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Aqueous solution of caustic potassium. Potassium hydroxide formula. Obtaining potassium hydroxide

Potassium hydroxide (caustic potassium, food additive E525, potassium hydroxide, potassium hydrate oxide, caustic potash)- caustic alkali of a wide range of applications.

Physiochemical properties.

Potassium hydroxide KOH is a colorless, odorless crystalline substance. Melting point 380 ° C. The boiling point is 1320 ° C. Density 2.12 g / cm 3. Strongly hygroscopic, crystals spread out in air due to moisture absorption. Decomposes materials of organic origin, aqueous solutions corrode glass, melts - porcelain, platinum; concentrated solutions cause severe burns to the skin and mucous membranes.

Application.

Potassium hydroxide is an almost universal chemical compound. Below are examples of materials and processes in which it is used:
- neutralization of acids,
- alkaline batteries,
- catalysis,
- detergents,
- drilling fluids,
- dyes,
- fertilizers,
- production food products,
- gas cleaning,
- metallurgical production,
- oil distillation,
- various organic and inorganic substances,
- paper production,
- pesticides,
- pharmaceuticals,
- pH regulation,
- potassium carbonate and other potassium compounds,
- soaps,
- synthetic rubber.

One of the most important applications for potassium hydroxide is in the production of mild soaps. Mixtures of potassium and sodium soaps are used to obtain liquid soaps, detergents, shampoos, shaving creams, bleaches and some pharmaceuticals. Another important area of ​​application is the production of various potassium salts. For example, potassium permanganate is produced by fusing manganese dioxide with caustic potash and then oxidizing the resulting potassium manganate in an electrolysis chamber. Potassium dichromate can be obtained in a similar way, although more often it is made by fusing finely ground chromite ore with potassium carbonate or hydroxide and exposing the resulting chromate to acid to form potassium dichromate. Potassium hydroxide is also used together with caustic soda in the production of many dyes and other organic compounds, as well as an adsorbent of gases, a dehydrating agent, a precipitator of insoluble metal hydroxides, in alkaline batteries, to obtain various potassium compounds.
In addition, potassium hydroxide is used for the disinfection of wastewater, in the nitrogen industry for drying gases, in the rubber industry as a "potassium soap" that prevents sticking of rubber crumbs, etc.

Liquid technical potassium hydroxide is used in the production of fertilizers, synthetic rubber, electrolytes, reagents, in the medical industry.

Flaked potassium hydroxide is used in the production of fertilizers and synthetic rubber, in the pharmaceutical industry and in other industries.

Technical potassium hydroxide is used for leaching steel castings, for maintaining the alkalinity of drilling fluids within specified limits, for the production of fertilizers, synthetic rubber and in other industries.

The acidity regulator E525 is permitted in cocoa and chocolate products in an amount of up to 70 g / kg of dry defatted substance; E525 is also used as a catalyst for the re-esterification of refined fats and salomas from cottonseed or sunflower oil with glycerin: the catalyst dosage is 0.3% by weight of fat.

Liquid complex humic fertilizers contain readily soluble salts of humic acids - sodium, potassium and ammonium humates. They are physiologically active forms of humic acids, the action of which is to increase the activity of enzymes, the rate of physiological and biochemical processes, as well as to stimulate the processes of respiration, the synthesis of proteins and carbohydrates in plants.

Along with this, they activate the development of the root system of plants, improve the flow of nutrients and microelements from the soil solution into the plant. This contributes to an increase in the utilization rate of mineral fertilizers, which makes it possible to reduce the dose of nitrogen fertilizers by 30-50% and save significant funds.

Currently, such fertilizers are obtained mainly from peat.

Humic acids are practically insoluble in water and mineral acids. To obtain a liquid complex fertilizer, peat is treated in a 0.1 mol / l potassium hydroxide solution at a temperature of 100 ° C and intensive mechanical stirring. Then the humate solution is separated from the solid phase by filtration using a metal mesh and nylon cloth.

Pectin (food additive E440) is a purified polysaccharide that is used in the production of confectionery fillings (sweets, marshmallows, marshmallows, marmalade, ice cream) and many other products: spreads, mayonnaise, ketchup, juices.

Beet pectin is widespread in our country.

Nitric, sulfuric, hydrochloric acids or potassium hydroxide can be used as hydrolyzing agents in the production of pectin. Of all the possible hydrolyzing agents, potassium hydroxide has the mildest effect - it reduces the degree of esterification and destruction of pectin molecules least of all.

