Describe the chemical element aluminum. Chemical and physical properties of aluminum
Lesson type. Combined.
Tasks:
Educational:
1. Update students' knowledge about the structure of the atom, the physical meanings of the serial number, group number, period number using aluminum as an example.
2. To form students' knowledge that aluminum in the free state has special, characteristic physical and chemical properties.
Developing:
1. Generate interest in the study of science by providing brief historical and scientific reports on the past, present and future of aluminum.
2. To continue the formation of students' research skills when working with literature, performing laboratory work.
3. Expand the concept of amphoteric by revealing the electronic structure of aluminum, the chemical properties of its compounds.
Educational:
1. Raise a respect for the environment by providing information about the possible use of aluminum yesterday, today, tomorrow.
2. To form the ability to work as a team for each student, to take into account the opinion of the whole group and defend their own correctly by doing laboratory work.
3. To introduce students to the scientific ethics, honesty and integrity of natural scientists of the past, providing information about the struggle for the right to be the discoverer of aluminum.
REVIEW on the topics of alkaline and alkaline earth M (REPEAT):
What is the number of electrons in the outer energy level of alkaline and alkaline earth M?
What products are formed when sodium or potassium reacts with oxygen? (peroxide), is lithium capable of producing peroxide in reaction with oxygen? (No, the reaction produces lithium oxide.)
How are sodium and potassium oxides obtained? (calcination of peroxides with the corresponding Me, Pr: 2Na+Na 2 O 2 =2Na 2 O).
Do alkali and alkaline earth metals exhibit negative oxidation states? (No, they do not, as they are strong reducing agents.).
How does the radius of an atom change in the main subgroups (from top to bottom) of the Periodic system? (increases) what is the reason for this? (with an increase in the number of energy levels).
Which of the groups of metals studied by us is lighter than water? (in alkaline).
Under what conditions does the formation of hydrides occur in alkaline earth metals? (at high temperatures).
Which substance calcium or magnesium reacts more actively with water? (Calcium reacts more actively. Magnesium reacts actively with water only when it is heated to 100 0 C).
How does the solubility of alkaline earth metal hydroxides in water change in the series from calcium to barium? (solubility in water increases).
Tell us about the features of storage of alkali and alkaline earth metals, why are they stored this way? (since these metals are very reactive, they are stored in a container under a layer of kerosene).
CONTROL WORK on the topics of alkaline and alkaline earth M:
LESSON SUMMARY (STUDYING NEW MATERIAL):
Teacher: Hello guys, today we are moving on to the study of the IIIA subgroup. List the elements located in the IIIA subgroup?
Trainees: It includes such elements as boron, aluminum, gallium, indium and thallium.
Teacher: How many electrons do they contain in their outer energy level, oxidation states?
Trainees: Three electrons, +3 oxidation state, although thallium has a more stable oxidation state of +1.
Teacher: The metallic properties of the elements of the boron subgroup are much less pronounced than those of the elements of the beryllium subgroup. Bor is a non-M. In the future, within the subgroup, with increasing nuclear charge M, the properties are enhanced. Al- already M, but not typical. Its hydroxide has amphoteric properties.
Of the M of the main subgroup of group III, aluminum is of the greatest importance, the properties of which we will study in detail. It is of interest to us because it is a transitional element.
DEFINITION
Aluminum located in the third period, group III of the main (A) subgroup of the Periodic Table. This is the first p-element of the 3rd period.
Metal. Designation - Al. Ordinal number - 13. Relative atomic mass - 26.981 a.m.u.
The electronic structure of the aluminum atom
The aluminum atom consists of a positively charged nucleus (+13), inside which there are 13 protons and 14 neutrons. The nucleus is surrounded by three shells, along which 13 electrons move.
Rice. 1. Schematic representation of the structure of the aluminum atom.
The distribution of electrons in orbitals is as follows:
13Al) 2) 8) 3 ;
1s 2 2s 2 2p 6 3s 2 3p 1 .
There are three electrons on the outer energy level of aluminum, all electrons of the 3rd sublevel. The energy diagram takes the following form:
Theoretically, an excited state is possible for an aluminum atom due to the presence of a vacant 3 d-orbitals. However, electron depairing 3 s- sublevel does not actually occur.
Examples of problem solving
EXAMPLE 1
Chemical element of group III of the periodical system of Mendeleev.
Latin name— Aluminium.
Designation— Al.
atomic number — 13.
