aluminum dioxide. Aluminum oxide, properties, production, chemical reactions
We send it into the air and launch it into space, put it on a stove, build buildings from it, make tires, smear it on the skin and treat ulcers with it ... Don't you understand yet? It's about aluminum.
Try to list all the applications of aluminum and be sure to be mistaken. You probably don't even know that many of them exist. Everyone knows that aluminum is the material of aircraft manufacturers. But what about the automotive industry or, let's say. medicine? Did you know that aluminum is an E-137 food additive that is commonly used as a coloring agent to give foods a silvery hue?
Aluminum is an element that easily forms stable compounds with any metals, oxygen, hydrogen, chlorine and many other substances. As a result of such chemical and physical influences, alloys and compounds diametrically different in their properties are obtained.
The use of aluminum oxides and hydroxides
The areas of application of aluminum are so extensive that in order to protect manufacturers, designers and engineers from unintentional mistakes, in our country the use of marking aluminum alloys has become mandatory. Each alloy or compound is assigned its own alphanumeric designation, which then allows you to quickly sort them and send them for further processing.
The most common natural aluminum compounds are its oxide and hydroxide. in nature, they exist exclusively in the form of minerals - corundum, bauxite, nepheline, etc. - and as alumina. The use of aluminum and its compounds is associated with the jewelry, cosmetology, medical fields, chemical industry and construction.
Colored, "pure" (not cloudy) corundums are the jewels known to all of us - rubies and sapphires. However, at their core, they are nothing more than the most common aluminum oxide. In addition to the jewelry sector, the use of aluminum oxide extends to the chemical industry, where it usually acts as an adsorbent, as well as to the production ceramic dishes. Ceramic pots, pots, cups have remarkable heat-resistant properties precisely because of the aluminum they contain. Aluminum oxide has also found its use as a material for the manufacture of catalysts. Often, aluminum oxides are added to concrete for its better hardening, and glass, to which aluminum is added, becomes heat-resistant.
The list of applications for aluminum hydroxide is even more impressive. Due to its ability to absorb acid and have a catalytic effect on human immunity, aluminum hydroxide is used in the manufacture of drugs and vaccines for hepatitis types "A" and "B" and tetanus infection. They are also treated for kidney failure due to the presence of a large number of phosphates in the body. Once in the body, aluminum hydroxide reacts with phosphates and forms inextricable bonds with them, and then naturally excreted from the body.
Hydroxide, due to its excellent solubility and non-toxicity, is often added to toothpaste, shampoo, soap, sunscreens, nourishing and moisturizing face and body creams, antiperspirants, tonics, cleansing lotions, foams, etc. If necessary to evenly and stably dye the fabric, then a little aluminum hydroxide is added to the dye and the color is literally "etched" into the surface of the matter.
Application of aluminum chlorides and sulfates
Chlorides and sulfates are also extremely important aluminum compounds. Aluminum chloride does not occur naturally, but it is quite easy to obtain it industrially from bauxite and kaolin. The use of aluminum chloride as a catalyst is rather one-sided, but practically invaluable for the oil refining industry.
Aluminum sulfates exist naturally as minerals in volcanic rocks and are known for their ability to absorb water from the air. The use of aluminum sulphate extends to the cosmetic and textile industries. In the first, it acts as an additive in antipersperands, in the second - in the form of a dye. An interesting use of aluminum sulfate in the composition of insect repellants. Sulphates not only repel mosquitoes, flies and midges, but also anesthetize the bite site. However, despite the tangible benefits, aluminum sulfates have an ambiguous effect on human health. If you inhale or swallow aluminum sulfate, you can get serious poisoning.
Aluminum alloys - main applications
Artificially obtained compounds of aluminum with metals (alloys), unlike natural formations, can have such properties as the manufacturer himself wishes - it is enough to change the composition and amount of alloying elements. Today, there are almost limitless possibilities for obtaining aluminum alloys and their applications.
The most famous industry for the use of aluminum alloys is the aircraft industry. Aircraft are almost entirely made of aluminum alloys. Alloys of zinc, magnesium and aluminum give unprecedented strength, used in aircraft skins and structural parts.
Aluminum alloys are used similarly in the construction of ships, submarines and small river transport. Here it is most profitable to make superstructures from aluminum, they reduce the weight of the vessel by more than half, without compromising their reliability.
Like airplanes and ships, cars are becoming more and more "aluminum" every year. Aluminum is used not only in body parts, but now it is also frames, beams, pillars and cabin panels. Due to the chemical inertness of aluminum alloys, low susceptibility to corrosion and thermal insulation properties, aluminum alloys are used to make tanks for the transport of liquid products.
