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Ammoniac, Gomme ammoniaque, so called from Ammonia in Lybia, whence it is brought. A gum-resin, the concrete juice of Dore'ma ammoni'acum, of Persia: a species of a genus allied to Ferula; and also the gum-resin of Fer'ula tingita'na. The latter is the ammoniacum of commerce. It is in irregular, dry masses and tears, yellow externally, whitish within. Its odour is peculiar, and not ungrateful: taste nauseous, sweet, and hitter. It forms a white emulsion with water: is soluble in vinegar; partially so in alcohol, ether, and solutions of the alcalies. Gum ammoniacum is expectorant, deobstruent (?), antispasmodic, discutient, and resolvent. It is chiefly used, however, in the first capacity, and in the formation of certain plasters. Two varieties are met with in the market, Guttce ammoni'aci, the best; and Lapis ammoni'aci, the more impure.