One of the most widely used substances in industry is aluminum hydroxide. In this article, we will talk about him.

What is Hydroxide?

It is a chemical compound that forms when an oxide interacts with water. There are three types of them: acidic, basic and amphoteric. The first and second are divided into groups depending on their chemical activity, properties and formula.

What are amphoteric substances?

Oxides and hydroxides can be amphoteric. These are substances that are characterized by both acidic and basic properties, depending on the reaction conditions, reagents used, etc. Amphoteric oxides include two types of iron oxide, manganese oxide, lead, beryllium, zinc, and aluminum ... The latter, by the way, is most often obtained from its hydroxide. Amphoteric hydroxides include beryllium hydroxide, iron hydroxide, as well as aluminum hydroxide, which we will consider today in our article.

Physical properties of aluminum hydroxide

This chemical compound is a white solid. It does not dissolve in water.

Aluminum hydroxide - chemical properties

As mentioned above, this is the most prominent representative of the group of amphoteric hydroxides. Depending on the reaction conditions, it can exhibit both basic and acidic properties. This substance is capable of dissolving in acids, and salt and water are formed.

For example, if you mix it with perchloric acid in equal amounts, then we get aluminum chloride with water also in equal proportions. Also another substance with which aluminum hydroxide reacts is sodium hydroxide. This is a typical basic hydroxide. If you mix the substance in question and a solution of sodium hydroxide in equal amounts, we get a compound called sodium tetrahydroxoaluminate. Its chemical structure contains a sodium atom, an aluminum atom, four oxygen and hydrogen atoms. However, when these substances melt, the reaction proceeds somewhat differently, and this compound is no longer formed. As a result of this process, it is possible to obtain sodium meta-aluminate (its formula includes one sodium and aluminum atom and two oxygen atoms) with water in equal proportions, provided that you mix the same amount of dry sodium and aluminum hydroxides and act on them with a high temperature. If you mix it with sodium hydroxide in other proportions, you can get sodium hexahydroxoaluminate, which contains three sodium atoms, one aluminum atom and six oxygen and hydrogen each. In order for this substance to form, you need to mix the substance in question and the sodium hydroxide solution in proportions of 1: 3, respectively. According to the principle described above, compounds called potassium tetrahydroxoaluminate and potassium hexahydroxoaluminate can be obtained. Also, the substance in question is subject to decomposition when exposed to very high temperatures. This kind of chemical reaction produces alumina, which is also amphoteric, and water. If we take 200 g of hydroxide and heat it, we get 50 g of oxide and 150 g of water. In addition to its peculiar chemical properties, this substance also exhibits the properties usual for all hydroxides. It interacts with metal salts, which have a lower chemical activity than aluminum. For example, you can consider the reaction between it and copper chloride, for which you need to take them in a ratio of 2: 3. This will release water-soluble aluminum chloride and a precipitate in the form of cuprum hydroxide in proportions of 2: 3. Also, the substance in question reacts with oxides of similar metals, for example, you can take a compound of the same copper. To carry out the reaction, aluminum hydroxide and copper oxide are required in a ratio of 2: 3, as a result of which we obtain aluminum oxide and copper hydroxide. Other amphoteric hydroxides such as iron or beryllium hydroxide also have the properties described above.

What is Sodium Hydroxide?

As seen above, there are many chemical reactions between aluminum hydroxide and sodium hydroxide. What is this substance? It is a typical basic hydroxide, i.e. a reactive, water-soluble base. It has all the chemical properties that are found in basic hydroxides.

That is, it can dissolve in acids, for example, when mixing sodium hydroxide with perchloric acid in equal amounts, you can get edible salt (sodium chloride) and water in a 1: 1 ratio. Also, this hydroxide reacts with metal salts, which have a lower chemical activity than sodium, and their oxides. In the first case, a standard exchange reaction occurs. When, for example, silver chloride is added to it, sodium chloride and silver hydroxide are formed, which precipitate (the exchange reaction is feasible only if one of the substances obtained as a result of it is a precipitate, gas or water). When added to sodium hydroxide, for example, zinc oxide, we get the latter's hydroxide and water. However, the reactions of this AlOH hydroxide, which were described above, are much more specific.