The use of aluminum in industry is widely known. Oil and gas production would not be where it is today if it were not for the extremely corrosion-resistant, chemically inert aluminum alloy pipelines. Drills made of aluminum weigh several times less, which means they are easy to transport and install. And this is not to mention all kinds of tanks, boilers and other containers ...
Pots, frying pans, baking sheets, ladles and other household utensils are made from aluminum and its alloys. Aluminum cookware conducts heat very well, heats up very quickly, and is easy to clean, does not harm health and food. We bake meat in the oven and bake pies on aluminum foil, oils and margarines, cheeses, chocolates and sweets are packed in aluminum.
An extremely important and promising area is the use of aluminum in medicine. In addition to the uses (vaccines, kidney drugs, adsorbents) mentioned earlier, the use of aluminum in medicines for ulcers and heartburn should also be mentioned.
From all of the above, one conclusion can be drawn - aluminum grades and their application are too diverse to dedicate one small article to them. It is better to write books about aluminum, because it is not for nothing that it is called the "metal of the future".
4.9.1; 4.10.1
4.4.1; 4.8.1; 4.9.1; 4.11.1
4.4.1; 4.8.1; 4.9.1
4.9.1; 4.10.1
5. The validity period was removed according to protocol N 5-94 of the Interstate Council for Standardization, Metrology and Certification (IUS 11-12-94)
6. EDITION (March 2004) with Amendment No. 1 approved in November 1988 (IUS 2-89)
This standard applies to active alumina - modifications in the form of cylindrical granules, used as a carrier of catalysts, catalysts, raw materials for the production of mixed catalysts, a desiccant in various processes of chemical, petrochemical industries, etc.
Formula -AlO.
Molecular weight (according to international atomic weights 1971) - 101.96.
1. TECHNICAL REQUIREMENTS
1. TECHNICAL REQUIREMENTS
1.1. Active alumina must be manufactured in accordance with the requirements of this standard according to the technological regulations approved in the prescribed manner.
1.2. Active alumina, depending on the field of application, is produced in three grades - AOA-1, AOA-2 and AOA-3. Grades AOA-1 and AOA-2 are used as carriers for catalysts, catalysts and a desiccant, grade AOA-3 is used as a raw material for the production of mixed catalysts.
1.3. According to the main indicators, active alumina must comply with the standards indicated in the table.
Name of indicator | Norm for the brand |
||
AOA-1 | AOA-2 | AOA-3 |
|
1. Appearance | Cylindrical granules white color, |
||
2. Dimensions of granules, mm: | |||
length, no more | Not standardized |
||
3. Bulk density, g/dm | No more than 650 |
||
4. Abrasion resistance, %, not less than | |||
5. Specific surface area, m/g | At least 200 | At least 200 |
|
6. Mass fraction of losses during ignition,%, no more | |||
7. Mass fraction of iron, %, no more | |||
8. Mass fraction of sodium, %, no more | |||
9. Mass fraction of dust and fines less than 2.0 mm in size,%, no more | |||
1.2, 1.3. (Changed edition, Rev. N 1).
2. SAFETY REQUIREMENTS
2.1. Active aluminum oxide is non-flammable and non-explosive. Causes irritation of the mucous membranes of the upper respiratory tract, mouth and eyes.
Prolonged inhalation of active alumina may cause clouding of the lungs.
2.2. The maximum permissible concentration of active aluminum oxide in the air of the working area is 2 mg/m.
According to the degree of impact on the human body, active alumina belongs to the 3rd hazard class according to GOST 12.1.005.
2.3. When working with active alumina, precautions should be taken and the means should be used. personal protection in accordance with the verification rules approved in the prescribed manner.
2.4. Premises where work with active alumina is carried out must be equipped with supply and exhaust ventilation that ensures the mass concentration of active alumina in the air of the working area within limits not exceeding the maximum allowable concentration.
(Changed edition, Rev. N 1).
2.5. Cleaning of working premises from dust should be carried out by a wet method or pneumatic (stationary or mobile vacuum cleaners).
Dust removal of machines and equipment should be carried out using a hose connected to a vacuum line.
3. ACCEPTANCE RULES
3.1. Active alumina is taken in batches. A batch is considered to be a quantity that is homogeneous in its quality indicators product accompanied by a single quality document. The mass of the batch should not exceed 4 tons.
Each batch must be accompanied by a quality document, which must contain:
name of the manufacturer or its trademark;
product name and brand;
batch number and date of manufacture;
the number of product units in the batch;
gross and net weight;
the results of the tests carried out or confirmation of compliance with the requirements of this standard;
technical control stamp;
designation of this standard.
3.2. To check the quality of active alumina for compliance with the requirements of this standard, a sample is taken from 10% of packaging units, but not less than from three packaging units.
(Changed edition, Rev. N 1).
