What is potassium made of? Properties of potassium and its interaction with water. Interaction with simple substances
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Potassium- denoted by the symbol K - a chemical element of group I of the periodic system of Mendeleev;
- atomic number 19,
- atomic mass 39.098;
Potassium is a silvery white, very light, soft and fusible metal.
The element consists of two stable isotopes - 39K (93.08%), 41K (6.91%) and one weakly radioactive 40K (0.01%) with a half-life of 1.32 109 years.
The element potassium is in the fourth period of the periodic system, which means that all electrons are located in four energy levels. Thus, the structure of the potassium atom is written as follows: +19 K: 2ё; 8th; 8th; 1st.
Based on the structure of the atom, it is possible to predict the degree of oxidation of C1 potassium in its compounds. Since in chemical reactions, the potassium atom gives up one external electron, exhibiting reducing properties, therefore, it acquires an oxidation state of +1.
The reducing properties of potassium are more pronounced than those of sodium, but weaker than those of rubidium, which is associated with an increase in the radii from Na to Rb.
Potassium is a simple substance, it is characterized by a metallic crystal lattice and a metallic chemical bond, and hence all the properties typical of metals.
The metallic properties of potassium are more pronounced than those of sodium, but weaker than those of rubidium, because. a potassium atom donates an electron more easily than a sodium atom, but harder than a rubidium atom.
The metallic properties of potassium are more pronounced than those of calcium, tk. one electron of a potassium atom is easier to remove than two electrons of a calcium atom.
Potassium oxide K 2 O is a basic oxide and exhibits all the typical properties of basic oxides. Interaction with acids and acid oxides.
K 2 O + 2HCl = 2KSl + H 2 O;
K 2 O + SO 3 \u003d K 2 SO 4
As a hydroxide, potassium corresponds to the base (alkali) KOH, which exhibits all the characteristic properties of bases: interaction with acids and acid oxides.
KOH + HNOz \u003d KNO 3 + H 2O;
2KOH + H 2 O 5 \u003d 2KNO 3 + H 2 O.
Potassium does not form a volatile hydrogen compound, but forms potassium hydride KH
In nature, potassium is found only in compounds with other elements, for example, in sea water, as well as in many minerals. It oxidizes very quickly in air and reacts very easily, especially with water, forming an alkali. In many ways, the chemical properties of potassium are very similar to sodium, but in terms of biological function and their use by the cells of living organisms, they are still different.
Potassium was discovered in the fall of 1807 by the English chemist Davy during the electrolysis of solid caustic potash. Having moistened caustic potash, the scientist isolated the metal, which he gave the name potassium, hinting at production potash(a necessary ingredient for the manufacture of 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 of the main subgroup of 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 in a free state is not found in nature, it is part of all cells. A fairly common metal, it occupies the 7th place 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, silver-white metal. It tends to paint an open fire in a bright purple-pink color.
Potassium has a high chemical activity, it is a strong reducing agent. When reacting with water, an explosion occurs; when exposed to air for a long time, it is completely destroyed. Therefore, potassium requires certain conditions for storage - it is poured with a layer of kerosene, silicone or gasoline to exclude contact with water and the atmosphere that is harmful to the metal.
The main food sources of potassium are dried, peanut butter, citrus fruits, all green leafy vegetables,. There is a lot of potassium in fish and. In general, potassium is part of almost all plants. and - champions in potassium content.
daily requirement for potassium
The daily requirement of the human body for potassium depends on age, physical condition and even place of residence. Adult healthy people need 2.5 g of potassium, pregnant women - 3.5 g, athletes - up to 5 grams of potassium daily. The amount of potassium needed for adolescents is calculated by weight - 20 mg of potassium per 1 kg of body weight.
Useful properties of potassium and its effect on the body
Potassium is involved in the process of conducting nerve impulses and transmitting them to the innervated organs. Promotes better brain activity, improving its supply. It has a positive effect in many allergic conditions. Potassium is essential for skeletal muscle contractions. Potassium regulates the content of salts, alkalis and acids in the body, which helps to reduce edema.
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 excreted from the body in the same way, it does not linger and does not accumulate. Obstacles to the normal absorption of potassium can serve as excessive consumption of coffee, sugar, alcohol.
Interaction with others
Potassium works in close contact with sodium and magnesium, with an increase in the concentration of potassium, sodium is rapidly excreted from the body, and a decrease in the amount of magnesium can disrupt the absorption of potassium.