AlOH production

When we have already examined its main chemical properties, we can talk about how it is mined. The main way to obtain this substance is to carry out a chemical reaction between an aluminum salt and sodium hydroxide (potassium hydroxide can also be used).

In this kind of reaction, AlOH itself is formed, which precipitates into a white precipitate, as well as a new salt. For example, if you take aluminum chloride and add three times more potassium hydroxide to it, then the resulting substances will be the chemical compound considered in the article and three times more potassium chloride. There is also a method for producing AlOH, which provides for a chemical reaction between a solution of an aluminum salt and a carbonate of the base metal, for example, let's take sodium. To obtain aluminum hydroxide, kitchen salt and carbon dioxide in a ratio of 2: 6: 3, it is necessary to mix aluminum chloride, sodium carbonate (soda) and water in a ratio of 2: 3: 3.

Where is aluminum hydroxide used?

Aluminum hydroxide is used in medicine.

Due to its ability to neutralize acids, preparations containing it are recommended for heartburn. It is also prescribed for ulcers, acute and chronic inflammatory bowel processes. In addition, aluminum hydroxide is used in the manufacture of elastomers. It is also widely used in the chemical industry for the synthesis of aluminum oxide, sodium aluminates - these processes were discussed above. In addition, it is often used during water purification from contamination. Also, this substance is widely used in the manufacture of cosmetics.

Where are the substances that can be obtained with its help are used?

Aluminum oxide, which can be obtained as a result of thermal decomposition of hydroxide, is used in the manufacture of ceramics, is used as a catalyst for various chemical reactions. Sodium tetrahydroxoaluminate finds its use in tissue dyeing technology.

Aluminum hydroxide

Chemical properties

Chemical formula of Aluminum Hydroxide: Al (OH) 3... It is a chemical compound of aluminum oxide with water. Synthesized in the form of a white jelly-like substance, which is poorly soluble in water. Hydroxide has 4 crystalline modifications: nordstrandite (β), monoclinic (γ) gibbsite, bayerite (γ) and hydragilite... There is also amorphous substance, the composition of which varies: Al2O3 nH2O.

Chemical properties... The compound exhibits amphoteric properties. Aluminum hydroxide reacts with alkalis: when reacting with sodium hydroxide in solution it turns out Na (Al (OH) 4); when substances fusion, water is formed and NaAlO2 When heated, the decomposition of Aluminum Hydroxide to water is observed and aluminum oxide ... Substance does not react with solution ammonia ... Reaction aluminum plus sodium hydroxide : 2Al + 2NaOH + 6H2O = 2Na + 3H2.

Obtaining Aluminum Hydroxide. Chemical compound are obtained from Al salts by their interaction with an aqueous solution of alkali in a deficiency, avoiding an excess. TO aluminum chloride AlCl3 add sodium hydroxide - as a result, the required substance precipitates out as a white precipitate and additionally forms sodium chloride .

Also, the agent can be obtained by the reaction of a water-soluble aluminum salt with an alkali metal carbonate. For example, to aluminum chloride add sodium carbonate and water - as a result we get sodium chloride , carbon dioxide and Al hydroxide .

Application:

• used for water purification as an adsorbent;
• can be synthesized aluminum sulfate in the interaction of Al hydroxide and sulfuric acid ;
• as an adjuvant in the manufacture of a vaccine;
• in medicine in the form antacid ;
• in the manufacture of plastic and other materials in the form of a suppressor of combustion processes.

pharmachologic effect

Antacid, absorbent, enveloping.

Pharmacodynamics and pharmacokinetics

Aluminum hydroxide neutralizes hydrochloric acid decomposing it into aluminum chloride and water. The substance gradually increases NS gastric juice up to 3-4.5 and keeps at this level for several hours. The acidity of gastric juice is significantly reduced, its proteolytic activity is inhibited. Upon penetration into the alkaline environment of the intestine, the agent forms chlorine ions and phosphates, which are not absorbed, ions Cl are reabsorbed.

