Related entries: Salix Nigra.—Black Willow - Salix.—Willow - Betula Lenta.—Black Birch - Oleum Betulae Volatile (U. S. P.)—Volatile Oil of Betula - Gaultheria.—Wintergreen - Oleum Gaultheriae (U. S. P.)—Oil of Gaultheria - Acidum Salicylicum (U. S. P.)—Salicylic Acid
FORMULA: CH3C7H5O3. MOLECULAR WEIGHT: 151.64.
"Methyl salicylate, produced synthetically. It should be kept in well-stoppered bottles, protected from light"—(U. S. P).
SYNONYMS: Artificial (or Synthetic) oil of wintergreen.
Preparation.—G. M. Beringer's (Amer. Jour. Pharm., 1887, p. 8) method is essentially as follows: In 2 fluid ounces of absolute methylic alcohol dissolve ½ ounce of salicylic acid, and add gradually to the solution 1 fluid ounce of sulphuric acid. Heat gently for a day. Distill from a retort into which a jet of steam is injected. Wash the distillate thoroughly and decant the product. The odor of the product is said to improve by time. In the bark of Betula lenta methyl salicylate results from the decomposition of gaultherin, a bitter, crystallizable glucosid discovered, in 1843, by Prof. Procter, and recently investigated by Schneegans and Gerock. (See review by F. X. Moerk, in Amer. Jour. Pharm., 1895, p. 8; also see an interesting review of the occurrence of methyl salicylate in plants, by Prof. Henry Kraemer, in Amer. Jour. Pharm., 1898, p. 412).
Description and Tests.—It is asserted that artificial oil of wintergreen is more uniform in quality, and gives better results than the natural oils from birch or gaultheria. It is now very extensively used. Methyl salicylate, according to the U. S. P., is "a colorless, or slightly yellowish liquid, having the characteristic, strongly aromatic odor, and the sweetish, warm, and aromatic taste of oil of gaultheria, with the essential constituent of which it is identical. It is wholly identical with volatile oil of betula (see Oleum Betulae Volatile). Specific gravity 1.183 to 1.185 at 15° C. (59° F.). Boiling point 219° to 221° C. (426.2° to 429.8° F). It is optically inactive. Soluble, in all proportions, in alcohol, glacial acetic acid, or carbon disulphide. The alcoholic solution is neutral or slightly acid to litmus paper. If a drop of methyl salicylate be shaken with a little water, and a drop of ferric chloride T.S., subsequently added, a deep-violet color will be produced. When heated on a water-bath, in a flask provided with a suitable condenser, it should yield no distillate having the characteristics of alcohol or chloroform. If to 1 Cc. of methyl salicylate, contained in a capacious test-tube, 10 Cc. of sodium hydrate T.S., be added, and the mixture agitated, a bulky, white, crystalline precipitate will be produced; then, if the test-tube, loosely corked, be allowed to stand in boiling water for about 5 minutes, with occasional agitation, the precipitate should dissolve, and form a clear, colorless, or faintly yellowish solution, without the separation of any oily drops, either on the surface or at the bottom of the liquid (absence of other volatile oils, or of petroleum). If the alkaline liquid thus obtained be subsequently diluted with about 3 times its volume of water, and a slight excess of hydrochloric acid added, a white, crystalline precipitate will be produced, which, when collected on a filter, washed with a little water, and recrystallized from hot water, should respond to the tests of identity and purity described under Acidum Salicylicum (absence of methyl benzoate, etc.)"—(U. S. P.).
Action and Uses.—Same as for oil of wintergreen (see Oleum Gaultheriae).