Aluminum is a kind ofmetallic element, the element symbol is Al, and the atomic number is 13.hisSimple substanceIt is a silver white light metal.It is malleable.Commodities are often made into rods, sheets, foils, powders, ribbons and filaments.It can form a layer in humid air to preventMetal corrosionOfOxide film。Aluminium powderWhen heated in the air, it can burn violently and emit dazzling white flames.Soluble inDilute sulfuric acid、nitric acid、hydrochloric acid、sodium hydroxideandPotassium hydroxideSolution, insolublewater。The relative density is 2.70.Melting point 660 ℃.The boiling point is 2327 ℃.The content of aluminum in the crust is second only tooxygenandsilicon, ranking third, is the most abundant metal element in the crust.The development of three important industries, aviation, construction and automobile, requires that the material properties have unique properties of aluminum and its alloys, which is greatly conducive to the production and application of this new metal aluminum.It is widely used.
The English name of aluminum comes from the ancient Roman alumen, that is, the sulfate double salt KAl (SOfour)two·12HtwoO。In prehistoric times, humans have used clay containing aluminum compounds (AltwoOthree·2SiOtwo·2HtwoO) Make pottery.The content of aluminum in the crust is only second to oxygen and silicon, ranking third.However, due to the weak oxidizability of aluminum compounds, aluminum is not easy to be reduced from its compounds, so it can not be separated from the metal aluminum for a long time.
In 1746, German J. H. Pott made a kind of oxide from alum, namely aluminum oxide.A.L. Lavoisier of France in the 18th century believed that it was an unknown metal oxide, which had a great affinity with oxygen, so it was impossible to reduce it with carbon and other known reducing agents at that time.In 1807, H. Davy, an Englishman, tried to electrolyze molten aluminum oxide to obtain metal without success. In 1809, he named this imaginary metal aluminum, and later changed it to aluminum.In 1825, H.C. Oersted, a Danish, reduced anhydrous aluminum chloride with potassium amalgam, and obtained several milligrams of metal aluminum for the first time, pointing out that it has the same color and luster as tin.In 1827, Germany Waller (F.W?Hler) reduced anhydrous aluminum chloride with potassium to obtain a small amount of metal powder.In 1845, he used aluminum chloride gas to pass through the surface of molten metal potassium to obtain some aluminum beads, each weighing about 10~15mg, thus making a preliminary determination of the density and ductility of aluminum, pointing out that the melting point of aluminum is not high.In 1854, S.C. Deville of France reduced NaAlCl4 complex salt with sodium instead of potassium to produce metal aluminum.In the same year, the factory was established and produced some aluminum helmets, tableware and toys[4]。
In a later period, aluminum was a treasure enjoyed by emperors and nobles, and the price of aluminum was close to gold at that time.Napoleon III, the French emperor, used aluminum forks at banquets;The King of Thailand used aluminum watch chains.In 1855, it was exhibited together with the jewels on the crown at the Paris Expo, and the label indicated "silver from clay".In 1889, Mendeleev also received aluminum alloy vases and cups from the London Chemical Society.By the end of the 19th century, the price of aluminum had dropped thousands of times.First of all, after Siemens improved the generator in the 1870s, it had cheap power;Secondly, due to Herault of France and CM. In 1886, Hall developed the method of dissolving alumina in cryolite (NathreeAlFsix）The method of electrolysis.They were both 22 years old.This pioneering work has enabled large-scale production of aluminum and laid the foundation for the industrial method of electrolytic aluminum in the world today.In 1888, the first electrolytic aluminum plant was established in Pittsburgh, the United States, and aluminum production entered a new stage.In 1956, the world's aluminum output began to exceed copper and ranked first in nonferrous metals.The price of aluminum is relatively cheap by volume among common nonferrous metals.[1]
On October 27, 2017, the list of carcinogens released by the International Agency for Research on Cancer of the World Health Organization (WHO) was preliminarily sorted out for reference, and the aluminum production process was included in the list of Class I carcinogens.