Signs of potassium deficiency
The lack of potassium in the body is characterized by muscle weakness, fatigue, decreased immunity, myocardial malfunctions, blood pressure disturbances, rapid and difficult breathing. The skin can peel off, the damage does not heal well, the hair becomes very dry and brittle. There are malfunctions in the work of the gastrointestinal tract - nausea, vomiting, indigestion up to 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, excessive 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.
The use of potassium in life
Potassium in the form of basic compounds is widely used in medicine, agriculture and industry. Potash fertilizers are necessary for the normal growth and maturation of plants, and the well-known potassium permanganate, this is nothing more than potassium permanganate, a time-tested antiseptic.
Mankind has been familiar with potassium for more than a century and a half. In a lecture given in London on November 20, 1807, Humphry Davy reported that during the electrolysis of caustic potassium he obtained "small balls with a strong metallic luster ... Some of them burned out with an explosion immediately after their formation." This was potassium.
Potassium is a wonderful metal. It is remarkable not only because it is cut with a knife, floats in water, flashes on it with an explosion and burns, coloring the flame in purple. And not only because this element is one of the most active chemically. All this can be considered natural, because it corresponds to the position of the alkali metal potassium in the periodic table. Potassium is remarkable for its indispensability for all living things and is remarkable as an all-around "odd" metal.
Please note: its atomic number is 19, atomic mass is 39, in the outer electron layer - one electron, valency 1+. According to chemists, this explains the exceptional mobility of potassium in nature. It is part of several hundred minerals. It is found in the soil, in plants, in the organisms of humans and animals. He is like a classic Figaro: here - there - everywhere.
Potassium and soil
It is hardly possible to explain by chance or the whim of linguists the fact that in the Russian language both our planet itself and its upper layer - the soil - are denoted by one word. "Earth-mother", "earth-nurse" is more about the soil than about the planet as a whole...
But what is soil? An independent and very peculiar natural body. It is formed from the surface layers of various rocks under the influence of air, water, temperature changes, and the vital activity of all kinds of inhabitants of the Earth. Below, under the soil, the so-called parent rocks, composed of various minerals, are hidden. They are gradually destroyed and replenish the "reserves" of the soil. And in the soil, in addition to purely mechanical, other destruction constantly occurs. It is called chemical weathering. Water and carbon dioxide (to a lesser extent other substances) gradually destroy minerals.
Almost 18% of the weight of the earth's crust falls on the potassium-containing mineral - orthoclase. This is a double salt of silicic acid K 2 Al 2 Si 6 O 16 or K 2 O-Al 2 O 3 -BSiO 2. Here is what happens to orthoclase as a result of chemical weathering:
K 2 O * AI 2 O 3 * 6SO 2 + 2H 2 O + CO 2 → K 2 CO 3 + Al 2 O 3 * 2SO 2 * 2H 2 O + + 4SiO 2.
Orthoclase turns into kaolin (a kind of clay), sand and potash. Sand and clay are used to build the mineral backbone of the soil, and K, which has passed from orthoclase to potash, is “liberated” and becomes available to plants. But not all at once.
In soil waters, K 2 CO 3 molecules dissociate: K 2 CO 3 ↔ + K + + KCO 3 - ↔ 2K + + CO 3 2-. Part of the potassium ions remains in the soil solution, which serves as a source of nutrition for plants. But most of the potassium ions are absorbed by the colloidal particles of the soil, from which it is rather difficult for plant roots to extract them. So it turns out that, although there is a lot of potassium in the earth, it is often not enough for plants. Due to the fact that soil lumps "lock" most of the potassium, the content of this element in sea water is almost 50 times less than sodium. It is estimated that out of a thousand potassium atoms released during chemical weathering, only two reach the sea basins, and 998 remain in the soil. “The soil absorbs potassium, and this is its miraculous power,” wrote Academician A.E. Fersman.
Potassium and plants
Potassium is found in all plants. The lack of potassium causes the plant to die. Almost all potassium is found in plants in the ionic form - K + . Part of the ions is in the cell juice, the other part is absorbed by the structural elements of the cell. Potassium ions are involved in many biochemical processes occurring in the plant. It has been established that in plant cells these ions are found mainly in the protoplasm. They are not found in the cell nucleus. Consequently, element No. 19 does not participate in the processes of reproduction and in the transmission of hereditary traits. But even without this, the role of potassium in the life of a plant is great and diverse.
Potassium is included in the fruits, and in the roots, and in the stems, and in the leaves, and in the vegetative organs, as a rule, it is more than in the fruits. Another characteristic feature: young plants have more potassium than old ones. It has also been noted that as individual plant organs age, potassium ions move to the points of the most intensive growth. With a lack of potassium, plants grow more slowly, their leaves, especially old ones, turn yellow and turn brown at the edges, the stem becomes thin and fragile, and the seeds lose their germination capacity.
