Aluminum

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Aluminum

This is aluminum.

Symbol Al
Atomic number 13
Atomic mass 26.9815 amu

Aluminum was discovered in 1827. It is a soft, light, silvery-coloured metal. Its surface has a strongly adhering layer of oxide which protects the metal from corrosion. Aluminum is the third most abundant element in the earth's crust after oxygen and silicon.

Distinguishing properties

One of the metal's most valuable properties is its corrosion resistance. This, together with its light weight, makes it an ideal construction material for the building and the automotive industries. An electrolytic process called anodizing can increase the corrosion resistance of the metal. The electrical conductivity is about two-thirds of copper, making it economical for power transmission. Other uses of aluminum include its use as

Occurrence

Aluminum occurs in the mineral bauxite (a mixture of the oxides of aluminum, iron and silicon. Bauxite occurs in large quantities in tropical and sub-tropical countries.

Usage

The Aluminum Company of Canada (ALCAN) obtains most of its supply of raw material from Jamaica in the form of alumina (Al2O3).

Ruby

Ruby belongs to the mineral family corundum. The beauty of ruby lies in the richness and intensity of its colour. Ruby crystals are usually flat. The finest ruby crystals are from the gem deposits of Mogok, Burma.

Small quantities of chromium give rise to the red colour of ruby.

Sapphire

Sapphire belongs to the mineral family corundum. The crystals are shaped like barrels. They feature zones of blue to yellow colour. Australia is the most abundant source of blue and yellow sapphires. Sri Lanka had been the supplier for blue and pink sapphires for at least 2000 years.

Tiny quantities of iron and titanium are responsible for the blue, yellow, and green of sapphire.

Common compounds

Aluminum chloride (AlCl3)

Used as a catalyst in the manufacture of synthetic rubbers in the U.S. during World War II.

Aluminum chlorohydrate (AlCl3)

H2O, a topical antiperspirant or body deodorant which acts by constricting the pores, thus inhibiting water loss.

Aluminum fluoride (AlF3)

An additive to the molten electrolyte of the aluminum production cell in order to lower the melting point and increase the electrical conductivity.

Aluminum hydroxide (Al(OH)3)

Used as a foaming agent in fire extinguishers and as a mordant in dyeing.

Corrundum, aluminum oxide (Al2O3)

One of the hardest minerals. Gemstones such as ruby and sapphire are essentially aluminum oxide with appropriate doping with other metals. These gemstones are used as laser crystals and in other solid state devices.

Aluminum sulfate (Al2(SO4)3)

Used in sizing and coating papers, as a flocculating agent in the purification of water and sewage, and as mordant in texture dyeing.

See also

Periodic table of the elements