Silver white light metal. It is malleable. The product is often formed into a rod shape, a sheet shape, a foil shape, a powder shape, a ribbon shape, and a filament shape. Aluminum Element
An oxide film that prevents corrosion of metals can be formed in the humid air. The aluminum powder is heated in the air to burn violently and emit a dazzling white flame.
Soluble in dilute sulfuric acid, nitric acid, hydrochloric acid, sodium hydroxide and potassium hydroxide solution, difficult to dissolve in water. The relative density is 2.70. The temperature of 660 °C. The boiling point is 2327 °C.
The content of the aluminum element in the earth’s crust is second only to oxygen and silicon, ranking third, and is the most abundant metal element in the earth’s crust.
The development of three important industries of aviation, construction, and automobile requires that the material properties have the unique properties of aluminum and its alloys, which is greatly beneficial to the production and application of this new metal aluminum. The application is extremely extensive.
On October 27, 2017, the World Health Organization’s International Agency for Research on Cancer published a preliminary list of carcinogens, and aluminum products were listed on a list of carcinogens.
Preparation Of Aluminum
In 1854, the French chemist Deville mixed aluminum bauxite, charcoal, and salt, and then introduced chlorine gas to obtain NaCl, AlCl3 double salt, and then melted the double salt with excess sodium to obtain metal aluminum.
In 1886, the United States’ Howe and France’s Hailangte, respectively, independently obtained a mixture of electrolytically molten bauxite and cryolite (Na3AlF6) to produce metallic aluminum, which laid the foundation for large-scale production of aluminum in the future.
Aluminum exists in various forms of rock or ore, such as feldspar, mica, kaolinite, bauxite, alum, and the like. Aluminum can be obtained by co-melting electrolysis of aluminum oxide and cryolite (Na3AlF6). The main reaction process is as follows:
Extraction of aluminum from bauxite
- Dissolution: dissolve bauxite in NaOH (aq): Al2O3 + 2NaOH + 3H2O = 2NaAl(OH)4 (sodium tetrahydroxy aluminate)
- Filtration: removal of residual ferrous oxide (FeO), sodium aluminosilicate, etc.
- Acidification: Excess CO2 is introduced into the filtrate: NaAl(OH)4+ CO2 = Al(OH)3↓ + NaHCO3
- Filtered, burned Al(OH)3:2Al(OH)3 = high temperature = Al2O3 + 3H2O
- Electrolysis: 2Al2O3(l) = energization = 4Al + 3O2↑
Note: In the electrolysis, in order to lower the melting temperature of alumina, cryolite (Na3AlF6) is added to Al2O3. Al is not electrolytically melted by AlCl3.
Reason: AlCl3 is a covalent compound. and its molten state is extremely poor in electrical conductivity.
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Aluminum element is a reactive metal. In the dry air, the surface of aluminum immediately forms a dense oxide film with a thickness of about 50 angstroms (1 angstrom = 0.1 nm), so that aluminum does not oxidize further and is resistant to water.
However, aluminum powder is easily mixed with air. Combustion, molten aluminum can violently with water, the corresponding metal; aluminum is amphoteric, easily soluble in the strong base, it can be dissolved in acid.
React with acid
2Al +6HCl ==== 2AlCl3+ 3H2↑
2Al + 3H2SO4(lean)==== Al2(SO4)3+ 3H2↑
Al + 6HNO3(concentration)==Δ==Al(NO3)3+ 3NO2 ↑ + 3H2O
Al + 4HNO3 (lean) ==== Al(NO3)3+ NO↑+
2H2O 8Al + 30HNO3 (thinner) ====8Al(NO3)3+ 3N2O↑+ 15H2O
8Al + 30HNO3(very thin)== ==8Al(NO3)3+ 3NH4NO3+ 9H2O
React with alkali
React with non-metal
2Al + Fe2O3==ignition== Al2O3+2Fe (aluminum thermal reaction)
8Al + 3Fe3O4==high temperature== 4Al2O3+9Fe
React with water
According to the reducibility of aluminum, it can be inferred that aluminum can react with water.
However, it has been found that aluminum has almost no reaction with boiling water, but aluminum can react with water vapor under heating conditions, but the reaction starts with oxygen generation in water. The dense oxide film prevents the reaction from proceeding further.
Basic physical property
Aluminum element is a silvery-white light metal. It is malleable. The product is often formed into a column, a rod, a sheet, a foil, a powder, a ribbon, and a filament.
