Potassium in nature (2.4% in the Earth's crust). Properties of potassium

Potassium

POTASSIUM-I; m.[Arab. kali] Chemical element (K), silvery metal white, extracted from carbonic potassium salt (potash).

◁ Potassium, oh, oh. K-th deposits. K salts. Potash, oh, oh. K industry. K fertilizers.

potassium

(lat. Kalium), chemical element of group I periodic table, refers to alkali metals. The name is from the Arabic al-kali - potash (a long-known potassium compound extracted from wood ash). Silver-white metal, soft, fusible; density 0.8629 g/cm 3, t pl 63.51ºC. It oxidizes quickly in air and reacts explosively with water. It ranks 7th in terms of prevalence in the earth's crust (minerals: sylvite, kainite, carnallite, etc.; see Potassium salts). It is part of the tissues of plant and animal organisms. About 90% of mined salts are used as fertilizers. Potassium metal is used in chemical current sources, as a getter in vacuum tubes, to produce superperoxide KO 2; alloys K with Na - coolants in nuclear reactors.

POTASSIUM

POTASSIUM (lat. Kalium), K (read “potassium”), chemical element with atomic number 19, atomic mass 39.0983.
Potassium occurs naturally as two stable nuclides (cm. NUCLIDE): 39 K (93.10% by mass) and 41 K (6.88%), as well as one radioactive 40 K (0.02%). The half-life of potassium-40 T 1/2 is approximately 3 times less than T 1/2 of uranium-238 and is 1.28 billion years. The b-decay of potassium-40 produces stable calcium-40, and the decay by electron capture (cm. ELECTRONIC CAPTURE) the inert gas argon-40 is formed.
Potassium belongs to the alkali metals (cm. ALKALI METALS). In Mendeleev's periodic table, potassium occupies a place in the fourth period in subgroup IA. Outer electron layer 4 configuration s 1, so potassium always exhibits an oxidation state of +1 (valency I).
The atomic radius of potassium is 0.227 nm, the radius of the K + ion is 0.133 nm. The energies of sequential ionization of the potassium atom are 4.34 and 31.8 eV. Electronegativity (cm. ELECTRONEGATIVITY) Potassium according to Pauling is 0.82, which indicates its pronounced metallic properties.
In its free form it is a soft, light, silvery metal.
History of discovery
Potassium compounds, as well as its closest chemical analogue - sodium (cm. SODIUM), have been known since antiquity and found application in various areas human activity. However, these metals themselves were first isolated in a free state only in 1807 during the experiments of the English scientist G. Davy (cm. DAVY Humphrey). Davy using galvanic cells as a source electric current, carried out electrolysis of potash melts (cm. POTASH) And caustic soda (cm. CAUSTIC SODA) and thus isolated metallic potassium and sodium, which he called “potassium” (hence the name of potassium preserved in English-speaking countries and France - potassium) and “sodium”. In 1809, the English chemist L. V. Gilbert proposed the name “potassium” (from the Arabic al-kali - potash).
Being in nature
The potassium content in the earth's crust is 2.41% by mass; potassium is one of the top ten most abundant elements in the earth's crust. Main minerals containing potassium: sylvite (cm. SYLVIN) KCl (52.44% K), sylvinite (Na,K)Cl (this mineral is a tightly compressed mechanical mixture of crystals of potassium chloride KCl and sodium chloride NaCl), carnallite (cm. CARNALLITE) KCl MgCl 2 6H 2 O (35.8% K), various aluminosilicates (cm. ALUMINUM SILICATES) containing potassium, kainite (cm. KAINIT) KCl MgSO 4 3H 2 O, polyhalite (cm. POLYHALITE) K 2 SO 4 MgSO 4 2CaSO 4 2H 2 O, alunite (cm. ALUNITE) KAl 3 (SO 4) 2 (OH) 6. Sea water contains about 0.04% potassium.
Receipt
Currently, potassium is obtained by reacting molten KOH (at 380-450°C) or KCl (at 760-890°C) with liquid sodium:
Na + KOH = NaOH + K
Potassium is also obtained by electrolysis of molten KCl mixed with K 2 CO 3 at temperatures close to 700 ° C:
2KCl = 2K + Cl 2
Potassium is purified from impurities by vacuum distillation.
Physical and chemical properties
Potassium metal is soft, it can be easily cut with a knife and can be pressed and rolled. It has a cubic body-centered cubic lattice, parameter A= 0.5344 nm. The density of potassium is less than the density of water and is equal to 0.8629 g/cm3. Like all alkali metals, potassium melts easily (melting point 63.51°C) and begins to evaporate even at relatively low temperatures (boiling point of potassium 761°C).
Potassium, like other alkali metals, is chemically very active. Easily interacts with atmospheric oxygen to form a mixture, mainly consisting of peroxide K 2 O 2 and superoxide KO 2 (K 2 O 4):
2K + O 2 = K 2 O 2, K + O 2 = KO 2.
When heated in air, potassium burns with a violet-red flame. Potassium reacts explosively with water and dilute acids (the resulting hydrogen ignites):
2K + 2H 2 O = 2KOH + H 2
Oxygen-containing acids can be reduced during this interaction. For example, the sulfur atom of sulfuric acid is reduced to S, SO 2 or S 2–:
8K + 4H 2 SO 4 = K 2 S + 3K 2 SO 4 + 4H 2 O.
When heated to 200-300 °C, potassium reacts with hydrogen to form the salt-like hydride KH:
2K + H 2 = 2KH
With halogens (cm. HALOGEN) potassium interacts with the explosion. It is interesting to note that potassium does not interact with nitrogen.
Like other alkali metals, potassium readily dissolves in liquid ammonia to form blue solutions. In this state, potassium is used to carry out certain reactions. During storage, potassium slowly reacts with ammonia to form the amide KNH 2:
2K + 2NH 3 l. = 2KNH 2 + H 2
The most important potassium compounds: K2O oxide, K2O2 peroxide, K2O4 superoxide, KOH hydroxide, KI iodide, K2CO3 carbonate and KCl chloride.
Potassium oxide K 2 O is usually obtained indirectly through the reaction of peroxide and potassium metal:
2K + K 2 O 2 = 2K 2 O
This oxide exhibits pronounced basic properties and easily reacts with water to form potassium hydroxide KOH:
K2O + H2O = 2KOH
Potassium hydroxide, or potassium hydroxide, is highly soluble in water (up to 49.10% by weight at 20°C). The resulting solution is a very strong alkali base ( cm. ALKALI). KOH reacts with acidic and amphoteric oxides:
SO 2 + 2KOH = K 2 SO 3 + H 2 O,
Al 2 O 3 + 2KOH + 3H 2 O = 2K (this is how the reaction occurs in solution) and
Al 2 O 3 + 2KOH = 2KAlO 2 + H 2 O (this is how the reaction occurs when the reagents fuse).
In industry, potassium hydroxide KOH is produced by electrolysis of aqueous solutions of KCl or K 2 CO 3 using ion exchange membranes and diaphragms:
2KCl + 2H 2 O = 2KOH + Cl 2 + H 2,
or due to exchange reactions of solutions of K 2 CO 3 or K 2 SO 4 with Ca(OH) 2 or Ba(OH) 2:
K 2 CO 3 + Ba(OH) 2 = 2KOH + BaCO 3
Contact of solid potassium hydroxide or drops of its solutions on the skin and eyes causes severe burns to the skin and mucous membranes, so you should only work with these caustic substances wearing protective glasses and gloves. Aqueous solutions of potassium hydroxide during storage destroy glass, and melts destroy porcelain.
Potassium carbonate K 2 CO 3 (common name potash) is obtained by neutralizing a solution of potassium hydroxide with carbon dioxide:
2KOH + CO 2 = K 2 CO 3 + H 2 O.
Potash is found in significant quantities in the ash of some plants.
Application
Potassium metal is a material for electrodes in chemical current sources. Alloy of potassium with another alkali metal- sodium is used as a coolant (cm. COOLANT) in nuclear reactors.
On a much larger scale than potassium metal, its compounds are used. Potassium is an important component of the mineral nutrition of plants; they need it in significant quantities for normal development, therefore potassium fertilizers are widely used (cm. POTASH FERTILIZERS): potassium chloride KCl, potassium nitrate, or potassium nitrate, KNO 3, potash K 2 CO 3 and other potassium salts. Potash is also used in the production of special optical glasses, as a hydrogen sulfide absorber for gas purification, as a dehydrating agent and for tanning leather.
Potassium iodide KI is used as a medicine. Potassium iodide is also used in photography and as a microfertilizer. A solution of potassium permanganate KMnO 4 (“potassium permanganate”) is used as an antiseptic.
By content in rocks ah radioactive 40 K determine their age.
Potassium in the body
Potassium is one of the most important biogenic elements (cm. BIOGENIC ELEMENTS), constantly present in all cells of all organisms. Potassium ions K+ participate in the functioning of ion channels (cm. ION CHANNELS) and regulation of permeability biological membranes (cm. BIOLOGICAL MEMBRANES), in the generation and conduction of nerve impulses, in the regulation of the activity of the heart and other muscles, in various processes metabolism. The potassium content in animal and human tissues is regulated by adrenal steroid hormones. The average human body (body weight 70 kg) contains about 140 g of potassium. Therefore, for normal life, the body must receive 2-3 g of potassium per day with food. Potassium-rich foods include raisins, dried apricots, peas and others.
Features of handling potassium metal
Potassium metal can cause very severe burns skin, when tiny particles of potassium get into the eyes, severe lesions with loss of vision occur, so you can work with potassium metal only in protective gloves and goggles. The ignited potassium is poured with mineral oil or covered with a mixture of talc and NaCl. Store potassium in hermetically sealed iron containers under a layer of dehydrated kerosene or mineral oil.