Atomic mass — 26,98154.
Density- 2.6989 g / cm 3.
Melting temperature- 660 °С.
Simple, light, paramagnetic metal of light gray or silvery white color. It has high thermal and electrical conductivity, corrosion resistance. Distribution in the earth's crust - 8.8% by weight - it is the most common metal and the third most common chemical element.
It is used as a structural material in the construction of buildings, aircraft and shipbuilding, for the manufacture of conductive products in electrical engineering, chemical equipment, consumer goods, the production of other metals using aluminothermy, as a component of solid rocket fuel, pyrotechnic compositions, and the like.
Metallic aluminum was first obtained by the Danish physicist Hans Christian Oersted.
In nature, it occurs exclusively in the form of compounds, as it has a high chemical activity. Forms a strong chemical bond with oxygen. Due to the reactivity, it is very difficult to obtain metal from ore. Now the Hall-Heroult method is used, which requires large amounts of electricity.
Aluminum forms alloys with almost all metals. The most famous are duralimium (an alloy with copper and magnesium) and silumin (an alloy with silicon). Under normal conditions, aluminum is covered with a strong oxide film, therefore it does not react with classical oxidizing agents water (H 2 O), oxygen (O 2) and nitric acid (HNO 3). Due to this, it is practically not subject to corrosion, which ensured its demand in the industry.
The name comes from the Latin "alumen", which means "alum".
The use of aluminum in medicine
traditional medicine
The role of aluminum in the body is not fully understood. It is known that its presence stimulates the growth of bone tissue, the development of epithelium and connective tissues. Under its influence, the activity of digestive enzymes increases. Aluminum is related to the recovery and regeneration processes of the body.
Aluminum is considered a toxic element for human immunity, but nevertheless, it is part of the cells. At the same time, it has the form of positively charged ions (Al3 +), which affect the parathyroid glands. Different types of cells contain different amounts of aluminum, but it is known for sure that the cells of the liver, brain and bones accumulate it faster than others.
Medicines with aluminum have analgesic and enveloping effects, antacid and adsorbent effects. The latter means that when interacting with hydrochloric acid, drugs can reduce the acidity of gastric juice. Aluminum is also prescribed for external use: in the treatment of wounds, trophic ulcers, acute conjunctivitis.
The toxicity of aluminum is manifested in its replacement of magnesium in the active centers of a number of enzymes. Its competitive relationship with phosphorus, calcium and iron also plays a role.
With a lack of aluminum, weakness in the limbs is observed. But such a phenomenon in the modern world is almost impossible, since the metal comes with water, food and through polluted air.
With an excess of aluminum in the body, changes in the lungs, convulsions, anemia, disorientation in space, apathy, and memory loss begin.
Ayurveda
Aluminum is considered to be poisonous and therefore should not be used for treatment. Just as you should not use aluminum utensils for preparing decoctions or storing herbs.
The use of aluminum in magic
Due to the difficulty of obtaining a pure element, the metal was used in magic along with it, jewelry was made from it. When the process of obtaining was simplified, the fashion for aluminum crafts immediately passed.
Protective Magic
Only aluminum foil is used, which has the properties to screen energy flows, preventing them from spreading. Therefore, as a rule, objects are wrapped in it that can spread negative energy around them. Very often dubious magical gifts are wrapped in foil - wands, masks, daggers, especially those brought from Africa or Egypt.
They do the same with unknown objects thrown up, found in the yard or under the door. Instead of lifting it with your hands or through a cloth, it is better to cover it with foil without touching the object itself.
Sometimes foil is used as a protective screen for amulets and talismans that are not currently needed, but may be required in the future.
Aluminum in astrology
Zodiac sign: Capricorn.
Aluminum in its pure form was first isolated by Friedrich Wöhler. A German chemist heated anhydrous element chloride with potassium metal. It happened in the second half of the 19th century. Before the 20th century kg of aluminum cost more.
Only the rich and the state could afford the new metal. The reason for the high cost is the difficulty of separating aluminum from other substances. The method of extracting the element on an industrial scale was proposed by Charles Hall.
In 1886, he dissolved the oxide in a cryolite melt. The German enclosed the mixture in a granite vessel and connected an electric current to it. Plaques of pure metal settled on the bottom of the container.
Chemical and physical properties of aluminum
What aluminum? Silvery white, shiny. Therefore, Friedrich Wöhler compared the metal granules he received with. But, there was a caveat - aluminum is much lighter.
