BALSAM, or NATIvE BALSAM, an oily, resinous, liquid substance, flowing either spontaneously, or by means of incision, from certain plants of sovereign virtue in the cure of several disorders.
The term balsam, or balm, was origin ally confined to a thick fragrant juice, ob tained from the amyris Gileadensis, and afterwards applied by chemists to all sub stances which possessed the same degree of consistence and a strong smell, whe ther natural or artificial. The word bal sam originally implied a substance pos sessing a certain degree of fluidity : but now there are two classes of balsams; the one fluid, and the other solid and brittle. A balsam, then, is a substance, which pos sesses the general properties of a resin ; but which, when heated or digested in acids, yields a portion of benzoic acid.
See BENZOIN.
Chemists, in general, have considered them as combinations of a resin with ben zoic acid; but Mr. Hatchet has made it probable, that the acid is formed at the time of its separation. They are insolu ble in water; but when boiled in that liquid, often give out a portion of benzoic acid. Alcohol and ether dissolve them readily. The strong acids, likewise, dis solve them, and during the solution, a por tion of benzoic acid is separated. Nitric acid, in some cases, evolves likewise traces of prussic acid. The alkalies act upon them nearly as on the resins. They may be divided into two classes; namely, liquid and solid balsams.
Liquid balsams. The liquid balsams at present known are five in number ; namely, • I. Opobalsamum. 4. Peru.
2. Copaiva. 5. Styrax.
3. Tolu.
1. Opobalsamum, or balm of Gilead.— This balsam is obtained from the amyris Gileadensis, a tree which grows in Ara bia, especially near Mecca. It is so much valued by the Turks, that it is seldom or never imported into Europe. We are of course ignorant of its composition. It it is said to be at first turbid and white,and of a strong aromatic smell, and bitter, acrid, astringent taste ; but by keeping it becomes limpid and thin, and its colour changes first to green, then to yellow, and at last it assumes the colour of honey,and the consistence of turpentine. It is also very tenacious and glutinous, sticking to the fingers, and may be drawn into long threads. The mode of ascertaining the purity of this balsam at Cairo and Mecca is, to drop it into a cup of clear cold wa ter; if it remain in one place on the sur face, it is of little or no value, but if it ex tend itself like a skin over the whole sur face, (and this skin is even, and almost transparent, and may be taken off the water with a hair,) it is of great worth.
The balsam of Gilead principally comes from Arabia Petrxa, from whence the Arabs carry it to Mecca for sale during the stay of the caravans from Egypt and Turkey. It grows also in the Holy Land, but not without much culture and atten tion, whereas in Arabia it grows without cultivation. It is the produce of a species of the amyris, rising to the height of the pomegranate tree, to which it has a great resemblance, both in its branches and flowers. See AMYRIS. The balsam is obtained by incision during the sum mer months, flowing over in a viscous juice, called Opobalsamum. It is white when it comes from the tree, and changes first to a green, and afterwards to a gold colour.
2. Copaiva.—This balsam is obtained from the Copaifera Officinalis; a tree which grows in South America, and some of the West Indian islands. It exudes from incisions made in the trunk of the tree. The juice thus obtained is trans parent, of a yellowish colour, 'an agreea ble smell, a pungent taste, at first of the consistence of oil, but it gradually be comes as thick as honey. Its specific gravity is 0.950. When mixed with wa ter and distilled, there comes over with the water a very large portion of volatile oil. The oil ceases to come over before allthe water has passed into the receiv er. The residuum of course consists of two substances; namely, the watery por tion, and a greyish yellow substance, lying at the bottom of the vessel, which, on exposure to the air, dries, and be Comes brittle and transparent. When heated it melts, and possesses the cha racters of a resin. Nitric acid acts upon this balsam with considerable energy. When one part of the balsam is mixed with four parts of nitric acid and two parts of water, and heated, a yellowish so lution is formed, similar to the original balsam, but darker. When distilled, there comes over with the liquid that passes into the receiver an apple-green oil, which lines the helm of the retort. The nature of the residue was not examined. When treated with sulphuric acid, it yields a portion of artificial tannin. Whe ther this balsam yields benzoic acid, has not been ascertained : its properties are rather against the probability of its doing so. Indeed it bears a striking resem= blance to turpentine in many respects ; and ought, along with it, to constitute a class of bodies intermediate between vo latile oils and resins, to which the name of turpentine might be given.