Materia Medica.

part II.

fixed oils and resins miscible with water, forming a white opaquemixture. Concentrated sulphuric acid blackens, and partiallydecomposes it, and acetic acid is produced : strong nitric acidconverts it into the oxalic, malic, and saccholactic acids; muria-tic exerts very little action on it; but the oxymuriatic changesit into citric acid. Solutions of the alkalis and alkaline earthsdissolve it without producing on it much change. For an ac-count of the action of other agents on it, see Mucilago acacia;.

The chemical analysis of gum, by Gay Lussac and Thenardshows, that its constituents are 42,23 of carbon, 6,93 of hydro-gen, and 50,82 of oxygen, v.ith a small proportion of ni-trogen and lime : which last element is supposed to render itincapable of undergoing the fermentative process. '

Medical 'properties. — Gum exerts no action on the living sys-tem *; but is a simple demulcent, serving to lubricate abradedsurfaces, and involve acrid matters in the prima? vias. In thesolid form it is scarcely ever given, unless to sheath the fauces,and allay the tickling irritation which occasions the cough in ca-tarrh and phthisis pulmonalis; in which cases a piece of it is al-lowed to dissolve slowly in the mouth. It is chiefly used in thestate of mucilage. Vide Mucilago acacia;.

Officinal preparations. Mucilago acacice. L. E. D. Emulsio aca-cia: Arabiccc. E. Emulsio arabica. D. Troc. gummosi. E.

ACETOS.E FOLIA. Vide Rumex Acetosa.

ACETOSELLA. Vide Oxalis Acetosella.

ACETUM. Land. Edin. Acetum Vini. Dub. Vinegar.

Syn. Vinaigre (F.) Fss'u (G.) Aceto (I.) Vinigre $.) Khull (Arab.) Ciiaoca (Malay.)

This is a well known acid liquor, produced by exciting theacetous fermentation in substances which have undergone, orare susceptible of, the vinous fermentation. Sugar and water,the saccharine vegetable juices, infusions of malt, malt liquors,cyder, and wine', may be converted into vinegar, by adding tothem yeast or any other ferment, and exposing them in vesselsto which the air has access, in a temperature between 75° and90°. In wine countries, as France and Italy, vinegar is madefrom the lees of wine, which are worked up with new wine, thenstrained, and exposed to the heat of the sun, or placed in stovedrooms, in casks set upright, with a hole cut through the head-ing, and left open until the whole of the liquor is thoroughlyacidified. In this country it is prepared chiefly from malt. Aninfusion of malt is made, then properly cooled, and put intolarge and deep fermenting tuns ; " where it is mixed with yeast,

i Murray's Chemistry, vol. iv. 180. The last analysis, which is by BerzeUns, makesthe components in 100 part? to be, Hydrogen 6,792, carbon 41,752, and oxygen 51,456.z It ib sometimes used a:, fo id by the Moors.3 New wines are better lor this purpose than old, as they contain more extractive matter.