When 0.1 mol / L potassium hydroxide is used, the degree of esterification decreases from 93.8 to 85.2%. With an increase in the concentration of potassium hydroxide to 0.5 and 1.0 mol / L, the degree of esterification decreases to 40.6 and 11.9%, respectively.

Stearic emulsions are found in a variety of cosmetic products. The bulk cosmetics make up emulsion systems.

Emulsions are composed of three components:

1) distilled water;

2) stearin, which is a mixture of palmitic and stearic acids in a ratio of 60: 40. These acids are part of almost all triglycerides vegetable oils and animal fats.

3) an emulsifier.

The emulsification mechanism is as follows. Large spherical droplets under mechanical action are deformed into cylindrical droplets or particles of a different shape, depending on the ratio of the viscosities of the dispersed phase and the dispersion medium. The cylindrical droplets spontaneously (at a certain ratio of length and diameter) break up into smaller droplets while stirring the system. The crushing process is repeated until the droplet size is 10–100 µm. Such a droplet size does not ensure the stability of the system, therefore, it is necessary to introduce a third component into the system - an emulsifier, which guarantees the stability of the emulsion and increases the efficiency of the emulsification process.

When potassium hydroxide is used as an emulsifier, the mechanical dispersion method involves separate heating of both the aqueous and oil phases to a certain temperature at which they are mixed.

The preparation of the emulsion is carried out in the following sequence. The required amount of stearin is melted at a temperature of 70–75 ° C. Separately, an aqueous solution of potassium hydroxide is heated to the same temperature. The oil phase is placed in a water bath with a stirrer and the aqueous phase is slowly added with stirring (stirrer speed 250–300 rpm). Then the emulsion is cooled to 60 ° C and emulsified for 5 minutes at a stirrer speed of 1200 rpm. After that, the emulsion is cooled to a temperature of 35–40 ° C with stirring at a rotation speed of 250–300 rpm.

The most stable and homogeneous are emulsions with a consumption of potassium hydroxide from 0.08 to 0.12 g / g of stearin. Such emulsions are well distributed over the skin and are absorbed into it. Have a pH value close to neutral.

At a potassium hydroxide consumption of less than 0.06 g / g stearin, a significant amount of solid inclusions is observed, and emulsions with a potassium hydroxide consumption of more than 1.6 g / g stearin are slightly homogeneous and soapy to the touch.

The use of potassium hydroxide to obtain betulin.

Betulin is an organic substance with antiseptic, antiviral (Herpes and Epstein-Barr virus), anti-inflammatory, hepatoprotective, antioxidant properties. And also, it is an inhibitor of the growth of cancer cells.

Betulin is taught from birch bark. It is used against the same diseases for which birch bark and birch bark are prescribed.

To obtain bitulin of high purity (96.7-99.0%) and high yield (about 38%), 50 kg of air-dry birch bark are loaded into a tank with a reflux condenser with a volume of 2000 liters, and 1500 liters of ethyl alcohol (conc. 96-%) and a solution of potassium hydroxide (90 kg of potassium hydroxide dissolved in 350 liters of water). After boiling for 8 hours, the mass is filtered off. The solution is allowed to stand for 12 hours. Betulin settles into the sediment. This precipitate is separated and dried at 20 ° C.

Ethyl alcohol is recovered by distillation at atmospheric pressure.

Potassium permanganate KMnO4 (potassium permanganate) is a strong oxidizing agent used in pharmacology and pyrotechnics.

There are many ways to obtain potassium permanganate, but there is only one industrial method - an electrochemical two-stage one. This process uses potassium hydroxide.

At the first stage, pyrolusite is mixed with potassium hydroxide and subjected to fusion in calcining pots, the reaction proceeds according to the equation 2MnO 2 + O 2 + 4KOH = 2K 2 MnO 4 + 2H 2 O.

High-grade pyrolusite finely ground in a ball mill and 50% KOH solution are alloyed at 473 ... 543 K. high temperatures(748 ... 1233 K) manganate (VI) decomposes to potassium manganate (V) with the release of oxygen according to the equation 3K 2 MnO 4 = 2K 3 MnO 4 + MnO 2 + O 2,

and a part according to the reaction 2K 2 MnO 4 = 2K 2 MnO 3 + O 2.

The manganate yield does not exceed 60%. The composition of the melt: 30–35% K 2 MnO 4, 25% KOH, a lot of MnO 2, in addition, there are potassium carbonate and other impurities.

In the second stage, the melt is leached and the resulting solution is subjected to electrolysis.

The overall equation is 2K 2 MnO 4 + 2H 2 O = 2KMnO 4 + 2KOH + H 2.