Plasticity is close to precious and. aluminum is a substance, without problems stretching into thin wire and sheets. Suffice it to recall the foil. It is made on the basis of the 13th element.
Aluminum is light due to its low density. It is three times less than that of iron. At the same time, the 13th element is almost not inferior in strength.
This combination has made the silver metal indispensable in industry, for example, the production of parts for automobiles. We are talking about handicraft production, because aluminum welding possible even at home.
aluminum formula allows you to actively reflect light, but also heat rays. The electrical conductivity of the element is also high. The main thing is not to overheat it. It will melt at 660 degrees. Raise the temperature a little higher - it will burn.
The metal will disappear, only aluminium oxide. It is also formed under standard conditions, but only in the form of a surface film. It protects the metal. Therefore, it resists corrosion well, because the access of oxygen is blocked.
The oxide film also protects the metal from water. If plaque is removed from the surface of aluminum, a reaction with H 2 O will start. Hydrogen gases will be released even at room temperature. So, aluminum boat does not turn into smoke only due to the oxide film and protective paint applied to the ship's hull.
Most active aluminum interaction with nonmetals. Reactions with bromine and chlorine proceed even under normal conditions. As a result, they form aluminum salts. Hydrogen salts are obtained by combining the 13th element with acid solutions. The reaction will also take place with alkalis, but only after the removal of the oxide film. Pure hydrogen will be released.
Application of aluminum
Metal is sprayed onto mirrors. Good light reflectance. The process takes place under vacuum conditions. They make not only standard mirrors, but objects with mirror surfaces. These are: ceramic tiles, household appliances, lamps.
Duet aluminum-copper- duralumin base. It is simply called Dural. As added. The composition is 7 times stronger than pure aluminum, therefore, it is suitable for the field of mechanical engineering and aircraft design.
Copper gives the 13th element strength, but not heaviness. Dural remains 3 times lighter than iron. small mass of aluminum- a pledge of lightness of cars, planes, ships. This simplifies transportation, operation, reduces the price of products.
Buy aluminum car manufacturers also strive because protective and decorative compounds are easily applied to its alloys. The paint lays down faster and more evenly than on steel, plastic.
At the same time, the alloys are malleable, easy to process. This is valuable, given the mass of bends and constructive transitions on modern car models.
The 13th element is not only easy to dye, but can also act as a dye itself. Purchased in the textile industry aluminum sulfate. It also comes in handy in printing, where insoluble pigments are required.
It's interesting that solution sulfate aluminum also used for water purification. In the presence of an “agent”, harmful impurities precipitate and are neutralized.
Neutralizes the 13th element and acids. He is especially good at this role. aluminum hydroxide. It is valued in pharmacology, medicine, adding to heartburn medicines.
Hydroxide is also prescribed for ulcers, inflammatory processes of the intestinal tract. So there is also a pharmacy drug aluminum. Acid in the stomach - a reason to learn more about such drugs.
In the USSR, bronzes with an 11% addition of aluminum were also minted. The value of the signs is 1, 2 and 5 kopecks. They began to produce in 1926, finished in 1957. But the production of aluminum cans for canned food has not been stopped.
Stewed meat, saury and other breakfasts of tourists are still packed in containers based on the 13th element. Such cans do not react with food, while they are light and cheap.
Aluminum powder is part of many explosive mixtures, including pyrotechnics. In industry, subversive mechanisms based on trinitrotoluene and crushed element 13 are used. A powerful explosive is also obtained by adding ammonium nitrate to aluminum.
The oil industry needs aluminum chloride. It plays the role of a catalyst in the decomposition of organic matter into fractions. Oil has the ability to release gaseous, light hydrocarbons of the gasoline type, interacting with the chloride of the 13th metal. The reagent must be anhydrous. After adding chloride, the mixture is heated to 280 degrees Celsius.
In construction, I often mix sodium And aluminum. It turns out an additive to concrete. Sodium aluminate accelerates its hardening by accelerating hydration.
The rate of microcrystallization increases, which means that the strength and hardness of concrete increases. In addition, sodium aluminate saves the fittings laid in the solution from corrosion.
Aluminum mining
Metal closes the top three most common on earth. This explains its availability and wide application. However, nature does not give the element to man in its pure form. Aluminum has to be isolated from various compounds. Most of the 13th element is in bauxites. These are clay-like rocks, concentrated mainly in the tropical zone.
