This section is from the "A Handbook of Useful Drugs" book, by State Medical Examining and Licensing Boards.
Crystallized potassium aluminum sulphate, A1K(S04)2 12H20.
Properties : Alum occurs as colorless crystals or a white powder without odor, but having a strongly astringent taste. It is freely soluble in water, practically insoluble in alcohol. It contains about 45 per cent. of water of hydration, which can be removed by heat, the product being exsiccated alum.
Incompatibilities: Alum is incompatible with alkalies and carbonates, which react with it with the formation of insoluble aluminum hydroxid. It is also incompatible with salts of lead because it precipitates the insoluble lead sulphate.
Action and Uses : Alum is astringent, styptic and hemostatic, but is seldom administered internally.
Dosage: Alum solution may be used as a gargle (from 1 to 5 per cent.) but it is somewhat injurious to the teeth; it may be given as an injection in gonorrhea (from 0.5 to 1 per cent.) and as a lotion in skin diseases (1 per cent.).