metallurgy

METALLURGY

ALUMINIUM :

EXTRACTION OF ALUMINIUM :

Aluminium is the most abundant element next to oxygen and silicon. It is the most abundant metal of about 7.2% on the earth's crust. It was first isolated by Wohler in 1827. It was obtained by the electrolysis of bauxite by Charles martin hall in 1886.

Occurrence :

Bauxite, Cryolite and Corundum are the three minerals of aluminium. Bauxite is the ore and is extracted by the purification and electrolytic reduction.

Purification by Bayer's process :

The bauxite ore is powered and digested with a solution of caustic soda at 150°C in an autoclave under high pressure. Finally as the end of the reaction pure alumina is produced.

Electrolytic reduction :

Molten alumina is dissolved in molten Cryolite in a cast iron tank lined with a layer of graphite. A bunch of graphite rods are suspended in the molten Cryolite is the anode. This reaction take place at 900-950°C. The oxygen gas evolved burns the graphite rods away.

Physical properties of aluminium :

Aluminium is a silvery white metal of light density (2.7gm/cm³).It is metal having high tensile strength and melting point of 660°C.

Uses of Aluminium :

Aluminium is used in making electric cables, utensils, airplane parts, silver paints, fireworks, flashlight powders and explosives.

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