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Aluminium Hydroxide Formula

Last updated date: 17th Jul 2024
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Chemical Formula of Aluminium Hydroxide

Gibbsite (also known as hydrargillite) and its three rarer polymorphs bayerite, doyleite, and nordstrandite are all examples of aluminium hydroxide, Al(OH)3. Aluminium hydroxide is amphoteric, which means it may be both basic and acidic. Aluminium oxide hydroxide, AlO(OH), and aluminium oxide or alumina (Al2O3), which is likewise amphoteric, are closely related. The primary components of the aluminium ore bauxite are these chemicals.

Aluminum Hydroxide Chemical Formula

The chemical formula of aluminium hydroxide/molecular formula of aluminium hydroxide is Al(OH)3.

Structure Formula of Aluminium Hydroxide  

Al(OH)3 is made up of two layers of hydroxyl groups, with aluminium ions filling two-thirds of the octahedral holes in between. There are four polymorphs that have been identified. Layers of octahedral aluminium hydroxide units with hydrogen bonds between them are present in all of them. The layers are stacked differently in the polymorphs. Al(OH)3 crystals are hexagonal in all their forms.

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As we have already discussed the chemical formula for aluminium hydroxide. Lets see the structure formula for aluminium hydroxide.


The Bayer method, which includes dissolving bauxite in sodium hydroxide at temperatures up to 270 °C (518 °F), produces about all of the aluminium hydroxide used commercially. Bauxite tailings are removed, and aluminium hydroxide is precipitated from the sodium aluminate solution that remains. Calcination can turn this aluminium hydroxide into aluminium oxide or alumina.

Due to residual sodium hydroxide, the residue or bauxite tailings, which is primarily iron oxide, is highly caustic. It was formerly stored in lagoons, which resulted in the Ajka alumina factory tragedy in Hungary in 2010, when a dam burst and nine people drowned. A further 122 people were treated for chemical burns. The muck covered 40 square kilometres (15 square miles) of land and made its way to the Danube. Despite the fact that the mud was deemed non-toxic due to low levels of heavy metals, the slurry it was mixed with had a pH of 13.

Applications of Aluminium Hydroxide 

1. Fire Retardant Filler 

Aluminium hydroxide is also used in polymer applications as a fire retardant filler. Because it is colourless (like other polymers), affordable, and has high fire retardant qualities, it is used for these applications. Huntite and hydromagnesite combinations, as well as magnesium hydroxide, are employed in the same way. It decomposes at around 180 °C (356 °F), absorbing a lot of heat and releasing water vapour in the process. It is exceptionally effective as a smoke suppressant in a wide range of polymers, including polyesters, acrylics, ethylene vinyl acetate, epoxies, PVC, and rubber, in addition to acting as a fire retardant.

2. Precursor to Al Compounds 

Aluminium hydroxide is used to make speciality calcined aluminas, aluminium sulphate, polyaluminium chloride, aluminium chloride, zeolites, sodium aluminate, activated alumina, and aluminium nitrate, among other aluminium compounds.

Aluminium hydroxide that has been freshly precipitated creates gels, which are the basis for using aluminium salts as flocculants in water purification. With time, this gel crystallises. Dehydrating aluminium hydroxide gels (for example, using water-miscible non-aqueous solvents like ethanol) yields an amorphous aluminium hydroxide powder that is acid soluble. It is transformed into activated aluminas by heating, which are employed as desiccants, adsorbents in gas purification, and catalytic supports.

3. Pharmaceuticals 

  • In both humans and animals, aluminium hydroxide is utilised as an antacid (mainly cats and dogs). It is recommended over other options such as sodium bicarbonate because Al(OH)3 is insoluble and hence does not raise the pH of the stomach over 7 and thus does not cause the stomach to secrete excess acid. Alu-Cap, Aludrox, Gaviscon, and Pepsamar are some of the brand names. It reacts with excess acid in the stomach, lowering the acidity of the stomach contents and perhaps alleviating ulcer, heartburn, and dyspepsia symptoms.

  • This molecule is also used to treat hyperphosphatemia (high blood levels of phosphate, or phosphorus) in people and animals with kidney failure. Excess phosphate is normally filtered out of the blood by the kidneys, but renal failure can cause phosphate to build up. When consumed, the aluminium salt binds to phosphate in the intestines, reducing the amount of phosphorus that may be absorbed.

  • Some vaccinations contain precipitated aluminium hydroxide as an adjuvant (e.g. anthrax vaccine). Brenntag Biosector's Alhydrogel is one of the most well-known brands of aluminium hydroxide adjuvant. Because it absorbs protein effectively, it helps to stabilise vaccines by preventing vaccine proteins from precipitating or clinging to the container walls during storage. Aluminium hydroxide is sometimes referred to as "alum," a name that refers to any of numerous sulphates.

  • Aluminium hydroxide in vaccine formulations stimulates the immune system by causing the release of uric acid, an immunological danger signal. Certain types of monocytes that develop into dendritic cells are attracted to this. The antigen is picked up by dendritic cells, which transport it to lymph nodes and excite T and B cells.


Aluminium hydroxide is an inorganic chemical with amphoteric characteristics, meaning it can function as both an acid and a base. An aluminium cation and three hydroxyl anions make up the aluminium hydroxide molecule. Its molar mass is 78.00 g/mol, and the structure of its lattice depends on the mineral from which it is derived. Aluminium Hydroxide offers a number of advantages and is commonly employed as an organic synthesis intermediary and as a medicinal ingredient. Aluminium hydroxide is used as a flame retardant, a glass additive, and other applications in the chemical industry.

Two layers of hydroxyl groups make up Al(OH)3, with aluminium ions filling two-thirds of the octahedral holes in between. A total of four polymorphs have been discovered. All of them have layers of octahedral aluminium hydroxide units with hydrogen bonds between them. In polymorphs, the layers are arranged differently. In all of their forms, Al(OH)3 crystals are hexagonal.

FAQs on Aluminium Hydroxide Formula

1. What is The Chemical Formula of Aluminium Hydroxide? How is It Produced?

Ans: The formula of aluminium hydroxide is Al(OH)3. It is done by dissolving bauxite in sodium hydroxide solution at a temperature of up to 270 degrees Celsius. The sodium aluminate solution is allowed to precipitate once the garbage is removed. As a result, aluminium hydroxide is the precipitate formed.

2. What is the pH of Aluminium Hydroxide? Is it an Acid or a Base?

Ans: Gibbsite (also known as hydrargillite) and its three rarer polymorphs bayerite, doyleite, and nordstrandite are all examples of aluminium hydroxide, Al(OH)3. Aluminium hydroxide is amphoteric, which means it may be both basic and acidic.

3. Is Aluminum Hydroxide a Toxic Substance?

Ans: Aluminium hydroxide's hazardous consequences include seizures, osteomalacia, and encephalopathy. Before administering aluminium hydroxide, patients should be questioned if they have any kidney problems, as these outcomes are strongly linked to the use of aluminium hydroxide as a phosphate binder in dialysis patients.