The bauxite is crushed, then dried, crushed again and ground in the presence of a small volume of water. It turns out a thick mass. It is heated with steam. At the same time, most of which bauxite is also not poor evaporates. The oxide of the 13th metal remains.
It is placed in industrial baths. They already contain molten cryolite. The temperature is kept at around 950 degrees Celsius. We also need an electric current with a power of at least 400 kA. That is, electrolysis is used, just like 200 years ago, when the element was isolated by Charles Hall.
Passing through a hot solution, the current breaks the bonds between the metal and oxygen. As a result, at the bottom of the baths remains clean aluminum. Reactions finished. The process is completed by casting from the sediment and sending them to the consumer, or, alternatively, using them to form various alloys.
The main aluminum production is located in the same place as the bauxite deposits. At the forefront is Guinea. Almost 8,000,000 tons of the 13th element are hidden in its bowels. Australia is in 2nd place with an indicator of 6,000,000. In Brazil, aluminum is already 2 times less. Global reserves are estimated at 29,000,000 tons.
aluminum price
For a ton of aluminum they ask for almost 1,500 US dollars. These are the data of non-ferrous metal exchanges as of January 20, 2016. The cost is set mainly by the industrialists. More precisely, the price of aluminum is affected by their demand for raw materials. It affects the requests of suppliers and the cost of electricity, because the production of the 13th element is energy intensive.
Other prices are set for aluminum. He goes to the meltdown. The cost is announced per kilogram, and the nature of the delivered material matters.
So, for electrical metal they give about 70 rubles. For food-grade aluminum, you can get 5-10 rubles less. The same is paid for motor metal. If a mixed variety is rented, its price is 50-55 rubles per kilogram.
The cheapest type of scrap is aluminum shavings. For it manages to gain only 15-20 rubles. A little more will be given for the 13th element. This refers to containers for drinks, canned food.
Aluminum radiators are also underestimated. The price per kilogram of scrap is about 30 rubles. These are average figures. In different regions, at different points, aluminum is accepted more expensively or cheaper. Often the cost of materials depends on the delivered volumes.
Aluminum characteristic
aluminum metal quality industry
Aluminum is the most common metal in the earth's crust. Its content is estimated at 7.45% (more than iron, which is only 4.2%). Aluminum as an element was discovered recently, in 1825, when the first small lumps of this metal were obtained. The beginning of its industrial development dates back to the end of the last century. The impetus for this was the development in 1886 of a method for its production by electrolysis of alumina dissolved in cryolite. The principle of the method underlies the modern industrial extraction of aluminum from alumina in all countries of the world.
In appearance, aluminum is a shiny, silvery white metal. In air, it quickly oxidizes, becoming covered with a thin white matte film of AlO. This film has high protective properties, therefore, being covered with such a film, aluminum is corrosion resistant.
Aluminum is easily destroyed by solutions of caustic alkalis, hydrochloric and sulfuric acids. In concentrated nitric acid and organic acids, it has a high resistance.
The most characteristic physical properties of aluminum are its low relative density of 2.7, as well as relatively high thermal and electrical conductivity. At 0C, the electrical conductivity of aluminum, i.e. the electrical conductivity of an aluminum wire with a cross section of 1 mm and a length of 1 m is 37 1 ohm.
Corrosion resistance and especially the electrical conductivity of aluminum is the higher, the purer it is, the less impurities it contains.
The melting point of aluminum is low, it is approximately 660C. However, its latent heat of fusion is very large - about 100 cal g, therefore, a large amount of heat is required to melt aluminum than to melt the same amount, for example, refractory copper, which has a melting point of 1083 C, a latent heat of fusion of 43 cal g.
The mechanical properties of aluminum are characterized by high ductility and low strength. Rolled and annealed aluminum has = 10 kg mm, and hardness HB25, = 80% and = 35%.
The crystal lattice of aluminum is a face-centered cube with a parameter (side size) of 4.04 at 20 C. Aluminum has no allotropic transformations.
In nature, aluminum is found in the form of aluminum ores: bauxites, nephelines, alunites and kaolins. The most important ore, on which most of the world's aluminum industry is based, is bauxite.
Obtaining aluminum from ores consists of two successive stages - first alumina (AlO) is produced, and then aluminum is obtained from it.
The currently known methods for producing alumina can be divided into three groups: alkaline, acidic, and electrothermal. Alkaline methods are the most widely used.
