Aluminum Oxide

It’s time that we take a deeper look into one of the inorganic compounds like aluminum oxide. It is also known as aluminum oxide and usually comes in the crystalline powdery form. It is insoluble to water, and both chemical and physical properties vary based on the method of preparation. The crystalline modifications are based on the different methods of preparation. Whatever varieties are formed, very high temperatures are applied to become chemically inert. 

Chemical and Physical Properties






15 – 19 GPa

Mechanical Strength

300 – 630 MPa

Compressive Strength

2,000 – 4,000 MPa

Melting Point

2,072°C (3,762°F, 2,345°K)

Boiling Point

2,977°C (5,391°F, 3,250°K)

Electrical Resistivity

1012 – 1013 Ωm

Thermal Conductivity 

20 -30 W/mK

Molecular mass

101.96 g/mol



What is the Formula of Aluminum Oxide?

The chemical formula for Aluminum oxide is Al2O3. Being amphoteric, it is used in multiple, industrial, chemical, and commercial applications. Also, it is considered as an indirect additive and, thus, used in food substances, which are further approved by the FDA.

Uses to Aluminum Oxide

Most people, when they hear about Aluminum, they think about the foils that are used to cover cooked dishes. In terms of chemical compound – aluminum oxide, it is not familiar with the previous concept. It is a chemical compound, and the same is ionic in nature. The structure has a metal (aluminum) in it along with non-metal (oxygen). As ionic compounds have occurred between metals and non-metals, it involves the exchange the electrons between both the atoms. The metal atom always promotes electrons, and non-metal form provides an ionic bond. 

When it comes to aluminum, it forms an ion with a charge of +3 and thus, forms an ion with an oxygen atom that always ends in forming an ion with a charge of -2. Now, the overall charge of a compound must end in zero, being neutral and, thus, requires two atoms of aluminum and three atoms of oxygen. This balances the charge, and the make the compound neutral. Therefore, the chemical formula for aluminum oxide is Al2O3.


How is Aluminum Oxide Produced?

Aluminum oxide is produced through the Bayer process. It is a process where bauxite is refined to form alumina. The process starts with drying and washing crushed bauxite that contains 30 - 55% of Al₂O₃. The crushed bauxite is formed into slurry by dissolving in caustic soda. Heated temperature is applied that ranges from 230 – 520 degrees Fahrenheit (110 -270 degrees Centigrade). Forming the mixture, it contains a residue called red mud impurities. These impurities are then flittered to come up with an alumina solution. This solution is chemically known as aluminum hydroxide, which is then transferred to a precipitator tank. This tank helps in the cooling and seeding process. The precipitation process allows the seeds to stimulate and forms solid and crystalized aluminum hydroxide. The aluminum hydroxide that settles at the bottom of the tank is then removed. The caustic soda that remains in the mixture is washed properly through several filtration processes. The final stage includes heating the mixture to completely remove any existence of water. It is then passed through a cooling process to form fine white powder in the form of aluminum oxide.

FAQ (Frequently Asked Questions)

1. What is the use of Aluminum Oxide?

Aluminum is known for its strength and hardness. Therefore, it is usually used as abrasives and less expensive substitutes for industrial diamonds. There are different types of sandpapers available that used crystals of aluminum oxide.

2. What is the Formula of Aluminum Oxide?

The formula of Aluminum oxide is Al2O3. This is because it forms an ion with a charge of +3 along with oxygen ion atom. This always ends in forming an ion with a charge of -2. Now, the overall charge of a compound must end in zero, being neutral and, thus, requires 2 atoms of aluminum and 3 atoms of oxygen. This balances the charge, and makes the compound neutral.

3. Is Aluminum Oxide Toxic to Humans?

Aluminum oxide is less toxic when compared with other compounds. However, the toxicity can become higher with greater concentrations.

4. Is Aluminum Oxide Acidic or Basic?

Aluminum oxide is an amphoteric oxide. This indicates that it can be used both as a base and an acid.