Indications for use

The medicine is used:

• for the treatment of the duodenum and stomach;
• with chronic with normal and increased secretory function of the stomach during an exacerbation;
• during therapy hernia esophageal opening of the diaphragm;
• to eliminate discomfort and pain in the stomach;
• after drinking alcohol, coffee or nicotine, certain medications;
• in case of non-compliance with the diet.

Contraindications

The remedy should not be taken:

• to patients with;
• with serious kidney disease.

Side effects

After taking Aluminum Hydroxide, adverse reactions are rare. Most likely to occur. The likelihood of developing side effects can be reduced if taken additionally.

Instructions for use (Method and dosage)

Aluminum hydroxide is prescribed for oral administration. The drug is most often taken in the form of a suspension, with an active ingredient concentration of 4%. As a rule, take 1 or 2 teaspoons of the drug, 4 or 6 times a day. The duration of treatment depends on the disease and the doctor's recommendations.

Overdose

There are no data on drug overdose.

Interaction

When combining the drug with magnesium trisilicate there is an optimization of the antacid effect and the constipation effect of the heartburn drug decreases.

special instructions

Particular care is taken when treating patients with phosphorus metabolism disorders.

Aluminum oxide Al 2 O 3 (alumina) is the most important aluminum compound. In its pure form, it is a white, very refractory substance, has several modifications, of which the most stable are crystalline - Al 2 O 3 and amorphous y - Al 2 O 3. In nature, it occurs in the form different breeds and minerals.

Of the important properties of Al 2 O 3, the following should be noted:

1) very solid(second only to diamond and some boron compounds);

2) amorphous Al 2 O 3 has a high surface activity and water-absorbing property - an effective adsorbent;

3) has a high catalytic activity, is especially widely used in organic synthesis;

4) is used as a carrier of catalysts - nickel, platinum, etc.

In terms of chemical properties, Al 2 O 3 is a typical amphoteric oxide.

It does not dissolve in water and does not interact with it.

I. Dissolves in acids and alkalis:

1) Al 2 O 3 + 6HCl = 2AlCl 3 + ЗН 2 O

Al 2 O 3 + 6Н + = 2Al 3+ + ЗН 2 O

2) Al 2 O 3 + 2NaOH + ЗН 2 O = 2Na

Al 2 O 3 + 20H - + 3H 2 O = 2 [Al (OH) 4] -

II. It fuses with solid alkalis and metal oxides, forming anhydrous meta-aluminates:

A 2 O 3 + 2KON = 2KAlO 2 + H 2 O

A 2 O 3 + MgO = Mg (AlO) 2

Methods for obtaining Al 2 O 3

1. Extraction from natural bauxite.

2. Combustion of Al powder in a stream of oxygen.

3. Thermal decomposition of Al (OH) 3.

4. Thermal decomposition of some salts.

4Al (NO 3) 3 = 2Al 2 O 3 + 12NO 2 + 3O 2

5. Aluminothermy, for example: Fe 2 O 3 + 2Al = Al 2 O 3 + 2Fe

Aluminum hydroxide Al (OH) 3 is a colorless solid, insoluble in water. Decomposes when heated:

2Al (OH) 3 = Al 2 O 3 + ЗН 2 O

The Al 2 O 3 obtained by this method is called alumogel.

According to its chemical properties, it is a typical amphoteric hydroxide; it dissolves in both acids and alkalis:

Al (OH) 3 + 3HCl = АlСl 3 + ЗН 2 Р

Al (OH) 3 + NaOH = Na sodium tetrahydroxoaluminate

When Al (OH) 3 is fused with solid alkalis, meta-aluminates are formed - salts of metahydroxide AlO (OH), which can be considered as salts of meta-aluminum acid HALO 2:

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

Aluminum salts

Due to the amphoteric nature of aluminum hydroxide and the possibility of its existence in the ortho- and metaphor, there are various types of salts. Since Al (OH) 3 exhibits very weak acidic and very weak basic properties, all types of salts in aqueous solutions are highly susceptible to hydrolysis, which ultimately forms insoluble Al (OH) 3. The presence in an aqueous solution of one or another type of aluminum salts is determined by the pH of this solution.

