST was adopted), and according to analysis, this soda is reagent grade - 99%, but is still considered not the purest. (Soda has 99.9% purity, reagent grade - 99.99%...).

If you don’t have ready-made caustic soda or potassium, you can prepare:

the first of soda ash or crystalline soda and slaked lime,

and the second is made of potash and slaked lime.

Sodium hydroxide. For 1 kg of soda ash, or for 2.85 kg of crystalline soda, take 900 g of slaked lime. Prepare a soda solution with a strength of 30°C at 23°B, for which 1 kg of soda is dissolved in 4.5-4.6 liters of water.

The soda solution is placed in a cauldron or the soda is immediately dissolved in a cooking cauldron, the liquid is heated to 60 C and slaked lime mixed with water - “milk of lime” - is poured in small portions. In this case, the solution foams very much and can go over the edge. Therefore, the boiler should be loaded only to 2/3 of its capacity and the liquid should be vigorously stirred during cooking.

The more thoroughly the liquid is mixed, the better the process of converting ordinary soda into caustic soda (caustic soda).

The mixture must be heated for 40--60 minutes, then it is allowed to settle and the clear solution is drained from the sediment.* The transparent liquid is a solution of caustic soda of approximately strength 20°--21° B, and part of the undissolved lime remains in the sediment, the remains of caustic soda , chalk and other impurities. After removing the clear solution, you can add water to the precipitate, boil it several times, let it settle and drain the clear liquid again, which will also be a solution of caustic soda, but of much lower strength.

When making caustic soda in this way, the solution is 20°-21° B. If a stronger alkali is needed to saponify the fat from which soap is supposed to be made, the resulting solution can be evaporated; As the water evaporates, the solution will become stronger. If a lower strength alkali is needed, the solution is diluted with water.

With this homemade production of caustic soda (caustic soda) from 1 kg of soda ash, 780-820 g of caustic soda is obtained.

It was indicated above that you need to take 1 kg of soda ash, and 2.85 kg of crystalline soda. The difference between soda ash and crystalline soda is that the latter contains water of crystallization.

If crystalline soda is calcined, it crumbles with a crash and turns into a white powder, already completely devoid of water (calcined).

Caustic potassium. Caustic potassium is prepared using the same method as caustic soda. For 1 kg of calcined potash, take 6.8-7 kg of slaked lime and 10-11 liters of water. A solution of potash in water is heated without bringing it to a boil, and slaked lime mixed with water (lime milk) is added to the boiler in small portions. The liquid is vigorously stirred all the time and heating is continued for 40-60 minutes. Then the mixture is allowed to settle, the clear liquid, which is a solution of caustic potassium with an approximate strength of 16-17° B, is poured off, and the sediment is again doused with water, heated to a boil, allowed to settle, and the clear liquid, which is a solution of a much lower strength, is poured off.

Potash can be prepared at home - by extracting it (by leaching) from plant ash, from ash obtained from burning wood, and in general from any wood or plant ash. The ash is placed in a vessel that has a hole in the bottom, lightly compacted and water is poured onto the ash. Water will seep through the ash and flow out of the hole in the bottom in the form of a cloudy liquid, which is collected in a separate vessel. Then the wet ash is removed, fresh ash is poured in, which is doused with the resulting cloudy liquid from the moistened first ash. This operation is repeated until the same water, passed through several portions of ash, becomes thick. The thick liquid is passed through a thin cloth to remove solid particles and heated in a deep iron pan until the water evaporates.

After the water evaporates, gray scale will remain on the bottom and walls of the pan, which is collected in another vessel. The collected scale is heated over high heat in a frying pan and a white powder is obtained - potash.

Potassium alkali can also be prepared from plant or wood ash as follows: the ash sifted through a sieve is placed in heaps on a compacted earthen or stone floor and a small amount of water is poured over it to make it moist. Then, depressions are made in the piles, about 8-10% of quicklime is poured in, poured in, everything is mixed well, and when all the lime is quenched, it is sprinkled with ash on top. The cooled and well-mixed mass is placed in a vat with two bottoms, of which the top has many small holes. A piece of rough canvas is placed on the upper bottom and a mixture of ash and lime is poured. Between both bottoms, on one side, a hole is made into which a tube is inserted to remove air, and on the opposite side a valve is attached to drain the liquor. Warm water is poured onto the ash and lime, mixed well and allowed to stand for 6-8 hours. After this, lye is released through the tap, having approximately a strength of 20-25 ° B.

