Lastly, we find, in the "Experiments and Observations" published by Poerner, a creditable German writer, in 1772, that a watery decoction, made of the resinous gum of the aloe, without any farther addition, produces a beautiful dark cherry-brown colour on woollen-cloth, by simple immersion. This fact may be easily ascertained by dyers.
Alopecurus pratensis, L. See Meadow Fox-tail.
Alopecurus agrestis, L. See Slender Fox-tail.
Alsine media, L. See Common Chickweed.
Althæa officinalis, L. See Marshmallow.
ALUM is a concrete salt, transparent, and of a very austere and astringent taste. It is in general a chemical preparation, being rarely found in a natural state, or freed from other ingredients. In Egypt, Sardinia, Spain, Bohemia, &c. it is said to be sometimes discovered in crystals.
There are various kinds, but that which is called the Roman alum, is preferable to any other. This is usually to be found in small crystals, and of a reddish colour, probably owing to a small quantity of calx of iron, which, however, does not in the least impair its qualities. The other kinds contain a proportion either of vitriolated tartar, or sal ammoniac.
In medicine, it has been considered as an astringent, and is of great service in restraining hemorrhages, and other immoderate secretions. It is likewise externally used in lotions and eye-waters: and one scruple of burnt alum has been found beneficial in removing violent colic-pains arising from flatulency, bile, or great relaxation of the bowels; but in other cases it may prove hurtful.
It is used for various purposes by dyers, to fix different colours upon cloth; in the making of candles, to give them a gloss and firm consistence; wood soaked in a solution of alum, does not readily take fire; and paper impregnated with it, is the most proper for the preservation of gunpowder, as it also excludes the moisture of the air. Tanners employ it to restore the cohesion of those skins which have been almost entirely destroyed by lime; and vintners in fining their wines, &c. Fishermen dry their cod-fish by means of it; and it is asserted, that bakers generally use it as an ingredient in bread: the truth of this assertion, however, has been much questioned, and the sole reason ascribed for its use, is, that corrupt flour, being mixed with good, thus acquires a proper degree of cohesion, as the aluminous particles equally pervade the whole mass, and render it of a due consistence. Although some writers have maintained, that this styptic salt "is entirely innocent, and now seldom used" in the process of making bread, yet we have but too much reason to believe the contrary. The English translator of Tissot's excellent "Advice to the People in general," &c. very pertinently remarks, that the abuse of alum, and other pernicious materials, introduced by our bakers, may too justly be considered as one lamentable source of the numerous diseases of children. The Monthly Reviewer of that book, or July 1765, adds, with equal justice, the following commentary: 'Hence obstructions in the bowels
