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.