The second pouring of water will give lye with a strength of 8--10° B, the third - at 4--2° B.

Long live scented soap,
And a fluffy towel,
And tooth powder
And a thick comb!
Let's wash, splash,
Swim, dive, tumble
And in the bath, and in the bathhouse, everywhere.
Eternal glory to the water!

K. Chukovsky

Goals and objectives. Consider the composition and structure of soap and detergents, show the relationship between the structure and properties of detergents; consolidate skills in working in small groups, broaden students’ horizons, and develop their thinking.

Equipment and reagents. Packaging for soap and detergents, information sheets for students, a set of chemical glassware (test tubes, alcohol lamps, beakers, test tube holders, glass rods); fat, margarine or butter, soap, synthetic detergent, liquid soap, 15% sodium hydroxide solution, sodium chloride solution (saturated), dilute sulfuric acid solution, lead acetate solutions, calcium chloride, copper sulfate, phenolphthalein solutions, containing calcium or magnesium ions, distilled water.

Studying the topic takes two lessons, one of which is a theoretical lesson, the second is practical work.

Students work in small groups, seated around the perimeter of the classroom. On their tables are containers of soap and synthetic detergents, a set of chemical glassware and reagents.

DURING THE CLASSES

Teacher. Guys, today’s lesson is devoted to the chemistry of soap and detergents and will consist of two parts.

In the first lesson we will look at theoretical questions:

Soap in ancient times, history of soap making;

The structure of soap, its properties;

Composition of soap and synthetic detergents;

Soap production;

Use of soap and synthetic detergents.

In the second lesson we will conduct laboratory experiments confirming the properties of soap and synthetic detergents.

Message on the topic
“Soap in ancient times, history of soap making”

Student.Soap was known to man before the new era. The earliest mention of soap in European countries is found in the Roman writer and scientist Pliny the Elder (23–79). In his treatise Natural History, Pliny wrote about methods for producing soap by saponification of fats. Moreover, he wrote about hard and soft soap made using soda and potash, respectively.

For washing and washing clothes in Rus', they used lye obtained by treating ash with water, because ash from burnt fuel of plant origin contains potash.

The development of soap making was facilitated by the availability of raw materials. For example, the Marseille soap industry, known since the early Middle Ages, had olive oil and soda. Soap making also developed in Italy, Greece, Spain, and Cyprus, i.e. in areas where olive trees are cultivated. The first German soap factories were founded in the 14th century.

The chemical essence of soap-making processes was not clear for a long time. Only at the end of the 18th century. The chemical nature of fats was clarified, and then their saponification reactions were understood. In 1779, the Swedish chemist K.V. Scheele showed that when olive oil reacts with lead oxide and water, a water-soluble sweet substance is formed. In 1817, the French chemist M.E. Chevrel discovered stearic, palmitic and oleic acids as products of the decomposition of fats when they are saponified with water and alkalis. The sweet substance obtained by Scheele was named glycerin by Chevreul. Forty years later, the French chemist P. E. M. Berthelot established the nature of glycerin and explained the chemical structure of fats.

Explanation of the topic
“The structure of soap, its properties”

Teacher. Soaps are sodium or potassium salts of higher fatty acids (Scheme 1), which hydrolyze in an aqueous solution to form acid and alkali.

General formula of solid soap:

Salts formed by strong alkali metal bases and weak carboxylic acids undergo hydrolysis:

Small group work

Using the information sheets (application) and handouts, students complete the following tasks.

1. Fill out the table.

Table

Composition of soap and synthetic detergents

2. Originally Answered: What are the benefits of using synthetic detergents over soap?

Role-playing game “Soap making”

One of the students acts as a technologist, talking about the stages of soap production. Each group selects a correspondent from the media: Soap magazine, Soap Bubble newspaper, SMS television company.

Technologist. Soap production consists of two stages: chemical and mechanical. At the first stage (soap cooking), an aqueous solution of sodium (less often potassium) salts, fatty acids or their substitutes is obtained.