3.3. Upon receipt of unsatisfactory results of the analysis for at least one of the indicators, a second test is carried out on a double sample. The retest results apply to the entire lot.
4. CONTROL METHODS
General instructions for conducting analyzes - according to GOST 27025.
(Changed edition, Rev. N 1).
4.1. Sample selection
4.1.1. Spot samples from the packaged product are taken with a probe made of stainless steel (Fig. 1), immersing it to the depths of the product, or by any similar means.
Damn.1
The mass of the selected point sample must be at least 200 g.
(Changed edition, Rev. N 1).
4.1.2. The selected point samples are combined together, thoroughly mixed, and a combined sample is obtained. The combined sample is reduced by quartering to obtain an average sample weighing at least 0.5 kg.
4.1.3. The average sample of active alumina is divided into two parts, placed in two clean dry jars and hermetically sealed with a lid or ground stopper.
Banks seal and stick paper labels with the designations:
product name and brand;
the name of the manufacturer or its trademark;
sampling dates;
lot numbers and weights;
designations of this standard.
One bank is transferred to the laboratory for control, the other is stored for 6 months in case of disagreement in the quality assessment.
4.2. The appearance of the product is determined visually
4.3. Granule size determination
4.3.1. Devices
Caliper according to GOST 166.
4.3.2. Conducting a test
From the average sample, 20 whole granules are taken, the diameter of each granule is measured with a caliper to the first decimal place.
The dimensions of each granule must be within the limits specified in the technical requirements.
It is allowed to determine the size of the granules using a dial indicator according to GOST 577.
(Changed edition, Rev. N 1).
4.4. Determination of bulk density
4.4.1. Equipment
Scales general purpose according to GOST 24104 *, 3rd accuracy class with weighing limits from 50 to 200 g.
________________
* Since July 1, 2002, GOST 24104-2001 has been put into effect (hereinafter).
Dimensional cylinder 1-100 according to GOST 1770.
Drying cabinet of any type, providing heating to a temperature of (110±10) °C.
Desiccator according to GOST 25336.
4.4.2. Conducting a test
100.00 g of active aluminum oxide crushed to 4-6 mm (using wire cutters) is dried in an oven at a temperature of (110 ± 10) ° C for 2 hours and cooled in a desiccator to room temperature. The cooled active alumina is placed in a pre-weighed measuring cylinder, compacted by tapping the cylinder on a wooden board or on a vibrator designed by GrozNII, type B.
The cylinder is filled to the mark, the contents are compacted until the volume of active alumina is constant and reaches 100 cm 3, after which the cylinder with active alumina is weighed.
4.4.3. Results processing
Bulk density () in g / dm is calculated by the formula
where is the mass of the cylinder with active alumina, g;
Mass of the empty cylinder, g;
- volume of active alumina, cm.
The measurement result is taken as the arithmetic mean of the results of two parallel determinations, the absolute discrepancy between which should not exceed 20 g/dm. Permissible total measurement error ±10 g/dm at a confidence level of 0.95.
In case of disagreement in assessing the bulk density, the method of shaking the active alumina by tapping the cylinder on a wooden board should be used.
4.4.1-4.4.3. (Changed edition, Rev. N 1).
4.5. Determination of abrasion resistance
Abrasion strength is determined according to GOST 16188.
Before testing, the sample is crushed with nippers or scissors to 4-6 mm granules and sieved on a No. 40 type I sieve. Then the sample is dried for 2 hours in a closed oven at a temperature of (110 ± 10) °C. Bulk density is determined according to this standard.
4.6. (Excluded, Rev. N 1).
4.7. The specific surface is determined according to GOST 23401.
A sample of 15-20 g is taken from the average sample, crushed in a mortar, sieved manually on a sieve with a mesh 04-20 according to GOST 6613 and a test sample weighing 0.1-0.2 g is taken.
Before measuring the specific surface area, the sample must first be dried at a temperature of 150-170 °C to a constant mass, if it is not subjected to a training process.
When carrying out daily calibration of the detector, calibration of the dosing valve is not required.
It is allowed to carry out the determination on the sorbtometer "Tsvet-211", "Tsvet-213" or "Tsvet-215".
4.8. Determination of the mass fraction of losses on ignition
4.8.1. Equipment
GOST 24104
Porcelain crucible according to GOST 9147.
Desiccator according to GOST 25336.
An electric furnace of any type that provides heating to a temperature of (800±10) °C.
(Changed edition, Rev. N 1).
4.8.2. Conducting an analysis
About 2.0000 g of active alumina are placed in a crucible, previously calcined at a temperature of (800 ± 10) ° C to constant weight, cooled in a desiccator and weighed. The crucible with contents is dried at a temperature of (110 ± 10) °C to constant weight, weighed and then calcined at a temperature of (800 ± 10) °C to constant weight, gradually raising the temperature.