On July 30, 2018, an international research team said that for the first time, they had clearly detected a radioactive molecule (aluminum fluoride, the radioactive isotope containing aluminum "alumin-26") in the universe, and that this molecule may have "splashed" into interstellar space due to the collision of two stars.[2]
Content distribution
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The content of aluminum in the crust is 8.3%, ranking the third after oxygen and silicon. It is the most abundant metal element in the crust, and its reserves rank the second among metals.Among the metal varieties, it is the second largest category of metals after steel.It mainly exists in aluminosilicate ore, bauxite and cryolite.Alumina is a white amorphous powder, which has many variants, of which the most familiar one isα－AltwoOthreeandβ－AltwoOthree。Corundum existing in nature belongs to α - AltwoOthreeIts hardness is second only to diamond, with high melting point and acid and alkali resistance. It is often used to make bearings, abrasives and refractory materials.For example, corundum crucible can withstand high temperature of 1800 ℃.AltwoOthreeIt has many colors due to different impurities.For example, those containing trace Cr (III) are red, called ruby;Containing Fe (II),Fe (III) or Ti (IV) is called sapphire[5]。
classification
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According to the composition of aluminum, it can be divided into three categories:
name
Aluminum content (%)
High grade pure aluminum
99.93~99.999
Industrial high-purity aluminum
99.85~99.9
Industrial pure aluminum
98~99.7
physical property
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Material structure
The external electronic configuration of the aluminum atom is 3s ² 3p ¹, which is often in the+3 oxidation state in compounds.The aluminum atom has an empty 3d orbital, and can form a stable complex with the coordination number of 6 or 4 with the electron pair donor.If the aluminum atom loses two 3s electrons and one 3p electron at the same time, it will generate trivalent aluminum ions (Al ³+);If one 3s electron and one 3p electron are lost, aluminum ions (Al ²+) will be generated;If one 3p electron is lost, univalent aluminum ions (Al+) will be generated, which are usually unstable at low temperatures[6]。
The lattice of aluminum is face centered cubic.Aluminum atoms (aluminum ions) are located on the nodes of the lattice and at the center of the face, which is equivalent to four aluminum atoms in each lattice.
Basic physical properties
Aluminium is a silver white light metal.It is malleable.Commodities are often made into columnar, rod, sheet, foil, powder, ribbon and silk.Melting point 660 ℃.The boiling point is 2327 ℃.The relative density is 2.70, and the density of aluminum liquid is 2.303 g/cm ³.The elastic modulus is 70Gpa and Poisson's ratio is 0.33.The conductivity of aluminum is about 60% of that of copper. If measured by unit mass, the conductivity of aluminum exceeds that of copper, and it often replaces copper in long-distance transmission.It is widely used for its light weight, good electrical and thermal conductivity, high reflectivity and oxidation resistance.The aluminum used for daily use is usually called "refined steel" or "steel grade".Thermal expansion coefficient of Al at 25 ℃ (room temperature) 0.0000236mm/℃ or 23.6ppm · k-1[7]。
isotope
Aluminium has 24 isotopes, of which only one is stable.Isotopes are listed as follows[10]：
Symbol
proton
neutron
quality
half life
spin
Relative abundance
nineteenAl
thirteen
six
19.0(218)#
twentyAl
thirteen
seven
(20.0194)#
twenty-oneAl
thirteen
eight
21.02804(32)#
1/2+#
twenty-twoAl
thirteen
nine
22.01952(10)#
59(3) ms
(3)+
twenty-threeAl
thirteen
ten
23.007267(20)
470(30) ms
5/2+#
twenty-fourAl
thirteen
eleven
23.9999389(30)
2.053(4) s
4+
twenty-fiveAl
thirteen
twelve
24.9904281(5)
7.183(12) s
5/2+
twenty-sixAl
thirteen
thirteen
25.98689169(6)
7.17(24)E+5 a
5+
twenty-sevenAl
thirteen
fourteen
26.98153863(12)
stable
5/2+
one
twenty-eightAl
thirteen
fifteen
27.98191031(14)
2.2414(12) min
3+
twenty-nineAl
thirteen
sixteen
28.9804450(13)
6.56(6) min
5/2+
thirtyAl
thirteen
seventeen
29.982960(15)
3.60(6) s
3+
thirty-oneAl
thirteen
eighteen
30.983947(22)
644(25) ms
(3/2,5/2)+
thirty-twoAl
thirteen
nineteen
31.98812(9)
31.7(8) ms
1+
thirty-threeAl
thirteen
twenty
32.99084(8)
41.7(2) ms
(5/2+)#
thirty-fourAl
thirteen
twenty-one
33.99685(12)
56.3(5) ms
4-#
thirty-fiveAl
thirteen
twenty-two
34.99986(19)
38.6(4) ms
5/2+#
thirty-sixAl
thirteen
twenty-three
36.00621(23)
90(40) ms
thirty-sevenAl
thirteen
twenty-four
37.01068(36)
10.7(13) ms
thirty-eightAl
thirteen
twenty-five
38.01723(78)
7.6(6) ms
thirty-nineAl
thirteen
twenty-six
39.02297(158)
7.6(16) ms
3/2+#
fortyAl
thirteen
twenty-seven
40.03145(75)#
10# ms [＞260 ns]
forty-oneAl
thirteen
twenty-eight
41.03833(86)#
2# ms [＞260 ns]
3/2+#
forty-twoAl
thirteen
twenty-nine
42.04689(97)#
1# ms
remarks:The data marked with # represents theoretical speculation without experimental proof, while the data enclosed in parentheses represents data uncertainty.