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Novolatinsk. kalium, from Arabic. kali, alkali. A soft and light metal that makes up the base of Kali. Devi was discovered in 1807. Explanation of 25,000 foreign words that have come into use in the Russian language, with the meaning of their roots. Mikhelson A.D., 1865.… … Dictionary of foreign words of the Russian language

- (Kalium), K, chemical element of group I of the periodic table, atomic number 19, atomic mass 39.0983; refers to alkali metals; melting point 63.51shC. In living organisms, potassium is the main intracellular cation and is involved in the generation of bioelectric... ... Modern encyclopedia

POTASSIUM- (Kalium, s. Potassium), chemical. element, symbol TO, serial number 19, silvery-white, shiny metal, having the usual density of wax; discovered by Devi in ​​1807. Ud. V. at 20° 0.8621, atomic weight 39.1, monovalent; melting temperature... Great Medical Encyclopedia

Potassium- (Kalium), K, chemical element of group I of the periodic table, atomic number 19, atomic mass 39.0983; refers to alkali metals; melting point 63.51°C. In living organisms, potassium is the main intracellular cation and is involved in the generation of bioelectric... ... Illustrated encyclopedic Dictionary

- (symbol K), a common chemical element belonging to ALKALI METALS. It was first isolated by Sir Humphry Davy in 1807. Its main ores are sylvite (potassium chloride), carnallite and polyhalite. Potassium is a coolant in ATOMIC... Scientific and technical encyclopedic dictionary

Husband. potassium, a metal that forms the base of potassium, very similar to sodium (sodium). Kali medium, uncl., vegetable alkali or alkaline salt; potassium carbonate, pure potash. Potassium, related to potassium. Calcite, containing potassium. Intelligent... ... Dahl's Explanatory Dictionary - POTASSIUM, potassium, many. no, male, and Kali, uncl., cf. (Arabic potash) (chemical). The chemical element is an alkali metal of silvery-white color, extracted from potassium carbonate. Ushakov's explanatory dictionary. D.N. Ushakov. 1935 1940 ... Ushakov's Explanatory Dictionary

The content of the article

POTASSIUM(Kalium) K, chemical element 1 (Ia) of group of the Periodic table, belongs to the alkaline elements. Atomic number 19, atomic mass 39.0983. Consists of two stable isotopes 39 K (93.259%) and 41 K (6.729%), as well as radioactive isotope 40 K with a half-life of ~10 9 years. This isotope plays a special role in nature. Its share in the mixture of isotopes is only 0.01%, but it is the source of almost all argon 40 Ar contained in the earth's atmosphere, which is formed during the radioactive decay of 40 K. In addition, 40 K is present in all living organisms, which may has a certain influence on their development.

The 40 K isotope is used to determine the age of rocks using the potassium-argon method. Artificial isotope 42 K, with a half-life of 15.52 years, is used as a radiotracer in medicine and biology.

Oxidation state +1.

Potassium compounds have been known since ancient times. Potash - potassium carbonate K 2 CO 3 - has long been isolated from wood ash.

Potassium metal was prepared by electrolysis of molten potassium hydroxide (KOH) in 1807 by the English chemist and physicist Humphry Davy. The name "potassium" chosen by Davy reflects the element's origins in potash. Latin name element is derived from the Arabic name for potash - “al-kali”. To Russian chemical nomenclature the word “potassium” was introduced in 1831 by St. Petersburg academician Hermann Hess (1802–1850).

Distribution of potassium in nature and its industrial extraction.

Large deposits of potassium salts in relatively pure form formed as a result of the evaporation of ancient seas. The most important potassium minerals for the chemical industry are sylvin (KCl) and sylvinite (a mixed salt of NaCl and KCl). Potassium is also found in the form of double chloride KCl MgCl 2 6H 2 O (carnallite) and sulfate K 2 Mg 2 (SO 4) 3 (langbeinite). Massive layers of potassium salts were first discovered in Stassfurt (Germany) in 1856. Of these, from 1861 to 1972 industrial scale potash was mined.

Ocean water contains about 0.06% potassium chloride. In some inland bodies of water, such as Salt Lake or the Dead Sea, its concentration can reach 1.5%, which makes the extraction of the element economically feasible. A huge plant has been built in Jordan, capable of extracting millions of tons of potassium salts from the Dead Sea.

Although sodium and potassium are almost equally abundant in rocks, the ocean contains about 30 times less potassium than sodium. This is due, in particular, to the fact that potassium salts, containing a larger cation, are less soluble than sodium salts, and potassium is more firmly bound in complex silicates and aluminosilicates in the soil due to ion exchange in clays. In addition, potassium, which is leached from rocks, is to a greater extent absorbed by plants. It is estimated that of the thousand potassium atoms released by chemical weathering, only two reach marine basins, and 998 remain in the soil. “The soil absorbs potassium, and this is its miraculous power,” wrote academician Alexander Evgenievich Fersman (1883–1945).