4.8.3. Results processing
The mass fraction of losses on ignition () as a percentage is calculated by the formula
where is the mass of dried active alumina, g;
Mass of calcined active alumina, g
The measurement result is taken as the arithmetic mean of the results of two parallel determinations, the absolute discrepancy between which should not exceed 0.2%. Permissible total measurement error ±0.1% at a confidence level of 0.95.
(Changed edition, Rev. N 1).
4.9. Measurement of the mass fraction of iron
The method is based on the photometric measurement of the intensity of the yellow color of the complex formed by the interaction of iron (III) with sulfosalicylic acid in an ammonia medium.
4.9.1. Equipment, reagents, solutions
General purpose laboratory scales according to GOST 24104, 2nd accuracy class with the maximum weighing limit of 200 g.
Electric stove with a power of 800 W according to GOST 14919 or another type of the specified power.
Photoelectrocolorimeter KFK-2 or other type.
Burette 7-2-10 or 6-2-5 according to GOST 29251.
Beaker 50 according to GOST 1770.
Flasks 2-50-2, 2-100-2, 2-1000-2 according to GOST 1770.
Pipettes 2-2-5, 2-2-20 according to GOST 29227.
Glass V-1-250 THS according to GOST 25336.
Watch glass.
Water ammonia according to GOST 3760.
Distilled water according to GOST 6709.
Signal clock according to GOST 3145 or other type.
Sulfuric acid according to GOST 4204, concentration solution (HSO) = 0.01 mol / dm (0.01 N.) and solution 1: 2.
Sulfosalicylic acid according to GOST 4478, solution with a mass fraction of 20%.
Standard solution of iron (III) mass concentration 1 mg/cm (solution A); prepared according to GOST 4212.
When using iron-ammonium alum of the "pure" qualification, it is necessary to first determine the mass fraction of the main substance by gravimetric or complexometric methods.
To build a calibration graph, by appropriately diluting solution A with sulfuric acid at a concentration of 0.01 mol / dm, prepare solution B of a mass concentration of 0.02 mg / cm of iron (III
4.9.2. Construction of a calibration graph
In a number of volumetric flasks with a capacity of 50 cm3, 0.5 is introduced from a microburette; 1.0; 2.0; 3.0; 4.0 ml of standard solution B. Add 5 ml of sulfosalicylic acid, 5 ml of aqueous ammonia to each flask, make up to the mark with water and mix. After 30 minutes, the optical density of the solution is measured on a photoelectrocolorimeter at a wavelength of 410 nm in a cuvette with a light-absorbing layer thickness of 50 mm.
The reference solution contains all reagents except for the standard iron solution.
Based on the data obtained, a calibration graph is constructed for the dependence of the optical density of solutions on the mass of iron in milligrams.
4.9.3. Preparation for analysis
About 2.0000 g of finely divided active alumina is placed in a beaker, moistened with water, 20 ml of a 1:2 sulfuric acid solution is added, and the sample is dissolved at a gentle boil. The beaker is removed from the hotplate, 20 ml of water are carefully added, transferred to a 100 ml volumetric flask, cooled to room temperature, topped up to the mark with water and mixed.
4.9.4. Conducting an analysis
5 cm3 of the solution prepared as indicated in paragraph 4.9.3 is placed in a flask with a capacity of 50 cm3, 5 cm3 of a solution of sulfosalicylic acid, 5 cm3 of aqueous ammonia are added, topped up to the mark with water and mixed.
Optical density is measured under the same conditions as when constructing a calibration graph.
According to the calibration graph, the mass of iron is found.
4.9.5. Results processing
The mass fraction of iron () as a percentage is calculated by the formula
where is the mass of iron found from the calibration curve, mg;
Weight of sample sample, g.
The result of the analysis is taken as the arithmetic mean of the results of two parallel determinations, the absolute discrepancy between which should not exceed 0.005%. Permissible total error of the analysis result is ±0.003% at a confidence level of 0.95.
4.10. Determination of the mass fraction of sodium
The method is based on a comparison of the emission intensity of sodium resonance lines in the spectrum of a propane-air flame obtained by spraying sample solutions and reference solutions into it.
4.10.1. Equipment, reagents, solutions
Flame photometer type Zeiss model III (manufactured by the GDR) with a set of interference filters for sodium or a device of any other brand with a sensitivity of at least 0.5 µg/cm for sodium.
Standard solution of sodium mass concentration 0.1 mg/cm; prepared as follows: 0.2542 g of sodium chloride, previously calcined to constant weight at a temperature of 500 ° C, is placed in a flask with a capacity of 1 dm3, dissolved in water, topped up to the mark with water and mixed.
