Alum is the sulphate of aluminum and potash and has a crystalline form and a taste which is both acid and sweetish, and also astringent. It is soluble in water, but insoluble in alcohol.

Physiological Actions

Alum is an astringent and styptic. In doses of ʒ i. it is an irritant but non-depressing emetic, and in large doses a purgative. Taken into the mouth, the flow of saliva is first increased by alum, and afterwards diminished, as it hardens the albumin of the secretions and contracts the capillaries.

The same effect is shown on the mucous membrane of the stomach. Alum is absorbed into the blood, notwithstanding its power of coagulating albumin, and checks capillary haemorrhage by constricting the vessels. Alum should always be given alone, and it is to be remembered that it has a very injurious action on the teeth.

Symptoms Of Poisoning

In large doses alum produces gastro-enteritis, with frothing at the mouth. The treatment consists in promoting vomiting and washing out the stomach, giving magnesium hydrate in large quantities, or a weak solution of ammonium carbonate at intervals. Death has been caused in eight hours in an adult by ℥ ii. of alum.

Preparations Of Alum

Alumini Hydroxidum. Aluminum Hydroxide

The average dose of alum is gr. viii.-0.5 Gm. Any preparation should be taken through a tube.

Alumen Exsiccatum. Exsiccated Alum

Alum which has been deprived of its water by heat, and powdered. Combined with alcohol (in which it is insoluble), in the proportion of ʒ i.-iv. to alcohol ℥ v.-vi., it is used to harden the skin, as a preventive of bed-sores.