Potassium is an essential element of plant life, and the development wild plants often limited by potassium availability. With a lack of potassium, plants grow more slowly, their leaves, especially old ones, turn yellow and brown at the edges, the stem becomes thin and fragile, and the seeds lose their viability. The fruits of such a plant - this is especially noticeable in fruits - will be less sweet than those of plants that received a normal dose of potassium. The lack of potassium is compensated with fertilizers.

Potash fertilizers are the main type of potassium-containing products (95%). KCl is the most used, accounting for more than 90% of the potassium used as fertilizer.

World production of potash fertilizers in 2003 was estimated at 27.8 million tons (in terms of K 2 O, the potassium content in potash fertilizers is usually converted to K 2 O). Of these, 33% were produced in Canada. The Uralkali and Belaruskali production associations account for 13% of the global production of potash fertilizers.

Characteristics of simple substances and industrial production of potassium metal.

Potassium is a soft silvery-white metal with a melting point of 63.51° C and a boiling point of 761° C. It gives the flame a characteristic red-violet color, which is associated with the ease of excitation of its outer electrons.

It is chemically very active, easily interacts with oxygen, and ignites when heated in air. The main product of this reaction is potassium superoxide KO 2.

With water and dilute acids, potassium reacts with explosion and ignition. Sulfuric acid reduces to hydrogen sulfide, sulfur and sulfur dioxide, and nitrogen - to nitrogen oxides and N 2.

When heated to 200–350° C, potassium reacts with hydrogen to form the hydride KH. Potassium metal ignites in a fluorine atmosphere, reacts weakly with liquid chlorine, but explodes on contact with bromine and trituration with iodine. Potassium reacts with chalcogens and phosphorus. With graphite at 250–500° C it forms layered compounds of the composition C 8 K–C 60 K.

Potassium dissolves in liquid ammonia (35.9 g per 100 ml at –70 ° C) to form bright blue metastable solutions with unusual properties. This phenomenon was apparently first observed by Sir Humphry Davy in 1808. Solutions of potassium in liquid ammonia have been widely studied since they were obtained by T. Weil in 1863.

Potassium does not dissolve in liquid lithium, magnesium, cadmium, zinc, aluminum and gallium and does not react with them. With sodium it forms the intermetallic compound KNa 2, which melts with decomposition at 7° C. With rubidium and cesium, potassium gives solid solutions with minimum melting points of about 35 ° C. With mercury it forms an amalgam containing two mercurides KHg 2 and KHg with melting points of 270 and 180 ° C, respectively.

Potassium reacts vigorously with many oxides, reducing them to simple substances. With alcohols it forms alcoholates.

Unlike sodium, potassium cannot be obtained by electrolysis of molten chloride, since potassium dissolves very well in molten chloride and does not float to the surface. An additional difficulty is created by the formation of superoxide, which reacts with potassium metal explosively, so the method of industrial production of potassium metal is to reduce molten potassium chloride with sodium metal at 850 ° C.

The reduction of potassium chloride with sodium, at first glance, contradicts the usual procedure reactivity(potassium is more reactive than sodium). However, at 850–880° C equilibrium is established:

Na(g) + K + (l) Na + (l) + K(g)

Since potassium is more volatile, it evaporates earlier, which shifts the equilibrium and promotes the reaction. Fractional distillation in a packed column can produce potassium of 99.5% purity, but usually a mixture of potassium and sodium is used for transportation. Alloys containing 15–55% sodium are (at room temperature) liquid, so they are easier to transport.

Sometimes potassium is reduced from chloride by other elements that form stable oxides:

6KCl + 2Al + 4CaO = 3CaCl 2 + CaO Al 2 O 3 + 6K

Potassium metal, which is more difficult and expensive to produce than sodium, is produced in much smaller quantities (world production is about 500 tons per year). One of the most important areas of application is the production of superoxide KO 2 by direct combustion of metal.

Potassium metal is used as a catalyst in the production of certain types of synthetic rubber, as well as in laboratory practice. An alloy of potassium and sodium serves as a coolant in nuclear reactors. It is also a reducing agent in the production of titanium.

Potassium causes severe skin burns. If even the smallest crumbs get into your eyes, loss of vision can occur. The ignited potassium is poured with mineral oil or covered with a mixture of talc and sodium chloride.

Store potassium in hermetically sealed boxes under a layer of dehydrated kerosene or mineral oil. Potassium waste is disposed of by treating it with dry ethanol or propanol, followed by decomposition of the resulting alcoholates with water.

Potassium compounds.

Potassium forms numerous binary compounds and salts. Almost all potassium salts are highly soluble. The exceptions are:

KHC 4 H 4 O 6 – potassium hydrogen tartrate

KClO 4 – potassium perchlorate

K 2 Na 6H 2 O – sodium dipotassium hexanitrocobaltate(III) hydrate

K 2 – potassium hexachloroplatinate(IV)

Potassium oxide K 2 O forms yellowish crystals. It is prepared by heating potassium with potassium hydroxide, peroxide, nitrate or nitrite:

2KNO 2 + 6K = 4K 2 O + N 2

Heating of a mixture of potassium azide KN 3 and potassium nitrite or oxidation of potassium dissolved in liquid ammonia with a calculated amount of oxygen is also used.

Potassium oxide is an activator of sponge iron, which is used as a catalyst in the synthesis of ammonia.

Potassium peroxide It is difficult to obtain K2O2 from simple substances, since it is easily oxidized to superoxide KО2, so metal oxidation with NO is used. However best method its preparation is the quantitative oxidation of a metal dissolved in liquid ammonia.

Potassium peroxide can be considered as a salt of the dibasic acid H 2 O 2. Therefore, when it reacts with acids or water in the cold, hydrogen peroxide is quantitatively formed.

Potassium superoxide KO 2 (orange) is formed by normal combustion of metal in air. This compound is used as a backup source of oxygen in breathing masks in mines, submarines and spacecraft.

With careful thermal decomposition KO 2 sesquioxide “K 2 O 3” is formed in the form of a dark paramagnetic powder. It can also be obtained by oxidation of a metal dissolved in liquid ammonia, or by controlled oxidation of peroxide. It is assumed to be a dinad peroxide peroxide [(K +) 4 (O 2 2–)(O 2 –) 2 ].

Potassium ozonide KO 3 can be obtained by the action of ozone on anhydrous potassium hydroxide powder at low temperature, followed by extraction of the product (red) with liquid ammonia. It is used as a component of compositions for air regeneration in closed systems.

Potassium hydroxide KOH is a strong base and belongs to alkalis. Its traditional name “caustic potassium” reflects the corrosive effect of this substance on living tissue.

In industry, potassium hydroxide is produced by electrolysis of aqueous solutions of potassium chloride or carbonate with an iron or mercury cathode (world production is about 0.7 million tons per year). Potassium hydroxide can be isolated from the filtrate after separating the precipitates formed by the reaction of potassium carbonate with calcium hydroxide or potassium sulfate with barium hydroxide.

Potassium hydroxide is used to produce liquid soap and various potassium compounds. In addition, it serves as an electrolyte in alkaline batteries.