The solution and water for the preparation of the stock solution are stored in a plastic container.
Sodium chloride according to GOST 4233.
Distilled water according to GOST 6709.
The background solution is distilled water.
4.10.2. Photometry conditions
Preparation of the device for operation should be carried out in accordance with the technical description and operating instructions of the flame photometer.
4.10.3. Construction of a calibration graph
In a series of volumetric flasks with a capacity of 100 ml, using a burette, place 1.0; 2.0; 3.0; 4.0; 5.0; 6.0; 7.0; 8.0; 9.0; 10.0 ml of standard sodium solution, dilute to the mark with water and mix. The device is prepared for analysis according to the instructions attached to it.
After preparing the device, photometry of the water taken for the preparation of standard solutions is carried out to determine the mass fraction of sodium impurities, as well as standard solutions in ascending order of sodium mass concentration, spraying water after each measurement. After that, the standard solutions are photometered in reverse order, starting with the highest concentration. Each point of the calibration curve is built according to the arithmetic mean of five to six measurements of the newly prepared series of standard solutions, taking into account the reading on the galvanometer when photometry of water as a correction. Based on the data obtained, a calibration graph is constructed for the dependence of the galvanometer readings on the mass concentrations of sodium in micrograms per cubic centimeter.
4.10.4. Conducting an analysis
After preparing the instrument for analysis, a background solution (distilled water) is sprayed into the flame of the burner, and the test solution, prepared in accordance with clause 4.9.3, is photometered according to the instructions and the instrument. According to the readings of the galvanometer and the calibration curve, the mass concentration of sodium is found.
4.10.5. Results processing
The mass fraction of sodium () as a percentage is calculated by the formula
where is the mass concentration of sodium found from the calibration curve, µg/cm;
Weight of active alumina sample, g
The result of the analysis is taken as the arithmetic mean of the results of two parallel determinations, the absolute discrepancy between which should not exceed 0.001%. Permissible total error of the analysis result is ±0.0006% at a confidence level of 0.95.
4.9-4.10.5. (Changed edition, Rev. N 1).
4.11. Determination of the mass fraction of dust and fines smaller than 2 mm
4.11.1. Devices
Sieve classifier with a set of stamped sieves of the RKF-IV type.
General purpose laboratory scales according to GOST 24104, 2nd accuracy class with the maximum weighing limit of 200 g.
Sieve 40 type I.
Signal clock - in accordance with GOST 3145-84 or another type.
(Changed edition, Rev. N 1).
4.11.2. Conducting a test
About 100.0 g of active alumina are placed on a 2 mm sieve. A pallet is installed below. Cover the top of the sieve with a lid. Sieving time 2 min. The oscillation amplitude is 1.2-1.5 mm.
In the absence of a lattice classifier, sieving is carried out on a sieve. Sieving time 2-3 minutes with 100-120 shakes per 1 minute.
4.11.3. Results processing
The mass fraction of dust and fines with a size of 2 mm () as a percentage is calculated by the formula
where is the weight of the sample, g;
- mass of particles on the pallet, g.
The test result is taken as the arithmetic mean of the results of two parallel determinations, the allowable discrepancies between which should not exceed 0.05% with a confidence level of 0.95.
5. PACKAGING, LABELING, TRANSPORT AND STORAGE
GOST 13950 of any design, polyethylene barrels for catalysts (with a capacity of 50, 60, 100, 120 dm3).
By agreement with the consumer, it is allowed to pack the product in barrels in accordance with GOST 13950 type I and flasks in accordance with GOST 5799 of any design (with a capacity of 40 dm3).
The inner surface of the metal container shall not contain traces of corrosion.
5.2. Marking
Transport marking - in accordance with GOST 14192 with the application of basic, additional, informational inscriptions and the handling sign "Sealed packaging".
A paper label No. 2 is attached to each packaging unit, including:
name of the manufacturer and its trademark;
Product name;
date of manufacture;
lot number;
designation of this standard;
gross net weight.
Marking can be applied directly to the container using a stencil or stamp with indelible paint.
5.3. Transportation
Active alumina is transported by all modes of transport, except for air, in covered vehicles in accordance with the transportation rules applicable to this type of transport, when transporting by railway- carload and small shipments.
5.4. Storage
Active alumina must be stored in dry rooms.
6. MANUFACTURER WARRANTY
6.1. The manufacturer guarantees the compliance of active alumina with the requirements of this standard, subject to the conditions of transportation and storage.
6.2. Guarantee period storage of aluminum oxide - 5 years from the date of manufacture of the product.
Electronic text of the document
prepared by CJSC "Kodeks" and checked against:
official publication
Moscow: IPK Standards Publishing House, 2004
The electronic configuration of the external level of aluminum … 3s 2 3p 1 .
