Oil of Wintergreen

Oil of Gaultheria is the oil distilled from the leaves of Gaultheria procumbens, Linn., or from the bark of Betula lenta, Linn.


Oil of gaultheria is no longer official in the U. S. P. IX. Under Methylis Salicylas the Pharmacopoeia directs that oil of gaultheria and oil of betula or sweet birch may be used.

The volatile oil of gaultheria is largely obtained in the United States by distillation of the plant.
It probably does not exist in the plant, but is formed by a reaction between water and a neutral principle analogous to amygdalin, to which Procter has given the name of gaultherin.

This substance, which was called by Schneegans betulase, probably exists in all the numerous plants which yield methyl salicylate on distillation. The oil occurs in various of our native plants, and has been detected in Polygala paucifolia, Spiraea Ulmaria, Spiraea lobata, and Gaultheria chiogenes (?).


Much of the so-called oil of wintergreen is obtained from Betula lenta, which yields a product physically indistinguishable and difficult to differentiate chemically from methyl salicylate.



preparation method

The still being filled with wintergreen to within about twelve inches of the top, a sufficient quantity of water is added, and this is allowed to macerate from ten to twelve hours. The fire being started, the distillation commences, and continues for about eight hours; but during the first two or three hours ninety per cent. of the oil has passed over.

, For collecting the distillate, The oil and the water separate, the oil going to the bottom


characteristics

Colorless or nearly colorless. Strong, characteristic odor; taste pungent. Specific gravity 1.180 to 1.187; optical rotation at 25° C. (77° F.) 0° to -1°; refractive index 1.537 to 1.539. Soluble in 6 parts of alcohol (70 per cent.) at 25° C. (77° F.). Contains not less than 99 per cent. of esters, calculated as methyl salicylate, CH3C7H5O3." Br.

Adulterations

It is stated to have been largely adulterated with chloroform.

This and other impurities are to be detected by a comparison of the specific gravities and boiling points, or by fractional distillation.

It is readily soluble in alcohol. When heated to about 80° C. (176° F.), the oil should not yield a colorless distillate having the characteristics of chloroform or of alcohol.

Another distinguishing property is that in aqueous solution it gives a purple color with ferric salts. Oil of sassafras may be detected by the separation of a deep-red resinous mass on treatment with nitric acid in the cold.

Japanese oil of camphor and other light volatile oils used as adulterants can be detected by simply dropping the suspected oil in water; if pure, it sinks in a few seconds; if adulterated, some minutes are required.


True oil of gaultheria contains about 99 per cent. of methyl salicylate. Synthetic oil of wintergreen is now extensively manufactured and used instead of the natural oil