Potassium fluoride KF forms the rare mineral carobbiite. Potassium fluoride is obtained by reacting aqueous solutions of hydrogen fluoride or ammonium fluoride with potassium hydroxide or its salts.

Potassium fluoride is used for the synthesis of various fluorine-containing potassium compounds, as a fluorinating agent in organic synthesis, and also as a component of acid-resistant putties and special glasses.

Potassium chloride KCl occurs naturally. The raw materials for its isolation are sylvin, sylvinite, and carnallite.

Potassium chloride is obtained from sylvinite using the methods of halurgy and flotation. Galurgy (translated from Greek as “salt work”) includes the study of the composition and properties of natural salt raw materials and the development of methods industrial production from it mineral salts. The halurgical separation method is based on the different solubilities of KCl and NaCl in water at elevated temperatures. At normal temperatures, the solubility of potassium and sodium chlorides is almost the same. With increasing temperature, the solubility of sodium chloride remains almost unchanged, but the solubility of potassium chloride increases sharply. A saturated solution of both salts is prepared in the cold, then it is heated and sylvinite is treated with it. In this case, the solution is additionally saturated with potassium chloride, and part of the sodium chloride is displaced from the solution, precipitates and is separated by filtration. The solution is cooled and excess potassium chloride crystallizes out of it. The crystals are separated in centrifuges and dried, and the mother liquor is used to process a new portion of sylvinite. To isolate potassium chloride, this method is used more widely than the flotation method, which is based on different wettability of substances.

Potassium chloride is the most common potash fertilizer. Apart from its use as a fertilizer, it is mainly used to produce potassium hydroxide by electrolysis. Other potassium compounds are also obtained from it.

Potassium bromide KBr is obtained by reacting bromine with potassium hydroxide in the presence of ammonia, as well as by reactions of bromine or bromides with potassium salts.

Potassium bromide is widely used in photography. It often serves as a source of bromine in organic synthesis. Previously, potassium bromide was used as a sedative in medicine (“bromine”). Potassium bromide single crystals are used in the manufacture of prisms for IR spectrometers, and also as a matrix for recording IR spectra of solids.

Potassium iodide KI forms colorless crystals, which in the light become yellowish due to oxidation by atmospheric oxygen and the release of iodine. Therefore, potassium iodide is stored in dark glass bottles.

Potassium iodide is obtained by reacting iodine with potassium hydroxide in the presence of formic acid or hydrogen peroxide, as well as by exchange reactions of iodides with potassium salts. It is oxidized by nitric acid to potassium iodate KIO 3. Potassium iodide reacts with iodine to form a water-soluble complex K, and with chlorine and bromine it gives K and K, respectively.

Potassium iodide is used as a medicine in human and veterinary medicine. It is a reagent in iodometry. Potassium iodide is an anti-foiling agent in photography, an electrolyte component in electrochemical converters, an additive for increasing the solubility of iodine in water and polar solvents, a microfertilizer.

Potassium sulfide K 2 S is highly soluble in water. During hydrolysis, it creates an alkaline environment in the solution:

K 2 S = 2K + + S 2– ; S 2– + H 2 O HS – + OH –

Potassium sulfide easily oxidizes in air and burns when ignited. It is obtained by reacting potassium or potassium carbonate with sulfur without access to air, as well as by reducing potassium sulfate with carbon.

Potassium sulfide is a component of photosensitive emulsions in photography. It is used as an analytical reagent for the separation of metal sulfides and as a component of compositions for the treatment of hides.

When an aqueous solution is saturated with hydrogen sulfide, potassium hydrosulfide KHS is formed, which can be isolated in the form of colorless crystals. It is used in analytical chemistry for the separation of heavy metals.

By heating potassium sulfide with sulfur, yellow or red potassium polysulfides KS are obtained n (n= 2–6). Aqueous solutions of potassium polysulfides can be obtained by boiling solutions of potassium hydroxide or sulfide with sulfur. When potassium carbonate is sintered with excess sulfur in air, the so-called sulfur liver is formed - KS mixture n and K 2 S 2 O 3 .

Polysulfides are used for sulfidation of steel and cast iron. Liver sulfur is used as a medicine to treat skin diseases and as a pesticide.

Potassium sulfate K 2 SO 4 occurs naturally in deposits of potassium salts and in the waters of salt lakes. It can be obtained by an exchange reaction between potassium chloride and sulfuric acid or sulfates of other elements.

Potassium sulfate is used as a fertilizer. This substance is more expensive than potassium chloride, but is not hygroscopic and does not caking; unlike potassium chloride, potassium sulfate can be used on any soil, including saline soils.

Alum and other potassium compounds are obtained from potassium sulfate. It is part of the charge in glass production.

Potassium nitrate KNO 3 is a strong oxidizing agent. It is often called potassium nitrate. In nature, it is formed during the decomposition of organic substances as a result of the activity of nitrifying bacteria.

Potassium nitrate is obtained by the exchange reaction between potassium chloride and sodium nitrate, as well as by the action nitric acid or nitrous gases to potassium carbonate or chloride.

Potassium nitrate is an excellent fertilizer containing both potassium and nitrogen, but is used less than potassium chloride due to the high cost of production. Potassium nitrate is also used for the manufacture of black powder and pyrotechnic compositions, in the production of matches and glass. In addition, it is used in canning meat products.

Potassium carbonate K 2 CO 3 is also called potash. Obtained by the action of carbon dioxide on solutions of potassium hydroxide or suspensions of magnesium carbonate in the presence of potassium chloride. It is a by-product during the processing of nepheline into alumina.

A significant amount of potassium carbonate is contained in plant ash. The most potassium is in sunflower ash – 36.3%. There is significantly less potassium oxide in the ash of firewood - from 3.2% (spruce firewood) to 13.8% (birch firewood). There is even less potassium in peat ash.

Potassium carbonate is used primarily to produce high-quality glass used in optical lenses, color television tubes, and fluorescent lamps. It is also used in the production of porcelain, dyes and pigments.

Potassium permanganate KMnO 4 forms dark purple crystals. Solutions of this substance have a red-violet color. Potassium permanganate is obtained by anodic oxidation of manganese or ferromanganese in a strongly alkaline medium.

Potassium permanganate is a strong oxidizing agent. It is used as a bleaching, whitening and cleansing agent. It is also used in organic synthesis, for example, in the production of saccharin.

Potassium hydride KH is a white solid that decomposes when heated to simple substances. Potassium hydride is the strongest reducing agent. It ignites in moist air and in fluorine or chlorine environments. Potassium hydride can be oxidized even by weak oxidizing agents such as water and carbon dioxide:

KH + H 2 O = KOH + H 2

KH + CO 2 = K(HCOO) (potassium formate)

Potassium hydride also reacts with acids and alcohols, which may cause fire. It reduces hydrogen sulfide, hydrogen chloride and other substances containing hydrogen (I):

2KH + H 2 S = K 2 S + 2H 2

KH + HCl = KCl + H2

Potassium hydride is used as a reducing agent in inorganic and organic syntheses.

Potassium cyanide KCN, known as potassium cyanide, forms colorless crystals that are highly soluble in water and some non-aqueous solvents. In an aqueous solution, it gradually hydrolyzes with the release of hydrogen cyanide HCN, and when aqueous solutions are boiled, it decomposes into potassium formate and ammonia.

