Related entries: Salix Nigra.—Black Willow - Salix.—Willow - Methyl Salicylas (U. S. P.)—Methyl Salicylate - Betula Lenta.—Black Birch - Gaultheria.—Wintergreen - Oleum Gaultheriae (U. S. P.)—Oil of Gaultheria
A volatile oil obtained by distillation from the bark of Betula lenta, Linné, Sweet birch (Nat. Ord.—Betulaceae). It is identical with methyl salicylate (CH3C7H5O3), and nearly identical with oil of gaultheria. It should be kept in well-stoppered bottles, protected from light"—(U. S. P.).
SYNONYM: Oil of sweet birch.
History and Chemical Composition.—This oil is formed in the bark by the action of the ferment betulase (Schneegans, 1896) upon the glucosid gaultherin (C14H18O8+H2O) (Procter, 1843; Schneegans and Gerock, 1894). Upon saponification, it yields salicylic acid and methyl alcohol. The oil was first distilled from sweet birch, in 1865, in Luzerne county, Pennsylvania, and although the yield is only 0.23 per cent, against 0.80 per cent from gaultheria, distillation of the former material is less expensive. (See, in this connection, two interesting papers by Mr. Geo. W. Kennedy, in Amer. Jour. Pharm., 1882, p. 49, and W. H. Breisch, ibid., 1891, p. 579.) The oil is frequently sold for Natural oil of wintergreen. Dr. F. B. Power and Dr. C. Kleber (Pharm. Rundschau, 1895, p. 228) summarize the differences between oil of wintergreen and oil of sweet birch as follows: (1) "Oil of wintergreen (Gaultheria) contains about 99 per cent of methyl salicylate, together with a small amount of a paraffin, which is probably triacontan (C30H62), an aldehyde or ketone, an apparently secondary alcohol (C8H16O), and an ester (C14H24O2). A pure, fresh oil of gaultheria deviates a ray of polarized light to the left, and the extent of this rotation should not be less than -0° 25' in a tube of 100 Mm. (2) Oil of sweet birch (Betula), in its unrectified state, contains about 99.8 per cent of methyl salicylate, together with a very small amount of the above-mentioned paraffin (C30H62), an aldehyde or ketone, and the ester (C14H24O2), but does not contain the alcohol (C8H16O), which is found in gaultheria oil. The oil of sweet birch is always optically inactive. (3) Both of these oils have a specific gravity varying from 1.180 to 1.187 at 15° C. (59° F.). Both of them, as well as synthetic methyl salicylate, form a clear solution with five times their volume of 70 per cent alcohol, at 20° to 25° C. (68° to 77° F.). Neither the oil of gaultheria nor the oil of sweet birch contains any trace of benzoic acid or its esters, nor do they contain any terpene or sesquiterpene."
Volatile oil of betula "has the same properties and conforms to the same reactions and tests as methyl salicylate"—(U. S. P.). (See Methyl Salicylas; also Oleum Gaultheriae.)
Action, Medical Uses, and Dosage.—Same as Oleum Gaultheriae (which see).