decomposed by sulphate of lime, hard water may be safely used for its solution. It has the effect of retarding, and in some instances of preventing, the acetous fermentation in vegetables; thus when added to common _paste_ it prevents its becoming sour; animal substances, as _glue_, are preserved by it in a similar manner. It has also the property of clearing turbid water, wine, and spirituous liquors, for which purpose it is extensively employed. OFFICINAL PREPARATIONS. _Liquor Alum: co._ L. _Pulv: Alum: co._ E. ALUMEN EXSICCATUM, L. Ustum. D. _Dried Alum._ By the action of heat alum undergoes watery fusion, yields its water of crystallization, and loses more than one third of its weight; if the heat be too intense, or long continued, it is deprived of a great part of its acid. It has been recommended in doses of a scruple, in cholic, when it has been said to operate gently upon the bowels, and to relieve the pain: I have myself experienced this good effect when the cholic has been produced by the action of lead: Dr. Grashuis, a Dutch Physician, first recommended its use in Cholica Pictonum. The preparation however is principally used as an external application, having a degree of escharotic power, which renders it serviceable in venereal chancres, as well as in other ulcers having weak and spongy granulations; it is also very frequently employed to destroy fungous excrescencies, but it should be remembered that, as it owes such power to an excess of acid, unless it be carefully prepared, it must be inefficient. It ought to redden syrup of violets. ALUMEN RUPEUM. _Roche_ or _Rock Alum_. This variety was originally brought from Roccha, formerly called Edessa, in Syria, in fragments of about the size of an almond, covered with an efflorescence of a pale rose colour; that however which is now sold under this name is common English alum, artificially coloured. It is unimportant. ALUMEN ROMANUM. _Roman Alum_ is in irregular octohedral masses, powdery on the surface; it is the purest kind, and contains no ammonia in its composition. AMMONIACUM. L.E.D. (_Heracleum Gummiferum._) Ammoniac.