In the presence of potassium cyanide, things may not go well common reactions, for example, copper reacts with water, releasing hydrogen from it and forming potassium dicyanocuprate(I):

In similar conditions, interaction occurs in the case of gold. True, this one is less active metal is not able to be oxidized by water, but in the presence of oxygen it goes into solution in the form of a cyano complex - potassium dicyanoaurate(I):

4Au + 8KCN + 2H 2 O + O 2 = 4K + 4NaOH

Potassium cyanide is prepared by reacting hydrogen cyanide with excess potassium hydroxide. It is a reagent for the extraction of silver and gold from low-grade ores, a component of electrolytes for the purification of platinum from silver and for electroplating gilding and silvering. Potassium cyanide is used as a reagent in chemical analysis for the determination of silver, nickel and mercury.

Potassium cyanide is very toxic. The lethal dose for humans is 120 mg.

Complex connections. Potassium forms the most stable complex compounds with polydentate ligands (molecules or ions that can be connected to an atom by several bonds), for example, with macrocyclic polyethers (crown ethers).

Crown ethers (from the English crown - crown) contain over 11 atoms in the ring, at least four of which are oxygen atoms. In the trivial names of crown ethers total number atoms in the ring and the number of oxygen atoms are indicated by numbers, which are placed, respectively, before and after the word “crown”. Such names are much shorter than systematic ones. For example, 12-crown-4 (Fig. 1) according to the international nomenclature is called 1,4,7,10,13-tetraoxocyclododecane.

Rice. 1. GRAPHIC FORMULA 12-crown-4 compounds.

Crown ethers form stable complexes with metal cations. In this case, the cation is included in the intramolecular cavity of the crown ether and is retained there due to the ion-dipole interaction with oxygen atoms. The most stable complexes are those with cations whose geometric parameters correspond to the cavity of the crown ether. With the potassium cation, the most stable complexes are formed by crown ethers containing 6 oxygen atoms, for example, 18-crown-6 (Fig. 2).

Rice. 2. GRAPHIC FORMULA complex kalias 18-crown-6 .

Biological role of potassium(and sodium). Potassium together with sodium regulate metabolic processes in living organisms. In the human body, inside the cells there is a large amount of potassium ions (0.12–0.16 mol/l), but relatively few sodium ions (0.01 mol/l). The content of sodium ions is much higher in the extracellular fluid (about 0.12 mol/l), therefore potassium ions control intracellular activity, and sodium ions control intercellular activity. These ions cannot replace each other.

The existence of a sodium-potassium gradient on the inner and outer sides of the cell membrane leads to the emergence of a potential difference across opposite sides membranes. Nerve fibers are able to transmit impulses and muscles to contract precisely due to the existence of an internal negative charge in relation to the outer surface of the membrane. Thus, in the body, sodium and potassium ions exercise physiological control and trigger mechanisms. They contribute to the transmission of nerve impulses. The human psyche depends on the balance of sodium and potassium ions in the body. The concentration of sodium and potassium ions retained and released through the kidneys is controlled by certain hormones. Thus, mineralocorticoids increase the release of potassium ions and reduce the release of sodium ions.

Potassium ions are part of enzymes that catalyze the transfer (transport) of ions through biomembranes, redox and hydrolytic processes. They also serve to maintain the structure of cell walls and control their condition. The sodium ion activates several enzymes that potassium cannot activate, just as the sodium ion cannot act on potassium-dependent enzymes. When these ions enter the cell, they are bound by suitable ligands according to their chemical activity. The role of such ligands is played by macrocyclic compounds, the model analogues of which are crown ethers. Some antibiotics (like valinomycin) transport potassium ions into the mitochondria.

It has been established that the operation of (Na + –K +)-ATPase (adenosine triphosphatase), a membrane enzyme that catalyzes the hydrolysis of ATP, requires both sodium and potassium ions. ATP transportase binds and releases sodium and potassium ions at certain stages of the enzymatic reaction, since the affinity of the active sites of the enzyme for sodium and potassium ions changes as the reaction proceeds. In this case, structural changes in the enzyme lead to the fact that sodium and potassium cations are accepted on one side of the membrane and released on the other. Thus, simultaneously with the hydrolysis of ATP, the selective movement of cations of alkaline elements occurs (the work of the so-called Na–K pump).

The daily potassium requirement for a child is 12–13 mg per 1 kg of weight, and for an adult – 2–3 mg, i.e. 4–6 times less. A person gets most of the potassium he needs from foods of plant origin.

Elena Savinkina

This article will characterize potassium from the point of view of physics and chemistry. The first of these sciences studies the mechanical and external properties of substances. And the second is their interaction with each other - this is chemistry. Potassium is the nineteenth element in the periodic table. It belongs to This article will discuss and electronic formula potassium, and its behavior with other substances, etc. It is one of the most active metals. The science that studies this and other elements is chemistry. Grade 8 involves studying their properties. Therefore, this article will be useful for schoolchildren. So, let's begin.

Characteristics of potassium from the point of view of physics

This is a simple substance that normal conditions is in solid state of aggregation. The melting point is sixty-three degrees Celsius. This metal boils when the temperature reaches seven hundred and sixty-one degrees Celsius. The substance in question has a silvery-white color. Has a metallic luster.

The density of potassium is eighty-six hundredths of a gram per cubic centimeter. This is a very light metal. The formula of potassium is very simple - it does not form molecules. This substance consists of atoms that are located close to each other and have a crystal lattice. The atomic mass of potassium is thirty-nine grams per mole. Its hardness is very low - it can be easily cut with a knife, like cheese.

Potassium and chemistry

Let's start with the fact that potassium is a chemical element that has very high chemical activity. You can’t even store it in the open air, as it instantly begins to react with the substances around it. Potassium is a chemical element that belongs to the first group and the fourth period of the periodic table. It has all the properties that are characteristic of metals.

Interaction with simple substances

These include: oxygen, nitrogen, sulfur, phosphorus, halogens (iodine, fluorine, chlorine, bromine). Let's consider the interaction of potassium with each of them in order. Interaction with oxygen is called oxidation. During this chemical reaction, potassium and oxygen are consumed in a molar ratio of four parts to one, resulting in the formation of an oxide of the metal in question in an amount of two parts. This interaction can be expressed using the following reaction equation: 4K + O2 = 2K2O. When potassium burns, a bright purple flame can be observed.

Therefore, this reaction is considered qualitative for the determination of potassium. Reactions with halogens are named according to the names of these chemical elements: this is iodization, fluoridation, chlorination, bromination. These interactions can be called addition reactions, since atoms of two different substances combine into one. An example of such a process is the reaction between potassium and chlorine, which results in the formation of chloride of the metal in question. To carry out this interaction, it is necessary to take two of these components - two moles of the first and one mole of the second. The result is two moles of potassium compound. This reaction is expressed by the following equation: 2К + СІ2 = 2КІ. Potassium can form compounds with nitrogen when burned in the open air. During this reaction, the metal in question and nitrogen are consumed in a molar ratio of six parts to one; as a result of this interaction, potassium nitride is formed in an amount of two parts. This can be shown as the following equation: 6K + N2 = 2K3N. This compound appears as green-black crystals. The metal in question reacts with phosphorus according to the same principle. If we take three moles of potassium and one mole of phosphorus, we get one mole of phosphide. Given chemical reaction can be written in the form of the following reaction equation: 3K + P = K3P. In addition, potassium can react with hydrogen to form a hydride. As an example, the following equation can be given: 2K + H2 = 2KN. All addition reactions occur only in the presence of high temperatures.

