Alum also called Potash Alum is a colorless soluble hydrated double sulphate of aluminium and potassium used in manufacturing of mordants and pigments, in dressing leather and sizing paper, and in medicine as a styptic and astringent.
It is uselful for various industrial processes. It is soluble in water, have a sweetish taste, react acid to litmus and crystallize in regular octahedra. When heated they liquefy; and if the heating is continued, the water of crystallization is driven off, the salt froths and swells, and at last an amorphous powder remains. They are astringent and acidic.
Alum is essentially aluminium sulphate with the empirical formula Al2 (SO4)3.18HO.
It is of two types (i) Ferric and (ii) Non Ferric.
Non ferric alum imparts better brightness to paper when used with rosin for sizing. It forms a complex resinate that spreads evenly over the surface of paper. It finds other uses in pharmaceutical and mordanting industry. In water purification the highly positively charged aluminum precipitates negative suspensions as sludge.
Ferric alumis a less pure form of aluminum sulphate. It is used in lower grades of paper for loading and sizing purposes. Ferric alum uses bauxite as the raw material. The raw material is cooked with sulphuric acid under suitable conditions. The resultant product is sold in liquid form.
Uses

• Used in purification of drinking water and industrial process water.
• Alum solution has the property of dissolving steels while not affecting aluminium or base metals, and can be used to recover workpieces madein these metals with broken toolbits lodged inside them.
• Alum in block form can be used as a blood coagulant.
• Alum is also used in depilatory waxes used for the removal of body hair or applied to freshly waxed skin as a soothing agent.
• Alum’s antiperspirant and antibacterial properties contribute to its traditional use as an underarm deodrant.
• Alum powder, found in the spice section of many grocery stores, may be used in pickling recipes as a preservative to maintain fruit andvegetable crispness.
• Alum is used as the acidic component of some commercial baking powders.
• Solutions containing alum may be used to treat cloth, wood, and paper materials to increase their resistance to fire.
• Alum is also used in fire extinguishers to smother chemical and oil fires.
• Alum is used in the tanning of animal hides to remove moisture, prevent rotting, and produce a type of leather.

 Alum also called Potash Alum is a colorless soluble hydrated double sulphate of aluminium and potassium used in manufacturing of mordants and pigments, in dressing leather and sizing paper, and in medicine as a styptic and astringent.
It is uselful for various industrial processes. It is soluble in water, have a sweetish taste, react acid to litmus and crystallize in regular octahedra. When heated they liquefy; and if the heating is continued, the water of crystallization is driven off, the salt froths and swells, and at last an amorphous powder remains. They are astringent and acidic.
Alum is essentially aluminium sulphate with the empirical formula Al2 (SO4)3.18HO.
It is of two types (i) Ferric and (ii) Non Ferric.
Non ferric alum imparts better brightness to paper when used with rosin for sizing. It forms a complex resinate that spreads evenly over the surface of paper. It finds other uses in pharmaceutical and mordanting industry. In water purification the highly positively charged aluminum precipitates negative suspensions as sludge.
Ferric alumis a less pure form of aluminum sulphate. It is used in lower grades of paper for loading and sizing purposes. Ferric alum uses bauxite as the raw material. The raw material is cooked with sulphuric acid under suitable conditions. The resultant product is sold in liquid form.
Uses

• Used in purification of drinking water and industrial process water.
• Alum solution has the property of dissolving steels while not affecting aluminium or base metals, and can be used to recover workpieces madein these metals with broken toolbits lodged inside them.
• Alum in block form can be used as a blood coagulant.
• Alum is also used in depilatory waxes used for the removal of body hair or applied to freshly waxed skin as a soothing agent.
• Alum’s antiperspirant and antibacterial properties contribute to its traditional use as an underarm deodrant.
• Alum powder, found in the spice section of many grocery stores, may be used in pickling recipes as a preservative to maintain fruit andvegetable crispness.
• Alum is used as the acidic component of some commercial baking powders.
• Solutions containing alum may be used to treat cloth, wood, and paper materials to increase their resistance to fire.
• Alum is also used in fire extinguishers to smother chemical and oil fires.
• Alum is used in the tanning of animal hides to remove moisture, prevent rotting, and produce a type of leather.