Of the hard resins, benzoin alone is used in perfumery; of the balsams, Peru balsam, Tolu balsam, and storax balsam; and of the gum-resins, the myrrh.
Benzoin is exclusively obtained from Styrax benzoïn, Dryand (Benzoïne officinale, Hayne), a tree which grows in Java, Sumatra, and Siam. The bark of the tree is slit to allow a fluid to flow out, which concretes on the trunk in the form of grains, or is collected in vessels in which it congeals and assumes the form of lumps ("tampangs"). Older trees which have been frequently tapped for resin yield a product of a lower quality; the grains ("tears") forming, as a rule, the better varieties. When the benzoin collects in large masses it always shows an amygdaloid structure, the grains ("almonds") of a roundish form, smooth termination, homogeneous structure, and paler color, appearing imbedded in a dark, porous, or resiniform mass.
According to the appearance of the product three varieties are distinguished: Benzoin in tears (B. in lacrimis), amygdaloid benzoin (B. amygdaloides), and lump benzoin (B. in sortis, B. in massis). The benzoin in tears forms loose, smoothly terminated, longish, homogeneously appearing masses of an opal-like lustre, and first of a whitish, and later on, of a yellowish, reddish, or brownish color. The separate pieces are up to 3 millimeters in diameter, though the Siam benzoin in tears frequently consists of still larger and generally decidedly flattened pieces.
Amygdaloid benzoin consists chiefly of white pieces, becoming, later on, brownish, of a waxy lustre and imbedded in a lustrous brown-red resinous mass. The lump benzoin or ordinary benzoin has also an amygdaloid structure but is not so rich in almonds as the preceding variety and possesses either a fine granular or colophony-like ground-mass and is frequently contaminated by parts of plants. The exterior of the variety occurring in commerce in large lumps shows, according to the mode of packing, the imprint of leaves or of coarse pack-cloth.
Benzoin generally consists of cinnamic and benzoic acids which occur in a crystalline state in the grains as well as the ground-mass; further, of several amorphous resins soluble in alcohol, and coloring matter. The content of cinnamic and benzoic acids amounts to from 12 to 20 per cent. The best varieties from Sumatra and Singapore contain no benzoic acid, and those from Siam no cinnamic acid.
All varieties of benzoin possess a peculiar odor, that of the better varieties being agreeable, and a sweet, aromatic, but pungent taste. The melting point generally lies between 176° and 203° F., that of the tears and of the almonds being lower than that of the ground-mass. A low melting-point is accepted as a mark of quality, Siam benzoin, which is considered the best, melting at 167° F. Some varieties, for instance, those recently imported from Singapore, have a pronounced vanilla-like odor; the presence of vanillin has been established in them. The Sumatra benzoin has a storax-like odor.
Benzoin is sparingly soluble in chloroform, only partially so in ether, and completely in alcohol. On mixing the alcoholic solution with water, the resin is separated. Petroleum-ether and benzine withdraw only benzoic acid from the dry, powdered benzoin. All varieties of benzoin dissolve in concentrated sulphuric acid to a beautiful purple colored fluid, from which benzoic acid, if present, is separated in crystals by the gradual addition of water. The establishment of the presence of cinnamic acid is best effected as follows: Boil the sample in milk of lime, filter, and treat the solution with hydrochloric acid. The precipitate thereby separated is thoroughly washed, triturated with potassium permanganate and water, and heated, whereby in the presence of cinnamic acid, oil of bitter almonds is formed from the latter, which is readily recognized by the odor.
If benzoin containing benzoic acid be heated, white vapors are emitted which, on cold surfaces, deposit in very delicate, lustrous, acicular, or foliated crystals of benzoic acid, the so-called benzoin flowers (Floris benzoes.) Benzoic acid thus prepared possesses an agreeable, vanilla-like odor, since by heating the benzoin the greater portion of the odoriferous substance contained in it escapes. Benzoic acid separated by the wet method is odorless.
Benzoin is especially used for fumigating pastilles. It is also of great importance on account of its property of preventing fats from becoming rancid, if added to them in small quantities.
Peru balsam (Balsamum Peruvianum) is the produce of the Balsam Coast, San Salvador, Central America, where Sansonate forms the central point of the industry. In the mountain forests, back of the coast, grows the balsam tree (Myroxylon Pereiræ, Klotzch; Toluiferæ Pereiræ, Baillon), natural order, Papilionaceæ. The gaining of balsam commences when the tree is five years old, the collecting time beginning in the dry season in the first days of November. The trunks of the trees are belabored with hammers on four places (according to other statements, on twenty to thirty), so that the bark is detached in strips. After a few days the bark thus loosened is burnt off by means of torches, whereupon a balsamic fluid oozes from the young wood, which is absorbed by pieces of cloth or rags, placed upon the denuded places. When the rags are thoroughly saturated with balsam, they are squeezed out and then thrown into an earthen pot filled with boiling water, whereby the balsam is detached and collects on the bottom of the vessel. By this process the Balsamo de trapó is obtained. By boiling the bark, which falls off, a small quantity of a poorer quality of balsam, called tacuasonte, is obtained, which, it would seem, is frequently added to the better quality. Crude Peruvian balsam is a gray-green to dirty-yellow fluid, of the consistency of syrup. The process of purification in use on the Balsamic Coast is as follows: The crude balsam is brought into large iron vessels, holding from 1300 to 1500 lbs. each, and allowed to clarify by quietly standing from 8 to 14 days, the heavy impurities settling on the bottom, while the light dirt, together with the water, appears as foam on the surface. After 8 to 14 days the balsam is drawn off through a cock, located about 4¾ inches above the bottom of the vessel, into a tinned iron boiler, and boiled over an open fire at a moderate heat for 2 to 3 hours. The foam which forms is skinned off, and boiling continued until no more foam appears.