In some varieties of alkaline methods, bauxite, dehydrated at 1000 C, is ground in ball mills, mixed in certain proportions with chalk and soda, and sintered to obtain a water-soluble solid sodium aluminate by the reaction
AlO + NaCO = AlO NaO + CO
The sintered mass is crushed and leached with water, while sodium aluminate goes into solution.
In other varieties of the alkaline method, the alumina contained in bauxite is bound into sodium aluminate by directly treating the ore with alkalis. In this case, a solution of aluminate in water is immediately obtained.
In both cases, the formation of an aqueous solution of sodium aluminate leads to its separation from the insoluble components of the ore, which are mainly oxides and hydroxides of silicon, iron and titanium. The separation of the solution from the insoluble precipitate, called red mud, is carried out in settling tanks.
Lime is added to the resulting solution at 125 C and a pressure of 5 am, which leads to desiliconization - CaSiO precipitates, forming a white sludge. The solution, purified from silicon, after separating it from white mud, is treated with carbon dioxide at 60-80 C, as a result of which crystalline aluminum oxide hydrate precipitates:
AlONaO + 3H2O + CO = 2Al(OH) + NaCO.
It is washed, dried and calcined. Calcination leads to the formation of alumina:
2Al(OH) = AlO + 3H2O.
The described method provides a fairly complete extraction of alumina from bauxite - about 80%.
Obtaining metallic aluminum from alumina consists in its electrolytic decomposition into its constituent parts - into aluminum and oxygen. The electrolyte in this process is a solution of alumina in cryolite (AlF 3NaF). Cryolite, having the ability to dissolve alumina, simultaneously lowers its melting point. Alumina melts at a temperature of about 2000 C, and the melting point of a solution consisting, for example, of 85% cryolite and 15% alumina, is 935 C.
The scheme of alumina electrolysis is quite simple, but technologically this process is complex and requires large amounts of electricity.
In the bottom of the bath with good thermal insulation 1 and carbon packing 2, cathode tires 3 are placed, connected to the negative pole of the electric current source. Electrodes 5 are attached to the anode bus 4. Before the start of electrolysis, a thin layer of coke is poured onto the bottom of the bath, the electrodes are lowered until they come into contact with it, and the current is switched on. When the carbon packing is heated, cryolite is gradually introduced. When the layer thickness of molten cryolite is 200-300 mm, alumina is loaded at the rate of 15% to the amount of cryolite. The process takes place at 950-1000 C.
Under the action of an electric current, alumina decomposes aluminum and oxygen. Liquid aluminum 6 accumulates on the coal bottom (the bottom of the coal bath), which is the cathode, and oxygen combines with the carbon of the anodes, gradually burning them. Cryolite is consumed insignificantly. Alumina is periodically added, the electrodes are gradually lowered down to compensate for the burnt part, and the accumulated liquid aluminum is released into ladle 8 at certain intervals.
During electrolysis, about 2 tons of alumina, 0.6 tons of carbon electrodes serving as anodes, 0.1 tons of cryolite and from 17,000 to 18,000 kWh of electricity are consumed per 1 ton of aluminum.
Raw aluminum obtained by electrolysis of alumina contains metallic impurities (iron, silicon, titanium and sodium), dissolved gases, the main of which is hydrogen, and non-metallic inclusions, which are particles of alumina, coal and cryolite. In this state, it is unsuitable for use, as it has low properties, so it must be refined. Non-metallic and gaseous impurities are removed by remelting and purging the metal with chlorine. Metallic impurities can only be removed by complex electrolytic methods.
After refining, commercial grades of aluminum are obtained.
The purity of aluminum is a decisive indicator that affects all of its properties, so the chemical composition is the basis for the classification of aluminum.
Iron and silicon are inevitable impurities from the production of aluminum. Both of them are harmful in aluminum. Iron does not dissolve in aluminum, but forms brittle chemical compounds FeAl and Fe2Al with it. Aluminum forms a eutectic mechanical mixture with silicon at 11.7% Si. Since the solubility of silicon at room temperature is very low (0.05%), even with a small amount of silicon, it forms the Fe + Si eutectic and inclusions of very hard (HB 800) brittle silicon crystals, which reduce the ductility of aluminum. With the joint presence of silicon and iron, a ternary chemical compound and a ternary eutectic are formed, which also reduce plasticity.