Production of higher carboxylic acids during cracking and oxidation of petroleum products:

Preparation of sodium salts:

WITH n H m COOH + NaOH = C n H m COONa + H 2 O.

Soap cooking is completed by treating the soap solution (soap glue) with excess alkali or sodium chloride solution. As a result, a concentrated layer of soap, called a core, floats to the surface of the solution. The resulting soap is called sound soap, and the process of isolating it from the solution is called salting out or salting out.

Mechanical processing consists of cooling and drying, grinding, finishing and packaging of finished products.

As a result of the soap-making process, we obtain a wide variety of products that you can familiarize yourself with.

Correspondent for Soap magazine. Are the production stages of laundry and toilet soap the same or different?

Technologist.The production of laundry soap is completed at the salting out stage, during which the soap is cleaned from protein, coloring and mechanical impurities. The production of toilet soap goes through all stages of mechanical processing. The most important of these is grinding, i.e. transferring sound soap into a solution by boiling with hot water and salting out again. In this case, the soap turns out to be especially clean and light.

Correspondent for the Soap Bubble newspaper. Are there by-products produced during soap production and how are they used?

Technologist.If the soap was made from animal or vegetable fats, then glycerin formed during saponification is separated from the solution after separating the kernel, which is widely used: in the production of explosives and polymer resins, as a fabric and leather softener, in the manufacture of perfumes, cosmetics and medical preparations, in production of confectionery products.

Correspondent for the SMS television company. Currently, some soaps and synthetic detergents are derived from petroleum products. What are the technological secrets of such production?

Technologist.In the production of soap, naphthenic acids are used, released during the purification of petroleum products (gasoline, kerosene). For this purpose, petroleum products are treated with a solution of sodium hydroxide and an aqueous solution of sodium salts of naphthenic acids is obtained. This solution is evaporated and treated with table salt, as a result of which a dark-colored, ointment-like mass—soap naft—floats to the surface of the solution. To clean soaponaft, it is treated with sulfuric acid. This water-insoluble product is called asidol or asidol-mylonaft. Soap is made directly from asidol.

Work according to scheme 2.

At the end of the first lesson, the teacher sums up the study of the educational material and points out preventive measures when using detergents.

Washing powders can:

Irritate the respiratory tract;

Stimulate the penetration of toxic substances into the skin;

Cause allergies and skin dermatitis.

In all these cases, you need to switch to using soap, the only drawback of which is that it dries out the skin.

Practical work
"Properties of soap and synthetic detergents"

(Before starting work - safety briefing.)

Experiment “Saponification of fats in aqueous-alcoholic solution”

Place fat, margarine and butter in a test tube, add 8–10 ml of a 15% alcohol solution of sodium hydroxide. Stir the mixture and heat to a boil. Continue saponification until the liquid becomes homogeneous. Add a saturated sodium chloride solution to the resulting thick liquid and boil the solution for 1–2 minutes.

1. What substance appeared on the surface as a result of the experiment?

3. For what practical purposes is the process of saponification of fats used?

Experiment “Isolation of fatty acids”

Place a piece of solid soap in a test tube, add 8–10 ml of distilled water to it, shake and heat the resulting solution. Add a solution of dilute sulfuric acid to the soap solution and heat to a boil.

Tasks for independent conclusions

1. What changes occur when a solution is heated and cooled?

2. Write the equation for the reaction occurring.

Experiment “Preparation of insoluble salts of fatty acids”

Place a piece of solid soap in a test tube, add 8–10 ml of distilled water to it, shake and heat the resulting solution. Divide the solution into three test tubes, add lead acetate solution to the first, calcium chloride solution to the second, and copper sulfate solution to the third.

Tasks for independent conclusions

1. Explain the changes that occur in each test tube.

2. Write the equations for the reactions occurring.

Experience “Comparison of soap and synthetic detergents”

Prepare 10 ml diluted solutions in three test tubes:

a) hard soap;

b) one of the synthetic powdered detergents;

c) liquid soap.

