Aluminium because of its low density, high tensile strength and resistance and resistance to corrosion is widely used for the manufacture of aeroplanes, automobiles lawn furniture as well as for aluminium cans. Being good conductor of electricity it is used for transmission of electricity. Aluminium is also used for making utensils. The recycling of aluminium cans and other aluminium products is a very positive contribution to saving our natural resources. Most of the recycled aluminium is melted and recast into other aluminium metal products or used in the production of various aluminium compounds, the most common of which are the alums. Alums are double sulphates having general formula X2SO4.M2(SO4)3.24H2O Introduction
Some important alums and their names are given below:
K2SO4.Al2(SO4)3.24H2O - Potash Alum
Na2SO4.Al2(SO4)3.24H2O - Soda Alum
K2SO4.Cr2(SO4)3.24H2O - Chrome Alum
(NH)2SO4.Fe2(SO4)3.24H2O - Ferric Alum
Potash alum is used in papermaking, in fire extinguishers in food stuffs and in purification of water soda alum used in baking powders and chrome alum is used in tanning leather and water proofing fabrics. In addition Lo these primary uses, alum is also used as
(i) on mirin^m A substance or preparation, that draws together or constricts body tissues and is effective in stopping the How of blood or other secretions Alum has also been used by conventional hairdressers for treating shaving cuts, (ii) a mordant Substances used in dyeing lo fix certain dyes on cloth. Hilher lhe mordant (If it is colloidal) or a colloid produced by the mordant adheres to the fiber, attracting and fixing the colloidal mordant dye. The insoluble, colored precipitate that is formed is called a lake! Alum is a basic mordant used for Fixing acid dyes (iii) for the removal of phosphate from natural and waste waters The alumi num ions of alum combine with the orihophosphaic around pH 6 to form Ihc...