Controlled impurities in aluminum are iron, silicon, copper and titanium.
Aluminum of all grades contains more than 99% Al. The quantitative excess of this value in hundredths or tenths of a percent is indicated in the brand name after the initial letter A. Thus, the A85 brand contains 99.85% Al. An exception to this marking principle is grades A AE, in which the aluminum content is the same as in grades A0 and A5, but a different ratio of iron and silicon impurities included in the composition.
The letter E in the AE brand means that aluminum of this brand is intended for the production of electrical wires. An additional requirement for the properties of aluminum is a low electrical resistance, which for a wire made from it should be no more than 0.0280 ohm mm m at 20 C.
Aluminum is used for the production of products and alloys based on it, the properties of which require a high degree of purity.
Depending on the purpose, aluminum can be produced in various forms. Aluminum of all grades (high and technical purity), intended for remelting, is cast in the form of ingots weighing 5; 15 and 1000 kg. Their limit values are as follows: height from 60 to 600 mm, width from 93 to 800 mm and length from 415 to 1000 mm.
If aluminum is intended for rolling sheet and strip, then flat ingots of seventeen sizes are cast by a continuous or semi-continuous method. Their thickness ranges from 140 to 400 mm, width - from 560 to 2025 mm, and the weight of 1 m of ingot length - from 210 to 2190 kg. The length of the ingot is agreed with the customer.
The main type of aluminum control, both in ingots and in flat ingots, is the verification of the chemical composition and its compliance with the branded one. Ingots and ingots intended for pressure treatment are subject to additional requirements, such as the absence of shells, gas bubbles, cracks, slag and other foreign inclusions.
For deoxidation of steel during its smelting, as well as for the production of ferroalloys and for aluminothermy, cheaper aluminum of lower purity can be used than indicated in the table “Aluminum Purity of Different Grades”. For this purpose, the industry produces six grades of aluminum in ingots weighing from 3 to 16.5 kg, containing from 98.0 to 87.0% Al. In them, the iron content reaches 2.5%, and silicon and copper up to 5% each.
The use of aluminum is due to the peculiarity of its properties. The combination of lightness with a sufficiently high electrical conductivity makes it possible to use aluminum as a conductor of electric current, replacing it with more expensive copper. The difference in the electrical conductivity of copper (631 ohms) and aluminum (371 ohms) is compensated by an increase in the cross section of the aluminum wire. The small mass of aluminum wires makes it possible to carry out their suspension with a much larger distance between supports than in the case of copper wires, without fear of wire breakage under the influence of its own weight. Cables, tires, capacitors, rectifiers are also made from it. The high corrosion resistance of aluminum makes it in some cases an indispensable material in chemical engineering, for example, for the manufacture of equipment used in the production, storage and transportation of nitric acid and its derivatives.
It is also widely used in the food industry - a variety of utensils for cooking are made from it. In this case, not only its resistance to organic acids is used, but also its high thermal conductivity.
High ductility allows aluminum to be rolled into foil, which has now completely replaced the more expensive tin foil used earlier. Foil serves as packaging for a wide variety of food products: tea, chocolate, tobacco, cheese, etc.
Aluminum is used in the same way as an anticorrosive coating of other metals and alloys. It can be applied by cladding, diffusion plating and other methods, including painting aluminum with paints and varnishes. Aluminum cladding of flat-rolled products made of less corrosion-resistant aluminum alloys is especially widespread.
The chemical activity of aluminum with respect to oxygen is used for deoxidation in the production of semi-quiet and calm steel and for the production of hard-to-recover metals by displacing aluminum from their oxygen compounds.
Aluminum is used as an alloying element in various steels and alloys. It gives them specific properties. For example, it increases the heat resistance of alloys based on iron, copper, titanium and some other metals.
You can name other areas of application of aluminum of varying degrees of purity, but the largest amount of it is spent on obtaining various light alloys based on it. Details of the main ones are given below.
In general, the use of aluminum in various sectors of the economy, using the example of developed capitalist countries, is estimated by the following figures: transport engineering 20-23% (including the automotive industry 15%), construction 17-18%, electrical engineering 10-12%, production of packaging materials 9-10% , production of consumer durables 9-10%, general engineering 8-10%.
Aluminum is gaining more and more new areas of application, despite the competition of other materials and especially plastics.
The main industrial ores containing aluminum are bauxite, nepheline, alunite and kaolin.