The electrolysis of an alkaline solution of manganate is carried out in baths, which are iron cylinders with a conical bottom, along which a coil is laid (for heating and cooling). The bath has a stirrer and a drain cock. Iron anodes in the form of concentric cylinders are located at a distance of 100 mm from each other (nickel anodes are also used). Iron cathodes are placed between the anodes - rods with a diameter of 20 ... 25 mm. The total surface of the cathodes is 10 times less than the surface of the anodes. During electrolysis, the current is maintained so that the anode current density is 60 ... 70 A / m 2; cathode current density 700 A / m 2. The anode and cathode plates are supported by glass and porcelain insulators.

The diameter of the bath is 1.3 ... 1.4 m, the height of the cylindrical part is 0.7 ... 0.8 m, the conical part is 0.5 m. The bath holds 900 ... 1000 dm 3 of the electrolyte solution. The electrolysis is carried out at 333 K. At the beginning of the electrolysis, the voltage is 2.7 V, the current is 1400… 1600 A; at the end of electrolysis 3V, and the current drops. Baths work in series of several pieces. The number of baths is determined by the characteristics of the source (generator) supplying them direct current... Energy consumption per 1 ton of KMnO 4 is 700 kWh.

Receiving.

IN industrial scale Potassium hydroxide is produced by electrolysis of potassium chloride. There are three options for carrying out electrolysis: electrolysis with a solid asbestos or polymer cathode (diaphragm and membrane production methods), electrolysis with a liquid mercury cathode (mercury production method). Among the electrochemical production methods, the easiest and most convenient method is electrolysis with a mercury cathode, but this method causes significant harm to the environment as a result of evaporation and leakage of metallic mercury. The membrane production method is the most efficient, but also the most complex. While the diaphragm and mercury methods have been known since 1885 and 1892, respectively, the membrane method appeared relatively recently - in the 1970s.

The main trend in the world production of potassium hydroxide in the last 10 years is the transition of manufacturers to the membrane electrolysis method. Mercury electrolysis is an outdated technology that is economically disadvantageous and has a negative impact on the environment. Membrane electrolysis completely eliminates the use of mercury. Environmental Safety membrane method is that wastewater after cleaning, they are again fed into the technological cycle, and not discharged into the sewage system. When using this method, the following tasks are solved: the stage of liquefaction and evaporation of chlorine is eliminated, hydrogen is used for process steam, gas emissions of chlorine and its compounds are excluded. The world leader in membrane technology is the Japanese company Asahi Kasei.
In Russia, the production of potassium hydroxide is carried out by mercury (ZP KChKhK) and diaphragm (Soda-Chlorate) methods.
A feature of the technological design of potassium hydroxide production is the fact that both caustic potassium and caustic soda can be produced at similar electrolysis plants. This allows manufacturers to switch to potassium hydroxide production without significant capital investments instead of caustic soda, the production of which is not so profitable, but sales in last years gets complicated. At the same time, in the event of changes in the market, a painless transfer of electrolyzers to the production of a previously produced product is possible.
An example of the transfer of a part of capacities from sodium hydroxide production to potassium hydroxide is OJSC Polymer Plant KChKhK, which began industrial production of caustic potash in five electrolyzers in 2007.

Kali caustic

KOH

Potassium hydroxide- an inorganic compound with the formula KOH.

Trivial names: caustic potassium, caustic potash, as well as potassium oxide hydrate, potassium hydroxide, potassium alkali, potassium lye.

Colorless, very hygroscopic crystals, but less hygroscopic than sodium hydroxide. Aqueous solutions of KOH are strongly alkaline. Obtained by electrolysis of KCl solutions, used in the production of liquid soaps, to obtain various potassium compounds.

Chemical properties

• Interaction with acids to form salt and water (neutralization reaction):

• Interaction with acidic oxides with the formation of salt and water:

• Interaction with some non-transition metals in solution to form a complex salt and hydrogen:

Potassium hydroxide is obtained by electrolysis of KCl solutions, usually using mercury cathodes, which gives a high-purity product that does not contain chloride impurities:

Application

Potassium hydroxide is an almost universal chemical compound. Below are examples of materials and processes in which it is used:

• neutralization of acids,
• alkaline elements,
• catalysis
• detergents,
• drilling fluids,
• dyes,
• fertilizers,
• food production,
• gas cleaning,
• metallurgical production,
• oil refining,
• various organic and inorganic substances,
• paper production,
• pesticides,
• pharmaceuticals,
• pH regulation,
• potassium carbonate and other potassium compounds,
• soap,
• synthetic rubber

In the food industry, it is referred to as a food additive E525... It is used as an acidity regulator, as a desiccant and as a peeling agent for vegetables, roots and fruits. It is also used as a catalyst in some reactions. In the Russian Federation, it is allowed in cocoa and chocolate products in an amount of up to 70 g / kg of dry fat-free substance, and is also allowed in other products in an amount according to the technological instructions. It is also used to produce methane, absorb acid gases and detect some cations in solutions.

