The ammoniacum of commerce is diatinguished as " tear" and "lump "; the former constitutes the hardened drops in their separate form, while the latter is composed of concreted masses of these drops, more or less contaminated with gross foreign matters. The tears are dry grains of roundish form, varying in size from a millet-seed to a nut. Externally, their colour is pale cream-yellow ; internally, opaque milk-white. Long keeping darkens their outer appearance to cinnamon-brown. At ordinary temperatures, the tears are hard and brittle, with a dull waxy lustre on the fractureel surface, which is conchoidal. They readily soften by heat, particularly if recent. The " lumps " bave a marbled or granitic appearance, and are sometimes softer, greasier, and more adhesive than the tears, sometimes harder, more brittle, and more lustrous, but always far less pure. The gum resin has always a characteristic, non-alliaceous odour, and a bitter, acrid flavour. Its prominent constituents are resiu (70 per cent.), essential oil (3-4 per cent.), gum, and water. It is used medicinally (see Drugs--Ammoniacum, Sumbul, pp. 793, 826), and in some cements.
Other Persian species of Dorema are capable of yielding gum-resins, though they are not known to contribute to the commercial eupply. The exudation from the plant called zah by the Kurds, D. Aucheri, affords a very good article. These species, however, are far less abundant than the one producing the officinal drug. No attempt seema to have been made to cultivate any of these plants in India or Australia, though the conditions for success would appear to be present.
Moroccan or African Ammoniacum must not be confounded with the Persian product just described. It is 9,n object of commerce with Egypt and Arabia, where it is employed, as of old, in fumigating. The plant affording it is called fashook in Arabic, and has been hitherto referred to Fonda orientalis, or F. tingitana ; but Hooker and Ball conaider it decidedly an Elmoselinum, probably E. humile. Leared was told that this plant grows at a place two days from ilogador, on the Morocco road ; but Hooker and Ball were assured that it is found nowhere along that route, nor nearer to it than El Araiche, a place lying north of Morocco city, which is confirmed by informa tion gathered by R. Drummond Hay, to thc effect that it occurs near Morocco, and chiefly around Tedla. Lindley and others would extend the habitat of the plant to all N . Africa, as far as Syria, Rhodes, and Chios, and into Armenia and the E. Caueasua. But the product is obtained only in a very circumscribed district of Morocco, as stated, and is shipped occasionally at Hazagan and Alogador. It occurs in large, compact masses, of dark colour, formed by the agglutination of greenish or fawn-coloured teara. The main constituents are 67 per cent. resin and 9 per cent. gum. It is readily distinguished from the Persian officinal article by resisting the effects of hypochlorites, while the latter assumes a bright-orange hue by their action.
The approximate London market value of ammoniacum is 30-10s. a cwt. for drop, and 12-363. for siftings and blocky.
Arabic (FR., Gornme Arabigue ; GER., Acaciengummi, Arabisches Gummi).—The term " gum Arabic " ia sanctioned by long commercial use, and is therefore retained here, but it is quite mis placed, only a trifling proportion of a single variety of the product being derived from Arabia. The plants yielding the many forma &this useful gum are all apecies of Acacia, a genus of shrubs or trees widely diffused in the warmer regions of the globe. The principal acacia-gums may bc best deseribed under the separate titles by which they are knovrn in commerce, viz. :—Picked Turkey, or White Belmar; Senegal ; Suakin, Savakin, Taloa, or Talha ; Morocco, Mogador, or Brown Barbary ; Cape ; E. Indian (Babul, Siris, and Kheir) ; and Australian or Wattle.
1. Picked Turkey or Whde Sennar.—This is the produce of Acacia Senegal [A. Verek, Mimosa Senegal], a speeies not exceeding 20 ft. in height, which grows abundantly, constituting extensive forests, in the sandy region of W. Africa, mostly north of the Senegal river. Its negro name in this district is verek. In S. Nubia, Kordofan, and the Atbara country of E. Africa, where the tree is also found, it is called haebab. Sehweinfurth's testimony, corroborated by other authorities, is to the effect that this tree alone affords the fine white gum of the Upper Nile and Kordofan. The gum usually exudes spontaneously from the trees, without requiring any mutilation of the bark ; but the natives of the Somali country, opposite Aden, are aceustomed to supplement the natural outflow by scoring long wounds on the stems and branches. In Kordofan, the masses of gum aete-re gated upon the bark are removed by an axe, and gathered in baskets. The most highly valued kind, the hashabi, from Dejara province (Kordofan), is despatched from El Obeid and Bara to Dabbeh, and thence down the Nile into Egypt, or from Mancljara down the White Nile. The Samhara mast, towards Berbera, produces a good gum, part of whieh is slapped at Massowa ; some, however, reaches Egypt by way of Jedda, in the Arabian Hejaz, whence it is called Hejazi or Jedda gum. The gum collected in the Somali country is of three grades, styled Felick, Zeila, and Berbera. The first is gathered ehiefly by the Mugartam Somalis, and those who inhabit the dis triet around Cape Gardafui. This is esteemed the best. Noue of it finds its way to Aden, but a little reaches Maculla and Shehr ou the Arabian coast, and the mass is bought up by Banians, nnd shipped direct to India. In Somali Land, when the gum of a district is gathered, it is sewn up in goat-skins, snd carried on camels to the great Berbera fair, or to some of the small coast settle ments, for shipment to Aden or Bombay. The plant is common in Yemen and Hadramaut, but the Arabs collect very little gnm from it. The natives on the S.-E. coast, tete tten Aden and Maeulla, also collect a little, but scarc(iy any of this is exported.