107. Oleum Betulae.—Volatile Oil of Betula. Oil of Sweet Birch.
A volatile oil distilled from the bark of Betula lenta Linné (Fam. Betulaceae, U.S.P. 1900).
BOTANICAL CHARACTERISTICS.—A tree often exceeding 60 feet in height, with a diameter of 2 or 3 feet. The trunk is invested with a dark brown or reddish bark, separating in thin layers. Remarkable for its agreeable fragrance and flavor. Leaves cordate, ovate-acuminate, acutely, finely, and doubly serrate, veined beneath. Flowers monoecious, sterile catkins 2 or 3 inches long, fertile much shorter and thicker; petals hairy; wood reddish, strong, compact.
DESCRIPTION.—This oil is identical with methyl salicylate, CH3C7H6O3, and nearly identical with oil of wintergreen (413a). Its specific gravity is 1.18. In fact, is one of the sources of commercial oil of wintergreen. Dose: 5 to 30 drops (0.3 to 2 Mils).
It should be kept in well-stoppered bottles, protected from the light.
107a. OLEUM BETULAE EMPYREUMATICUM RECTIFICATUM, N.F.—Obtained by the dry distillation of the bark and wood of Betula alba and rectified by steam distillation. Is used mainly as an external remedy in cutaneous diseases.