A popular product in the production of cosmetic products, reacting with fatty oils, it breaks down and saponifies the oils.

In zirconium production, it is used to obtain defluorinated zirconium hydroxide.

In the field of industrial washing, products based on potassium hydroxide, heated to 50-60 ° C, are used to clean stainless steel products from grease and other oily substances, as well as mechanical processing residues.

Used as an electrolyte in alkaline (alkaline) batteries.

Also used in resomation - an alternative way of "burying" bodies.

5% potassium hydroxide solution is used medicinally to treat warts.

In photography it is used as a component of developers, toners, indicators of thiosulfates and for removing emulsions from photographic materials.

Production

On an industrial scale, potassium hydroxide is produced by electrolysis of potassium chloride.

There are three options for carrying out electrolysis:

• electrolysis with solid asbestos cathode (diaphragm production method),
• electrolysis with polymer cathode (membrane production method),
• electrolysis with liquid mercury cathode (mercury production method).

Among the electrochemical production methods, the easiest and most convenient method is electrolysis with a mercury cathode, but this method causes significant harm to the environment as a result of evaporation and leakage of metallic mercury. The membrane production method is the most efficient, but also the most complex.

While the diaphragm and mercury methods have been known since 1885 and 1892, respectively, the membrane method appeared relatively recently - in the 1970s.

The main trend in the global production of potassium hydroxide in the last 10 years is the transition of manufacturers to the membrane electrolysis method. Mercury electrolysis is an outdated technology that is economically disadvantageous and has a negative impact on the environment. Membrane electrolysis completely eliminates the use of mercury. The ecological safety of the membrane method lies in the fact that the wastewater after treatment is again fed into the technological cycle, and not discharged into the sewage system.

When using this method, the following tasks are solved:

• the stage of liquefaction and evaporation of chlorine is excluded,
• hydrogen is used for process steam, gas emissions of chlorine and its compounds are excluded.

The world leader in membrane technology is the Japanese company Asahi Kasei.

In Russia, the production of potassium hydroxide is carried out by mercury (ZP KChKhK) and diaphragm (Soda-Chlorate) methods.

A feature of the technological design of potassium hydroxide production is the fact that both caustic potassium and caustic soda can be produced at similar electrolysis plants. This allows manufacturers to switch to potassium hydroxide production without significant capital investments instead of caustic soda, the production of which is not so profitable, and marketing has become more difficult in recent years. At the same time, in the event of changes in the market, a painless transfer of electrolyzers to the production of a previously produced product is possible.

An example of the transfer of a part of capacities from sodium hydroxide production to potassium hydroxide is OJSC Polymer Plant KChKhK, which started industrial production of caustic potash in five electrolyzers in 2007.

Danger

Very strong alkali. In its pure form, it acts on the skin and mucous membranes in a cauterizing manner. It is especially dangerous if even the smallest particles of potassium hydroxide get into the eyes, so all work with this substance should be carried out with rubber gloves and goggles. Potassium hydroxide destroys paper, leather and other organic materials.

Brief characteristics of potassium hydroxide:

Potassium hydroxide- white inorganic substance.

Chemical formula of potassium hydroxide KON.

Possesses high hygroscopicity, but less than that of sodium hydroxide... Actively absorbs water vapor from the air.

It dissolves well in water, while releasing a large amount of thermal energy.

Potassium hydroxide is caustic, toxic and corrosive. It belongs to the substances of the second hazard class. Therefore, when working with it, you need to be careful. In case of contact with skin, mucous membranes and eyes, serious chemical burns are formed.

Physical properties of potassium hydroxide:

Parameter name:	Meaning:
Chemical formula	KON
Synonyms and names of a foreign language	potassium hydroxide caustic potassium (Russian) potassium hydroxide (Russian)
Substance type	inorganic
Appearance	colorless monoclinic crystals
Colour	white, colorless
Taste	—*
Smell	—
State of aggregation (at 20 ° C and atmospheric pressure of 1 atm.)	solid
Density (state of matter - solid, at 20 ° C), kg / m 3	2044-2120
Density (state of matter - solid, at 20 ° C), g / cm 3	2,044-2,12
Evaporating temperature, ° C	1327
Melting point, ° C	380−406
Hygroscopicity	high hygroscopicity
Molar mass, g / mol	56,1056

* Note:

- no data.