An oxide film that prevents corrosion of metals can be formed in the humid air. The acid-treated aluminum powder is heated in the air to burn violently and emit a dazzling white flame.
Soluble in dilute sulfuric acid, dilute nitric acid, hydrochloric acid, sodium hydroxide, and potassium hydroxide solution, insoluble in water, but can react slowly with hot water to form the aluminum hydroxide, relative density 2.70, elastic modulus 70Gpa, mooring The ratio is 0.33.
The temperature of 660 ° C. The boiling point is 2327 ° C. I ts light, good electrical and thermal conductivity performance, high reflectivity and resistance to oxidation are widely used.
The aluminum element used to make a daily dish is usually called “steel” or “steel.” Al has a coefficient of thermal expansion of 0.0000236 mm/°C or 23.6 ppm*k -1 at (room temperature) 25 °C.
The use of a substance depends to a large extent on the nature of the substance. Because the aluminum element has many excellent properties, aluminum has an extremely wide range of uses.
Aluminum and aluminum alloys are among the most economical materials available today. Since the beginning of 1956, the world’s aluminum production has been the largest in the world.
At present, the output and dosage of aluminum (in tons) is second only to steel and the second-largest metal for human applications.
Moreover, aluminum is rich in resources. According to preliminary calculations, the storage of aluminum accounts for more than 8% of the constituents of the earth’s crust.
Aluminum’s lightweight and corrosion resistance are two of its outstanding features.
The density of aluminum is very small, only 2.7 g/cm3. Although it is relatively soft, it can be made into various aluminum alloys such as hard aluminum, super-hard aluminum, rust-proof aluminum, cast aluminum and the like.
These aluminum alloys are widely used in the manufacturing industries of airplanes, automobiles, trains, and ships. In addition, a large number of aluminum and its aluminum alloys are used in space rockets, space shuttles, and satellites.
For example, a supersonic aircraft consists of approximately 70% aluminum and its aluminum alloy. Aluminum is also used extensively in the construction of ships, and the amount of aluminum used in a large passenger ship often reaches several thousand tons.
The conductivity of aluminum is second only to silver, copper, and gold. Although its conductivity is only 2/3 of that of copper, the density is only 1/3 of that of copper. Therefore, the same amount of electricity is delivered.
The quality of the aluminum wire is only half of that of copper wire. The oxide film on the aluminum surface is not only resistant to corrosion but also has a certain degree of insulation, so aluminum has a wide range of uses in the electrical appliance manufacturing industry, the wire and cable industry, and the radio industry.
Aluminum element is a good conductor of heat. Its thermal conductivity is three times higher than that of iron. Aluminum can be used in the manufacture of various heat exchangers, heat-dissipating materials and cookware.
Aluminum has good ductility (its ductility is second only to gold and silver) and can be made into aluminum foil thinner than 0.01 mm at 100 °C to 150 °C. These aluminum foils are widely used for packaging cigarettes, candy, etc., and can also be made into aluminum wire, aluminum strips, and can roll various aluminum products.
The surface of aluminum is resistant to corrosion due to its dense oxide protective film and is often used in the manufacture of chemical reactors, medical devices, refrigeration units, petroleum refining units, and oil and gas pipelines.
Aluminum powder has a silver-white luster (generally the color of the metal is mostly black in the powder), commonly used as a coating, commonly known as silver powder, silver paint, to protect the iron products from corrosion, and beautiful.
Aluminum burning in oxygen can release a lot of heat and dazzling light, often used in the manufacture of explosive mixtures, such as ammonium aluminum explosives ( mixed with ammonium nitrate , charcoal powder, aluminum powder, soot and other combustible organic matter), combustion mixture (such as bombs and shells made of aluminothermic agents can be used to attack hard-to-fire targets or tanks, cannons, etc.) and lighting mixtures (such as 68% cerium nitrate, 28% aluminum powder, 4% shellac).
Aluminotherms are commonly used to smelt refractory metals and welded rails. Aluminum is also used as a deoxidizer in steel making. Aluminum powder and graphite, titanium dioxide (or other high melting point metal oxide) are uniformly mixed at a certain ratio, coated on metal, and calcined at high temperature to form high-temperature resistant cermet. It has important applications in rocket and missile technology.
