The name of this balsam has been obtained from its being chiefly procured from the province of Tolu, on the north coast of South America, near the isthmus of Panama. Incisions are made in the bark of the trees, at a particular season of the year, and a resinous fluid of yellowish white colour oozes out. This is collected in small gourd shells. At first it is about the consistence of treacle, but it thickens by being kept; and by age it becomes hard and brittle. Its smell is peculiarly grateful, somewhat resembling that of lemons; and its taste is warm and sweetish. On being chewed, it adheres to the teeth.
This balsam is used in medicine both in the form of a tincture, and a syrup; and, in its medicinal virtues, it agrees with most other balsams. The syrup of Tolu is used in several medicines; and is also made into lozenges, which may be procured of almost any chemist, and which are considered serviceable in appeasing the irritation occasioned by severe coughing.
140. BENZOIN or GUM BENJAMIN, is a concrete or solid and fragrant balsamic substance, the produce of a tree (Styrax benzoe) which grows chiefly in the island of Sumatra.
This tree has oblong leaves which taper to a pointy and are smooth on the upper surface, and downy beneath. The flowers are in loose bunches; they usually hang all on the same side; and are generally closed, which gives them the appearance of buds.
In some of the northern parts of Sumatra, particularly near the sea coast, there are several extensive plantations of Benzoin trees. The seeds or nuts are sown in the rice fields, and they afterwards require no other attention than that the surrounding shrubs should be cleared away from about the young plants.
When the trees have attained the age of six or seven years, incisions are made into the bark; and from these the balsam exudes, in the form of a thick, whitish, resinous juice. By exposure to the air, this juice soon hardens; it is then pared from the bark with a knife or chisel. For the first three years the trees yield the purest resins: this is of a white colour inclining to yellow, is soft and fragrant. Afterwards, for the next seven or eight years, an inferior sort is yielded; this is of reddish yellow colour, degenerating to brown. At length the trees, unable to bear a repetition of the process, are cut down, and split into pieces. From these is procured by scraping, a still worse sort of benzoin, which is dark-coloured, hard, and mixed, more or less, with parings of the wood and other impurities.
The inferior sorts of benzoin are exported to Arabia, Persia, and some parts of India, where they are burned, to perfume, with their smoke, the temples and the houses of the inhabitants; to expel troublesome insects, and obviate the pernicious effects of unwholesome air or noxious exhalations.
Benzoin is brought for sale to the mercantile parts of Sumatra, in large cakes, covered with mats. In order to pack it in chests, it is necessary to break these cakes, and to expose it to the heat of the sun. The greater part of the benzoin which is brought to England is re-exported to countries where the Roman Catholic and Mahometan religions prevail; to be there burned as incense in the churches and temples. The annual exportation of benzoin from London to Mogadore only has been estimated at 30,000 pounds' weight per annum.
That which is consumed in England is chiefly employed in medicine, in perfumes, and as cosmetics. It constitutes the basis of what are called Turlington's or Friar's balsam, and Jesuit's drops; the salutary effects of which, particularly in healing recent wounds, is well known. This balsam is composed of benzoin, balsam of Tolu ([139]), Socotrine aloes ([107]), and rectified spirit of wine. Benzoin is also used in the preparation of what is called ladies' court plaster; but in this it is supposed to be unnecessary if not prejudicial; not only as it renders the plaster more difficult to be moistened, previously to its application, but as the irritating quality of the benzoin may in some instances dispose a fresh wound to fester. The mode of making court plaster is very simple. Five ounces of isinglass are dissolved in a pint of water. A quantity of thin black sarsnet being then stretched on a frame, a warm solution of the isinglass is applied with a brush equally over the surface; and, when dry, this is repeated a second or third time. It is finally brushed over with a weak solution of benzoin in spirits of wine, which communicates to it a pleasant aromatic smell.
If powdered benzoin be put into an earthen vessel over a slow fire, and the fumes of it be made to sublime into a paper cone fixed to the top of the pot, the substance thus formed is the flowers of benzoin of the shops, or Benzoic acid, as it is termed, by chemists.