It has been established that potassium ions activate the synthesis of organic substances in plant cells. They have a particularly strong influence on the processes of formation of carbohydrates. If there is not enough potassium, the plant absorbs carbon dioxide worse, and for the synthesis of new carbohydrate molecules it lacks carbon "raw materials". At the same time, the processes of respiration increase, and the sugars contained in the cell sap are oxidized. Thus, the reserves of carbohydrates in plants that are on a starvation diet (for potassium) are not replenished, but consumed. The fruits of such a plant - this is especially noticeable on fruits - will be less sweet than those of plants that have received a normal dose of potassium. Starch is also a carbohydrate, therefore element No. 19 strongly affects its content in fruits.
But that's not all. Plants that have received enough potassium can more easily tolerate drought and frosty winters. This is due to the fact that element No. 19 affects the ability of colloidal substances of plant cells to absorb water and swell. Not enough potassium - cells absorb and retain moisture worse, shrink, die.
Potassium ions also affect nitrogen metabolism. With a lack of potassium, an excess of ammonia accumulates in the cells. This can lead to poisoning and death of the plant.
It has already been mentioned that K also affects the respiration of plants, and increased respiration affects not only the content of carbohydrates. The more intense the breathing, the more active all oxidative processes are, and many organic substances are converted into organic acids. Excess acids can cause protein breakdown. The products of this decay are a very favorable environment for fungi and bacteria. That is why, with potassium starvation, plants are much more likely to be affected by diseases and pests. Fruits and vegetables containing protein breakdown products do not tolerate transportation well, they cannot be stored for a long time. In a word, if you want to get tasty and well-preserved fruits, feed the plant plenty of potassium. And for cereals, potassium is important for another reason: it increases the strength of the straw and thereby prevents lodging of bread...
- MEETING WITH POTASSIUM? If in a warehouse or at a freight station you see steel boxes with the inscriptions: “Flammable!”, “Explodes from water”, then it is very likely that you have met with potassium.
Many precautions are taken when transporting this metal. Therefore, when you open a steel box, you will not see potassium, but you will see carefully sealed steel cans. In them - potassium and an inert gas - the only environment safe for potassium. Large quantities of potassium are transported in hermetic containers under an inert gas pressure of 1.5 atm.
- WHY DO METALLIC POTASSIUM NEED? Metallic K is used as a catalyst in the production of some types of synthetic rubber, as well as in laboratory practice. Recently, the main use of this metal has been the production of potassium peroxide K 2 O 2 used for oxygen regeneration. An alloy of potassium and sodium serves as a coolant in nuclear reactors, and in the production of titanium - as a reducing agent.
- FROM SALT AND ALKALINE. Element No. 19 is most often obtained in the exchange reaction of molten caustic potassium and metallic sodium: KOH + Na → NaOH + K. The process takes place in a nickel distillation column at a temperature of 380-440 ° C. Similarly, element No. 19 is obtained from potassium chloride, only in this case the process temperature is higher - 760-800°C. At this temperature, both sodium and potassium turn into steam, and potassium chloride (with additives) melts. Sodium vapor is passed through the molten salt and the resulting potassium vapor is condensed. Sodium-potassium alloys are obtained in the same way. The composition of the alloy is highly dependent on the process conditions.
- HOW TO BE IF you are dealing with potassium metal for the first time. It is necessary to remember the highest reactivity of this metal, that potassium ignites from the slightest traces of water. Working with potassium is mandatory in rubber gloves and goggles, and preferably in a mask that covers the entire face. Large quantities of potassium are handled in special chambers filled with nitrogen or argon. (Of course, in special spacesuits.) And if K does ignite, it is extinguished not with water, but with soda or table salt.
- HOW TO DEAL WITH WASTE. Safety rules categorically prohibit the accumulation in laboratories of more than two grams of residues or waste of any alkali metal, including potassium. Waste must be disposed of on site. The classic method is the formation of potassium ethoxide C 2 H 5 OK under the action of ethyl alcohol: they simply pour alcohol into the waste. But there is another - alcohol-free way. Waste is filled with kerosene or gasoline. Potassium does not react with them and, being lighter than water, but heavier than these organic liquids, it settles to the bottom. And then they begin to add water drop by drop into the inclined vessel. When the water reaches the metal, a reaction will occur and the K will turn into caustic potash. Layers of an alkaline solution and kerosene or gasoline are quite easily separated on a separating funnel.
