Alum (Ferric / Non Ferric )

Alums are useful for a range of industrial processes. They are soluble in water, have an astringent, acid, and 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.



Uses:

Industrial use:

Alum is also used in purification of drinking water in industries. In a holding tank, some alum (phitkari) is added to the water so that the negatively charged light colloidal parts stick together and get heavy (flocculate) when alum makes the colloidal particles neutralized by making its aluminum ions get loaded with the colloidal parts. When the colloidal parts get heavy they can be easily separated from the tank prior to further filtration and disinfection of the water.

Cosmetic:

• Alum in block form (usually potassium alum) is used as a blood coagulant.
• Styptic pencils containing aluminium sulphate or potassium aluminium sulphate are used as astringents to prevent bleeding from small shaving cuts.