Getting potassium hydroxide:

Potassium hydroxide on an industrial scale is obtained by electrolysis of potassium chloride with a solid asbestos cathode (diaphragm production method), with a polymer cathode (membrane production method), with a liquid mercury cathode (mercury production method).

The main trend in the global production of potassium hydroxide in the last 10 years is the transition of manufacturers to the membrane electrolysis method.

Chemical properties of potassium hydroxide. Chemical reactions of potassium hydroxide:

Potassium hydroxide is a chemically active substance, a strong chemical base.

Aqueous solutions of KOH are strongly alkaline.

Chemical properties potassium hydroxide are similar to other alkali metal hydroxides. Therefore, it is characterized by the following chemical reactions:

1. reaction of potassium hydroxide with sodium:

KOH + Na → NaOH + K (t = 380-450 ° C).

As a result of the reaction, sodium hydroxide and potassium.

2. reaction of potassium hydroxide with chlorine:

2KOH + Cl 2 → KCl + KClO + H 2 O.

The reaction produces potassium chloride, potassium hypochlorite and water. In this case, potassium hydroxide as a starting material is used in the form of a cold concentrated solution.

3.reaction of potassium hydroxide with iodine:

6KOH + 3I 2 → 5KI + KIO 3 + H 2 O (t = 80 ° C).

The reaction produces potassium iodide, potassium iodate and water. In this case, potassium hydroxide as a starting material is used in the form of a hot concentrated solution.

4. reaction of potassium hydroxide with aluminum and water:

2Al + 2KOH + 6H 2 O → 2K + 3H 2.

As a result of the reaction, potassium tetrahydroxoaluminate and hydrogen are formed. In this case, potassium hydroxide as a starting material is used in the form of a hot concentrated solution.

5. reaction of potassium hydroxide with zinc and water:

Zn + 2KOH + 2H 2 O → K 2 + H 2.

The reaction produces sodium tetrahydroxozincate and hydrogen.

6. reaction of potassium hydroxide with phosphoric acid:

H 3 PO 4 + KOH → KH 2 PO 4 + H 2 O.

As a result of the reaction, potassium dihydrogen phosphate is formed and water... In this case, the starting materials used are: phosphoric acid in the form of a concentrated solution, potassium hydroxide in the form of a dilute solution.

The reactions of potassium hydroxide with other acids proceed in a similar way.

7. reaction of potassium hydroxide with hydrogen sulfide:

H 2 S + KOH → KHS + H 2 O.

The reaction produces potassium hydrosulfide and water. In this case, potassium hydroxide is used as a starting material in the form of a dilute solution.

8. reaction of potassium hydroxide with hydrogen fluoride:

HF + KOH → KF + H 2 O,

2HF + KOH → KHF 2 + H 2 O.

As a result of the reaction, in the first case, potassium fluoride and water are formed, in the second, potassium hydrofluoride and water. In this case, potassium hydroxide and hydrogen fluoride in the first case are used as a starting substance in the form of a dilute solution, in the second case potassium hydroxide and hydrogen fluoride are used in the form of a concentrated solution.

9. reaction of potassium hydroxide with hydrogen bromide:

HBr + KOH → KBr + H 2 O.

The reaction produces potassium bromide and water.

10. reaction of potassium hydroxide with hydrogen iodide:

HI + KOH → KI + H 2 O.

The reaction produces potassium iodide and water.

11. reaction of potassium hydroxide with aluminum oxide:

Al 2 O 3 + 2KOH → 2KAlO 2 + H 2 O (t = 900-1100 ° C).

Aluminum oxide is an amphoteric oxide. The reaction produces potassium aluminate and water. The reaction takes place during sintering of the starting materials.

12. reaction of potassium hydroxide with aluminum oxide and water:

Al 2 O 3 + 2KOH + 3H 2 O → 2K.

Aluminum oxide is an amphoteric oxide. As a result of the reaction, potassium tetrahydroxoaluminate is formed. In this case, potassium hydroxide as a starting material is used in the form of a hot concentrated solution.

13. the reaction of potassium hydroxide with carbon monoxide ( carbon dioxide ):

KOH + CO 2 → KHCO 3,

2CO 3 + KOH → KCO 3 + H 2 O.