chemical property
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Aluminum is an active metal, and a dense oxide film about 50 A (1 A=0.1 nm) thick is formed on the surface of aluminum in dry air immediately, so that aluminum will not be further oxidized and can resist water;But when aluminum powder is mixed with air, it burns violently and emits a dazzling white flame;Molten aluminum can react violently with water;Aluminum is amphoteric and extremely soluble in strong alkali and dilute acid.Insoluble in water, but can slowly react with hot water to generate aluminum hydroxide[8]。
chemical property
Reaction equation
React with acid
Reaction with alkali
(There are also some documents written as)
React with nonmetals
Thermite reaction
React with water
According to the reducibility of aluminum, it can be inferred that aluminum can react with water, but the experiment found that there is almost no reaction between aluminum and boiling water. However, aluminum can react obviously with water vapor under heating conditions, but at the beginning of the reaction, it forms a dense oxide film with oxygen in water to prevent further reaction[9]。
Main purpose
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The use of a substance depends to a large extent on its nature.Because aluminum has many excellent properties, it has a very wide range of uses.
Aluminum and aluminum alloys are one of the most widely used and economical materials.Since 1956, the output of aluminum in the world has exceeded that of copper, ranking first among nonferrous metals.At present, the output and consumption of aluminum (calculated by ton) is only second to steel, becoming the second largest metal used by human beings;Moreover, aluminum resources are very rich. According to preliminary calculation, aluminum reserves account for more than 8% of the crustal composition.
The light weight and corrosion resistance of aluminum are two outstanding characteristics of its performance.
1. The density of aluminum is very small, only 2.7 g/cm ³. Although it is relatively soft, it can be made into various aluminum alloys, such as duralumin, ultra duralumin, rust proof aluminum, cast aluminum, etc.These aluminum alloys are widely used in aircraft, automobile, train, ship and other manufacturing industries.In addition, space rockets, space shuttles and artificial satellites also use a large amount of aluminum and its alloys.For example, a supersonic aircraft is composed of about 70% aluminum and its alloy.Aluminum is also widely used in ship building. A large passenger ship often uses thousands of tons of aluminum.
2. The conductivity of aluminum is only second to silver, copper and gold. Although its conductivity is only 2/3 of copper, its density is only 1/3 of copper, so the quality of aluminum wire is only half of that of copper wire when delivering the same amount of electricity.The oxide film on the aluminum surface not only has corrosion resistance, but also has a certain degree of insulation, so aluminum has a wide range of applications in the electrical manufacturing industry, wire and cable industry and radio industry.
3. Aluminum is a good conductor of heat. Its thermal conductivity is three times greater than that of iron. In industry, aluminum can be used to manufacture various heat exchangers, heat dissipating materials and cookware.
4. Aluminum has good ductility (its ductility is only inferior to gold and silver), and aluminum foil thinner than 0.01mm can be made at 100 ℃~150 ℃.These aluminum foils are widely used to package cigarettes, candy, etc. They can also be made into aluminum wires, aluminum bars, and can roll various aluminum products.
5. Due to the dense oxide protective film on the surface of aluminum, it is not easy to be corroded, and is often used to manufacture chemical reactors, medical devices, refrigeration devices, oil refining devices, oil and natural gas pipelines, etc.
6. Aluminum powder has silver white luster (generally, the color of metal in powder form is black). It is often used as paint, commonly known as silver powder and silver paint, to protect iron products from corrosion and beautiful.
7. Aluminum burning in oxygen can give off a lot of heat and dazzling light, and is often used to make explosive mixtures, such as ammonium aluminum explosives (mixed with ammonium nitrate, charcoal powder, aluminum powder, soot and other combustible organic substances), combustion mixtures (such as thermite bombs and shells can be used to attack targets that are difficult to fire or tanks, artillery, etc.)And lighting mixture (such as barium nitrate 68%, aluminum powder 28%, shellac 4%).
8. Thermit is often used to melt refractory metals and weld rails.Aluminum is also used as deoxidizer in steelmaking.Aluminum powder, graphite, titanium dioxide (or other oxides of high melting point metals) are uniformly mixed at a certain ratio, coated on metal, and calcined at high temperature to make high-temperature cermets, which have important applications in rocket and missile technology.