Divide the resulting solutions into two parts (each of them contains three test tubes).

a) Add a few drops of phenolphthalein to each of the three test tubes of the first part with different solutions. (If the detergent is intended for cotton fabrics, then the medium is alkaline, and if for silk and woolen fabrics, it is neutral.)

b) In the three remaining test tubes of the second part with solutions of soap and synthetic detergents, add 2–3 ml of water containing Ca 2+ and Mg 2+ ions while shaking.

Tasks for independent conclusions

1. Why is a soap solution alkaline? Explain your answer using the reaction equation.

2. Which of the above detergents should be used for washing:

a) cotton fabrics;

b) silk and wool fabrics;

c) in hard water?

At the end of the lesson, the teacher sums up the work in the lesson, briefly repeating its main stages.

APPLICATION

Information sheet

Animal fats are an ancient and very valuable raw material of the soap industry. They contain up to 40% saturated fatty acids.

Synthetic fatty acids are obtained from petroleum paraffin by catalytic oxidation with atmospheric oxygen:

CH 3 (CH 2) m CH 2 –CH 2 (CH 2) n CH 3 + 2.5O 2 = CH 3 (CH 2) m COOH + CH 3 (CH 2) n COOH + H2O.

In the production of soap, two fractions are used: C 10 – C 16 and C 17 – C 20. Laundry soap contains 35–40% synthetic acids.

In the production of soap, rosin is used, obtained by processing the resin of coniferous trees. Rosin consists of a mixture of resin acids containing about 20 carbon atoms in the chain. 12–15% of rosin by weight of fatty acids is added to the formulation of laundry soap, and no more than 10% to the formulation of toilet soaps. The introduction of rosin makes the soap soft and sticky.

To improve the characteristics of laundry and toilet soap, as well as to reduce its cost, fillers are introduced into it. These include sodium salts, casein and starch. Casein and starch are used for foaming and foam stability. The main filler of toilet soap is saponin, obtained by leaching of certain plants.

When washing clothes in hard water containing calcium and magnesium ions, soap consumption increases by 25–30%. Slightly soluble calcium and magnesium salts settle on the fabric, making it rough, less elastic, faded, and reducing its strength.

To eliminate the harmful effects of hard water, sodium decaoxotriphosphate (V) Na 5 P 3 O 10 is added to soap. P 3 O 10 5– ions bind calcium and magnesium ions into strong insoluble compounds. Essentially they act as a water softener. For the same purpose, Na 5 P 3 O 10 is added to washing powders in a volume of up to 20%.

The basis of synthetic detergents (detergents) is Na-salt of alkane sulfonic acid,

whose share reaches 30%.

General formula of synthetic detergents:

The production of these substances is based on petroleum products.

Synthetic detergents are a complex composition containing bleaches (ultramarine, sodium perborate) and foaming agents (amino alcohols). They clean equally well in both soft and hard water.

At the same time, detergents biodegrade very slowly. Accumulating in water bodies, they lead to strong growth of green plants, which causes waterlogging.

Saponification- This is the hydrolysis of esters under the influence of alkali. This produces a salt of an organic acid and an alcohol. Historically, this name comes from the process of making soap - hydrolysis of fats with lye, which produces a mixture of salts of higher fatty acids (actually soap) and glycerin (trihydric alcohol).
Respectively saponification is the reaction of an ester with an alkali.

Before the invention of soap, fat and dirt were removed from the skin using ash and fine river sand. The technology for making soap from animal fats evolved over many centuries. Let's see how you can make soap in a chemistry laboratory. First, a fat mixture is prepared, which is melted and saponified - boiled with alkali. To hydrolyze fat in an alkaline environment, take a little rendered lard, about 10 ml of ethyl alcohol and 10 ml of alkali solution. Table salt is also added here and the resulting mixture is heated. This produces soap and glycerin. Salt is added to precipitate glycerin and impurities. Soap is also produced industrially.

Soap composition
Soaps are sodium or potassium salts of higher carboxylic acids (acids containing more than 10 carbon atoms), obtained as a result of the hydrolysis of fats in an alkaline environment (most often from fats containing stearic acid C 17 H 35 COOH) - C 17 H 35 COONa – sodium stearate.
Fat + alkali = fatty acid salts and glycerol.