1. Salts Al 3+ with anions strong acids(AlCl 3, Al 2 (SO 4) 3, Al (NO 3) 3, AlBr 3) exist in acidified solutions. In a neutral medium, meta-aluminates containing aluminum in the composition of the AlO 2 anion exist in the solid state. Distributed in nature. When dissolved in water, they are converted to hydroxoaluminates.

2. Hydroxoaluminates containing aluminum in the - anion exist in alkaline solutions. In a neutral environment, they are highly hydrolyzed.

3. Meta-aluminates containing aluminum as part of the AlO 2 anion. They exist in a solid state. Distributed in nature. When dissolved in water, they are converted to hydroxoaluminates.

The interconversions of aluminum salts are described by the following scheme:

Methods of precipitation (production) of Al (OH) 3 from solutions of its salts

I. Precipitation from solutions containing Al 3+ salts:

Al 3+ + ZON - = Al (OH) 3 ↓

a) the action of strong alkalis added without excess

АlСl 3 + 3NaOH = Аl (ОН) 3 ↓ + ЗН 2 O

b) the action of aqueous solutions of ammonia (weak base)

АlСl 3 + 3NH 3 + ЗН 2 O = Аl (ОН) 3 ↓ + 3NH 4 Cl

c) the action of salts of very weak acids, solutions of which due to hydrolysis have an alkaline medium (excess OH -)

2АlСl 3 + 3Na 2 CO 3 + 3Н 2 O = Аl (ОН) 3 ↓ + ЗСО 2 + 6NaCl

Al 2 (SO 4) 3 + 3K 2 S + 6H 2 O = 2Аl (OH) 3 ↓ + 3K 2 SO 4 + 3H 2 S

II. Precipitation from solutions containing hydroxoaluminates:

[Al (OH) 4] - + H + = Al (OH) 3 ↓ + H 2 O

a) the action of strong acids added without excess

Na [Al (OH) 4] + HCl = Al (OH) 3 ↓ + NaCl + H 2 O

2 [Аl (ОН) 4] + H 2 SO 4 = 2Аl (ОН) 3 ↓ + Na 2 SO 4 + 2Н 2 O

b) the action of weak acids, for example, the transmission of CO 2

Na [Al (OH) 4] + CO 2 = Al (OH) 3 ↓ + NaHCO 3

III. Precipitation as a result of reversible or irreversible hydrolysis of Al 3+ salts (enhanced by diluting the solution with water and by heating)

a) reversible hydrolysis

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

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

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

b) irreversible hydrolysis

Al 2 S 3 + 6H 2 O = 2Аl (OH) 3 ↓ + 3H 2 S

Aluminum hydroxide, characteristics, properties and production, chemical reactions.

Aluminum hydroxide - inorganic substance, It has chemical formula Al (OH) 3.

Brief characteristics of aluminum hydroxide:

Aluminum hydroxide- white inorganic substance.

Chemical formula of aluminum hydroxide Al (OH) 3.

Poorly soluble in water.

Has the ability to adsorb various substances.

Aluminum hydroxide modifications:

There are 4 known crystalline modifications of aluminum hydroxide: gibbsite, bayerite, doyleite, and nordstrandite.

Gibbsite is designated by the γ-form of aluminum hydroxide and bayerite by the α-form of aluminum hydroxide.

Gibbsite is the most chemically stable form of aluminum hydroxide.

Physical properties of aluminum hydroxide:

* Note:

- there is no data.

Receiving aluminum hydroxide:

Aluminum hydroxide is obtained as a result of the following chemical reactions:

1. 1. as a result of the interaction of aluminum chloride and sodium hydroxide :

AlCl 3 + 3NaOH → Al (OH) 3 + 3NaCl.

Aluminum hydroxide is also obtained by the interaction of aluminum salts with aqueous solutions alkalis, avoiding their excess.

