AMMONIAC, a concrete, gummy, resinous juice, brought from the East Indies, usually in large masses, composed of little lumps or tears, of a milky colour, but soon changing, upon being exposed to the air, to a yellowish hue. We have no certain account of the plant which affords this juice: the seeds usually found among the tears resemble those of the umbelliferous class. It has, however, been alleged, and not without some degree of probability, that it is an exudation from a species of the FERULA, another species of which produces the assafetida. The plant producing it is said to grow in Nubia, Abyssinia, and the interior parts of Egypt. It is brought to the western parts of Europe from Egypt, and to England from the Red Sea, by some of the ships belonging to the East India Company trading to those parts. Such tears as are large, dry, free from little stones, seeds, or other impurities, should be picked out, and preferred for internal use: the coarser kind is purified by solution and colature, and then carefully inspissating it; unless this be artfully managed, the gum will lose a considerable portion of its more volatile parts. There is often vended in the shops, under the name of strained gum ammoniacum, a composition of ingredients much inferior in virtue. Ammoniac has a nauseous, sweet taste, followed by a bitter one; and a peculiar smell, somewhat like that of galbanum, but more grateful; it softens in the mouth, and grows of a whiter colour when chewed. Thrown upon live coals, it burns away in flame. It is in some measure soluble in water and in vinegar, with which it assumes the appearance of milk; but the resinous part, amounting to about one half, subsides on standing. It is of considerable use in the Materia Medica.