- IS THERE POTASSIUM IONS IN THE SOLUTION? It's easy to find out. Dip the wire ring into the solution, and then bring it into the flame of a gas burner. If potassium is present, the flame will turn purple, although not as bright as the yellow color imparted to the flame by sodium compounds. It is more difficult to determine how much potassium is in the solution. There are few water-insoluble compounds in this metal. Potassium is usually precipitated as perchlorate, a salt of the very strong perchloric acid HClO 4 . By the way, potassium perchlorate is a very strong oxidizing agent and as such is used in the production of some explosives and rocket fuels.
- WHAT IS POTASSIUM CYANIDE FOR? To extract gold and silver from ores. For galvanic gilding and silvering of non-precious metals. For obtaining many organic substances. For nitriding steel - this gives its surface greater strength. Unfortunately, this much-needed substance is extremely poisonous. And KCN looks quite harmless: small white crystals with a brownish or gray tint.
- WHAT IS CHROMPIK? More precisely - potassium chromic peak. These are orange crystals of composition K 2 Cr 2 O 7 . Chrompic is used in the production of dyes, and its solutions are used for "chrome" tanning of leather, and also as a mordant in dyeing and printing fabrics. A solution of chromic acid in sulfuric acid is a chromic mixture that is used in all laboratories for washing glassware.
- WHY DO YOU NEED CALIZE KALI? Indeed, why? After all, the properties of this alkali and cheaper caustic soda are almost the same. The difference between these substances was discovered by chemists only in the 18th century. The most notable difference between NaOH and KOH is that caustic potash is even more soluble in water than caustic soda. KOH is produced by electrolysis of potassium chloride solutions. To minimize the admixture of chlorides, mercury cathodes are used. And this substance is needed primarily as an initial product for obtaining various potassium salts. In addition, caustic potash is indispensable in the production of liquid soaps, some dyes and organic compounds. A solution of caustic potash is used as an electrolyte in alkaline batteries.
- SALTETRE OR SALTETRE? More correctly - saltpeter. This is the common name for nitrate salts of alkali and alkaline earth metals. If they just say “saltpeter” (not “sodium” or “calcium” or “ammonia”, but simply “saltpeter”), then they mean potassium nitrate. Mankind has been using this substance for more than a thousand years - to obtain black powder. In addition, saltpeter is the first double fertilizer: of the three most important elements for plants, it contains two - nitrogen and potassium. Here is how D. I. Mendeleev described saltpeter in Fundamentals of Chemistry:
“Saltpeter is a colorless salt that has a special refreshing taste. It easily crystallizes in long, striated, rhombic, hexagonal prisms ending in the same pyramids. Its crystals (sp. weight 1.93) do not contain water. At low incandescence (339 °), saltpeter melts into a completely colorless liquid. At ordinary temperatures, in solid form, KNO 3 is inactive and unchanged, but at elevated temperatures it acts as a very strong oxidizing agent, because it can give off a significant amount of oxygen to substances mixed with it. Saltpeter thrown onto hot coal produces its rapid combustion, and its mechanical mixture with crushed coal ignites on contact with a hot body and continues to burn by itself. In this case, nitrogen is released, and the oxygen of the saltpeter is used to oxidize the coal, as a result of which carbon-potassium salt and carbon dioxide are obtained ...
In chemical practice and technology, saltpeter is used in many cases as an oxidative affinity that acts at high temperatures. This is also the basis for its use for ordinary gunpowder, which is a mechanical mixture of finely ground: sulfur, saltpeter and coal.
- WHERE AND WHAT ARE OTHER POTASSIUM SALTS USED FOR? Potassium bromide KBr - in photography, to protect the negative or print from a veil.
- Potassium iodide KI - in medicine and as a chemical reagent.
- Potassium fluoride KF - in the composition of metallurgical fluxes and for the introduction of fluorine into organic compounds.
- Potassium carbonate (potash) K 2 CO 3 - in glass and soap industries, as well as fertilizer.
- Potassium phosphates, in particular K 4 P 2 O 7 and K 5 P 3 O 10 - as components of detergents.
- Potassium chlorate (bertolet salt) KClO 3 - in match production and pyrotechnics.
- Potassium fluorosilicon K 2 SiF 6 - as an additive to the mixture in the extraction of rare earth elements from minerals.
- Ferrocyanide potassium (yellow blood salt) K 4 Fe (CN) 6 -SH 2 O - as a mordant in dyeing fabrics and in photography.
- WHY IS POTASSIUM CALLED POTASSIUM? The word is of Arabic origin. In Arabic, "al-kali" is the ashes of plants. For the first time, potassium was obtained from caustic potash, and caustic potash - from potash isolated from plant ash ... However, in English and other European languages, the name potassium, given to potassium by its discoverer H. Davy, has been preserved. The name "potassium" was introduced into the Russian chemical nomenclature in 1831 by G. I. Hess.
- NOT ONLY IN CURAGE. Hearts, especially people who have had a heart attack, are strongly recommended to eat dried apricots to make up for the loss of potassium in the body. Or at least raisins. In 100 grams of dried apricots up to 2 g of potassium. The same amount is in apricots (but for accuracy, when calculating, you must subtract the weight of the bones). Raisins contain about half as much potassium. But do not think that dried fruits are the only source of potassium. There is quite a lot of it in almost any plant food. For example, forty grams of fried potatoes are equivalent to 10 grams of selected dried apricots. Legumes, tea, cocoa powder are rich in potassium. In a word, it is not difficult to obtain a daily dose of potassium (2.5-5 g) with a normal diet.
Potassium is an elemental substance, a metal so active that it does not occur in nature in the form of nuggets. Potassium is a part of minerals and sea water, in organisms of plants and animals, and occupies the 7th place in terms of prevalence. It is of great biogenic importance, as it is necessary for the vital activity of living cells.
Physical and chemical properties of potassium
Potassium is a soft substance (can be cut with a knife), silvery, light (lighter than water), fusible. Burns with a pink-violet flame.
Alkali metal, actively reacts with oxygen, water, halogens, dilute acids, the reactions are often accompanied by an explosion. Does not react with nitrogen. Reacts with alkalis, alcohols.
Working with pure potassium requires the use of protective equipment, since contact with even the smallest particles on the skin or in the eyes causes serious burns.
Potassium should be stored in hermetic iron vessels under a layer of substances that prevent contact with air: mineral oil, silicone, dehydrated kerosene.
The use of potassium and its compounds
In the form of a pure metal, the substance is used in a limited area of \u200b\u200bfields:
- electrodes are made from it in some current sources;
- used in electronic lamps as an adsorbent of gases that maintains a vacuum; in photocells, in gas-discharge lamps and devices, in thermionic converters, in photomultipliers;
- for the production of superoxide;
- using the potassium-40 isotope, the age of the rocks is calculated;
- artificial isotope potassium-42 is used as a radioactive tracer in medicine and biology;
- an alloy of potassium and sodium - a liquid substance under normal conditions, used as a coolant in nuclear reactors. Other liquid potassium alloys are also used.
Various potassium compounds are much more in demand.
- In medical practice, potassium chloride, potassium iodide, permanganate, potassium bromide are used. Potassium is necessarily a part of complex vitamin and mineral preparations. It is necessary for our body to work muscles, including cardiac; to maintain a balanced blood composition, water and acid-base balance.
- The lion's share of the potassium received by the industry (more than 90%) goes to the production of potash fertilizers, which are vital for the development of plants. For this purpose, various potassium salts are used in agriculture. The most popular is the potassium salt of nitric acid, known as potassium nitrate, Indian or potassium nitrate.
- KOH (potassium hydroxide) is used in batteries to dry gases.
- Potash (potassium carbonate) is used to produce potash optical glass, in the production of fertilizers, in the processes of gas purification, drying, and tanning of leather.
- Potassium peroxide and superoxide absorb carbon dioxide and release oxygen. This property is used to regenerate oxygen in gas masks, mines, submarines, spaceships.
- By means of peroxides bleach fabrics.
- Potassium compounds are part of various explosive and combustible substances.
- Potassium permanganate is used for laboratory production of O2.
- Potassium compounds are used in electroplating and organic synthesis, in laser technology and photography, in the production of acetylene and steels and piezoelectronics. They are used for soldering non-ferrous metals and steels, for washing chemical dishes.
Potassium iodide, potassium nitrate, potassium carbonate are just a small part of the potassium compounds that our chemical reagent store offers. In Moscow and the Moscow region, buying goods for laboratories and production at PrimeChemicalsGroup is convenient and profitable. We have an excellent service, we have delivery and the possibility of self-delivery.
Potassium (Kalium, from Arabic, qili - potash) K - element of group I of the 4th period of the periodic system of D. I. Mendeleev, p. 19, atomic mass 39.102.
Physical and chemical properties
Potassium metal is soft, easily cut with a knife, and amenable to pressing and rolling. 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/cm 3 . Like all alkali metals, potassium easily melts (melting point 63.51°C) and begins to evaporate even at relatively low heat (potassium boiling point 761°C).
Potassium, like other alkali metals, is chemically very active. Easily interacts with atmospheric oxygen to form a mixture, mainly consisting of K 2 O 2 peroxide and KO 2 superoxide (K 2 O 4):
2K + O 2 \u003d K 22, K + O 2 \u003d KO 2.
When heated in air, potassium burns with a violet-red flame. With water and dilute acids, potassium interacts with an explosion (the resulting hydrogen (H) ignites):
2K + 2H 2 O = 2KOH + H 2
8K + 4H 2 SO 4 \u003d K 2 S + 3K 2 SO 4 + 4H 2 O.
When heated to 200-300°C, potassium reacts with hydrogen (H) to form a salt-like hydride KH:
With halogens, potassium interacts with an explosion. It is interesting to note that potassium does not interact with nitrogen (N).
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 fl. \u003d 2KNH 2 + H 2
The most important potassium compounds are K 2 O oxide, K 2 O 2 peroxide, K 2 O 4 superoxide, KOH hydroxide, KI iodide, K 2 CO 3 carbonate and KCl chloride.
Potassium oxide K 2 O, as a rule, is obtained indirectly due to the reaction of peroxide and metallic potassium:
2K + K 2 O 2 \u003d 2K 2 O
This oxide exhibits pronounced basic properties, easily reacts with water to form potassium hydroxide KOH:
K 2 O + H 2 O \u003d 2KOH
Potassium hydroxide, or caustic potash, is highly soluble in water (up to 49.10% by weight at 20°C). The resulting solution is a very strong alkali base. KOH reacts with acidic and amphoteric oxides:
SO 2 + 2KOH \u003d K 2 SO 3 + H 2 O,
Al 2 O 3 + 2KOH + 3H 2 O \u003d 2K (so the reaction proceeds in solution) and
Al 2 O 3 + 2KOH \u003d 2KAlO 2 + H 2 O (this is how the reaction proceeds when the reagents are fused).
In industry, potassium hydroxide KOH is obtained by electrolysis of aqueous solutions of KCl or K 2 CO 3 using ion-exchange membranes and diaphragms:
2KCl + 2H 2 O \u003d 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 with solid potassium hydroxide or drops of its solutions on the skin and eyes causes severe burns of the skin and mucous membranes, so you should only work with these caustic substances with goggles and gloves. Aqueous solutions of potassium hydroxide during storage destroy glass, melts - porcelain.
Potassium carbonate K 2 CO 3 (commonly called potash) is obtained by neutralizing a solution of potassium hydroxide with carbon dioxide:
2KOH + CO 2 \u003d K 2 CO 3 + H 2 O.
Significant amounts of potash are found in the ashes of some plants.
Name: from the Arabic "al-kali potash" (a long-known potassium compound extracted from wood ash).
The history of the discovery of potassium
Potassium (English Potassium, French Potassium, German Kalium) was discovered in 1807 by Davy, who produced the electrolysis of solid, slightly moistened caustic potash. Davy called the new metal Potassium, but the name did not stick. The godfather of the metal turned out to be Hilbert, the well-known publisher of the journal "Annalen deg Physik", who suggested the name "potassium"; it was adopted in Germany and Russia. Both names are derived from terms used long before the discovery of potassium metal. The word potasium is derived from the word potash, which probably appeared in the 16th century. It is found at Van Helmont and in the second half of the 17th century. is widely used as the name of a commercial product - potash - in Russia, England and Holland. Translated into Russian, the word potashe means "pot ash or ash boiled in a pot"; in the XVI - XVII centuries. potash was obtained in large quantities from wood ash, which was boiled in large boilers. From potash, mainly litreed (purified) saltpeter was prepared, which was used to make gunpowder. Especially a lot of potash was produced in Russia, in the forests near Arzamas and Ardatov in mobile factories (Maidans) that belonged to a relative of Tsar Alexei Mikhailovich, a close boyar B.I. Morozov. As for the word potassium, it comes from the Arabic term alkali (alkaline substances). In the Middle Ages, alkalis, or, as they said then, alkali salts, almost did not differ from each other and called them names that had the same meaning: natron, borax, varek, etc. The word kali (qila) occurs around 850 in Arab writers, then the word Qali (al-Qali) begins to be used, which denoted a product obtained from the ashes of certain plants, the Arabic qiljin or qaljan (ash) and qalaj (burn) are associated with these words. In the era of iatrochemistry, alkalis began to be subdivided into "fixed" and "volatile". In the 17th century there are names alkali fixum minerale (mineral fixed alkali or caustic soda), alkali fixum. vegetabile (vegetable fixed alkali or potash and caustic potash), as well as alkali volatile (volatile alkali or NH3). Black distinguished between caustic and soft or carbonic alkalis. Alkalis do not appear in the Table of Simple Bodies, but in a footnote to the table, Lavoisier indicates that fixed alkalis (potash and soda) are probably complex substances, although the nature of their constituents has not yet been studied. In Russian chemical literature of the first quarter of the 19th century. potassium was called potassium (Soloviev, 1824), potash (Insurance, 1825), potash (Shcheglov, 1830); in the "Dvigubsky Shop" already in 1828. along with the name potash (potash sulphate) there is the name kali (caustic potash, potassium hydroxide, etc.). The name potassium became generally accepted after the publication of Hess's textbook.
Finding potassium in nature
In the earth's crust, potassium is one of the most common petrogenic elements. In much lower concentrations, it is found in ocean water, containing only 0.029% of it, although rivers and groundwater annually carry 8.4 107 dissolved potassium into the oceans.
In the surface rocks of the earth's crust, two main groups of potassium-containing minerals are distinguished: aluminosilicate, halogen, and sulfate. The aluminosilicate group is very common, but its minerals are difficult or insoluble. The group of halogen and sulfate potassium-containing minerals is characterized by good solubility and forms the main raw material base for the production of potash fertilizers.
The main minerals containing potassium: sylvin KCl (52.44% K), sylvinite (Na, K) Cl (this mineral is a densely compressed mechanical mixture of crystals of potassium chloride KCl and sodium chloride (Na) NaCl), carnallite KCl MgCl 2 6H 2 O (35.8% K), various aluminosilicates containing potassium, kainite KCl MgSO 4 3H 2 O, polyhalite K 2 SO 4 MgSO 4 2CaSO 4 2H 2 O, alunite KAl 3 (SO 4 ) 2 (OH) 6 . Sea water contains about 0.04% potassium (see also Potassium salts).
Getting Potassium
Sodium chloride is also found in sea water and salt springs. Typically, the upper layers of deposits contain potassium salts. They are found in sea water, but in much smaller quantities than sodium salts. The world's largest reserves of potassium salts are located in the Urals near Solikamsk (minerals sylvinite NaCl * KCl * MgCl * 6H2O). Large deposits of potash salts have been explored and exploited in Belarus (Salihorsk).
Currently, potassium is obtained by reacting with liquid sodium (Na) molten KOH (at 380-450°C) or KCl (at 760-890°C):
Na + KOH = NaOH + K
Potassium is also obtained by electrolysis of a KCl melt mixed with K 2 CO 3 at temperatures close to 700 ° C:
2KCl \u003d 2K + Cl 2
Potassium is purified from impurities by vacuum distillation.
Potassium can also be obtained by electrolysis of molten KCl and KOH. However, this method of obtaining potassium has not found wide distribution due to technical difficulties (low current efficiency, difficulty in ensuring safety). Modern industrial production of potassium is based on the following reactions: KCl + Na (NaCl + K (a) KOH + Na (NaOH + K (b) (b) the interaction between molten potassium hydroxide and liquid sodium is carried out in countercurrent at 4400C in a nickel reaction column (. The same methods are used to obtain an alloy of potassium with sodium, which is used as a liquid metal coolant in nuclear reactors. An alloy of potassium with sodium is also used as a reducing agent in the production of titanium .
Application of potassium
Potassium metal is a material for electrodes in chemical current sources. An alloy of potassium with another alkali metal - sodium (Na) is used as a coolant in nuclear reactors.
On a much larger scale than metallic potassium, its compounds are used. Potassium is an important component of the mineral nutrition of plants (it takes about 90% of the extracted potassium salts), they need it in significant quantities for normal development, therefore potash fertilizers are widely used: 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 an absorber of hydrogen sulfide in the purification of gases, as a dehydrating agent and in tanning leather.
Potassium iodide KI is used as a drug. 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.
The biological role of potassium
Potassium is one of the most important biogenic elements, constantly present in all cells of all organisms. Potassium ions K + are involved in the work of ion channels and the regulation of the permeability of biological membranes, in the generation and conduction of a nerve impulse, in the regulation of the activity of the heart and other muscles, in various metabolic processes. The content of potassium in the tissues of animals and humans is regulated by steroid hormones of the adrenal glands. On average, the human body (body weight 70 kg) contains about 140 g of potassium. Therefore, for normal life with food, the body should receive 2-3 g of potassium per day. Potassium-rich foods such as raisins, dried apricots, peas and others.
Features of handling metallic potassium
potassium metal can cause very severe skin burns, if the smallest particles of potassium get into the eyes, severe lesions with loss of vision occur, so working with potassium metal can only be done with protective gloves and goggles. Ignite potash is poured with mineral oil or covered with a mixture of talc and NaCl. Potassium is stored in hermetically sealed iron containers under a layer of dehydrated kerosene or mineral oil.
Reserves and production of potassium in the world
The main raw materials for the production of potassium chloride are natural potash ores (sylvinite and carnallite - salts with a pure substance content of 12-15% with impurities of sodium and magnesium salts).
World reserves of potash ore are characterized by a high level of concentration - only 3 countries have about 85% of the reserves. Just over 38% is in Canada, followed by Russia with about 33%. In third place is Belarus - 9% of the level of all world reserves of potash ore. The content of potassium in deposits located in Russia is higher than in other countries.
Every year, potash producers extract 8.6 billion tons of carnallite-sylvinite ore (World Geological Survey estimate), but even with such intensive mining, the ore reserves will last for more than a hundred years.
Potassium reserves in Russia
The production of potash fertilizers in Russia is organized in the Urals on the basis of the Verkhne-Kamskoye deposit, which accounts for 84% of the explored reserves of potash salts in Russia. The maximum production volume was reached in 1988 and amounted to 5.26 Mt K2O.
Extraction and processing of potash ores is carried out by two largest enterprises - Uralkaliy and Silvinit, developing the Verkhnekamskoye potassium-magnesium salt deposit with reserves of about 3.8 billion tons of ore. The potassium content in the licensed areas of Uralkali and Silvinit is 30% and 25%, respectively, which are the best indicators in the global industry.
For the production of one ton of potash fertilizers, it is necessary to extract at least four tons of ore; in 2008, the cost of potassium chloride on Russian stock exchanges exceeds 4.5 thousand rubles per ton.
In 2008, Solikamsk "Silvinit" started construction of a new mining and processing complex at the Polovodovsky site of the Verkhnekamskoye deposit in the Perm Territory. In terms of scale, this construction is in no way inferior to the shock construction projects of the past. For 8-10 years "Silvinit" plans to invest more than 1.5 billion dollars in the construction of the mine and the processing plant at the new site. Potassium mining is closely intertwined with the development of the transport infrastructure of the Upper Kama region and the fate of the titanium and magnesium industry. In 2008, a large-scale construction of a 53-kilometer section of the railway to Solikamsk will begin, bypassing Berezniki. And the metallurgists of VSMPO-AVISMa will receive guarantees for the supply of carnallite, which is vital for them, problems with which began after the flooding of the second mine of Berezniki Uralkali. At today's pace of development of the reserves of the Polovodovsky site, "Silvinit" will last at least 150 years. In 2007, Silvinit produced 100 million tons of potash fertilizers from the start of the company's operations.
The increase in exports to China, Japan, and India urgently requires the development of the Nepskoye deposit in Siberia. At the same time, savings due to reduced transportation costs will double the profit from the commissioning of this field. Particularly promising is the use of geotechnological methods in its development, which ensure the production of brines with the production of valuable and scarce chloride-free fertilizers. It should be noted that the geotechnological method makes it possible to increase production productivity by 4 times while reducing specific capital investments by 7 times.
In addition to increasing production at the Verkhnekamskoye deposit and developing the Nepskoye deposit, the development of the Gremyachenskoye deposit in the Volgograd region, whose sylvinite reserves in the C2 category are 250 million tons of K2O with an average useful component content of 21-26%, as well as the Eltonskoye deposit, is also very promising. In the most explored Ulagan area of the latter, the total reserves of sylvinites, carnallites and kieserite-carnalite-sylvinite ores in category С1+С2 amount to 430 million tons of K2O. In the other two areas, C2 category reserves and predicted resources are estimated at 580 million tons of K2O.
The development of these deposits is attractive due to their proximity to the main consumers of potash fertilizers - the Volga, Central, Central Black Earth and North Caucasian economic regions.
Application of potassium
Potassium salts and their compounds are widely used in various sectors of the national economy. Together with phosphorus and nitrogen, potassium is included in the triad of elements that are most necessary for plants and are the basis of mineral fertilizers.
In addition to the fertilizer industry, potash ores are used to produce detergents and various chemicals - potassium nitrate, caustic potassium, potash, bertolet salt, potassium cyanide, potassium bromide, etc. Magnesium chloride obtained during the processing of carnallite is the starting product for the production of magnesium oxide and metallic magnesium.