Syn. Gomme Arabique (F.), Das Arabischegummi ( G.), Gomma Arabica(I.), Goraa Arabiga (S), Tolh. (A.), Vullam pisin ( Tarn.), Kapitha (Sans.), Kavit ka gard (Duk.), Jewol latoo (Cyng.).

This species of acacia is found in almost every part of Africa; but the tree that yields the gum which is exported from Bar-bary to Great Britain, grows principally in the Atlas mountains, and at Bled-eljerrede; flowering in July. It has a hard withered aspect, and in general does not rise many feet in height, although it occasionally attains the altitude of forty feet. The stem is crooked, and covered with a grey bark, which on the branches has a purplish tinge: the leaves are alternate, bipinnate, composed of from six to eight pairs of opposite pinnae, with a small gland on the common petiole, between the base of each pair, and having numerous pairs of narrow, elliptical, smooth leaflets. On each side of the base of the leaves are two long, diverging, white spines. The flowers are hermaphrodite and male, crowded into globular heads (capitula), rather than spikes, which are supported on slender peduncles, and rise, four or five together, from the axillae of the leaves: the calyx is small, bell-shaped, and five-toothed; the corolla is divided into five narrow yellowish segments; the filaments are numerous, capillary, bearing roundish yellow anthers; the germen is conical, with a slender stile and simple stigma: and the pods, which are three or four inches long, and half an inch broad, contain several flattish brown seeds.1

Ilippocratis.

Dioscoridis. In Barbary it is named attaleh -Jackson's Morocco, 4to. p. 33. At the Cape of Good Hope it is called Domboom, Sparmaun. The Arabs in Upper Egypt call it Sant.

The gum exudes naturally from the bark of the trunk and the branches of the tree, in a soft, nearly fluid state, and hardens in the air without losing its transparency. It is collected about the middle of December. "It appears," Mr. Jackson informs us, "to be the product of disease: for in the hottest seasons, and from the most sickly trees, the greatest quantity is procured. Very little or none is got in a moist, cool, or mild summer. It is gathered in July and August, when the weather is hot and parching. It has a faint smell when first stowed in the warehouses, and is heard to crack spontaneously for many weeks. The best gum is procured from Morocco, Rasel-wed in the province of Suse, and Bledhummer in the province of Abda."2 When Gum Arabic was first brought to Europe, Marseilles was the sole depot; and as the gum was supposed to come from the ports of Gidda and Tor, in the Red Sea, it was called Gomme Gedda and Gomme Turique. It is now imported from Barbary and Morocco in large casks. Three kinds of gum are known in commerce: Gum Arabic, in white, much cracked, round pieces; Barbary Gum, in small compact, transparent, yellowish or brownish-yellow pieces, very brittle; Gum Gedda, in longer, roundish, brownish-red, not very brittle pieces; and Gum Senegal, which was introduced into Europe by the Dutch, in the 17th century, and is often mixed with the Barbary gum.

The Senegal gum is obtained from various trees, but chiefly from two; one called verec, which yields a white gum, the other called nebuel, which yields a red gum, varieties of the Acacia gummifera.3

Qualities.-Gum is generally in irregularly shaped pieces, hard, brittle, semitransparent, its fracture possessing a considerable degree of lustre; and is neither fusible nor volatile. When pure, it is almost colourless, or of a pale yellowish hue; is insipid, inodorous, and dissolves completely away in the mouth. Its specific gravity varies from 1.3161 to 1.4317. It is often mixed with the Gum Senegal, which is nearly as pure, but in larger masses, generally of a darker colour and more clammy and tenacious, and with other gums less pure, particularly a kind brought from the East Indies, which is still darker coloured and less soluble.1

1 From the unripe pods the acacia vera succus of the ancients was expressed. Vide Murray, App. Med. ii. 412. The seeds yield a reddish dye. Jackson, 1. c.

