DETERMINE THE MASS OF ALUM CRYSTALS

    INTRODUCTION

Aluminium because of its low density, high tensile strength and resistance to corrosion is widely used for the manufacture of airplanes, automobiles, lawn furniture as well as for aluminium cans. Being good conductor of electricity, it is also used for transmission of electricity. Aluminium foil is used for wrapping cigarettes, confectionery items, etc. 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 where,

X = monovalent cation such as Na⁺, K⁺, NH⁴⁺, etc.

M = trivalent cation such as Al⁺³, Cr⁺³, Fe⁺³, etc.

Some important alums and their names are given below:

Potash Alum: K₂SO₄.Al₂(SO₄)₃.24H₂O

Soda Alum Na₂SO₄.Al₂(SO₄)₃.24H₂O

Chrome Alum K₂SO₄.Cr₂(SO₄)₃.24H₂O

Ferric Alum (NH₄)₂SO₄.Fe₂(SO₄)₃.24H₂O

Alums are isomorphous crystalline solids, which are soluble in water. Potash alum is used in paper making, in fire extinguisher, in foodstuffs and in purification of water. Soda alum is used in baking powders and chrome alum is used in tanning leather and waterproofing fabrics. Ferric alum is used in antiseptics. The shape of a potash alum crystal is octahedral.