Carbon monoxide is an acidic oxide. As a result of the reaction, in the first case, potassium bicarbonate is formed, in the second case, potassium carbonate and water. The reaction in the first case takes place in ethanol.

14. reaction of potassium hydroxide with sulfur oxide:

SO 2 + KOH → KHSO 3,

2SO 3 + KOH → K 2 SO 3 + H 2 O.

Sulfur oxide is an acidic oxide. As a result of the reaction, in the first case, potassium hydrosulfite is formed, in the second case, potassium sulfite and water. The reaction in the first case takes place in ethanol.

15. reaction of potassium hydroxide with silicon oxide:

4KOH + 2SiO 2 → K 2 SiO 3 + K 2 Si 4 O 5 + 2H 2 O (t = 900-1000 ° C),

6KOH + 5SiO 2 → K 4 SiO 4 + K 2 Si 4 O 9 + 3H 2 O.

As a result of the reaction, in the first case, potassium metasilicate, potassium metatetrasilicate and water are formed, in the second case, potassium orthosilicate, potassium tetrasilicate and water. In this case, potassium hydroxide as a starting material is used in the second case in the form of a concentrated solution.

16. reaction of potassium hydroxide with aluminum hydroxide:

Al (OH) 3 + KOH → KAlO 2 + 2H 2 O (t = 1000 ° C),

Al (OH) 3 + KOH → K.

Aluminum hydroxide is an amphoteric base. As a result of the reaction, in the first case, potassium aluminate and water are formed, in the second case, sodium tetrahydroxoaluminate. In this case, potassium hydroxide as a starting material is used in the second case in the form of a concentrated solution.

17. reaction of potassium hydroxide with zinc hydroxide:

Zn (OH) 2 + 2KOH → K 2.

Zinc hydroxide is an amphoteric base. As a result of the reaction, potassium tetrahydroxozincate is formed.

18. reaction of potassium hydroxide with ferrous sulfate:

FeSO 4 + 2KOH → Fe (OH) 2 + K 2 SO 4.

gland and potassium sulfate.

19. reaction of potassium hydroxide with copper chloride:

CuCl 2 + 2KOH → Cu (OH) 2 + 2KCl.

As a result of the reaction, hydroxide is formed copper and potassium chloride.

20. reaction of potassium hydroxide with aluminum chloride:

AlCl 3 + 3KOH → Al (OH) 3 + 3KCl.

As a result of the reaction, hydroxide is formed aluminum and potassium chloride.

The reactions of potassium hydroxide with other salts proceed in a similar way.

Potassium hydroxide is an alkali which is called E525 additive in the food industry.

Other common names for potassium hydroxide are potassium hydroxide, caustic potash, potassium lye, potassium hydroxide, potassium hydrate, caustic potash, potassium hydroxide.

The use of potassium hydroxide as food additive allowed in EU countries, in Russia, Ukraine.

Potassium hydroxide properties

Externally, potassium hydroxide is a crystalline colorless rods, balls, flakes.

E525 additive melts at a temperature of 404 ° C, quickly absorbs moisture and therefore requires special storage conditions, dissolves in methanol, ethanol and water.

Potassium hydroxide can dissolve organic materials.

Potassium hydroxide is obtained by electrolysis of a potassium chlorine solution. The substance is exposed to a polymer, asbestos or mercury cathode. The latter method is used most often, although the first two methods for producing potassium hydroxide that do not use mercury are considered safer.

E525 additive is considered a strong substance that violently reacts with tin, aluminum, zinc, lead and acids.

In the food industry, such a property of potassium hydroxide is used as the ability to influence the acidity of products. In fact, the E525 additive is an acidity regulator.

Potassium hydroxide application

If we take into account exclusively food industry, here, most often, E525 is used by manufacturers of chocolate, cocoa and products from them.

In addition, potassium hydroxide can be found in baby food, frozen potatoes are treated with it.

Potassium lye can be used as an aid in the production of vegetable and fruit products - with the help of the substance, fruits, vegetables and root crops are cleaned.

In the cosmetic industry, potassium hydroxide is used for the production of shampoos, soaps, bleaches, and shaving products.

The harm of potassium hydroxide

When working in a production facility with E525 additive, one must not forget that it is still an alkali, which belongs to the second class of hazard. Potassium hydroxide can corrode skin and mucous membranes, causing chemical burns. An excess of potassium hydroxide, that is, prolonged contact with the substance, provokes the appearance of chronic skin diseases.

Serious precautions must be taken in the workplace using potassium hydroxide. Especially dangerous is the contact of alkali with human eyes - cases of complete loss of vision have been recorded.