In the excited state, one of the s-electrons passes to a free cell of the p-sublevel, this state corresponds to valence III and the oxidation state +3.
There are free d-sublevels in the outer electron layer of the aluminum atom. Due to this, its coordination number in compounds can be not only 4 ([A1 (OH) 4] -), but also 6 - ([A1 (OH) 6] 3-).
Being in nature
The most common metal in the earth's crust, the total aluminum content in the earth's crust is 8.8%.
It does not occur in free form in nature.
The most important natural compounds are aluminosilicates:
White clay Al 2 O 3 ∙ 2SiO 2 ∙ 2H 2 O, feldspar K 2 O ∙ Al 2 O 3 ∙ 6SiO 2, mica K 2 O ∙ Al 2 O 3 ∙ 6SiO 2 ∙ H 2 O
From other natural forms of aluminum highest value have bauxites A1 2 Oz ∙ nH 2 O, minerals corundum A1 2 Oz and cryolite A1Fz ∙3NaF.
Receipt
At present, aluminum is produced in industry by electrolysis of aluminum oxide Al 2 O 3 in a cryolite melt.
The process of electrolysis is ultimately reduced to the decomposition of Al 2 Oz by electric current
2A1 2 Oz \u003d 4A1 + 3O 2 (950 0 C, A1Fz ∙3NaF, electric current)
Liquid aluminum is released at the cathode:
A1 3+ + 3e-=Al0
Oxygen is released at the anode.
Lightweight, silvery-white, ductile metal, conducts electricity and heat well.
In air, aluminum is covered with the thinnest (0.00001 mm), but very dense oxide film, which protects the metal from further oxidation and gives it a matte appearance.
Aluminum is easily drawn into wire and rolled into thin sheets. Aluminium foil(thickness 0.005 mm) is used in the food and pharmaceutical industries for packaging products and preparations.
Chemical properties
Aluminum is a very active metal, slightly inferior in activity to the elements of the beginning of the period - sodium and magnesium.
1. aluminum easily combines with oxygen at room temperature, while an oxide film is formed on the aluminum surface (A1 2 O 3 layer). This film is very thin (≈ 10 -5 mm), but strong. It protects aluminum from further oxidation and is therefore called a protective film.
4Al + 3O 2 \u003d 2Al 2 O 3
2. when interacting with halogens, halides are formed:
with chlorine and bromine, the interaction occurs already at ordinary temperature, with iodine and sulfur - when heated.
2Al + 3Cl 2 = 2AlCl 3
2Al + 3S \u003d Al 2 S 3
3. At very high temperatures, aluminum also combines directly with nitrogen and carbon.
2Al + N 2 = 2AlN aluminum nitride
4Al + 3C \u003d Al 4 C 3 aluminum carbide
Aluminum does not react with hydrogen.
4. aluminum is quite resistant to water. But if the protective effect of the oxide film is removed mechanically or by amalgamation, then an energetic reaction occurs:
2Al + 6H 2 O \u003d 2Al (OH) 3 + 3H 2
5. interaction of aluminum with acids
From razb. acids (HCl, H 2 SO 4) aluminum interacts with the formation of hydrogen.
2Al + 6HCl = 2AlCl 3 + 3H 2
In the cold, aluminum does not interact with concentrated sulfuric and nitric acid.
Interacts with conc. sulfuric acid when heated
8Al + 15H 2 SO 4 = 4Al 2 (SO 4) 3 + 3H 2 S + 12H 2 O
Aluminum reacts with dilute nitric acid to form NO
Al + 4HNO 3 \u003d Al (NO 3) 3 + NO + 2H 2 O
6. interaction of aluminum with alkalis
Aluminum, like other metals that form amphoteric oxides and hydroxides, interacts with alkali solutions.
Aluminum under normal conditions, as already noted, is covered with a protective film of Al 2 O 3 . Under the action of aqueous solutions of alkalis on aluminum, the layer of aluminum oxide A1 2 O 3 dissolves, and aluminates are formed - salts containing aluminum in the composition of the anion:
A1 2 O 3 + 2NaOH + 3H 2 O \u003d 2Na
Aluminum, devoid of a protective film, interacts with water, displacing hydrogen from it.
2Al + 6H 2 O \u003d 2Al (OH) 3 + 3H 2
The resulting aluminum hydroxide reacts with an excess of alkali, forming tetrahydroxoaluminate
Al (OH) 3 + NaOH \u003d Na
The overall equation for the dissolution of aluminum in an aqueous solution of alkali:
2Al + 2NaOH + 6H 2 O \u003d 2Na + 3H 2
Aluminum oxide A1 2 O 3
White solid, insoluble in water, melting point 2050 0 C.
