Derivation.—From alum slate, shale, schist, a native mixture of aluminum silicate and iron sulphide. This is roasted and exposed to the air, when the sulphur is oxidized into sulphuric acid and combined in part with aluminum and iron to form sulphates. The mass is lixiviated with water, and aluminum and iron sulphates together with sulphuric acid are recovered in solution. The solution is concentrated and to it is added potassium chloride. The double sulphate of potassium and aluminum (alum) is formed, which crystallizes out on cooling, while potassium sulphate and ferric chloride remain as by-products. Alum is purified by recrystallization.

Properties.—Large, colorless, octahedral crystals, sometimes modified by cubes or crystalline fragments; without odor, but having a sweetish and strongly astringent taste. On exposure to the air the crystals are liable to absorb ammonia and acquire a whitish coating. Soluble in nine parts of water, insoluble in alcohol.

Dose.—Horses and cattle, 2 to 4 dr.; sheep and pigs, 20 gr. to 1 dr.; emetic for dogs, ¹/₂ to 1 dr.

ALUMEN EXSICCATUM—DRIED ALUM

Commonly termed burnt alum, is alum deprived of its water of crystallization by heat.

Properties.—A white granular powder, odorless, having a sweetish astringent taste, soluble in twenty parts of water at 60° F. Is a powerful astringent and escharotic.

ALUMINI HYDROXIDUM—ALUMINUM HYDROXIDE

Derivation.—Made from alum, 100 parts; monohydrate sodium carbonate, 43 parts; water, a sufficient quantity. Mix hot, boiling solutions of alum and sodium carbonate. Precipitate strained, washed and dried.

Properties.—A white, light, amorphous powder; odorless and tasteless; permanent in dry air; insoluble in water or alcohol.

Dose.—Same as alum.

ALUMINI SULPHAS—ALUMINUM SULPHATE

Derivation.—Aluminum hydroxide is dissolved in diluted sulphuric acid, and the solution is filtered and evaporated to dryness.

Properties.—A white, crystalline powder, without odor, having a sweetish and afterwards astringent taste; permanent in the air; soluble in one part of water; insoluble in alcohol.

Dose.—Same as alum.

Actions.—Astringent, at first excites flow of saliva, then markedly decreases it; coagulates pepsin, thus it would derange or entirely arrest digestion; it also stops peristalsis and produces constipation, though sometimes it induces diarrhoea by irritation. It arrests secretions in general and in the circulation contracts the capillaries; it is in this way it arrests secretions, especially those of mucous surfaces, and stops capillary hemorrhage. The sulphate of aluminum is mildly caustic, astringent and antiseptic. Dried alum is caustic and astringent.

Externally.—Dried alum is a caustic, in contact with raw sores, on account of its affinity for water. Alum has no action on unbroken skin, but applied to mucous membranes or denuded parts it is antiseptic and astringent; coagulates albumin of discharges; precipitates or coagulates albumin of the tissues; squeeze blood out of the vessels; reduces inflammation and makes the part whiter, brings together and denser. Alum is a hemostatic, stopping bleeding by compression of the structures surrounding the vessels and by causing blood to clot.

Uses.—In diarrhoea and dysentery, but other astringents are safer and better, as it may lock the bowels too tight, may be used in weeping sores or weeping skin diseases; in long standing nail wounds by putting one-half to one pound into the soaking tub, also in same way for injured coronets, with raw bulging surfaces that bleed easily, also for sore mouth, sometimes mix a little boric acid; useful in bleeding piles, and in mild solution alum one ounce to water one pint for sore throat; also used internally for bloody urine (haematuria) and for open joints apply the powdered alum to arrest the flow of joint oil (synovia). For catarrhal ophthalmia, after the acute stage, an alum lotion five grains to one ounce of water is very serviceable; for granular lids rub with a crystal of alum. Alum should never be used too strong over the eye as it seems to have the power of dissolving the cornea; a solution containing ten grains of alum to the ounce of water may be used in canker of the ear of dogs; also for leucorrhoea and prolapsus of the rectum; dried alum may be used as a caustic whenever a caustic is indicated, but is not recommended for this purpose. For a powerful drying powder, especially useful when excessive granulation exists. It causes sloughing of the dead tissues and is indicated when the use of the knife is inadmissible.