Potassium hydroxide (lat. Potassium hydroxide, "potassium lye") - KOH. Trivial names: caustic potash, caustic potash, as well as potassium oxide hydrate, potassium hydroxide, potassium hydroxide, potassium hydroxide, potassium alkali.

Potassium hydroxide properties
Colorless, highly hygroscopic crystals. Aqueous solutions of KOH have a strongly alkaline reaction. Potassium oxide hydrate (potassium hydroxide) is obtained by diaphragm electrolysis of a potassium chloride solution. Physical constants: Mr = 56.11, r = 2.04 g / cm3, melting point = 404 ° C, boiling point = 1324 ° C
Potassium hydroxide is sold in the form of solid blocks, flocculent mass, granules or small lumps, as well as 40-50% solutions. Potassium compounds are less common and therefore more expensive than the corresponding sodium compounds. They are used only in cases where the inherent complex is needed. physical and chemical properties not provided by sodium compounds.
Potassium oxide hydrate is non-combustible and explosion-proof, according to the degree of effect on the body it belongs to substances of the 2nd class. Corrosive substance, when in contact with the skin and mucous membranes, especially the eyes, causes severe chemical burns and chronic diseases skin. Eye contact is especially dangerous.
The potassium hydroxide solution is poured into clean steel containers or drums with a capacity of 100, 200 and 275 liters. Solid potassium oxide hydrate is packed in clean dry steel drums with a capacity of 50-180 dm³. The product in the form of flakes may be packed in steel drums with a capacity of 50-180 dm³ with polyethylene liners or in polyethylene bags.
In Russia, technical potassium oxide hydrate is produced in accordance with GOST 9285-78, a chemically pure product is produced in accordance with GOST 24363-80. The foreign product complies with CAS 1310-58-3.
Below are the specifications liquid and flaked potassium hydroxide of Russian production, as well as the characteristics of the imported product.

Physicochemical parameters of potassium hydroxide produced in Russia

Indicator name	Norm for brand and grade
	Solid		Liquid
	Higher	First	Higher	First
1. Appearance	Green, lilac or gray scales	Flakes or melt green, lilac or gray	Blue solution, green or gray, sediment allowed
2. Mass fraction of caustic alkalis (KOH + NaOH) in terms of KOH,%, not less	95.0	95.0	54.0	52.0
3. Mass fraction of potassium carbonate (K 2 CO 3),%, no more	1.4	1.5	0.4	0.8
4. Mass fraction of chlorides in terms of Cl -,%, no more	0.7	0.7	0.7	0.8
5. Mass fraction of sulfates (SO 4 ²־),%, no more	0.025	0.05	0.03	0.1
6. Mass fraction of iron (Fe 2+),%, no more	0.03	0.03	0.004	0.01
7. Mass fraction of hypochlorous potassium (KClO 3),%, no more	0.1	0.2	0.15	0.3
8. Mass fraction of silicon (Si),%, no more	0.01	0.02	0.015	-
9. Mass fraction of sodium in terms of NaOH,%, no more	1.5	2.0	1.7	2.0
10. Mass fraction of calcium (Ca 2+),%, no more	0.01	0.01	0.005	-
11. Mass fraction of aluminum (Al 3+),%, no more	0.003	0.005	0.003	-
12. Mass fraction of nitrates and nitrites in terms of nitrogen (N),%, no more	0.003	0.003	0.003	-

Examples of physicochemical indicators of potassium hydroxide of foreign production

Name	Potassium hydroxideCAS 1310-58-3
Origin	Made in France	Manufactured in South Korea	Made in China
Appearance	White scales
1. Mas. proportion of potassium hydroxide (KOH),% not less	90,0	90,0	90 .0; 95.0
2. Mas. the proportion of potassium carbonate (K2CO3),% no more	0,5	0,5	2,0
3. Mas. the proportion of chlorides (Cl)% no more	0,001	0,005	1,0
4. Mas. the proportion of iron (Fe),% no more	0,0003	0,0003	0.0005
5. Mas. share of sulfates (SO4),% no more	0,001	0,003	0.005
6. Mas. share of nitrates and nitrites in terms of nitrogen (N),% no more	0,0005	0,0005	0.0005
7. Mas. the proportion of potassium perchloric acid (KClO3). % no more	Not def.	Not def.	Not def.
8. Mas. share of silicon (Si),%, no more	Not def.	Not def.	Not def.
9. Mas. the proportion of sodium (Na) in terms of NaOH,% no more	1.0	1,0	0.8
10.Mass. the proportion of phosphates (PO4),% no more	0,0002	0,001	0.005
11. Mas. share of silicic acid (SiO2),%, not more	0,002	0,002	0.01
12. Mass fraction of aluminum (Al)% no more	0,0001	0,001	0.002
13. Mass fraction of calcium (Ca),%, no more	0,001	0,001	0.005
14. Mas. share of nickel (Ni),%, no more	0,0005	0,0005	0.0005
15. Mas. the proportion of heavy metals (Pb). % no more	0,0005	0,0005	0.002