7. The aluminum plate also has a good reflective performance to light. The reflective ultraviolet light is stronger than silver. The purer aluminum, the better its reflective ability. Therefore, it is often used to manufacture high-quality mirrors, such as solar cooker mirrors.
8. Aluminum has sound absorption performance and sound effect is also good, so the ceiling of broadcasting room and modern large buildings also use aluminum.Low temperature resistance. When the temperature is low, the strength of aluminum increases without brittleness. Therefore, it is an ideal production device for cryogenic devices, such as cold storage, freezer, and vehicles on Antarctic snow.
9. Aluminum air battery, as its name implies, is a new type of battery that uses aluminum and air as battery materials.It is a pollution-free, long-term, stable and reliable power supply, and is a very environmentally friendly battery.The structure and raw materials of the battery can be changed according to different practical environments and requirements. It has great adaptability. It can be used not only on land but also in deep sea. It can be used as power battery and signal battery with long service life and high specific energy[12]。
Toxicological properties
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On October 27, 2017, the list of carcinogens released by the International Agency for Research on Cancer of the World Health Organization (WHO) was preliminarily sorted out for reference, and the aluminum production process was included in the list of Class I carcinogens.
Research has found that aluminum can damage human brain cells.According to the assessment of the World Health Organization, the daily intake of aluminum is 0~0.6mg/kg, where kg refers to the weight of a person, that is, the allowable intake of a 60kg person is 36mg.The Standard for the Use of Food Additives GB2760-2011 stipulates that the residual amount of aluminum should be less than or equal to 100mg/kg.Based on this calculation, a person weighing 60kg does not need to worry if he eats no more than 360g of fried dough sticks every day[11]。
Aluminum is slowly accumulated in the human body, and its toxicity is slow and difficult to detect. However, once the toxic reaction of metabolic disorder occurs, the consequences are very serious.Therefore, we must pay attention to prevent the absorption of aluminum in our daily life and reduce the use of aluminum products.The harm of aluminum and its compounds to human beings can not be compared with their contributions. As long as people pay attention to it, it will play a more important role in human society.
Avoidance:
1. Avoid cooking utensils made of aluminum.
2. Eat less fried dough sticks, candy packed with aluminum and other foods, and drink less soft drinks in cans.
3. Some drugs are made of aluminous substances, so it is necessary to reduce the use of drugs containing aluminum elements, such as Al (OH), which can neutralize gastric acidthree。
Determination method
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Method name
Determination of sucralfate aluminum complexometric titration
Scope of application
The content of aluminum in sucralfate is determined by complexometric titration, which is suitable for the determination of aluminum in sucralfate.
Methodology
Take an appropriate amount of the test sample, dissolve, dilute and neutralize it, add acetic acid ammonium acetate buffer solution, precisely add ethylenediamine tetraacetic acid disodium titrant (0.05mol/L), boil it for 3-5 minutes, and cool it to room temperature.Every 1mL of ethylenediamine tetraacetic acid sodium titrant (0.05mol/L) is equivalent to 1.349mg of aluminum.
Take about 1.0g of this product, precisely weigh it, put it into a 200mL measuring flask, add 10mL of dilute hydrochloric acid to dissolve it, add water to dilute it to the scale, shake it up, precisely measure 20mL, add ammonia test solution to neutralize it until just precipitate, add dilute hydrochloric acid to drip until just precipitate is dissolved, add 20mL of acetic acid ammonium acetate buffer solution (pH=6.0), add 25mL of ethylene diamine tetraacetic acid disodium titrant (0.05mol/L) precisely, boil it for 3-5 minutes,Cool to room temperature, add 1mL of xylenol orange indicator solution, titrate with zinc titrant (0.05mol/L) until the solution turns from yellow to red, and correct the titration result with blank test.
Note 1: "Precise weighing" means that the weighing shall be accurate to one thousandth of the weighing, and "Precise weighing" means that the accuracy of measuring the volume shall meet the accuracy requirements of the national standard for the volume of pipette.
Note 2: "Moisture determination" uses the drying method. Take 2-5g of the test sample and lay it in a flat weighing bottle dried to constant weight. The thickness is not more than 5mm, and the loose test sample is not more than 10mm. Weigh it precisely. Open the bottle cap and dry it at 100~105 ℃ for 5 hours. Cover the bottle cap, transfer it to a dryer, cool it for 30 minutes, weigh it precisely, dry it at the above temperature for 1 hour, cool it, weigh it,Until the difference between two successive weighing does not exceed 5mg.Calculate the water content (%) of the test article according to the weight loss.
Encyclopedia x Miscellaneous: Illustrate the purification of aluminum
