"Take of acacia, powdered, ten ounces; boiling water, a pint. Rub the acacia with the water gradually poured in, and dissolve it."

Mucilago Acaciae Arabicae2, Edin. Mucilage of Gum Arabic.

"Take of gum arabic, in powder, one part; boiling water, two parts. Digest with occasional agitation until the gum be dissolved; then strain the mucilage through linen."

Mucilago Gummi Arabici, Dub. Mucilage of Gum Arabic.

"Take of gum arabic, in coarse powder, four ounces; boiling water, eight ounces. Digest with frequent agitation, until the gum be dissolved; then strain the mucilage through linen."

Syn. Mucilage de Gomme Arabique (F.), Schlieim de Arabiche Gummi (G.) Mucilagine de Gomma Arabica (I.).

1 Mucilago Acaciae. P. L. 1809. 1824.

2 This appellation is certainly exceptionable. It is a mucilage of gum of the Acacia vera,

The straining through linen is very necessary, as the gum is often mixed with small pieces of wood and other impurities. The mucilage thus obtained is viscid, thick, and adhesive; semipellucid, and nearly colourless, if the gum be good. It has a faint, peculiar odour, is insipid, and may be kept without altering for a considerable time; but at length it becomes sour, and acetic acid is formed. The strong acids act on it as they do on gum; but when diluted, they do not alter mucilage. Alcohol converts it into a white curd; but proof spirit produces scarcely any alteration; no change is produced by spirit of nitric aether; but sulphuric aether and compound spirit of aether precipitate a thick, white, tenacious curd. Tincture-of sesquichloride of iron, even when diluted, converts mucilage into a brownish or orange-coloured, insoluble jelly; and diacetate of lead gives a copious, dense, flaky precipitate, which is a compound of gum and oxide of lead; while no change is produced by the solution of the following metallic substances: - acetate of lead, green sulphate of iron, sulphate of zinc, bichloride of mercury, and tartarised antimony; nor by the alkalies or the neutral salts.

Mucilage, like gum, serves to combine resins, oils, and balsams with water, for which purpose, and to give tenacity to pills, it is much employed in pharmacy.

Medical properties and uses. - The properties of mucilage are the same as those of gum. (See Part ii.) It is the usual basis of demulcent mixtures for allaying the tickling, which excites cough, in catarrh, and phthisis1; and, combined with opium and other narcotics, it is useful in diarrhoea, dysentery, calculous affections, and ardor urinae The dose of mucilage may be from f ss. to f j., frequently repeated.

Officinal preparations. - Mistura Guataci, L. Potio Carbonatis Calcis, E.