Main areas of consumption
Potassium hydroxide is an almost universal chemical compound. Below are examples of materials and processes in which it is used:
- neutralization of acids,
- alkaline batteries,
- catalysis,
- detergents,
- drilling fluids,
- dyes,
- fertilizers,
- food production,
- gas cleaning,
- metallurgical production,
- oil distillation,
- various organic and inorganic substances,
- paper production,
- pesticides,
- pharmaceuticals,
- pH regulation,
- potassium carbonate and other potassium compounds,
- soaps,
- synthetic rubber.

One of the most important applications for potassium hydroxide is in the production of mild soaps. Blends of potassium and sodium soaps are used to make liquid soaps, detergents, shampoos, shaving creams, bleaches, and some pharmaceuticals. Another important area of ​​application is the production of various potassium salts. For example, potassium permanganate is produced by fusing manganese dioxide with caustic potash and then oxidizing the resulting potassium manganate in an electrolysis chamber. Potassium dichromate can be obtained in a similar way, although more often it is made by fusing finely ground chromite ore with potassium carbonate or hydroxide and exposing the resulting chromate to acid to form potassium dichromate. Potassium hydroxide is also used together with caustic soda in the production of many dyes and other organic compounds, as well as an adsorbent of gases, a dehydrating agent, a precipitator of insoluble metal hydroxides, in alkaline batteries, to obtain various potassium compounds.
In addition, potassium hydroxide is used for the disinfection of wastewater, in the nitrogen industry for drying gases, in the rubber industry as a "potassium soap" that prevents sticking of rubber crumbs, etc.

Liquid technical potassium hydroxide is used in the production of fertilizers, synthetic rubber, electrolytes, reagents, in the medical industry.

Flaked potassium hydroxide is used in the production of fertilizers and synthetic rubber, in the pharmaceutical industry and in other industries.

Technical potassium hydroxide is used for leaching steel castings, for maintaining the alkalinity of drilling fluids within specified limits, for the production of fertilizers, synthetic rubber and in other industries.

Features and trends of production technologies
On an industrial scale, potassium hydroxide is produced by electrolysis of potassium chloride. There are three options for carrying out electrolysis: electrolysis with a solid asbestos or polymer cathode (diaphragm and membrane production methods), electrolysis with a liquid mercury cathode (mercury production method). Among the electrochemical production methods, the easiest and most convenient method is electrolysis with a mercury cathode, but this method causes significant harm to the environment as a result of evaporation and leakage of metallic mercury. The membrane production method is the most efficient, but also the most complex. While the diaphragm and mercury methods have been known since 1885 and 1892, respectively, the membrane method appeared relatively recently - in the 1970s.

Rice. 1.1. Membrane cell

The main trend in the global production of potassium hydroxide in the last 10 years is the transition of manufacturers to the membrane electrolysis method. Mercury electrolysis is an outdated technology that is economically disadvantageous and has a negative impact on the environment. Membrane electrolysis completely eliminates the use of mercury. The ecological safety of the membrane method lies in the fact that the wastewater after treatment is again fed into the technological cycle, and not discharged into the sewage system. When using this method, the following tasks are solved: the stage of liquefaction and evaporation of chlorine is eliminated, hydrogen is used for process steam, gas emissions of chlorine and its compounds are excluded. The world leader in membrane technology is the Japanese company Asahi Kasei.
In Russia, the production of potassium hydroxide is carried out by mercury (ZP KChKhK) and diaphragm (Soda-Chlorate) methods.
A feature of the technological design of potassium hydroxide production is the fact that both caustic potassium and caustic soda can be produced at similar electrolysis plants. This allows manufacturers to switch to potassium hydroxide production without significant capital investments instead of caustic soda, the production of which is not so profitable, and marketing has become more difficult in recent years. At the same time, in the event of changes in the market, a painless transfer of electrolyzers to the production of a previously produced product is possible.
An example of the transfer of a part of capacities from sodium hydroxide production to potassium hydroxide is OJSC Polymer Plant KChKhK, which started industrial production of caustic potash in five electrolyzers in 2007.