Natural A1 2 O 3 - the mineral corundum. Transparent colored corundum crystals - red ruby - contains an admixture of chromium - and blue sapphire - an admixture of titanium and iron - gems. They are also obtained artificially and used for technical purposes, for example, for the manufacture of parts for precision instruments, stones in watches, etc.
Chemical properties
Aluminum oxide exhibits amphoteric properties
1. interaction with acids
A1 2 O 3 + 6HCl \u003d 2AlCl 3 + 3H 2 O
2. interaction with alkalis
A1 2 O 3 + 2NaOH - 2NaAlO 2 + H 2 O
Al 2 O 3 + 2NaOH + 5H 2 O \u003d 2Na
3. 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 with Al (aluminum) is often used to obtain a number of elements (Cr, Mn, V, W, etc.) in a free state
2A1 + WO 3 \u003d A1 2 Oz + W
4. interaction with salts having a strongly alkaline environment due to hydrolysis
Al 2 O 3 + Na 2 CO 3 \u003d 2 NaAlO 2 + CO 2
Aluminum hydroxide A1(OH) 3
A1(OH) 3 is a voluminous white gelatinous precipitate, practically insoluble in water, but easily soluble in acids and strong alkalis. It therefore has an amphoteric character.
Aluminum hydroxide is obtained by the exchange reaction of soluble aluminum salts with alkalis.
AlCl 3 + 3NaOH = Al(OH) 3 ↓ + 3NaCl
Al 3+ + 3OH - \u003d Al (OH) 3 ↓
This reaction can be used as a qualitative reaction for the Al 3+ ion
Chemical properties
1. interaction with acids
Al(OH) 3 + 3HCl = 2AlCl 3 + 3H 2 O
2. when interacting with strong alkalis, the corresponding aluminates are formed:
NaOH + A1(OH)3 = Na
3. thermal decomposition
2Al(OH) 3 \u003d Al 2 O 3 + 3H 2 O
aluminum salts undergo hydrolysis by the cation, the medium is acidic (pH< 7)
Al 3+ + H + OH - ↔ AlOH 2+ + H +
Al(NO 3) 3 + H 2 O↔ AlOH(NO 3) 2 + HNO 3
Soluble salts of aluminum and weak acids undergo complete (irreversible hydrolysis)
Al 2 S 3 + 3H 2 O \u003d 2Al (OH) 3 + 3H 2 S
Application in medicine and the national economy of aluminum and its compounds.
The lightness of aluminum and its alloys and high resistance to air and water determine their use in mechanical engineering and aircraft construction. As a pure metal, aluminum is used to make electrical wires.
Aluminum foil (thickness 0.005 mm) is used in the food and pharmaceutical industry for packaging products and preparations.
Aluminum oxide Al 2 O 3 - is part of some antacids (for example, Almagel), used for increased acidity of gastric juice.
KAl (SO 4) 3 12H 2 O - potassium alum is used in medicine for the treatment of skin diseases, as a hemostatic agent. It is also used as a tannin in the leather industry.
(CH 3 COO) 3 Al - Burov's liquid - 8% solution of aluminum acetate has an astringent and anti-inflammatory effect, in high concentrations it has moderate antiseptic properties. It is used in diluted form for rinsing, lotions, for inflammatory diseases of the skin and mucous membranes.
AlCl 3 - used as a catalyst in organic synthesis.
Al 2 (SO 4) 3 18 H 2 0 - used in water purification.
test questions to fix:
1. What is the highest valency of the oxidation state of the elements of III A group. Explain in terms of the structure of the atom.
2. Name the most important boron compounds. What is a qualitative reaction to a borate ion?
3. What Chemical properties have aluminum oxide and hydroxide?
Mandatory
Pustovalova L.M., Nikanorova I.E. . Inorganic chemistry. Rostov-on-Don. Phoenix. 2005. -352p. ch. 2.1 p. 283-294
Additional
1. Akhmetov N.S. General and inorganic chemistry. M.: Higher school, 2009.- 368s.
2. Glinka N.L. General chemistry. KnoRus, 2009.-436 p.
3. Erokhin Yu.M. Chemistry. Textbook for students. Middle professional education - M .: Academy, 2006.- 384s.
Electronic resources
1. Open chemistry: a complete interactive chemistry course for students of schools, lyceums, gymnasiums, colleges, students. technical universities: version 2.5-M.: Physicon, 2006. Electronic optical disk CD-ROM
2. .1C: Tutor - Chemistry, for applicants, high school students and teachers, 1C CJSC, 1998-2005. Electronic optical disc CD-ROM
3. Chemistry. Fundamentals of theoretical chemistry. [Electronic resource]. URL: http://chemistry.narod.ru/himiya/default.html
4. E-library teaching materials on chemistry [Electronic resource]. URL: http://www.chem.msu.su/rus/elibrary/
Aluminum oxide - Al2O3. Physical properties: aluminum oxide is a white amorphous powder or very hard white crystals. Molecular weight = 101.96, density - 3.97 g / cm3, melting point - 2053 ° C, boiling point - 3000 ° C.