1. 2. as a result of the interaction of aluminum chloride, sodium carbonate and water:

2AlCl 3 + 3Na 2 CO 3 + 3H 2 O → 2Al (OH) 3 + 3CO 2 + 6NaCl.

In this case, aluminum hydroxide precipitates in the form of a white gelatinous precipitate.

Aluminum hydroxide is also obtained by the interaction of water-soluble salts aluminum with carbonates of alkali metals.

Chemical properties of aluminum hydroxide. Chemical reactions of aluminum hydroxide:

Aluminum hydroxide has amphoteric properties, that is, it has both basic and acidic properties.

The chemical properties of aluminum hydroxide are similar to those of other amphoteric metal hydroxides. Therefore, it is characterized by the following chemical reactions:

1.reaction of aluminum hydroxide with sodium hydroxide:

Al (OH) 3 + NaOH → NaAlO 2 + 2H 2 O (t = 1000 ° C),

Al (OH) 3 + 3NaOH → Na 3,

Al (OH) 3 + NaOH → Na.

As a result of the reaction, in the first case, sodium aluminate and water are formed, in the second, sodium hexahydroxoaluminate, and in the third, sodium tetrahydroxoaluminate. In the third case, as sodium hydroxide

2. reaction of aluminum hydroxide with potassium hydroxide:

Al (OH) 3 + KOH → KAlO 2 + 2H 2 O (t = 1000 ° C),

Al (OH) 3 + KOH → K.

As a result of the reaction, in the first case, potassium aluminate and water are formed, in the second, potassium tetrahydroxoaluminate. In the second case, as potassium hydroxide a concentrated solution is used.

3. reaction of aluminum hydroxide with nitric acid:

Al (OH) 3 + 3HNO 3 → Al (NO 3) 3 + 3H 2 O.

As a result of the reaction, aluminum nitrate is formed and water.

The reactions of aluminum hydroxide with other acids proceed in a similar way.

4. reaction of aluminum hydroxide with hydrogen fluoride:

Al (OH) 3 + 3HF → AlF 3 + 3H 2 O,

6HF + Al (OH) 3 → H 3 + 3H 2 O.

As a result of the reaction, in the first case, aluminum fluoride and water are formed, in the second, hydrogen hexafluoroaluminate and water. In this case, hydrogen fluoride in the first case is used as a starting substance in the form of a solution.

5. reaction of aluminum hydroxide with hydrogen bromide:

Al (OH) 3 + 3HBr → AlBr 3 + 3H 2 O.

The reaction produces aluminum bromide and water.

6. reaction of aluminum hydroxide with hydrogen iodide:

Al (OH) 3 + 3HI → AlI 3 + 3H 2 O.

The reaction produces aluminum iodide and water.

7. thermal decomposition reaction of aluminum hydroxide:

Al (OH) 3 → AlO (OH) + H 2 O (t = 200 ° C),

2Al (OH) 3 → Al 2 O 3 + 3H 2 O (t = 575 ° C).

As a result of the reaction, in the first case, aluminum metahydroxide and water are formed, in the second, aluminum oxide and water.

8. reaction of aluminum hydroxide and sodium carbonate:

2Al (OH) 3 + Na 2 CO 3 → 2NaAlO 2 + CO 2 + 3H 2 O.

As a result of the reaction, sodium aluminate, carbon monoxide (IV) and water are formed.

10. reaction of aluminum hydroxide and calcium hydroxide:

Ca (OH) 2 + 2Al (OH) 3 → Ca 2.

As a result of the reaction, calcium tetrahydroxoaluminate is formed.

Application and use of aluminum hydroxide:

Aluminum hydroxide is used in water purification (as an adsorbent), in medicine, as a filler in toothpaste (as an abrasive), plastics and plastics (as a fire retardant).

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Aluminum- an element of the 13th (III) group of the periodic table of chemical elements with atomic number 13. It is designated by the symbol Al. Belongs to the group of light metals. Most common metal and third most common chemical element v earth crust(after oxygen and silicon).

Aluminium oxide Al2O3- in nature, it is widespread as alumina, a white refractory powder, in hardness close to diamond.

