Also known as Acacia nilotica.
All the gum-yielding Acacias have the same general appearance. They are spiny shrubs or small trees, preferring sandy or sterile regions, with a dry climate for most of the year.
The gum harvest from the various species starts in November and lasts for about five weeks. The gum exudes spontaneously from the trunk and principal branches, but the flow is generally stimulated by incisions in the bark - a thin strip, 2-3 feet in length and 1-3 inches wide being torn off. In about fifteen days it thickens in the furrow down which it runs, hardening on exposure to the air usually in the form of round or oval ‘tears’, of various sizes, colourless or pale yellow, or broken into angular fragments with a glass-like, sometimes iridescent fracture. The masses of gum are then collected, either while adhering to the bark, or after it falls to the ground, and packed.
It has an insipid taste, is mucilaginous and is nearly inodorous. It should be almost entirely soluble in water, forming a viscid neutral solution, or mucilage, which, when evaporated, yields the gum unchanged. It is insoluble in alcohol and ether, but soluble in diluted alcohol in proportion to the amount of water present.
Acacia consists principally of Arabin (Arabic Acid), with varying amounts of the magnesium and potassium salts of the same acid being present. It is believed that small amounts of other salts of these bases also occur. The gum also contains 12-17 per cent of moisture, and a very small amount of sugar, and yields 2.7 - 4.0 per cent of ash, consisting almost entirely of calcium, magnesium and potassium carbonates.
Gum Acacia is a demulcent and the viscidity of its solution is ideal for covering inflamed surfaces. It is usually administered in the form of a mucilage. Mucilage of Acacia is a nearly transparent, colourless or slightly yellowish, viscid liquid, with a faint, agreeable odour and an insipid taste.
It is also used for suspending insoluble powders in mixtures, for emulsifying oils and other liquids that are not miscible with water, and as an ingredient of many cough tinctures. Compound Mucilage of Acacia (Pill-coating Acacia) is made from Gum Acacia, with tragacanth, chloroform and water, and is used for moistening pills before the coating stage.
Gum Acacia is highly nutritious. During the time of the gum harvest, the Moors of the desert are said to live almost entirely on it, and it has been proved that 6 oz. is sufficient to support an adult nutritionally for twenty-four hours.