2 Jackson; p. 83. In 1805, the quantity exported from Mogodor to London was 277,534 lbs. lb. L c.

3 Although, by the treaty which delivered up Senegal to France in 1783, the gum trade was reserved to England, and has never been annulled, yet no advantage was taken of this right by the English; until the commencement of the present year (1821); when the trade was again renewed at Portendic, under the protection of Commodore Sir George Collier.-Portendic is in latitude 18° 19' north, by 16° 10' west of Greenwich. The Acacia forest of Sahel, which yields a very pure white gum, is sixty miles, and the forest of El-Hiebar eighty miles from Portendic. The gum is collected and brought to the coast by the Trarzhar Moors, who receive in exchange baft and other English goods : "the usual quantity given for a piece of blue baft, which costs from fifteen to thirty shillings, is from 100 to 133 lbs. weight of gum." Sierra Leone Royal Gazette, May 26th, 1821.

Gum is soluble in water, either cold or hot, and forms a viscid solution; which, if evaporated, becomes very thick and adhesive, and at length the gum is obtained in a concrete form, equally soluble as before. It is also soluble in the vegetable acids; but is insoluble in alcohol, in ether, and in bland and volatile oils : yet, owing to its viscidity, it renders by trituration both the volatile and fixed oils and resins miscible with water, forming a white opaque mixture. Concentrated sulphuric acid blackens, and partially decomposes it, and acetic acid is produced : strong nitric acid converts it into the oxalic, mucic, malic, and saccholactic acids; muriatic exerts very little action on it; but chlorine changes it into citric acid. Solutions of the alkalies and alkaline earths dissolve it without producing any change on it. For an account of the action of other agents on it, see Mucilago Acaciae.

The chymical analysis of gum, by Gay-Lussac and Thenard, shows, that its constituents are 42.23 of carbon, 6.93 of hydrogen, and 50.82 of oxygen, with a small proportion of nitrogen and lime; which last element is supposed to render it incapable of undergoing the fermentative process.2 According to Dr. Prout, its constituents are, carbon 36.3, water 63.7. I have found, however, that it nevertheless contains a small proportion of gluten; for when rubbed up with a spirituous solution of guaiac, a blue colour is evolved.

Medical properties.-Gum exerts no action on the living system; but is a simple demulcent, serving to lubricate abraded surfaces, and involve acrid matters in the primae viae; and it effects these purposes the more readily from its passing through the bowels, scarcely acted upon by the assimilative functions.3

1 The gum which exudes from the cherry, plum, and other trees of the genus Prunus, in this country, is Cerasin; but the gum alluded to is very similar to gum arabic, and is furnished by the Acacia Arabica (Roxburgh's Coromandel Plants, t. 149.) or Babul tree of Hindostan. The gum is called Bdbuled gund, by the natives. But the pure gum of India is furnished by different species of Ter-minalia; and by the Feronia Elephantum.

2 Murray's Chymistry, vol. iv. 180. The last analysis, which is by Berzelius, makes the components in 100 parts to be, hydrogen (6.792, carbon 41.752, oxygen 51.456, and a trace of nitrogen.

3 It is nevertheless sometimes used as food by the Moors, and also by the Boschis-men, of Southern Africa; and at Senaar, in Dongola, is much employed in cookery : six ounces are sufficient for the daily support of an adult.

In the solid form it is scarcely ever given, unless to sheathe the fauces, and allay the tickling irritation which occasions the cough in catarrh and phthisis pulmonalis, in which cases a piece of it is allowed to dissolve slowly in the mouth. It is chiefly used in the state of mucilage. Vide Mucilago Acacias.

Officinal preparations.-Mucilago Acaciae, E. Mucilago gummi Arabics, D. Emulsio Acaciae Arabicae, E. Emulsio Arabica, D. Pulvis Tragacanthai comp. L. Confectio Amygdalae, L. D. Troc. gummosi, et varii, E.