Fig. 161. Liquidambar styraciflua. Photo: Liquidambar styraciflua. Preparation: Syrup of Sweet-Gum
Related entry: Styrax (U. S. P.)—Storax

The balsamic exudate, or concrete juice of Liquidambar styraciflua, Linné.
Nat. Ord.—Hamamelaceae.
COMMON NAMES: (Tree) Sweet-gum, tree, Bilsted, Copalm; (Gum) Sweet-gum, Gum wax.

Botanical Source.—The sweet-gum tree attains the height of 50 to 60 feet, with a diameter of 3 to 5 feet. It is covered with a gray, deeply furrowed bark, with corky ridges on the branchlets. The leaves are palmate, deeply 5 to 7-lobed, rounded, smooth, shining, of a rich green color; the lobes finely glandular, serrate, and acuminate; the veins villous at their bases. When bruised the leaves, which are fragrant, turn crimson or deep-red in autumn. The sterile flowers are in a conical cluster of several globular heads, naked or achlamydeous; the aments monoecious, roundish, and surrounded with a 4-leaved involucre; the stamens numerous and intermixed with minute scales; the filaments short, and the anthers numerous, oblong, and subsessile. The fertile flowers consist of 2-celled ovaries, subtended by minute scales, all more or less cohering and hardening in fruit, forming a spherical catkin or head. The catkins are racemed, nodding, inclosed in the bud by a 4-leaved, deciduous involucre. Styles 2, long. Fruit a kind of strobile, composed of the indurated scales and capsules. Capsules or pods 2-beaked, 2-celled, opening between the two awl-shaped, or prickly diverging styles. Seeds small, several, amphitropous, with sparing albumen, and a straight embryo; cotyledons foliaceous (G.—W.).

History and Description.—This is a large and beautiful tree, with finegrained wood, growing throughout the United States in moist woods from Connecticut and New Jersey, southward; but found in greater abundance in the southern and middle states, as well as in Guatemala and Mexico. In warm climates, a whitish-yellow, somewhat limpid juice exudes from the incisions made into the tree, especially during the warm seasons; it has the density of thick syrup, but by standing it forms a soft, resinous-like, adhesive mass, somewhat like white turpentine, but opaque and almost black. Or, it may become hard, breaking with a resinous fracture. It is known as Sweet-gum, Gum wax, or Liquidambar (Liquidum Liquidambar Styracifluae); it has a pleasant, benzoinic odor, and a benzoinic, somewhat bitter, and pungent taste. It is soluble in alcohol, chloroform, ether, oil, lard, or fats, softens in warm weather, and becomes harder in cold. Its tincture slightly reddens litmus paper.

Chemical Composition.—Liquidambar is closely allied in its composition to storax, an exudation of the bark of Liquidambar orientalis, Miller (see Styrax). William L. Harrison (Amer. Jour. Pharm., 1874, p. 161), from a semiliquid specimen collected in Virginia, obtained by distillation with an aqueous solution of sodium carbonate 1.5 per cent of volatile styrol, a hydrocarbon of a peculiar aromatic odor. The yield is stated to have been as high as 7 per cent (Bonastre). When extracting sweet-gum with petroleum benzin, a mixture of cinnamic acid (C6H5CH:CH.COOH) and styracin (cinnamyl-cinnamate, [C6H5.CH:CH.COO.C9H9] discovered by Bonastre, 1827), results, from which diluted ammonia extracts all of the cinnamic acid which may be precipitated by means of diluted acids (see Prof. Maisch, Amer. Jour. Pharm., 1874, p. 166). The total yield of cinnamic acid was 5 ½ per cent. No benzoic acid could be detected.

W. von Miller (Archiv der Pharm., 1882, p. 648), obtained by the distillation with steam of a rather firm specimen of the resin styrol contaminated with an oxygenated oil; in the residue was found cinnamic acid, melting at 133° C. (211.4° F.), but no benzoic acid; styracin, in beautiful crystals, melting at 44° C. (112° F.) and a thick, yellow oil, consisting chiefly of phenyl-propyl-cinnamate (C6H5.CH:CH.COO.CH2CH2CH2C6H5). The ethyl- and benzyl-esters of cinnamic acid were found to be absent. Storesin, a peculiar, complex alcohol occurring in storax free and as cinnamate, in large quantity (von Miller, 1877), is also present in liquidambar. The leaves of Liquidambar styraciflua contain tannin and small quantities of a volatile oil. Sweet-gum contains nearly 10 per cent of impurities,. such as portions of the bark, etc.

Action, Medical Uses, and Dosage.—Sweet-gum probably has virtues similar to the concrete juice of Styrax officinale, which see. It makes an excellent and agreeable ointment when melted with equal parts of lard or tallow, which I have found decidedly useful in hemorrhoids, psora, ringworm of the scalp, porrigo scutulata, and many other cutaneous affections; also in that indolent species of ulcer, known as "fever sores on the legs." In anal fistula, it maintains an increased discharge, softens the callosity of the walls of the sinus, and produces a normal result, and effects this without pain to the patient. If necessary, in fistula, a little creosote, or other stimulant may be added to it. This employment of sweet-gum is not generally known, and physicians would do well to avail themselves of its use in the above diseases. It is also used in chronic catarrh, coughs, and pulmonary affections. The dose internally is from 10 to 20 grains (J. King).

King's American Dispensatory, 1898, was written by Harvey Wickes Felter, M.D., and John Uri Lloyd, Phr. M., Ph. D.