The crude gum rapidly hardens on exposure to the air, especially in the shade; in dry weather, 2-3 days suffice to give the surface the colour and consistence of leather. The slabs are turned occasionally till the whole mass is dry, and are then packed in leaves, or moulded into blocks by means of hot water. The sp. gr. of clean, dry, solid balata is 1.042. In many of its properties, it occupies an intermediate position between indiarubber and guttapercba, possessing the elasticity of the one and ductility of the other, without the intractability of the former or the brittleness of the latter, thus becoming under certain circumstances more valuable than either for industrial purposes. Heated to 49° (120° F.), it softens and may be welded, while it does not melt below 132° (270°F.). It is quite soluble in benzol and carbon bisulphide, in the cold; and in turpentine, chloroform, and petroleum, when heated ; but is only partially soluble in anhydrous alcohol and ether. R is not acted upon by caustic alkalies, nor by hydrochloric acid ; but is much affected by concentrated sulphuric and nitric acids. It vulcanizes readily. It was originally introduced exclusively as a manufacturing article, for insulating telegraph wires, and such purposes ; but since it has become familiar in the United States,attention has been attracted to its excellent qualities as a masticatory, and factories have been established in New York, New Eagl md, Ohio, Illinois, and Tennessee, for its preparation as a chewiag material, the consumption in this way amounting to 50 tons annually. Despite the industrial value of balata, its employment is decreasing, mainly owing to the difficulty of procuring supplies, by reason of the unhealthiness of the occupation. Systematic cultivation of the tree would greatly obviate this, but has not yet been attempted. Berbice exported 20,000 lb. in 1865. (See Chicle, p. 1639.) Balm of Gilead, Mecca Balsam, or Balsatnodendron gileadetase [Opobalsamum], a native of Arabia and Abyssinia, possesses a grateful fragrance in every part, due to the presence of an oleo-resin, which exudes when incisions are made in the bark. This product was reg,arded with most exaggerated esteem in biblical and classical times, and still has a boundless repute in the East, but is almost unknown in European commerce. An allied or identical balsam is afforded by an Indian species, and equally valued. This latter has a syrupy consistence, and is limpid and yellow ; it thickens and hardens with age. The pure article is almost completely soluble in alcohol, but it is nearly always adulterated with turpentine, olive-oil, or wax. According to Wiesner, the little bnlm which reaches Europe is obtained by boiling the twigs of the plant in water, and is very much inferior to the article in Oriental use.
Other Balsantodendron products are described under Bdellium (below) and Myrrh (p. 1674). Bdelliuna.—The myrrh-like gum-resin known as "bdelliurn " is of three kinds, termed respectively Indian, African, and opaque, all afforded by species of Balsamodendron.
1. Indian Bd.ellium, Googul, or Afuhul.—This is a product of two or more species, chiefly B. .Roxburghii [agallocha] of Silhet and Assam, and B. Mukul of Sind. Tbe former is a very hardy plant, and readily propagated by cuttings. The bark is scuffled, and the liquid exudation is placed in bottles, where it clarifies by age and exposure to the sun. This is by far the less important of the two species. B. Mukul is a native of Arabia, and is found on rocky ground throughout Sind, at Disa in Marwar, and in Beluchistan. Both the shrub and its gum-resin are called googul or guggur by the Hill Beluehis. The gum-resin is collected by them in the cold season, by iacising the tree with a knife, and allowing the exudation to fall to the ground, by which it acquires the dirty, impure state commonly exhibited 'by that met with in the native shops.
The yiel4 arnmmts to seer (of 2.2 lb.). The best is clear, pure, brilliant, viscous, adhesive, soft, yellow, bitterish, and of fragrant odour. By age, it increases in bitterness, darkens in colour, and becomes hard and dry. It is largely soluble in water. It is brought into the bazars of Hyderabad and Karachi, where it sells for 2 rupees (4s.) a maund (80 lb). Locally it is used medicinally, both for men and horses, but chiefly as incense for burning in the ternples, and (in solution) as a strengthening ingredient for mortar. The article is sometimes sold for and considered as an inferior kind of myrrh. Portions of the birch-like bark of the tree are often found adhering to it. A third species that may be mentioned is B. pubescens, inhabiting Beluchistan, and tbe hills separating that province from Sind, probably also Afghanistan, and reaching its S. limit about Karachi. It is called bayee by the Hill Beluchis, but is not availed of by them. In the cold season, it exudes a small quantity of a brittle gum, almost completely soluble in water, but devoid of odour and flavour, though the young shoots and buds are remarkably fragrant when bruised. The imports of hdellium tido the Bombay Presidency in 1872-3 were :-200 cwt. from the Red Sea, 7 from Aden, 70 from the Persian Gulf, and 426 from Sind ; total, 703 cwt.
The googul of the Coromandel coast is obtained from Boswellia glabra, that of Khandeish from Bosweilia serrata.
2. African Bdellium.—The Afr:can kind is produce,1 by B. [Heudelotia] africanum, a shrub growing, in S. Arabia, Abyssinia, Mozambique, and throughout the whole of tropical Africa to Senegambia. The bulk of the gum-resin comes from Senegal, where its collection is not separately conducted, but is performed by the seekers after gum arabic, the produce being mixed with the latter gum. This does not occur through confusion of the plants yielding the two articles, but rather to increase the harvest of gum araide. Classification takes place NNhen the mass reaches Bordeaux. African bdollium is hard, translucent in thin layers, red by transmitted light, with a bitter flavour, and a slight aromatic odour of black pepper ; its fracture is of dull, slaty hue, the margins having a powdery resinous appearance. Triturated with water, it forms en emulsion.
R. H. Parker states that on standing, it gives a nearly bright mucilage, with a, copious brown sediment, the mucilage indicating presence of a considerable proportion of gum allied to tregacanth. This authority gives the cornposition of African bdullium as-15.4 per cent. soluble in alcohol (by difference), 33.2 gum soluble in water, 37.8 gum insoluble in water, 13.6 moisture. Other analyses differ extremely. There are no statistics concerning the trade in African bdellium. It appears to be employed only in Continental pharmacy.
3. Opaque Bdellium.—This is attributed by Parker to B. Ploopirii, which is stated by Hanbury to produoe hotai gum, a whiter and more brittle substance, used by the Arabs for washing their hair. It is a very hard, ochre-yellow coloured, opaque gum-resin, with but slight odour, and a bitter flavour. The tears of this substance frequently have portions of papery bark attached to their surface. Triturated with water, it forms a very good cream-coloured emulsion. Cold absolute elcohol dissolves about 50 per cent. ; a considerable portion of the residue resembles bassoriue. The composition is given as-47.42 per cent. soluble in alcohol (by difference), 30.01 gum soluble in water, 11.07 gum insoluble in water, 11.50 water. It occurs among the "spurious gums" imported with myrrh.