Properties of soap
The surface layer of distilled water is in a tense state like an elastic film. When soap and some other water-soluble substances are added, the surface tension of water decreases. Soap and other detergents are classified as surfactants (surfactants). They reduce the surface tension of water, thereby enhancing the cleaning properties of water.

Molecules located on the surface of a liquid have an excess of potential energy and therefore tend to be drawn inward so that a minimum number of molecules remain on the surface. Due to this, a force always acts along the surface of the liquid, tending to reduce the surface. This phenomenon in physics is called surface tension of a liquid.

The surfactant molecules on the boundary surface are arranged in such a way that the hydrophilic groups of carboxyl anions are directed into the water, and the hydrophobic hydrocarbon groups are pushed out of it. As a result, the surface of the water is covered with a palisade of surfactant molecules. Such a water surface has lower surface tension, which facilitates rapid and complete wetting of contaminated surfaces. By reducing the tension surface of water, we increase its wetting ability.

The secret of the cleansing effect of soap

SMC (synthetic detergents) are sodium salts of synthetic acids (sulfonic acids, esters of higher alcohols and sulfuric acid).
Let's consider the properties of detergents and compare soap and SMS (washing powder). First, let's check what environment is typical for our detergents. How do we do this?
Using indicators.
We will use indicators known to us - litmus and phenolphthalein. When litmus is added to a soap solution and to an SMS solution, it becomes blue, and phenolphthalein becomes crimson, that is, the reaction of the medium is alkaline.

What happens to soap and SMS in hard water? (it’s clear why soap makers don’t make soap using tap water, but use decoctions, distilled water, milk, etc.)
Add the soap solution to one test tube and the SMS solution to the other, shake them up. What are you observing? Add calcium chloride to the same test tubes and shake the contents of the test tubes. What are you observing now? The SMS solution foams, and insoluble salts form in the soap solution:
2C 17 H 35 COO – + Ca 2+ = Ca(C 17 H 35 COO) 2
And SMCs form soluble calcium salts, which also have surface-active properties.
Using excessive amounts of these products leads to environmental pollution. Let's listen to a message about the environmental consequences of using surfactants.
Many surfactants are difficult to biodegrade. When wastewater enters rivers and lakes, it pollutes the environment. As a result, whole mountains of foam are formed in sewer pipes, rivers, lakes, where industrial and domestic wastewater ends up. The use of some surfactants leads to the death of all living inhabitants in the water.

Why does a soap solution quickly decompose when it gets into a river or lake, but some surfactants do not? The fact is that soaps made from fats contain unbranched hydrocarbon chains that are destroyed by bacteria. At the same time, some SMCs contain alkyl sulfates or alkyl (aryl) sulfonates with hydrocarbon chains having a branched or aromatic structure. Bacteria cannot “digest” such compounds. Therefore, when creating new surfactants, it is necessary to take into account not only their effectiveness, but also their ability to biodegrade - to be destroyed by certain types of microorganisms.

The structure of soap, its properties

Soaps are sodium or potassium salts of higher fatty acids (Scheme 1), which hydrolyze in an aqueous solution to form acid and alkali.

General formula of solid soap:

Salts formed by strong alkali metal bases and weak carboxylic acids undergo hydrolysis:

Production of higher carboxylic acids during cracking and oxidation of petroleum products:

Preparation of sodium salts:

WITH n H m COOH + NaOH = C n H m COONa + H 2 O.

Mechanical processing consists of cooling and drying, grinding, finishing and packaging of finished products.

As a result of the soap-making process, we obtain a wide variety of products that you can familiarize yourself with.

Washing powders can:

Irritate the respiratory tract;

Stimulate the penetration of toxic substances into the skin;

Cause allergies and skin dermatitis.

In all these cases, you need to switch to using soap, the only drawback of which is that it dries the skin.

In the production of soap, naphthenic acids are used, released during the purification of petroleum products (gasoline, kerosene). For this purpose, petroleum products are treated with a solution of sodium hydroxide and an aqueous solution of sodium salts of naphthenic acids is obtained. This solution is evaporated and treated with table salt, as a result of which a dark-colored, ointment-like mass—soap naft—floats to the surface of the solution. To clean soaponaft, it is treated with sulfuric acid. This water-insoluble product is called asidol or asidol-mylonaft. Soap is made directly from asidol.