Chemical properties: aluminum oxide exhibits amphoteric properties - the properties of acidic oxides and basic oxides, and reacts with both acids and bases. Crystalline Al2O3 is chemically passive, amorphous is more active. Interaction with acid solutions gives average aluminum salts, and with base solutions - complex salts - metal hydroxoaluminates:
When aluminum oxide is fused with solid metal alkalis, double salts are formed - metaaluminates(anhydrous aluminates):
Aluminum oxide does not interact with water and does not dissolve in it.
Receipt: aluminum oxide is obtained by the method of aluminum reduction of metals from their oxides: chromium, molybdenum, tungsten, vanadium, etc. - metallothermy, open Beketov:
Application: aluminum oxide is used for the production of aluminum, in the form of a powder - for refractory, chemically resistant and abrasive materials, in the form of crystals - for the manufacture of lasers and synthetic precious stones (rubies, sapphires, etc.), colored with impurities of other metal oxides - Cr2O3 ( red), Ti2O3 and Fe2O3 (blue).
Aluminum hydroxide - A1 (OH) 3. Physical properties: aluminum hydroxide - white amorphous (gel-like) or crystalline. Almost insoluble in water; molecular weight - 78.00, density - 3.97 g/cm3.
Chemical properties: a typical amphoteric hydroxide reacts:
1) with acids, forming medium salts: Al(OH)3 + 3НNO3 = Al(NO3)3 + 3Н2О;
2) with alkali solutions, forming complex salts - hydroxoaluminates: Al(OH)3 + KOH + 2H2O = K.
When Al(OH)3 is fused with dry alkalis, metaaluminates are formed: Al(OH)3 + KOH = KAlO2 + 2H2O.
Receipt:
1) from aluminum salts under the action of an alkali solution: AlCl3 + 3NaOH = Al(OH)3 + 3H2O;
2) decomposition of aluminum nitride with water: AlN + 3H2O = Al(OH)3 + NH3?;
3) passing CO2 through a solution of the hydroxo complex: [Al(OH)4]-+ CO2 = Al(OH)3 + HCO3-;
4) action on Al salts with ammonia hydrate; Al(OH)3 is formed at room temperature.
62. General characteristics of the chromium subgroup
Elements chromium subgroups occupy an intermediate position in the series of transition metals. They have high melting and boiling points, free places in electronic orbitals. Elements chromium and molybdenum have an atypical electronic structure - they have one electron in the outer s-orbital (as in Nb from the VB subgroup). These elements have 6 electrons in the outer d- and s-orbitals, so all the orbitals are half-filled, that is, each has one electron. With such an electronic configuration, the element is particularly stable and resistant to oxidation. Tungsten has a stronger metallic bond than molybdenum. The oxidation state of the elements of the chromium subgroup varies greatly. Under proper conditions, all elements exhibit a positive oxidation state from 2 to 6, with the maximum oxidation state corresponding to the group number. Not all oxidation states of the elements are stable, chromium has the most stable - +3.
All elements form the MVIO3 oxide; oxides with lower oxidation states are also known. All elements of this subgroup are amphoteric - they form complex compounds and acids.
Chrome, molybdenum and tungsten in demand in metallurgy and electrical engineering. All metals under consideration are covered with a passivating oxide film when stored in air or in an oxidizing acid medium. By removing the film by chemical or mechanical means, it is possible to increase the chemical activity of metals.
Chromium. The element is obtained from chromite ore Fe(CrO2)2 by reducing with coal: Fe(CrO2)2 + 4C = (Fe + 2Cr) + 4CO?.
Pure chromium is obtained by reducing Cr2O3 with aluminum or by electrolysis of a solution containing chromium ions. By recovering chromium by electrolysis, chromium plating can be obtained, which is used as decorative and protective films.
Chromium is used to produce ferrochromium, which is used in the production of steel.
Molybdenum. Obtained from sulfide ore. Its compounds are used in the production of steel. The metal itself is obtained by reducing its oxide. By calcining molybdenum oxide with iron, ferromolybdenum can be obtained. Used for the manufacture of threads and tubes for winding furnaces and electrical contacts. Steel with the addition of molybdenum is used in the automotive industry.
Tungsten. Received from the oxide extracted from the enriched ore. Aluminum or hydrogen is used as a reducing agent. The resulting tungsten in the powder idea is subsequently molded under high pressure and heat treatment (powder metallurgy). In this form, tungsten is used to make filaments, added to steel.