370

ELEMENTS OF MATERIA MEDICA.

lips, alumina to be a protoxide of aluminum, and that its equivalent is 18.Berzelius and Turner regard it as a sesquioxide, and adopt 5T4 as itsequivalent. According to the views of the latter chemists the equivalent

for alum (KS + A1 S 3 -f- 25 h) is 474'95.

Purity. —Alum should be colourless, completely soluble in water (bywhich the absence of uncombined earthy matter is shewn), with a solutionof caustic potash or ammonia should form a colourless precipitate ofhydrate of alumina soluble in excess of alkali, and should not suffer anychange of colour by the addition of tincture of nutgalls or hydrosulphuricacid. The ferro-sulphate of potash, sometimes mixed with alum, cannotbe distinguished from the latter, by its form, colour, or taste ; but isreadily detected by potash, which throwsdown oxide of iron, and by tinc-ture of nutgalls, which communicates a bluish black colour to it.

Physiological Effects, (a.) On vegetables. —Alum is probably inju-rious to plants. (Decandolle, Physiol. Veg'et. 1341).

(b.) On animals. —Dogs support large doses of alum with impunity.Orfila {Ann. d’Hyg.Publiq. et de Med. Leg. i. 235) gave seven drachms ofcrystallized alum in powder to dogs : the animals retained it for from tento thirty minutes, then vomited, and in an hour or two were apparentlywell. Two ounces of burnt alum in four ounces of cold water occa-sioned vomiting only. When the oesophagus was tied to preventvomiting, death took place in five hours with symptoms of great ex-haustion and diminished sensibility. On a post-mortem examinationthe mucous membrane of the stomach was found inflamed in the whole ofits extent. One ounce of finely-powdered burnt alum applied to thesubcutaneous cellular tissue of the thigh, caused excessive suppurationand death in fifteen hours. Devergie (Med. Legale, ii. 653) found burntalum somewhat more active: he says Of drachms killed a dog when theoesophagus was tied, and 2 ounces when it was not tied. Moreover, hefound burnt alum suspended in cold water, more active than when dis-solved in warm water. Veterinarians employ it in doses of from 1 to 6drachms for large animals. Bourgelat lias seen a phthisical conditioninduced in horses by the use of alum in too great quantities. (Moiroud,Pharm. Veter. 225.)

(c.) On man. —-Tlie immediate topical effect of a solution of alum isthat of an astringent, namely, corrugation of fibres and contraction ofsmall vessels, by virtue of which it checks or temporarily stops exhala-tion and secretion, and produces paleness of parts by diminishing thediameters of the small blood-vessels. It is by these local effects thatalum, when taken internally, causes dryness of the mouth and throat,somewhat increases thirst, checks the secretions of the alimentary canal,and thereby diminishes the frequency and increases the consistency ofthe stools, as observed by Wibmer ( die Wirkung, &c. i. 114) in his expe-riments made on himself, with alum in doses of 3 grains dissolved in 5drachms of water, and taken several times during the day.

But when alum is applied to a part in larger quantities, and for alonger period, the astriction is soon followed by irritation, the palenessby preternatural redness. And thus taken internally in large doses, alumexcites nausea, vomiting, griping, purging, and even an inflammatorycondition of the intestinal canal,—effects which may be perhaps inducedby small quantities in persons endowed with unusual or morbid sensibi-