The quality of these ores is evaluated by their content of alumina Al O, which contains 53% Al. Of the other indicators of the quality of aluminum ores, the most important is the composition of impurities, the harmfulness and usefulness of which are determined by the use of the ore.
Bauxite is the world's best and main raw material for aluminum production. It is also used for the production of artificial corundum, highly refractory products, and for other purposes. According to the chemical composition, this sedimentary rock is a mixture of alumina hydrates AlO nH2O with oxides of iron, silicon, titanium and other elements. The most common alumina hydrates that make up bauxites are the minerals diaspore, boehmite, and hydrargellite. The content of alumina in bauxite, even in one deposit, varies over a very wide range, from 35 to 70%.
The minerals included in the composition of bauxite form a very thin mixture, which makes enrichment difficult. In industry, raw ore is mainly used. The process of extracting aluminum from ore is complex, very energy intensive and consists of two stages: first, alumina is extracted, and then aluminum is obtained from it.
The subject of world trade is both bauxite itself and alumina extracted from it or other ores.
On the territory of the CIS, bauxite deposits are unevenly distributed, and bauxite from different deposits is unequal in quality. The deposits of the highest quality bauxites are located in the Urals. There are also large reserves of bauxite in the European part of the CIS and in Western Kazakhstan.
Of the industrialized countries, only France is now practically provided, where its development first began. Its reliable and probable reserves in this group of states in 1975 were estimated at 4.8 billion tons (including 4.6 billion tons in Australia), while in developing countries at 12.5 billion tons, mainly in Africa and Latin America ( the richest are Guinea, Cameroon, Brazil, Jamaica).
During the post-war period, the circle of countries where bauxite is mined and primary aluminum is produced has sharply expanded. In 1950, bauxite was mined only in 11 countries, not counting the USSR, including three in excess of 1 million tons (Suriname, Guyana, USA) and four more than 0.1 million tons each (France, Indonesia, Italy, Ghana). By 1977, the volume of production increased 12 times and its geography changed dramatically (more than half of the production of the capitalist world came from developing countries).
Unlike developing countries, fuel-rich Australia processes most of the bauxite mined (mainly on the York Peninsula, the largest bauxite deposit in the world) into alumina, playing a decisive role in its world exports. Not an example for her, the Caribbean and West African countries mainly export bauxite. This affects both political reasons (world aluminum monopolies prefer the production of alumina outside the bauxite-producing, dependent countries), and purely economic ones: bauxites, unlike ores of heavy non-ferrous metals, are transportable (contain 35-65% aluminum dioxide), and alumina production requires significant specific costs, which the vast majority of bauxite-producing countries do not have.
In an effort to resist the dictates of the world's aluminum monopolies, the bauxite-exporting countries in 1973 created the organization "International Association of Bauxite Mining Countries" (IABS). It included Australia, Guinea, Guyana, Jamaica, and Yugoslavia; later the Dominican Republic, Haiti, Ghana, Sierra Leone, Suriname joined, while Greece and India became observer countries. In the year of creation, these states accounted for approximately 85% of bauxite mining in non-socialist states.
The aluminum industry is characterized by a territorial gap both between the extraction of bauxite and the production of alumina, and between the latter and the smelting of primary aluminum. The largest alumina production (up to 1-1.3 million tons per year) is localized both at aluminum plants (for example, at the Canadian plant in Arvida in Quebec, which occupies 0.4 million tons of aluminum per year in terms of production capacity) and in bauxite exporting ports (for example , Paranam in Suriname), as well as on the routes of bauxite from the second to the first - for example, in the USA on the coast of the Gulf of Mexico (Corpus Christi, Point Comfort).
In our country, all mined bauxites are divided into ten grades. The main difference between bauxites of different grades is that they contain different amounts of the main extractable component, alumina, and have different silicon modulus values, i.e. different content of alumina to the content of silica impurities harmful in bauxites (AlO SiO). The silicon modulus is a very important indicator of the quality of bauxites; their application and processing technology to a large extent depend on it.
The moisture content in bauxites of any grades is established depending on their deposit: the lowest moisture content (no more than 7%) is established for bauxites of the South Ural deposits, and for the North Ural, Kamensk-Ural and Tikhvin deposits, respectively, no more than 12, 16 and 22% . The humidity indicator is not a rejection sign and serves only for settlements with the consumer.
Bauxite is supplied in pieces no larger than 500 mm. It is transported in bulk on platforms or in gondolas.