Aluminum oxide is a natural compound that can be obtained from bauxite or by thermal decomposition of aluminum hydroxides:

2Al (OH) 3 = Al2O3 + 3H2O;

Al2O3 - amphoteric oxide, chemically inert due to its strong crystal lattice... It does not dissolve in water, does not interact with solutions of acids and alkalis, and can only react with molten alkali.

At about 1000 ° C, it intensively interacts with alkalis and alkali metal carbonates to form aluminates:

Al2O3 + 2KOH = 2KAlO2 + H2O; Al2O3 + Na2CO3 = 2NaAlO2 + CO2.

Other forms of Al2O3 are more active, can react with solutions of acids and alkalis, α-Al2O3 interacts only with hot concentrated solutions: Al2O3 + 6HCl = 2AlCl3 + 3H2O;

The amphoteric properties of aluminum oxide are manifested when interacting with acidic and basic oxides with the formation of salts:

Al2O3 + 3SO3 = Al2 (SO4) 3 (basic properties), Al2O3 + Na2O = 2NaAlO2 (acidic properties).

Aluminum hydroxide, Al (OH) 3- compound of aluminum oxide with water. White gelatinous substance, poorly soluble in water, has amphoteric properties. Obtained by the interaction of aluminum salts with aqueous alkali solutions: AlCl3 + 3NaOH = Al (OH) 3 + 3NaCl

Aluminum hydroxide is a typical amphoteric compound; freshly obtained hydroxide dissolves in acids and alkalis:

2Al (OH) 3 + 6HCl = 2AlCl3 + 6H2O. Al (OH) 3 + NaOH + 2H2O = Na.

When heated, it decomposes, the dehydration process is rather complicated and can be schematically represented as follows:

Al (OH) 3 = AlOOH + H2O. 2AlOOH = Al2O3 + H2O.

Aluminates - salts formed by the action of alkali on freshly precipitated aluminum hydroxide: Al (OH) 3 + NaOH = Na (sodium tetrahydroxoaluminate)

Aluminates are also obtained by dissolving metallic aluminum (or Al2O3) in alkalis: 2Al + 2NaOH + 6H2O = 2Na + 3H2

Hydroxoaluminates formed by the interaction of Al (OH) 3 with an excess of alkali: Al (OH) 3 + NaOH (g) = Na

Aluminum salts. Almost all aluminum salts can be obtained from aluminum hydroxide. Almost all aluminum salts are readily soluble in water; poorly soluble in water aluminum phosphate.
In solution, aluminum salts show an acidic reaction. An example is the reversible effect of aluminum chloride with water:
AlCl3 + 3H2O «Al (OH) 3 + 3HCl
Many aluminum salts are of practical importance. For example, anhydrous aluminum chloride AlCl3 is used in chemical practice as a catalyst in oil refining.
Aluminum sulfate Al2 (SO4) 3 18H2O is used as a coagulant in the purification of tap water, as well as in the production of paper.
Double aluminum salts are widely used - alum KAl (SO4) 2 12H2O, NaAl (SO4) 2 12H2O, NH4Al (SO4) 2 12H2O, etc. - have strong astringent properties and are used in leather tanning, as well as in medical practice as a hemostatic agent.

Application- Due to a complex of properties, it is widely used in thermal equipment. - Aluminum and its alloys retain their strength at ultra-low temperatures. Due to this, it is widely used in cryogenic technology - aluminum is an ideal material for the manufacture of mirrors - In production building materials as a gas-forming agent. - Aluminizing gives corrosion and scale resistance to steel and other alloys, - Aluminum sulphide is used for the production of hydrogen sulfide. - Research is underway to develop aluminum foam as a particularly strong and lightweight material.

As a reducing agent- As a component of termite, mixtures for aluminothermy - In pyrotechnics. - Aluminum is used for the reduction of rare metals from their oxides or halides. (Aluminothermy)

Aluminothermy.- a method of obtaining metals, non-metals (as well as alloys) by reducing their oxides with metallic aluminum.