The aluminum plate also has good reflection performance for light. The reflected ultraviolet light is stronger than silver. The purer the aluminum, the better the reflection ability, so it is commonly used to manufacture high-quality mirrors, such as solar cooker mirrors.
Aluminum element has sound-absorbing properties and sound effects are good, so aluminum is also used in broadcasting rooms and ceilings in modern large-scale architectural rooms.
Low-temperature resistance, aluminum at the low temperature, its strength is increased without brittleness, so it is ideal for low-temperature device materials, such as refrigerators, freezer, Antarctic snowmobile, hydrogen oxide production equipment.
Studies have found that aluminum can damage human brain cells. According to the World Health Organization’s assessment, the daily intake of aluminum is specified to be 0-0.6 mg/kg, where kg refers to the human body weight, that is, a 60 kg person is allowed to consume 36 mg.
China’s “Food Additives Use Standard GB2760-2011” stipulates that the residual amount of aluminum should be less than or equal to 100mg/kg. In this calculation, a person weighing 60 kg does not have to worry about eating any more than 360 g of fritters a day.
Aluminum element is slowly accumulated in the human body, and its toxicity is slow and not easy to detect. However, in the event of a metabolic disorder, the consequences are very serious.
Therefore, we must pay attention to it, in daily life to prevent the absorption of aluminum, reduce the use of aluminum products. The harm of aluminum and its compounds to human beings is incomparable compared with its contribution.
As long as people pay attention to it and promote its strengths and avoid weaknesses, it will play a more important role in human society.
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Ways to avoid:
- Avoid using cookware made of aluminum element
- Eat less fried dough sticks, candy wrapped in aluminum, etc., and drink less soft drinks in cans.
- Some medicines are made of aluminum-containing substances, and medicines containing aluminum should be reduced, such as Al (OH)3, which can neutralize gastric acid.
Method name: Determination of sucralfate-aluminum-complex 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.
Principle of the method: take the appropriate amount of the test sample, after dissolution and dilution, neutralize the treatment, add acetic acid -ammonium acetate buffer solution, and add the ethylenediaminetetraacetic acid disodium titration solution (0.05mol/L), boil for 3 to 5 minutes, put Cool to room temperature. Each 1 mL of sodium edetate tetraacetate titration solution (0.05 mol/L) is equivalent to 1.349 mg of aluminum, which is calculated.
- Water (new boiling to room temperature)
- Acetic acid-ammonium acetate buffer (pH 6.0)
- Xylenol orange indicator solution
- Zinc titrant (0.05mol/L)
- Ethylenediaminetetraacetic acid disodium titration solution (0.05mol/L)
- Benchmark zinc oxide
- Dilute hydrochloric acid
- Methyl red ethanol solution (0.025%)
- Ammonia test solution
- Chrome black T indicator
- Ammonia- ammonium chloride buffer (pH10.0)
Take about 1.0g of this product, accurately weigh it, put it in a 200mL volumetric flask, add 10mL of dilute hydrochloric acid, dissolve it, dilute it to the mark with water, shake it up, accurately measure 20mL, add ammonia test solution to neutralize the precipitate, then drop Add dilute hydrochloric acid until the precipitate dissolves, add 20 mL of acetic acid-ammonium acetate buffer (pH 6.0), and then add 25 mL of Ethylenediaminetetraacetic acid disodium titration solution (0.05 mol/L), boil for 3-5 minutes, put After cooling to room temperature, 1 mL of xylenol orange indicator solution was added, and titrated with zinc titration solution (0.05 mol/L) until the solution changed from yellow to red, and the titration result was corrected by a blank test.
Note 1: “Precision weighing” means that the weight should be accurate to one-thousandth of the weight weighed. “Precision measurement” means that the accuracy of the volume should be in accordance with the national standard for the volumetric pipette. Precision requirements.
Note 2: “Moisture measurement” is carried out by the drying method, taking 2 to 5 g of the test sample, and tiling it in a flat weighing bottle which is dry to constant weight, the thickness is not more than 5 mm, the loose test sample is not more than 10 mm, and is accurately weighed.
Open the cap and dry it at 100-105 °C for 5 hours, cover the cap, displace it in the desiccator, cool for 30 minutes, accurately weigh the weight, then dry at the above temperature for 1 hour, cool, weigh until two consecutive times. The difference in weighing does not exceed 5 mg. Calculate the water content (%) in the test sample based on weight loss.
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