399. Ammoniacum.—Gum Ammoniac.

399. AMMONIACUM.—GUM AMMONIAC. A gum-resin exuding from Dore'ma ammoni'acum Don. Off. U.S.P., 1890. Roundish tears varying in size from 1.5 to 12 mm. (1/16 to ½ in.) in diameter, externally yellow or pale yellowish-brown. When warm it is of the consistence of wax, but it becomes brittle when cold, breaking with a milk-white, waxy fracture, translucent at the edges; odor balsamic, stronger on heating; taste acrid, bitter, and nauseous. Lump ammoniac is an inferior quality in which the tears are agglutinated. Cake ammoniac is a very impure, dark-colored, resinous mass exuding from the roots; imbedded in it are a few tears and much vegetable and earthy trash; it is not used internally. Constituents.—Volatile oil, gum resembling acacia, resin (about 70 per cent. composed of two, one acrid resin and one indifferent resin); it yields no umbelliferone. By fusing with KOH, yields protocatechuic acid and resorcin, C₆H₆O₂, Among the derivatives of the acid resin are salicylic acid, ammoresinotannol, etc. Similar to asafoetida—stimulating expectorant, antispasmodic and laxative-but less powerful. Dose: 10 to 30 gr. (0. 6 to 2 Gm.).

Emulsum Ammoniaci (4 per cent.), U.S.P. 1890 Dose: ½ to 1 fl. oz. (1.5 to 30 mils).

Emplastrum Ammomaci cum Hydrargyro (72 per cent., with mercury, oleate of mercury, dilute acetic acid, and lead plaster), U.S.P. 1890.

A Manual of Organic Materia Medica and Pharmacognosy, 1917, was written by Lucius E. Sayre, B.S. Ph. M.