Oleum Rutae. Oil of Rue.
Related entries: Rue
Oil of rue is obtained by distillation from the garden rue, Ruta graveolens, Linn. (N.O. Rutaceae), a plant which is cultivated in countries of temperate climate. It occurs as a pale yellow liquid having a characteristic, sharp, unpleasant odour, becoming pleasant on considerable dilution. Specific gravity, 0.830 to 0.840 at 25°, the lowest of all the essential oils. