What practical significance does aluminum have? Characteristics of aluminum. Aluminum: general characteristics. Use in construction

Metals are easy-to-process materials, and the leader among them is aluminum, the chemical properties of which have long been known to people. This metal, due to its characteristics, is widely used in everyday life, and almost every person can find an aluminum product at home. It is necessary to consider in detail the properties of this metal as an element and as a simple substance.

How aluminum was discovered

Since ancient times, people have used potassium alum, an aluminum compound that can impart strength and stability to fabrics and skin. This property of the metal found its application in leatherworking: with the help of aluminum-potassium alum, furriers tanned leather, giving it strength and stability. People learned that aluminum oxide is present in nature in a pure form only in the second half of the 18th century, but at that time they had not yet learned how to obtain a pure substance.

This was first done by Hans Christian Oersted, who treated the salt with potassium amalgam, then isolating a gray powder from the resulting mixture. Thus, this chemical reaction helped produce pure . At the same time, such characteristics of the metal as high reducing ability and strong activity were established.

Interaction with oxides the reaction of replacing metal atoms in the oxide with aluminum allows one to obtain a large amount of heat and a new metal in free form.

Interaction with salts, namely with solutions of some less active salts.

Interaction with alkalis: due to strong interaction with alkali solutions, their solutions cannot be stored in aluminum containers.

Aluminothermy- the process of reducing metals, alloys and non-metals by exposing their oxides to metallic aluminum. Thanks to this feature of aluminum, metallurgists can mine such refractory metals as molybdenum, tungsten, zirconium, and vanadium.

Physical properties of aluminum as a simple substance

As a simple substance, aluminum is a silver-colored metal. It is capable of oxidizing in air, becoming covered with a dense oxide film.

This feature of the metal ensures its high resistance to corrosion. This property of aluminum, along with other characteristics, makes it an extremely popular metal, widely used in everyday life. In addition, aluminum is lightweight while maintaining high strength and ductility.

Not every substance known to people has a set of similar characteristics.

Physical properties of aluminum

Aluminum is a ductile and malleable metal, used to make the thinnest foil; wire is rolled from aluminum.

The boiling point of the metal is 2518 °C.

The melting point of aluminum is 660 °C.

The density of aluminum is 2.7 g/cm³.

The widespread use of aluminum in areas of life is due to its chemical and physical properties.

DEFINITION

Aluminum– chemical element of the 3rd period of group IIIA. Serial number – 13. Metal. Aluminum belongs to the elements of the p-family. Symbol – Al.

Atomic mass – 27 amu. The electronic configuration of the outer energy level is 3s 2 3p 1. In its compounds, aluminum exhibits an oxidation state of “+3”.

Chemical properties of aluminum

Aluminum exhibits reducing properties in reactions. Since an oxide film forms on its surface when exposed to air, it is resistant to interaction with other substances. For example, aluminum is passivated in water, concentrated nitric acid and a solution of potassium dichromate. However, after removing the oxide film from its surface, it is able to interact with simple substances. Most reactions occur when heated:

2Al powder +3/2O 2 = Al 2 O 3;

2Al + 3F 2 = 2AlF 3 (t);

2Al powder + 3Hal 2 = 2AlHal 3 (t = 25C);

2Al + N 2 = 2AlN (t);

2Al +3S = Al 2 S 3 (t);

4Al + 3C graphite = Al 4 C 3 (t);

4Al + P 4 = 4AlP (t, in an atmosphere of H 2).

Also, after removing the oxide film from its surface, aluminum is able to interact with water to form hydroxide:

2Al + 6H 2 O = 2Al(OH) 3 + 3H 2.

Aluminum exhibits amphoteric properties, so it is able to dissolve in dilute solutions of acids and alkalis:

2Al + 3H 2 SO 4 (dilute) = Al 2 (SO 4) 3 + 3H 2;

2Al + 6HCl dilute = 2AlCl 3 + 3 H 2 ;

8Al + 30HNO 3 (dilute) = 8Al(NO 3) 3 + 3N 2 O + 15H 2 O;

2Al +2NaOH +3H 2 O = 2Na + 3H 2;

2Al + 2(NaOH×H 2 O) = 2NaAlO 2 + 3 H 2.

Aluminothermy is a method of producing metals from their oxides, based on the reduction of these metals with aluminum:

8Al + 3Fe 3 O 4 = 4Al 2 O 3 + 9Fe;

2Al + Cr 2 O 3 = Al 2 O 3 + 2Cr.

Physical properties of aluminum

Aluminum is a silvery-white color. The main physical properties of aluminum are lightness, high thermal and electrical conductivity. In the free state, when exposed to air, aluminum is covered with a durable film of Al 2 O 3 oxide, which makes it resistant to the action of concentrated acids. Melting point – 660.37C, boiling point – 2500C.

Production and use of aluminum

Aluminum is produced by electrolysis of the molten oxide of this element:

2Al 2 O 3 = 4Al + 3O 2

However, due to the low yield of the product, the method of producing aluminum by electrolysis of a mixture of Na 3 and Al 2 O 3 is more often used. The reaction occurs when heated to 960C and in the presence of catalysts - fluorides (AlF 3, CaF 2, etc.), while the release of aluminum occurs at the cathode, and oxygen is released at the anode.

Aluminum has found wide application in industry; aluminum-based alloys are the main structural materials in aircraft and shipbuilding.

Examples of problem solving

EXAMPLE 1

Exercise	When aluminum reacted with sulfuric acid, aluminum sulfate weighing 3.42 g was formed. Determine the mass and amount of the aluminum substance that reacted.
Solution	Let's write the reaction equation: 2Al + 3H 2 SO 4 = Al 2 (SO 4) 3 + 3H 2. Molar masses of aluminum and aluminum sulfate, calculated using the table of chemical elements by D.I. Mendeleev – 27 and 342 g/mol, respectively. Then, the amount of substance of the formed aluminum sulfate will be equal to: n(Al 2 (SO 4) 3) = m(Al 2 (SO 4) 3) / M(Al 2 (SO 4) 3); n(Al 2 (SO 4) 3) = 3.42 / 342 = 0.01 mol. According to the reaction equation n(Al 2 (SO 4) 3): n(Al) = 1:2, therefore n(Al) = 2×n(Al 2 (SO 4) 3) = 0.02 mol. Then, the mass of aluminum will be equal to: m(Al) = n(Al)×M(Al); m(Al) = 0.02×27 = 0.54 g.
Answer	The amount of aluminum substance is 0.02 mol; aluminum mass – 0.54 g.

One of the most common elements on the planet is aluminum. The physical and chemical properties of aluminum are used in industry. You will find everything you need to know about this metal in our article.

Atomic structure

Aluminum is the 13th element of the periodic table. It is in the third period, group III, the main subgroup.

The properties and uses of aluminum are related to its electronic structure. The aluminum atom has a positively charged nucleus (+13) and 13 negatively charged electrons, located at three energy levels. The electronic configuration of the atom is 1s 2 2s 2 2p 6 3s 2 3p 1.

The outer energy level contains three electrons, which determine the constant valence of III. In reactions with substances, aluminum goes into an excited state and is able to give up all three electrons, forming covalent bonds. Like other active metals, aluminum is a powerful reducing agent.

Rice. 1. Structure of the aluminum atom.

Aluminum is an amphoteric metal that forms amphoteric oxides and hydroxides. Depending on the conditions, the compounds exhibit acidic or basic properties.

Physical Description

Aluminum has:

• lightness (density 2.7 g/cm 3);
• silver-gray color;
• high electrical conductivity;
• malleability;
• plasticity;
• melting point - 658°C;
• boiling point - 2518.8°C.

Tin containers, foil, wire, and alloys are made from metal. Aluminum is used in the manufacture of microcircuits, mirrors, and composite materials.

Rice. 2. Tin containers.

Aluminum is paramagnetic. Metal is attracted to a magnet only in the presence of a magnetic field.

Chemical properties

In air, aluminum quickly oxidizes, becoming covered with an oxide film. It protects the metal from corrosion and also prevents interaction with concentrated acids (nitric, sulfuric). Therefore, acids are stored and transported in aluminum containers.

Under normal conditions, reactions with aluminum are possible only after removing the oxide film. Most reactions occur at high temperatures.

The main chemical properties of the element are described in the table.

Reaction	Description	The equation
With oxygen	Burns at high temperatures releasing heat	4Al + 3O 2 → 2Al 2 O 3
With non-metal	Reacts with sulfur at temperatures above 200°C, with phosphorus - at 500°C, with nitrogen - at 800°C, with carbon - at 2000°C	2Al + 3S → Al 2 S 3 ; Al + P → AlP; 2Al + N 2 → 2AlN; 4Al + 3C → Al 4 C 3
With halogens	Reacts under normal conditions, with iodine - when heated in the presence of a catalyst (water)	2Al + 3Cl 2 → 2AlCl 3 ; 2Al + 3I 2 → 2AlI 3 ; 2Al + 3Br 2 → 2AlBr 3
With acids	Reacts with dilute acids under normal conditions, with concentrated acids when heated	2Al + 3H 2 SO 4 (diluted) → Al 2 (SO 4) 3 + 3H 2; Al + 6HNO 3 (conc.) → Al(NO 3) 3 + 3NO 2 + 3H 2 O
With alkalis	Reacts with aqueous solutions of alkalis and upon fusion	2Al + 2NaOH + 10H 2 O → 2Na + 3H 2; 2Al + 6KOH → 2KAlO 2 + 2K 2 O + 3H 2
With oxides	Displaces less active metals	2Al + Fe 2 O 3 → 2Fe + Al 2 O 3

Aluminum does not react directly with hydrogen. Reaction with water is possible after removing the oxide film.

Rice. 3. Reaction of aluminum with water.

What have we learned?

Aluminum is an amphoteric active metal with constant valence. It has low density, high electrical conductivity, and plasticity. Attracted by a magnet only in the presence of a magnetic field. Aluminum reacts with oxygen, forming a protective film that prevents reactions with water, concentrated nitric and sulfuric acids. When heated, it interacts with non-metals and concentrated acids, and under normal conditions - with halogens and dilute acids. In oxides it displaces less active metals. Does not react with hydrogen.

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There is a lot of aluminum in the earth's crust: 8.6% by weight. It ranks first among all metals and third among other elements (after oxygen and silicon). There is twice as much aluminum as iron, and 350 times more than copper, zinc, chromium, tin and lead combined! As he wrote more than 100 years ago in his classic textbook Basics of Chemistry D.I. Mendeleev, of all metals, “aluminum is the most common in nature; It is enough to point out that it is part of clay to make clear the universal distribution of aluminum in the earth’s crust. Aluminum, or alum metal (alumen), is also called clay because it is found in clay.”

The most important mineral of aluminum is bauxite, a mixture of the basic oxide AlO(OH) and hydroxide Al(OH) 3. The largest bauxite deposits are located in Australia, Brazil, Guinea and Jamaica; industrial production is also carried out in other countries. Alunite (alum stone) (Na,K) 2 SO 4 ·Al 2 (SO 4) 3 ·4Al(OH) 3 and nepheline (Na,K) 2 O·Al 2 O 3 ·2SiO 2 are also rich in aluminum. In total, more than 250 minerals are known that contain aluminum; most of them are aluminosilicates, from which the earth’s crust is mainly formed. When they weather, clay is formed, the basis of which is the mineral kaolinite Al 2 O 3 · 2SiO 2 · 2H 2 O. Iron impurities usually color the clay brown, but there is also white clay - kaolin, which is used to make porcelain and earthenware products.

Occasionally, an exceptionally hard (second only to diamond) mineral corundum is found - crystalline oxide Al 2 O 3, often colored by impurities in different colors. Its blue variety (an admixture of titanium and iron) is called sapphire, the red one (an admixture of chromium) is called ruby. Various impurities can also color the so-called noble corundum green, yellow, orange, purple and other colors and shades.

Until recently, it was believed that aluminum, as a highly active metal, could not occur in nature in a free state, but in 1978, native aluminum was discovered in the rocks of the Siberian Platform - in the form of thread-like crystals only 0.5 mm long (with a thread thickness of several micrometers). Native aluminum was also discovered in lunar soil brought to Earth from the regions of the Seas of Crisis and Abundance. It is believed that aluminum metal can be formed by condensation from gas. It is known that when aluminum halides - chloride, bromide, fluoride - are heated, they can evaporate with greater or less ease (for example, AlCl 3 sublimes already at 180 ° C). With a strong increase in temperature, aluminum halides decompose, transforming into a state with a lower metal valency, for example, AlCl. When such a compound condenses with a decrease in temperature and the absence of oxygen, a disproportionation reaction occurs in the solid phase: some of the aluminum atoms are oxidized and pass into the usual trivalent state, and some are reduced. Monivalent aluminum can only be reduced to metal: 3AlCl ® 2Al + AlCl 3 . This assumption is also supported by the thread-like shape of native aluminum crystals. Typically, crystals of this structure are formed due to rapid growth from the gas phase. It is likely that microscopic aluminum nuggets in the lunar soil were formed in a similar way.

The name aluminum comes from the Latin alumen (genus aluminis). This was the name of alum, double potassium-aluminum sulfate KAl(SO 4) 2 ·12H 2 O), which was used as a mordant for dyeing fabrics. The Latin name probably goes back to the Greek “halme” - brine, salt solution. It is curious that in England aluminum is aluminum, and in the USA it is aluminum.

Many popular books on chemistry contain a legend that a certain inventor, whose name has not been preserved by history, brought to the Emperor Tiberius, who ruled Rome in 14–27 AD, a bowl made of a metal resembling the color of silver, but lighter. This gift cost the master his life: Tiberius ordered his execution and the destruction of the workshop, because he was afraid that the new metal could depreciate the value of silver in the imperial treasury.

This legend is based on a story by Pliny the Elder, a Roman writer and scholar, author Natural history– encyclopedia of natural science knowledge of ancient times. According to Pliny, the new metal was obtained from "clayey earth." But clay does contain aluminum.

Modern authors almost always make a reservation that this whole story is nothing more than a beautiful fairy tale. And this is not surprising: aluminum in rocks is extremely tightly bound to oxygen, and a lot of energy must be spent to release it. However, recently new data have appeared on the fundamental possibility of obtaining metallic aluminum in ancient times. As spectral analysis showed, the decorations on the tomb of the Chinese commander Zhou-Zhu, who died at the beginning of the 3rd century. AD, are made of an alloy consisting of 85% aluminum. Could the ancients have obtained free aluminum? All known methods (electrolysis, reduction with metallic sodium or potassium) are automatically eliminated. Could native aluminum be found in ancient times, like, for example, nuggets of gold, silver, and copper? This is also excluded: native aluminum is a rare mineral that is found in insignificant quantities, so the ancient craftsmen could not find and collect such nuggets in the required quantity.

However, another explanation for Pliny's story is possible. Aluminum can be recovered from ores not only with the help of electricity and alkali metals. There is a reducing agent available and widely used since ancient times - coal, with the help of which the oxides of many metals are reduced to free metals when heated. In the late 1970s, German chemists decided to test whether aluminum could have been produced in ancient times by reduction with coal. They heated a mixture of clay with coal powder and table salt or potash (potassium carbonate) in a clay crucible to red heat. Salt was obtained from sea water, and potash from plant ash, in order to use only those substances and methods that were available in ancient times. After some time, slag with aluminum balls floated to the surface of the crucible! The metal yield was small, but it is possible that it was in this way that the ancient metallurgists could obtain the “metal of the 20th century.”

Properties of aluminum.

The color of pure aluminum resembles silver; it is a very light metal: its density is only 2.7 g/cm 3 . The only metals lighter than aluminum are alkali and alkaline earth metals (except barium), beryllium and magnesium. Aluminum also melts easily - at 600 ° C (thin aluminum wire can be melted on a regular kitchen burner), but it boils only at 2452 ° C. In terms of electrical conductivity, aluminum is in 4th place, second only to silver (it is in first place), copper and gold, which, given the cheapness of aluminum, is of great practical importance. The thermal conductivity of metals changes in the same order. It is easy to verify the high thermal conductivity of aluminum by dipping an aluminum spoon into hot tea. And one more remarkable property of this metal: its smooth, shiny surface perfectly reflects light: from 80 to 93% in the visible region of the spectrum, depending on the wavelength. In the ultraviolet region, aluminum has no equal in this regard, and only in the red region is it slightly inferior to silver (in the ultraviolet, silver has a very low reflectivity).

Pure aluminum is a fairly soft metal - almost three times softer than copper, so even relatively thick aluminum plates and rods are easy to bend, but when aluminum forms alloys (there are a huge number of them), its hardness can increase tenfold.

The characteristic oxidation state of aluminum is +3, but due to the presence of unfilled 3 R- and 3 d-orbitals, aluminum atoms can form additional donor-acceptor bonds. Therefore, the Al 3+ ion with a small radius is very prone to complex formation, forming a variety of cationic and anionic complexes: AlCl 4 –, AlF 6 3–, 3+, Al(OH) 4 –, Al(OH) 6 3–, AlH 4 – and many others. Complexes with organic compounds are also known.

The chemical activity of aluminum is very high; in the series of electrode potentials it stands immediately behind magnesium. At first glance, such a statement may seem strange: after all, an aluminum pan or spoon is quite stable in the air and does not collapse in boiling water. Aluminum, unlike iron, does not rust. It turns out that when exposed to air, the metal is covered with a colorless, thin but durable “armor” of oxide, which protects the metal from oxidation. So, if you introduce a thick aluminum wire or plate 0.5–1 mm thick into the burner flame, the metal melts, but the aluminum does not flow, since it remains in a bag of its oxide. If you deprive aluminum of its protective film or make it loose (for example, by immersing it in a solution of mercury salts), aluminum will immediately reveal its true essence: already at room temperature it will begin to react vigorously with water, releasing hydrogen: 2Al + 6H 2 O ® 2Al(OH) 3 + 3H 2 . In air, aluminum, stripped of its protective film, turns into loose oxide powder right before our eyes: 2Al + 3O 2 ® 2Al 2 O 3 . Aluminum is especially active in a finely crushed state; When blown into a flame, aluminum dust burns instantly. If you mix aluminum dust with sodium peroxide on a ceramic plate and drop water on the mixture, the aluminum also flares up and burns with a white flame.

The very high affinity of aluminum for oxygen allows it to “take away” oxygen from the oxides of a number of other metals, reducing them (aluminothermy method). The most famous example is the thermite mixture, which, when burned, releases so much heat that the resulting iron melts: 8Al + 3Fe 3 O 4 ® 4Al 2 O 3 + 9Fe. This reaction was discovered in 1856 by N.N. Beketov. In this way, Fe 2 O 3, CoO, NiO, MoO 3, V 2 O 5, SnO 2, CuO, and a number of other oxides can be reduced to metals. When reducing Cr 2 O 3, Nb 2 O 5, Ta 2 O 5, SiO 2, TiO 2, ZrO 2, B 2 O 3 with aluminum, the heat of reaction is not enough to heat the reaction products above their melting point.

Aluminum easily dissolves in dilute mineral acids to form salts. Concentrated nitric acid, oxidizing the surface of aluminum, promotes thickening and strengthening of the oxide film (the so-called passivation of the metal). Aluminum treated in this way does not react even with hydrochloric acid. Using electrochemical anodic oxidation (anodizing), a thick film can be created on the surface of aluminum, which can be easily painted in different colors.

The displacement of less active metals by aluminum from solutions of salts is often hindered by a protective film on the surface of aluminum. This film is quickly destroyed by copper chloride, so the reaction 3CuCl 2 + 2Al ® 2AlCl 3 + 3Cu occurs easily, which is accompanied by strong heating. In strong alkali solutions, aluminum easily dissolves with the release of hydrogen: 2Al + 6NaOH + 6H 2 O ® 2Na 3 + 3H 2 (other anionic hydroxo complexes are also formed). The amphoteric nature of aluminum compounds is also manifested in the easy dissolution of its freshly precipitated oxide and hydroxide in alkalis. Crystalline oxide (corundum) is very resistant to acids and alkalis. When fused with alkalis, anhydrous aluminates are formed: Al 2 O 3 + 2NaOH ® 2NaAlO 2 + H 2 O. Magnesium aluminate Mg(AlO 2) 2 is a semi-precious spinel stone, usually colored with impurities in a wide variety of colors.

The reaction of aluminum with halogens occurs rapidly. If a thin aluminum wire is introduced into a test tube with 1 ml of bromine, then after a short time the aluminum ignites and burns with a bright flame. The reaction of a mixture of aluminum and iodine powders is initiated by a drop of water (water with iodine forms an acid that destroys the oxide film), after which a bright flame appears with clouds of violet iodine vapor. Aluminum halides in aqueous solutions have an acidic reaction due to hydrolysis: AlCl 3 + H 2 O Al(OH)Cl 2 + HCl.

The reaction of aluminum with nitrogen occurs only above 800 ° C with the formation of nitride AlN, with sulfur - at 200 ° C (sulfide Al 2 S 3 is formed), with phosphorus - at 500 ° C (phosphide AlP is formed). When boron is added to molten aluminum, borides of the composition AlB 2 and AlB 12 are formed - refractory compounds resistant to acids. Hydride (AlH) x (x = 1.2) is formed only in vacuum at low temperatures in the reaction of atomic hydrogen with aluminum vapor. AlH 3 hydride, stable in the absence of moisture at room temperature, is obtained in a solution of anhydrous ether: AlCl 3 + LiH ® AlH 3 + 3LiCl. With an excess of LiH, salt-like lithium aluminum hydride LiAlH 4 is formed - a very strong reducing agent used in organic syntheses. It instantly decomposes with water: LiAlH 4 + 4H 2 O ® LiOH + Al(OH) 3 + 4H 2.

Production of aluminum.

The documented discovery of aluminum occurred in 1825. This metal was first obtained by the Danish physicist Hans Christian Oersted, when he isolated it by the action of potassium amalgam on anhydrous aluminum chloride (obtained by passing chlorine through a hot mixture of aluminum oxide and coal). Having distilled off the mercury, Oersted obtained aluminum, although it was contaminated with impurities. In 1827, the German chemist Friedrich Wöhler obtained aluminum in powder form by reducing hexafluoroaluminate with potassium:

Na 3 AlF 6 + 3K ® Al + 3NaF + 3KF. Later he managed to obtain aluminum in the form of shiny metal balls. In 1854, the French chemist Henri Etienne Saint-Clair Deville developed the first industrial method for producing aluminum - by reducing the melt of tetrachloroaluminate with sodium: NaAlCl 4 + 3Na ® Al + 4NaCl. However, aluminum continued to be an extremely rare and expensive metal; it was not much cheaper than gold and 1500 times more expensive than iron (now only three times). A rattle was made from gold, aluminum and precious stones in the 1850s for the son of French Emperor Napoleon III. When a large ingot of aluminum produced by a new method was exhibited at the World Exhibition in Paris in 1855, it was looked upon as if it were a jewel. The upper part (in the form of a pyramid) of the Washington Monument in the US capital was made from precious aluminum. At that time, aluminum was not much cheaper than silver: in the USA, for example, in 1856 it was sold at a price of 12 dollars per pound (454 g), and silver for 15 dollars. In the 1st volume of the famous Brockhaus Encyclopedic Dictionary published in 1890, Efron said that “aluminum is still used primarily for the manufacture of... luxury goods.” By that time, only 2.5 tons of metal were mined annually throughout the world. Only towards the end of the 19th century, when an electrolytic method for producing aluminum was developed, its annual production began to amount to thousands of tons, and in the 20th century. – million tons. This transformed aluminum from a semi-precious metal to a widely available metal.

The modern method of producing aluminum was discovered in 1886 by a young American researcher, Charles Martin Hall. He became interested in chemistry as a child. Having found his father's old chemistry textbook, he began to diligently study it and carry out experiments, once even receiving a scolding from his mother for damaging the dinner tablecloth. And 10 years later he made an outstanding discovery that made him famous throughout the world.

As a student at age 16, Hall heard from his teacher, F. F. Jewett, that if someone could develop a cheap way to produce aluminum, that person would not only do a great service to humanity, but also make a huge fortune. Jewett knew what he was saying: he had previously trained in Germany, worked with Wöhler, and discussed with him the problems of producing aluminum. Jewett also brought a sample of the rare metal with him to America, which he showed to his students. Suddenly Hall declared publicly: “I will get this metal!”

Six years of hard work continued. Hall tried to obtain aluminum using different methods, but without success. Finally, he tried to extract this metal by electrolysis. At that time there were no power plants; current had to be generated using large homemade batteries from coal, zinc, nitric and sulfuric acids. Hall worked in a barn where he set up a small laboratory. He was helped by his sister Julia, who was very interested in her brother’s experiments. She preserved all his letters and work journals, which make it possible to literally trace the history of the discovery day by day. Here is an excerpt from her memoirs:

“Charles was always in a good mood, and even on the worst days he was able to laugh at the fate of unlucky inventors. In times of failure, he found solace at our old piano. In his home laboratory he worked for long hours without a break; and when he could leave the set up for a while, he would rush across our long house to play a little... I knew that, playing with such charm and feeling, he was constantly thinking about his work. And music helped him with this.”

The most difficult thing was to select an electrolyte and protect the aluminum from oxidation. After six months of exhausting labor, several small silver balls finally appeared in the crucible. Hall immediately ran to his former teacher to tell him about his success. “Professor, I got it!” he exclaimed, holding out his hand: in his palm lay a dozen small aluminum balls. This happened on February 23, 1886. And exactly two months later, on April 23 of the same year, the Frenchman Paul Héroux took out a patent for a similar invention, which he made independently and almost simultaneously (two other coincidences are also striking: both Hall and Héroux were born in 1863 and died in 1914).

Now the first balls of aluminum produced by Hall are kept at the American Aluminum Company in Pittsburgh as a national relic, and at his college there is a monument to Hall, cast from aluminum. Jewett subsequently wrote: “My most important discovery was the discovery of man. It was Charles M. Hall who, at the age of 21, discovered a method of reducing aluminum from ore, and thus made aluminum that wonderful metal which is now widely used throughout the world.” Jewett's prophecy came true: Hall received wide recognition and became an honorary member of many scientific societies. But his personal life was unsuccessful: the bride did not want to come to terms with the fact that her fiancé spends all his time in the laboratory, and broke off the engagement. Hall found solace in his native college, where he worked for the rest of his life. As Charles’s brother wrote, “College was his wife, his children, and everything else—his whole life.” Hall bequeathed the majority of his inheritance to the college - $5 million. Hall died of leukemia at the age of 51.

Hall's method made it possible to produce relatively inexpensive aluminum on a large scale using electricity. If from 1855 to 1890 only 200 tons of aluminum were obtained, then over the next decade, using Hall’s method, 28,000 tons of this metal were already obtained worldwide! By 1930, global annual aluminum production reached 300 thousand tons. Now more than 15 million tons of aluminum are produced annually. In special baths at a temperature of 960–970 ° C, a solution of alumina (technical Al 2 O 3) in molten cryolite Na 3 AlF 6, which is partially mined in the form of a mineral, and partially specially synthesized, is subjected to electrolysis. Liquid aluminum accumulates at the bottom of the bath (cathode), oxygen is released at the carbon anodes, which gradually burn. At low voltage (about 4.5 V), electrolysers consume enormous currents - up to 250,000 A! One electrolyzer produces about a ton of aluminum per day. Production requires a lot of electricity: it takes 15,000 kilowatt-hours of electricity to produce 1 ton of metal. This amount of electricity is consumed by a large 150-apartment building for a whole month. Aluminum production is environmentally hazardous, since the atmospheric air is polluted with volatile fluorine compounds.

Application of aluminum.

Even D.I. Mendeleev wrote that “metallic aluminum, having great lightness and strength and low variability in air, is very suitable for some products.” Aluminum is one of the most common and cheapest metals. It is difficult to imagine modern life without it. No wonder aluminum is called the metal of the 20th century. It lends itself well to processing: forging, stamping, rolling, drawing, pressing. Pure aluminum is a fairly soft metal; It is used to make electrical wires, structural parts, food foil, kitchen utensils and “silver” paint. This beautiful and lightweight metal is widely used in construction and aviation technology. Aluminum reflects light very well. Therefore, it is used to make mirrors using the method of metal deposition in a vacuum.

In aircraft and mechanical engineering, in the manufacture of building structures, much harder aluminum alloys are used. One of the most famous is an alloy of aluminum with copper and magnesium (duralumin, or simply “duralumin”; the name comes from the German city of Duren). After hardening, this alloy acquires special hardness and becomes approximately 7 times stronger than pure aluminum. At the same time, it is almost three times lighter than iron. It is obtained by alloying aluminum with small additions of copper, magnesium, manganese, silicon and iron. Silumins are widely used - casting alloys of aluminum and silicon. High-strength, cryogenic (frost-resistant) and heat-resistant alloys are also produced. Protective and decorative coatings are easily applied to products made of aluminum alloys. The lightness and strength of aluminum alloys are especially useful in aviation technology. For example, helicopter rotors are made from an alloy of aluminum, magnesium and silicon. Relatively cheap aluminum bronze (up to 11% Al) has high mechanical properties, it is stable in sea water and even in dilute hydrochloric acid. From 1926 to 1957, coins in denominations of 1, 2, 3 and 5 kopecks were minted from aluminum bronze in the USSR.

Currently, a quarter of all aluminum is used for construction needs, the same amount is consumed by transport engineering, approximately 17% is spent on packaging materials and cans, and 10% in electrical engineering.

Many flammable and explosive mixtures also contain aluminum. Alumotol, a cast mixture of trinitrotoluene and aluminum powder, is one of the most powerful industrial explosives. Ammonal is an explosive substance consisting of ammonium nitrate, trinitrotoluene and aluminum powder. Incendiary compositions contain aluminum and an oxidizing agent - nitrate, perchlorate. Zvezdochka pyrotechnic compositions also contain powdered aluminum.

A mixture of aluminum powder with metal oxides (thermite) is used to produce certain metals and alloys, for welding rails, and in incendiary ammunition.

Aluminum has also found practical use as rocket fuel. To completely burn 1 kg of aluminum, almost four times less oxygen is required than for 1 kg of kerosene. In addition, aluminum can be oxidized not only by free oxygen, but also by bound oxygen, which is part of water or carbon dioxide. When aluminum “burns” in water, 8800 kJ is released per 1 kg of products; this is 1.8 times less than during combustion of metal in pure oxygen, but 1.3 times more than during combustion in air. This means that instead of dangerous and expensive compounds, simple water can be used as an oxidizer for such fuel. The idea of ​​using aluminum as a fuel was proposed back in 1924 by the domestic scientist and inventor F.A. Tsander. According to his plan, it is possible to use aluminum elements of a spacecraft as additional fuel. This bold project has not yet been practically implemented, but most currently known solid rocket fuels contain metallic aluminum in the form of fine powder. Adding 15% aluminum to the fuel can increase the temperature of combustion products by a thousand degrees (from 2200 to 3200 K); The rate of flow of combustion products from the engine nozzle also increases noticeably - the main energy indicator that determines the efficiency of rocket fuel. In this regard, only lithium, beryllium and magnesium can compete with aluminum, but all of them are much more expensive than aluminum.

Aluminum compounds are also widely used. Aluminum oxide is a refractory and abrasive (emery) material, a raw material for the production of ceramics. It is also used to make laser materials, watch bearings, and jewelry stones (artificial rubies). Calcined aluminum oxide is an adsorbent for purifying gases and liquids and a catalyst for a number of organic reactions. Anhydrous aluminum chloride is a catalyst in organic synthesis (Friedel-Crafts reaction), the starting material for the production of high-purity aluminum. Aluminum sulfate is used for water purification; reacting with the calcium bicarbonate it contains:

Al 2 (SO 4) 3 + 3Ca(HCO 3) 2 ® 2AlO(OH) + 3CaSO 4 + 6CO 2 + 2H 2 O, it forms oxide-hydroxide flakes, which, settling, capture and also sorb on the surface those in suspended impurities and even microorganisms in water. In addition, aluminum sulfate is used as a mordant for dyeing fabrics, tanning leather, preserving wood, and sizing paper. Calcium aluminate is a component of cementitious materials, including Portland cement. Yttrium aluminum garnet (YAG) YAlO 3 is a laser material. Aluminum nitride is a refractory material for electric furnaces. Synthetic zeolites (they belong to aluminosilicates) are adsorbents in chromatography and catalysts. Organoaluminum compounds (for example, triethylaluminum) are components of Ziegler-Natta catalysts, which are used for the synthesis of polymers, including high-quality synthetic rubber.

Ilya Leenson

Literature:

Tikhonov V.N. Analytical chemistry of aluminum. M., “Science”, 1971
Popular library of chemical elements. M., “Science”, 1983
Craig N.C. Charles Martin Hall and his Metal. J.Chem.Educ. 1986, vol. 63, no. 7
Kumar V., Milewski L. Charles Martin Hall and the Great Aluminum Revolution. J.Chem.Educ., 1987, vol. 64, no. 8



Preparation of potassium alum

Aluminum(Latin: Aluminum), – in the periodic table, aluminum is in the third period, in the main subgroup of the third group. Core charge +13. The electronic structure of the atom is 1s 2 2s 2 2p 6 3s 2 3p 1. The metallic atomic radius is 0.143 nm, the covalent radius is 0.126 nm, the conventional radius of the Al 3+ ion is 0.057 nm. Ionization energy Al – Al + 5.99 eV.

The most characteristic oxidation state of the aluminum atom is +3. Negative oxidation states rarely occur. There are free d-sublevels in the outer electron layer of the atom. Due to this, its coordination number in compounds can be not only 4 (AlCl 4-, AlH 4-, aluminosilicates), but also 6 (Al 2 O 3, 3+).

Historical reference. The name Aluminum comes from the Latin. alumen - so back in 500 BC. called aluminum alum, which was used as a mordant for dyeing fabrics and for tanning leather. The Danish scientist H. K. Oersted in 1825, acting with potassium amalgam on anhydrous AlCl 3 and then distilling off mercury, obtained relatively pure Aluminum. The first industrial method of producing aluminum was proposed in 1854 by the French chemist A.E. Sainte-Clair Deville: the method consisted in the reduction of double aluminum and sodium chloride Na 3 AlCl 6 with metallic sodium. Similar in color to silver, Aluminum was very expensive at first. From 1855 to 1890, only 200 tons of aluminum were produced. The modern method of producing aluminum by electrolysis of cryolite-alumina melt was developed in 1886 simultaneously and independently by C. Hall in the USA and P. Heroux in France.

Being in nature

Aluminum is the most common metal in the earth's crust. It accounts for 5.5–6.6 mol. fraction% or 8 wt.%. Its main mass is concentrated in aluminosilicates. An extremely common product of the destruction of rocks formed by them is clay, the main composition of which corresponds to the formula Al 2 O 3. 2SiO2. 2H 2 O. Of the other natural forms of aluminum, bauxite Al 2 O 3 is of greatest importance. xH 2 O and minerals corundum Al 2 O 3 and cryolite AlF 3 . 3NaF.

Receipt

Currently, in industry, aluminum is produced by electrolysis of a solution of alumina Al 2 O 3 in molten cryolite. Al 2 O 3 must be fairly pure, since impurities are difficult to remove from smelted aluminum. The melting point of Al 2 O 3 is about 2050 o C, and cryolite is 1100 o C. A molten mixture of cryolite and Al 2 O 3 containing about 10 wt.% Al 2 O 3 is subjected to electrolysis, which melts at 960 o C and has electrical conductivity , density and viscosity, most favorable for the process. With the addition of AlF 3, CaF 2 and MgF 2, electrolysis becomes possible at 950 o C.

The electrolyzer for smelting aluminum is an iron casing lined with refractory bricks on the inside. Its bottom (under), assembled from blocks of compressed coal, serves as a cathode. The anodes are located on top: these are aluminum frames filled with coal briquettes.

Al 2 O 3 = Al 3+ + AlO 3 3-

Liquid aluminum is released at the cathode:

Al 3+ + 3е - = Al

Aluminum is collected at the bottom of the furnace, from where it is periodically released. Oxygen is released at the anode:

4AlO 3 3- – 12e - = 2Al 2 O 3 + 3O 2

Oxygen oxidizes graphite to carbon oxides. As the carbon burns, the anode is built up.

Aluminum is also used as an alloying additive to many alloys to impart heat resistance to them.

Physical properties of aluminum. Aluminum combines a very valuable set of properties: low density, high thermal and electrical conductivity, high ductility and good corrosion resistance. It can be easily forged, stamped, rolled, drawn. Aluminum is well welded by gas, contact and other types of welding. Aluminum lattice is cubic face-centered with parameter a = 4.0413 Å. The properties of Aluminum, like all metals, therefore depend on its purity. Properties of high purity Aluminum (99.996%): density (at 20 °C) 2698.9 kg/m 3 ; t pl 660.24 °C; boiling point about 2500 °C; coefficient of thermal expansion (from 20° to 100 °C) 23.86·10 -6; thermal conductivity (at 190 °C) 343 W/m·K, specific heat capacity (at 100 °С) 931.98 J/kg·K. ; electrical conductivity with respect to copper (at 20 °C) 65.5%. Aluminum has low strength (tensile strength 50–60 Mn/m2), hardness (170 Mn/m2 according to Brinell) and high ductility (up to 50%). During cold rolling, the tensile strength of Aluminum increases to 115 Mn/m2, hardness - up to 270 Mn/m2, relative elongation decreases to 5% (1 Mn/m2 ~ and 0.1 kgf/mm2). Aluminum is highly polished, anodized and has a high reflectivity close to silver (it reflects up to 90% of the incident light energy). Having a high affinity for oxygen, aluminum in air is covered with a thin but very strong film of Al 2 O 3 oxide, which protects the metal from further oxidation and determines its high anti-corrosion properties. The strength of the oxide film and its protective effect greatly decrease in the presence of impurities of mercury, sodium, magnesium, copper, etc. Aluminum is resistant to atmospheric corrosion, sea and fresh water, practically does not interact with concentrated or highly diluted nitric acid, organic acids, food products.

Chemical properties

When finely crushed aluminum is heated, it burns vigorously in air. Its interaction with sulfur proceeds similarly. The combination with chlorine and bromine occurs at ordinary temperatures, and with iodine - upon heating. At very high temperatures, aluminum also combines directly with nitrogen and carbon. On the contrary, it does not interact with hydrogen.

Aluminum is quite resistant to water. But if the protective effect of the oxide film is removed mechanically or by amalgamation, a vigorous reaction occurs:

Highly diluted and very concentrated HNO3 and H2SO4 have almost no effect on aluminum (in the cold), while at medium concentrations of these acids it gradually dissolves. Pure aluminum is quite resistant to hydrochloric acid, but ordinary industrial metal dissolves in it.

When aluminum is exposed to aqueous solutions of alkalis, the oxide layer dissolves, and aluminates are formed - salts containing aluminum as part of the anion:

Al 2 O 3 + 2NaOH + 3H 2 O = 2Na

Aluminum, devoid of a protective film, interacts with water, displacing hydrogen from it:

2Al + 6H 2 O = 2Al(OH) 3 + 3H 2

The resulting aluminum hydroxide reacts with excess alkali, forming hydroxoaluminate:

Al(OH) 3 + NaOH = Na

The overall equation for the dissolution of aluminum in an aqueous alkali solution:

2Al + 2NaOH + 6H 2 O = 2Na + 3H 2

Aluminum dissolves noticeably in solutions of salts that, due to their hydrolysis, have an acidic or alkaline reaction, for example, in a solution of Na 2 CO 3.

In the stress series it is located between Mg and Zn. In all its stable compounds, aluminum is trivalent.

The combination of aluminum with oxygen is accompanied by an enormous release of heat (1676 kJ/mol Al 2 O 3), significantly greater than that of many other metals. In view of this, when a mixture of the oxide of the corresponding metal with aluminum powder is heated, a violent reaction occurs, leading to the release of free metal from the taken oxide. The reduction method using Al (aluminothermy) is often used to obtain a number of elements (Cr, Mn, V, W, etc.) in a free state.

Aluminothermy is sometimes used for welding individual steel parts, in particular the joints of tram rails. The mixture used (“thermite”) usually consists of fine powders of aluminum and Fe 3 O 4 . It is ignited using a fuse made from a mixture of Al and BaO 2. The main reaction follows the equation:

8Al + 3Fe 3 O 4 = 4Al 2 O 3 + 9Fe + 3350 kJ

Moreover, the temperature develops around 3000 o C.

Aluminum oxide is a white, very refractory (mp 2050 o C) and insoluble in water mass. Natural Al 2 O 3 (mineral corundum), as well as those obtained artificially and then highly calcined, are distinguished by high hardness and insolubility in acids. Al 2 O 3 (so-called alumina) can be converted into a soluble state by fusion with alkalis.

Typically, natural corundum contaminated with iron oxide, due to its extreme hardness, is used to make grinding wheels, whetstones, etc. In finely crushed form, it is called emery and is used to clean metal surfaces and make sandpaper. For the same purposes, Al 2 O 3 is often used, obtained by fusing bauxite (technical name - alundum).

Transparent colored corundum crystals - red ruby ​​- an admixture of chromium - and blue sapphire - an admixture of titanium and iron - precious stones. They are also obtained artificially and used for technical purposes, for example, for the manufacture of parts for precision instruments, watch stones, etc. Ruby crystals containing a small admixture of Cr 2 O 3 are used as quantum generators - lasers that create a directed beam of monochromatic radiation.

Due to the insolubility of Al 2 O 3 in water, the hydroxide Al(OH) 3 corresponding to this oxide can be obtained only indirectly from salts. The preparation of hydroxide can be represented as the following scheme. Under the action of alkalis, OH – ions are gradually replaced by 3+ water molecules in aqua complexes:

3+ + OH - = 2+ + H 2 O

2+ + OH - = + + H 2 O

OH - = 0 + H 2 O

Al(OH) 3 is a voluminous gelatinous white precipitate, practically insoluble in water, but easily soluble in acids and strong alkalis. It therefore has an amphoteric character. However, its basic and especially acidic properties are rather weakly expressed. Aluminum hydroxide is insoluble in excess NH 4 OH. One of the forms of dehydrated hydroxide, aluminum gel, is used in technology as an adsorbent.

When interacting with strong alkalis, the corresponding aluminates are formed:

NaOH + Al(OH) 3 = Na

Aluminates of the most active monovalent metals are highly soluble in water, but due to strong hydrolysis, their solutions are stable only in the presence of a sufficient excess of alkali. Aluminates, produced from weaker bases, are almost completely hydrolyzed in solution and therefore can only be obtained dryly (by fusing Al 2 O 3 with oxides of the corresponding metals). Metaaluminates are formed, whose composition is derived from metaaluminum acid HAlO 2. Most of them are insoluble in water.

Al(OH) 3 forms salts with acids. Derivatives of most strong acids are highly soluble in water, but are quite significantly hydrolyzed, and therefore their solutions exhibit an acidic reaction. Soluble aluminum salts and weak acids are even more hydrolyzed. Due to hydrolysis, sulfide, carbonate, cyanide and some other aluminum salts cannot be obtained from aqueous solutions.

In an aqueous environment, the Al 3+ anion is directly surrounded by six water molecules. Such a hydrated ion is somewhat dissociated according to the scheme:

3+ + H 2 O = 2+ + OH 3 +

Its dissociation constant is 1. 10 -5, i.e. it is a weak acid (close in strength to acetic acid). The octahedral environment of Al 3+ with six water molecules is also preserved in crystalline hydrates of a number of aluminum salts.

Aluminosilicates can be considered as silicates in which part of the silicon-oxygen tetrahedra SiO 4 4 - is replaced by aluminum-oxygen tetrahedra AlO 4 5. Of the aluminosilicates, the most common are feldspars, which account for more than half the mass of the earth's crust. Their main representatives are minerals

orthoclase K 2 Al 2 Si 6 O 16 or K 2 O . Al 2 O 3 . 6SiO2

albite Na 2 Al 2 Si 6 O 16 or Na 2 O. Al 2 O 3 . 6SiO2

anorthite CaAl 2 Si 2 O 8 or CaO. Al 2 O 3 . 2SiO2

Minerals of the mica group are very common, for example muscovite Kal 2 (AlSi 3 O 10) (OH) 2. The mineral nepheline (Na, K) 2, which is used to produce alumina, soda products and cement, is of great practical importance. This production consists of the following operations: a) nepheline and limestone are sintered in tube furnaces at 1200 o C:

(Na, K) 2 + 2CaCO 3 = 2CaSiO 3 + NaAlO 2 + KAlO 2 + 2CO 2

b) the resulting mass is leached with water - a solution of sodium and potassium aluminates and CaSiO 3 slurry are formed:

NaAlO 2 + KAlO 2 + 4H 2 O = Na + K

c) CO 2 formed during sintering is passed through the aluminate solution:

Na + K + 2CO 2 = NaHCO 3 + KHCO 3 + 2Al(OH) 3

d) by heating Al(OH) 3 alumina is obtained:

2Al(OH) 3 = Al 2 O 3 + 3H 2 O

e) by evaporating the mother liquor, soda and potage are separated, and the previously obtained sludge is used for cement production.

When producing 1 ton of Al 2 O 3, 1 ton of soda products and 7.5 tons of cement are obtained.

Some aluminosilicates have a loose structure and are capable of ion exchange. Such silicates – natural and especially artificial – are used for water softening. In addition, due to their highly developed surface, they are used as catalyst supports, i.e. as materials impregnated with a catalyst.

Aluminum halides under normal conditions are colorless crystalline substances. In the series of aluminum halides, AlF 3 is very different in properties from its analogues. It is refractory, slightly soluble in water, and chemically inactive. The main method for producing AlF 3 is based on the action of anhydrous HF on Al 2 O 3 or Al:

Al 2 O 3 + 6HF = 2AlF 3 + 3H 2 O

Aluminum compounds with chlorine, bromine and iodine are fusible, very reactive and highly soluble not only in water, but also in many organic solvents. The interaction of aluminum halides with water is accompanied by a significant release of heat. In aqueous solution they are all highly hydrolyzed, but unlike typical acidic nonmetal halides, their hydrolysis is incomplete and reversible. Being noticeably volatile even under normal conditions, AlCl 3, AlBr 3 and AlI 3 smoke in moist air (due to hydrolysis). They can be obtained by direct interaction of simple substances.

The vapor densities of AlCl 3, AlBr 3 and AlI 3 at relatively low temperatures more or less exactly correspond to the double formulas - Al 2 Hal 6. The spatial structure of these molecules corresponds to two tetrahedra with a common edge. Each aluminum atom is bonded to four halogen atoms, and each of the central halogen atoms is bonded to both aluminum atoms. Of the two bonds of the central halogen atom, one is donor-acceptor, with aluminum functioning as an acceptor.

With halide salts of a number of monovalent metals, aluminum halides form complex compounds, mainly of the M 3 and M types (where Hal is chlorine, bromine or iodine). The tendency to addition reactions is generally very pronounced in the halides under consideration. This is precisely the reason for the most important technical use of AlCl 3 as a catalyst (in oil refining and in organic syntheses).

Of the fluoroaluminates, the greatest use (for the production of Al, F 2, enamels, glass, etc.) is Na 3 cryolite. Industrial production of artificial cryolite is based on the treatment of aluminum hydroxide with hydrofluoric acid and soda:

2Al(OH) 3 + 12HF + 3Na 2 CO 3 = 2Na 3 + 3CO 2 + 9H 2 O

Chloro-, bromo- and iodoaluminates are obtained by fusing aluminum trihalides with halides of the corresponding metals.

Although aluminum does not react chemically with hydrogen, aluminum hydride can be obtained indirectly. It is a white amorphous mass of composition (AlH 3) n. Decomposes when heated above 105 o C with the release of hydrogen.

When AlH 3 interacts with basic hydrides in an ethereal solution, hydroaluminates are formed:

LiH + AlH 3 = Li

Hydridoaluminates are white solids. Rapidly decomposes with water. They are strong reducing agents. They are used (especially Li) in organic synthesis.

Aluminum sulfate Al 2 (SO 4) 3. 18H 2 O is obtained by the action of hot sulfuric acid on aluminum oxide or kaolin. It is used for water purification, as well as in the preparation of certain types of paper.

Potassium aluminum alum KAl(SO 4) 2. 12H 2 O is used in large quantities for tanning leather, and also in the dyeing industry as a mordant for cotton fabrics. In the latter case, the effect of alum is based on the fact that aluminum hydroxide formed as a result of its hydrolysis is deposited in the fabric fibers in a finely dispersed state and, adsorbing the dye, firmly holds it on the fiber.

Of the other aluminum derivatives, mention should be made of its acetate (otherwise acetic acid salt) Al(CH 3 COO) 3, used in dyeing fabrics (as a mordant) and in medicine (lotions and compresses). Aluminum nitrate is easily soluble in water. Aluminum phosphate is insoluble in water and acetic acid, but soluble in strong acids and alkalis.

Aluminum in the body. Aluminum is part of the tissues of animals and plants; in the organs of mammals, from 10 -3 to 10 -5% of Aluminum (on a crude basis) was found. Aluminum accumulates in the liver, pancreas and thyroid glands. In plant products, the Aluminum content ranges from 4 mg per 1 kg of dry matter (potatoes) to 46 mg (yellow turnips), in products of animal origin - from 4 mg (honey) to 72 mg per 1 kg of dry matter (beef). In the daily human diet, the aluminum content reaches 35–40 mg. Organisms that concentrate aluminum are known, for example, mosses (Lycopodiaceae), which contain up to 5.3% aluminum in their ash, and mollusks (Helix and Lithorina), which contain 0.2–0.8% aluminum in their ash. By forming insoluble compounds with phosphates, aluminum disrupts the nutrition of plants (absorption of phosphates by roots) and animals (absorption of phosphates in the intestines).

Geochemistry of aluminum. The geochemical features of aluminum are determined by its high affinity for oxygen (in minerals, aluminum is included in oxygen octahedra and tetrahedrons), constant valence (3), and low solubility of most natural compounds. In endogenous processes during the solidification of magma and the formation of igneous rocks, aluminum enters the crystal lattice of feldspars, micas and other minerals - aluminosilicates. In the biosphere, aluminum is a weak migrant; it is scarce in organisms and the hydrosphere. In a humid climate, where the decomposing remains of abundant vegetation form many organic acids, aluminum migrates in soils and waters in the form of organomineral colloidal compounds; aluminum is adsorbed by colloids and deposited in the lower part of soils. The bond between aluminum and silicon is partially broken and in some places in the tropics minerals are formed - aluminum hydroxides - boehmite, diaspores, hydrargillite. Most of the aluminum is part of aluminosilicates - kaolinite, beidellite and other clay minerals. Weak mobility determines the residual accumulation of aluminum in the weathering crust of the humid tropics. As a result, eluvial bauxite is formed. In past geological epochs, bauxite also accumulated in lakes and coastal zones of seas in tropical regions (for example, sedimentary bauxites of Kazakhstan). In steppes and deserts, where there is little living matter and the waters are neutral and alkaline, aluminum almost does not migrate. The migration of aluminum is most energetic in volcanic areas, where highly acidic river and groundwater rich in aluminum are observed. In places where acidic waters mix with alkaline sea waters (at the mouths of rivers and others), aluminum precipitates with the formation of bauxite deposits.

Application of Aluminum. The combination of physical, mechanical and chemical properties of Aluminum determines its widespread use in almost all areas of technology, especially in the form of its alloys with other metals. In electrical engineering, Aluminum successfully replaces copper, especially in the production of massive conductors, for example, in overhead lines, high-voltage cables, switchgear buses, transformers (the electrical conductivity of Aluminum reaches 65.5% of the electrical conductivity of copper, and it is more than three times lighter than copper; with a cross section providing the same conductivity, the mass of aluminum wires is half that of copper). Ultra-pure Aluminum is used in the production of electrical capacitors and rectifiers, the action of which is based on the ability of the Aluminum oxide film to pass electric current in only one direction. Ultrapure Aluminum, purified by zone melting, is used for the synthesis of semiconductor compounds of type A III B V, used for the production of semiconductor devices. Pure Aluminum is used in the production of various types of mirror reflectors. High-purity aluminum is used to protect metal surfaces from atmospheric corrosion (cladding, aluminum paint). Possessing a relatively low neutron absorption cross section, aluminum is used as a structural material in nuclear reactors.

Large-capacity aluminum tanks store and transport liquid gases (methane, oxygen, hydrogen, etc.), nitric and acetic acids, clean water, hydrogen peroxide and edible oils. Aluminum is widely used in food industry equipment and apparatus, for food packaging (in the form of foil), and for the production of various types of household products. The consumption of aluminum for finishing buildings, architectural, transport and sports structures has increased sharply.

In metallurgy, Aluminum (in addition to alloys based on it) is one of the most common alloying additives in alloys based on Cu, Mg, Ti, Ni, Zn and Fe. Aluminum is also used to deoxidize steel before pouring it into a mold, as well as in the processes of producing certain metals using the aluminothermy method. Based on Aluminum, SAP (sintered aluminum powder) was created using powder metallurgy, which has high heat resistance at temperatures above 300 °C.

Aluminum is used in the production of explosives (ammonal, alumotol). Various aluminum compounds are widely used.

Aluminum production and consumption is continuously growing, significantly outpacing the growth rate of production of steel, copper, lead, and zinc.

List of used literature

1. V.A. Rabinovich, Z.Ya. Khavin "A short chemical reference book"

2. L.S. Guzey "Lectures on general chemistry"

3. N.S. Akhmetov “General and inorganic chemistry”

4. B.V. Nekrasov “Textbook of General Chemistry”

5. N.L. Glinka “General Chemistry”