Interaction with complex substances

The characteristics of potassium from a chemical point of view include consideration of this topic. The types of compounds that potassium can react with include water, acids, salts, and oxides. The metal in question reacts differently with all of them.

Potassium and water

This chemical element reacts violently with it. This produces hydroxide as well as hydrogen. If we take two moles of potassium and water, we get the same amount and one mole of hydrogen. This chemical interaction can be expressed using the following equation: 2K + 2H2O = 2KOH = H2.

Reactions with acids

Since potassium is an active metal, it easily displaces hydrogen atoms from their compounds. An example would be a reaction that occurs between the substance in question and hydrochloric acid. To carry it out, you need to take two moles of potassium, as well as acid in the same amount. As a result, two moles and hydrogen are formed - one mole. This process can be written by the following equation: 2K + 2НІ = 2КІ + Н2.

Potassium and oxides

The metal in question reacts with this group of inorganic substances only upon significant heating. If the metal atom that is part of the oxide is more passive than the one we are talking about in this article, essentially an exchange reaction occurs. For example, if you take two moles of potassium and one mole of cuprum oxide, then as a result of their interaction you can get one mole of the oxide of the chemical element in question and pure cuprum. This can be shown in the form of the following equation: 2K + CuO = K2O + Cu. This is where the powerful reducing properties of potassium come into play.

Interaction with bases

Potassium is capable of reacting with metal hydroxides that are to the right of it in the electrochemical activity series. In this case, its restorative properties also appear. For example, if we take two moles of potassium and one mole of barium hydroxide, then as a result of the substitution reaction we will obtain substances such as potassium hydroxide in an amount of two moles and pure barium (one mole) - it will precipitate. The chemical interaction presented can be represented as the following equation: 2K + Ba(OH)2 = 2KOH + Ba.

Reactions with salts

IN in this case potassium still exhibits its properties as a strong reducing agent. By replacing atoms of chemically more passive elements, it allows you to obtain pure metal. For example, if you add three moles of potassium to an amount of two moles, then as a result of this reaction we get three moles of potassium chloride and two moles of aluminum. This process can be expressed using the equation as follows: 3К + 2АІСІ3 = 3КІ2 + 2АІ.

Reactions with fats

If you add potassium to any organic substance of this group, it will also displace one of the hydrogen atoms. For example, when stearin is mixed with the metal in question, potassium stearate and hydrogen are formed. The resulting substance is used to make liquid soap. This is where the characterization of potassium and its interactions with other substances ends.

Use of potassium and its compounds

Like all metals, the one discussed in this article is necessary for many industrial processes. The main use of potassium occurs in the chemical industry. Due to its high chemical activity, pronounced alkali metal and reducing properties, it is used as a reagent for many interactions and the production of various substances. In addition, alloys containing potassium are used as coolants in nuclear reactors. The metal discussed in this article also finds its application in electrical engineering. In addition to all of the above, it is one of the main components of plant fertilizers. In addition, its compounds are used in a wide variety of industries. Thus, in gold mining, potassium cyanide is used, which serves as a reagent for separating valuable metals from ores. Phosphates of the chemical element in question are used in glass production and are components of all kinds of cleaning products and powders. Matches contain chlorate of this metal. In the manufacture of films for old cameras, bromide of the element in question was used. As you already know, it can be obtained by bromination of potassium at high temperatures. In medicine, the chloride of this chemical element is used. In soap making - stearate and other fat derivatives.

Obtaining the metal in question

Nowadays, potassium is extracted in laboratories in two main ways. The first is its reduction from hydroxide with the help of sodium, which is chemically even more active than potassium. And the second is to obtain it from chloride, also with the help of sodium. If you add the same amount of sodium to one mole of potassium hydroxide, one mole of sodium alkali and pure potassium are formed. The equation for this reaction is as follows: KOH + Na = NaOH + K. To carry out the second type of reaction, you need to mix the chloride of the metal in question and sodium in equal molar proportions. As a result of this, substances such as kitchen salt and potassium are formed in the same ratio. This chemical interaction can be expressed using the following reaction equation: KCI + Na = NaCl + K.

The structure of potassium

The atom of this chemical element, like all others, consists of a nucleus that contains protons and neutrons, as well as electrons that revolve around it. The number of electrons is always equal to the number of protons that are inside the nucleus. If any electron is detached or attached to an atom, then it ceases to be neutral and turns into an ion. They come in two types: cations and anions. The first ones have positive charge, and the second - negative. If an electron is added to an atom, it turns into an anion, but if any of the electrons leaves its orbit, the neutral atom becomes a cation. Since the serial number of potassium, according to the periodic table, is nineteen, there are the same number of protons in the nucleus of this chemical element. Therefore, we can conclude that there are nineteen electrons around the nucleus. The number of protons contained in the structure of an atom can be determined by subtracting from atomic mass serial number of a chemical element. So we can conclude that there are twenty protons in the potassium nucleus. Since the metal considered in this article belongs to the fourth period, it has four orbits in which electrons are evenly distributed, which are constantly in motion. The diagram of potassium is as follows: the first orbit has two electrons, the second has eight; just like in the third, in the last, fourth, orbit only one electron rotates. This explains high level chemical activity of a given metal - its last orbit is not completely filled, so it tends to combine with some other atoms, as a result of which the electrons of their last orbits will become common.

Where can this element be found in nature?

Since it has extremely high chemical activity, it is not found anywhere on the planet in its pure form. It can only be seen in various compounds. potassium in the earth's crust is 2.4 percent. The most common minerals containing potassium are salvinite and carnallite. The first has the following chemical formula: NaCl.KCl. It has a variegated color and consists of many crystals of various colors. Depending on the ratio of potassium chloride and sodium, as well as the presence of impurities, it may contain red, blue, pink, and orange components. The second mineral - carnallite - looks like transparent, soft blue, light pink or pale yellow crystals. His chemical formula looks like this: KCl.MgCl2.6H2O. It is a crystalline hydrate.

The role of potassium in the body, symptoms of deficiency and excess

It, together with sodium, maintains the water-salt balance of the cell. It is also involved in the transmission of nerve impulses between membranes. In addition, it regulates the acid-base balance in the cell and throughout the body as a whole. It takes part in metabolic processes, counteracts the occurrence of edema, and is part of the cytoplasm - about fifty percent of it - the salt of the metal in question. The main signs that the body does not have enough potassium are swelling, the occurrence of diseases such as dropsy, irritability and disturbances in work nervous system, slow reaction and memory impairment.

In addition, an insufficient amount of this microelement negatively affects the cardiovascular and muscular systems. A lack of potassium over a very long period of time can cause a heart attack or stroke. But due to excess potassium in the body, a small intestinal ulcer can develop. To balance your diet so that you get the normal amount of potassium, you need to know what foods contain it.

Foods high in the micronutrient in question

First of all, these are nuts such as cashews, walnuts, hazelnuts, peanuts, almonds. Also, a large amount of it is found in potatoes. In addition, potassium is found in dried fruits such as raisins, dried apricots, and prunes. Pine nuts are also rich in this element. Its high concentration is also observed in legumes: beans, peas, lentils. Sea kale is also rich in this chemical element. Other products that contain this element in large quantities are green tea and cocoa. Besides, in high concentration It is also found in many fruits, such as avocados, bananas, peaches, oranges, grapefruits, and apples. Many cereals are rich in this microelement. This is primarily pearl barley, as well as wheat and buckwheat. Parsley and Brussels sprouts also have a lot of potassium. In addition, it is found in carrots and melon. Onions and garlic contain a considerable amount of the chemical element in question. Chicken eggs, milk and cheese are also high in potassium. Daily norm of this chemical element for the average person is from three to five grams.

Conclusion

After reading this article, we can conclude that potassium is an extremely important chemical element. It is necessary for the synthesis of many compounds in the chemical industry. In addition, it is used in many other industries. It is also very important for the human body, so it should be regularly and required quantity go there with food.

In nature, potassium is found only in combination with other elements, for example, in sea water, and also in many minerals. It oxidizes very quickly in air and very easily enters into chemical reactions, especially with water, forming an alkali.

In many properties, potassium is very close to sodium, but from the point of view biological function and use by cells of living organisms, they are antagonistic.

History and origin of the name

Potassium compounds have been used since ancient times. Thus, the production of potash (which was used as a detergent) existed already in the 11th century. The ash formed when burning straw or wood was treated with water, and the resulting solution (lye) was evaporated after filtering. The dry residue, in addition to potassium carbonate, contained potassium sulfate K2SO4, soda and potassium chloride KCl.

Place of Birth

The largest potash deposits are located in Canada (manufacturer PotashCorp), Russia (PJSC "Uralkali", Berezniki, Solikamsk, Perm Territory, Verkhnekamskoye potassium ore deposit), Belarus (PO "Belaruskali", Soligorsk, Starobinskoye potash deposit ore).

Receipt

Potassium, like other alkali metals, is obtained by electrolysis of molten chlorides or alkalis. Since chlorides have a higher melting point (600-650 °C), electrolysis of molten alkalis is more often carried out with the addition of soda or potash (up to 12%). During the electrolysis of molten chlorides, molten potassium is released at the cathode, and chlorine is released at the anode:

K + + e − → K (\displaystyle (\mathsf (K^(+)+e^(-)\rightarrow K))) 2 C l − → C l 2 (\displaystyle (\mathsf (2Cl^(-)\rightarrow Cl_(2))))

During the electrolysis of alkalis, molten potassium is also released at the cathode, and oxygen at the anode:

4 O H − → 2 H 2 O + O 2 (\displaystyle (\mathsf (4OH^(-)\rightarrow 2H_(2)O+O_(2))))

The water from the melt evaporates quickly. To prevent potassium from interacting with chlorine or oxygen, the cathode is made of copper and a copper cylinder is placed above it. The resulting potassium is collected in molten form in a cylinder. The anode is also made in the form of a cylinder of nickel (for the electrolysis of alkalis) or of graphite (for the electrolysis of chlorides).

Thermochemical reduction methods are also of industrial importance:

N a + K O H → N 2 380 − 450 o C N a O H + K (\displaystyle (\mathsf (Na+KOH(\xrightarrow[(N_(2))](380-450^(o)C))NaOH+ K)))

and reduction of potassium chloride from the melt with calcium carbide, aluminum or silicon.

Physical properties

Potassium is a silvery metal with a characteristic shine on a freshly formed surface. Very light and fusible. It dissolves relatively well in, forming amalgams. When introduced into the burner flame, potassium (as well as its compounds) colors the flame a characteristic pink-violet color.

Interaction with simple substances

Potassium at room temperature reacts with atmospheric oxygen and halogens; practically does not react with nitrogen (unlike lithium and sodium). When heated moderately, it reacts with hydrogen to form a hydride (200-350 °C):

2 K + H 2 ⟶ 2 K H (\displaystyle (\mathsf (2K+H_(2)\longrightarrow 2KH))) 2 K + 2 N H 3 ⟶ 2 K N H 2 + H 2 (\displaystyle (\mathsf (2K+2NH_(3)\longrightarrow 2KNH_(2)+H_(2))))

Potassium metal reacts with alcohols to form alcoholates:

2 K + 2 C 2 H 5 O H ⟶ 2 C 2 H 5 O K + H 2 (\displaystyle (\mathsf (2K+2C_(2)H_(5)OH\longrightarrow 2C_(2)H_(5)OK+H_ (2)\uparrow )))

Alkali metal alcoholates (in this case, potassium ethanolate) are very strong bases and are widely used in organic synthesis.

Oxygen compounds

K + O 2 ⟶ K O 2 (\displaystyle (\mathsf (K+O_(2)\longrightarrow KO_(2))))

Potassium oxide can be obtained by heating the metal to a temperature not exceeding 180 °C in an environment containing very little oxygen, or by heating a mixture of potassium superoxide with potassium metal:

K O 2 + 3 K ⟶ 2 K 2 O (\displaystyle (\mathsf (KO_(2)+3K\longrightarrow 2K_(2)O)))

Potassium oxides have pronounced basic properties and react violently with water, acids and acid oxides. Practical significance they do not have. Peroxides are yellowish-white powders that, soluble in water, form alkalis and hydrogen peroxide:

K 2 O 2 + 2 H 2 O ⟶ 2 K O H + H 2 O 2 (\displaystyle (\mathsf (K_(2)O_(2)+2H_(2)O\longrightarrow 2KOH+H_(2)O_(2) ))) 4 K O 2 + 2 H 2 O ⟶ 4 K O H + 3 O 2 (\displaystyle (\mathsf (4KO_(2)+2H_(2)O\longrightarrow 4KOH+3O_(2)\uparrow ))) 4 K O 2 + 2 C O 2 ⟶ 2 K 2 C O 3 + 3 O 2 (\displaystyle (\mathsf (4KO_(2)+2CO_(2)\longrightarrow 2K_(2)CO_(3)+3O_(2)\uparrow )))

Property to exchange carbon dioxide for oxygen is used in insulating gas masks and on submarines. An equimolar mixture of potassium superoxide and sodium peroxide is used as an absorber. If the mixture is not equimolar, then in the case of an excess of sodium peroxide, more gas will be absorbed than released (when absorbing two volumes of CO 2, one volume of O 2 is released), and the pressure in a confined space will drop, and in the case of an excess of potassium superoxide (when absorbing two volumes of CO 2 three volumes of O are released 2) more gas is released than absorbed, and the pressure will increase.

In the case of an equimolar mixture (Na 2 O 2:K 2 O 4 = 1:1), the volumes of absorbed and released gases will be equal (when four volumes of CO 2 are absorbed, four volumes of O 2 are released).

Peroxides are strong oxidizing agents, so they are used to bleach fabrics in the textile industry.

Peroxides are obtained by calcining metals in air freed from carbon dioxide.

Also known is potassium ozonide KO 3, orange-red color. It can be obtained by reacting potassium hydroxide with ozone at a temperature not exceeding 20 °C:

4 K O H + 4 O 3 ⟶ 4 K O 3 + O 2 + 2 H 2 O (\displaystyle (\mathsf (4KOH+4O_(3)\longrightarrow 4KO_(3)+O_(2)+2H_(2)O)) )

Potassium ozonide is a very strong oxidizing agent, for example, it oxidizes elemental sulfur to sulfate and disulfate already at 50 °C:

6 K O 3 + 5 S ⟶ K 2 S O 4 + 2 K 2 S 2 O 7 (\displaystyle (\mathsf (6KO_(3)+5S\longrightarrow K_(2)SO_(4)+2K_(2)S_(2 )O_(7))))

Hydroxide

Potassium hydroxide (or caustic potassium) are hard white opaque, very hygroscopic crystals that melt at a temperature of 360 °C. Potassium hydroxide is an alkali. It dissolves well in water and releases a large amount of heat. The solubility of potassium hydroxide at 20 °C in 100 g of water is 112 g.

Application

• Liquid at room temperature, an alloy of potassium and sodium is used as a coolant in closed systems, such as fast neutron nuclear power plants. In addition, its liquid alloys with rubidium and cesium are widely used. The alloy composition: sodium 12%, potassium 47%, cesium 41% - has a record low melting point of −78 °C.
• Potassium compounds are the most important biogenic element and are therefore used as fertilizers. Potassium is one of three basic elements that are essential for plant growth, along with nitrogen and phosphorus. Unlike nitrogen and phosphorus, potassium is the main cellular cation. When it is deficient in a plant, the structure of the chloroplast membranes is first damaged - cell organelles in which photosynthesis takes place. Outwardly, this manifests itself in the yellowing and subsequent death of leaves. When applying potassium fertilizers, plants increase their vegetative mass, yield and resistance to pests.
• Potassium salts are widely used in electroplating, since, despite the relatively high cost, they are often more soluble than the corresponding sodium salts, and therefore provide intensive work of electrolytes at increased current densities.

Important Connections

• Potassium bromide is used in medicine and as a sedative for the nervous system.
• Potassium hydroxide (caustic potash) is used in alkaline batteries and when drying gases.
• Potassium carbonate (potash) is used as a fertilizer, in glass melting, and as a feed additive for poultry.
• Potassium chloride (sylvine, " potassium salt") is used as fertilizer.
• Potassium nitrate (potassium nitrate) is a fertilizer, a component of black powder.
• Potassium perchlorate and chlorate (Bertholet salt) are used in the production of matches, rocket powders, lighting charges, explosives, and in electroplating.
• Potassium dichromate (chrompic) is a strong oxidizing agent, used to prepare a “chromium mixture” for washing chemical dishes and in leather processing (tanning). Also used to purify acetylene in acetylene plants to remove ammonia, hydrogen sulfide and phosphine.

• Potassium permanganate is a strong oxidizing agent, used as an antiseptic in medicine and for the laboratory production of oxygen.
• Sodium potassium tartrate (Rochelle salt) as a piezoelectric.
• Potassium dihydrogen phosphate and dideuterophosphate in the form of single crystals in laser technology.
• Potassium peroxide and potassium superoxide are used for air regeneration in submarines and in insulating gas masks (absorbs carbon dioxide to release oxygen).
• Potassium fluoroborate is an important flux for soldering steels and non-ferrous metals.
• Potassium cyanide is used in electroplating (silvering, gilding), gold mining and nitrocarburizing of steel.
• Potassium, together with potassium peroxide, is used in the thermochemical decomposition of water into hydrogen and oxygen (potassium cycle "Gaz de France", France).
• Potassium sulfate - used as fertilizer.

Biological role

Potassium is the most important biogenic element, especially in flora. If there is a lack of potassium in the soil, plants develop very poorly, the yield decreases, therefore about 90% of the extracted potassium salts are used as fertilizers.

Potassium was discovered in the fall of 1807 by the English chemist Davy during the electrolysis of solid caustic potassium. Having moistened caustic potassium, the scientist isolated the metal, which he gave the name potassius, hinting at production potash(a necessary ingredient for making detergents) from ash. The metal received its usual name two years later, in 1809, the initiator of the renaming of the substance was L.V. Gilbert, who suggested the name potassium(from Arabic al-kali- potash).

Potassium (lat. Kalium) is a soft alkali metal, an element main subgroup Group I, period IV of the periodic system of chemical elements D.I. Mendeleev, has atomic number 19 and the designation - TO.

Being in nature

Potassium does not occur in a free state in nature; it is part of all cells. A fairly common metal, it ranks 7th in terms of content in the earth’s crust (calorizator). The main suppliers of potassium are Canada, Belarus and Russia, which have large deposits of this substance.

Physical and chemical properties

Potassium is a low-melting metal with a silvery-white color. It has the property of turning open fires a bright purple-pink color.

Potassium has high chemical activity and is a strong reducing agent. When reacting with water, an explosion occurs; when exposed to air for a long time, it completely collapses. Therefore, potassium requires certain conditions for storage - it is filled with a layer of kerosene, silicone or gasoline to prevent contact with water and the atmosphere that is harmful to the metal.

The main food sources of potassium are dried nut butters, citrus fruits, and all green leafy vegetables. There is quite a lot of potassium in fish and... In general, potassium is included in almost all plants. and - champions in potassium content.

Daily potassium requirement

The daily requirement of the human body for potassium depends on age, physical condition and even places of residence. Healthy adults need 2.5 g of potassium, pregnant women - 3.5 g, athletes - up to 5 grams of potassium daily. The amount of potassium required for adolescents is calculated by weight - 20 mg of potassium per 1 kg of body weight.

Beneficial properties of potassium and its effect on the body

Potassium is involved in the process of nerve impulses and transferring them to innervated organs. Promotes better brain activity by improving its supply. Renders positive influence for many allergic conditions. Potassium is necessary for skeletal muscle contractions. Potassium regulates the content of salts, alkalis and acids in the body, which helps reduce swelling.

Potassium is found in all intracellular fluids; it is necessary for the normal functioning of soft tissues (muscles, blood vessels and capillaries, endocrine glands, etc.)

Potassium absorption

Potassium is absorbed into the body from the intestines, where it enters with food, and is excreted in the urine, usually in the same amount. Excess potassium is eliminated from the body in the same way and is not retained or accumulated. Excessive consumption of coffee, sugar, and alcohol can interfere with the normal absorption of potassium.

Interaction with others

Potassium works closely with sodium and magnesium; with an increase in potassium concentration, sodium is rapidly removed from the body, and a decrease in the amount of magnesium can interfere with the absorption of potassium.

Signs of potassium deficiency

A lack of potassium in the body is characterized by muscle weakness, fatigue, decreased immunity, malfunction of the myocardium, abnormal blood pressure, rapid and difficult breathing. The skin may peel, damage does not heal well, and hair becomes very dry and brittle. Malfunctions in the gastrointestinal tract occur - nausea, vomiting, indigestion, even gastritis and ulcers.

Signs of excess potassium

An excess of potassium occurs with an overdose of drugs containing potassium and is characterized by neuromuscular disorders, increased sweating, excitability, irritability and tearfulness. A person constantly experiences a feeling of thirst, which leads to frequent urination. The gastrointestinal tract reacts with intestinal colic, alternating constipation and diarrhea.

Uses of potassium in life

Potassium in the form of basic compounds is widely used in medicine, agriculture and industry. Potassium fertilizers are necessary for normal growth and ripening of plants, and everyone knows potassium permanganate, this is nothing more than potassium permanganate, a time-tested antiseptic.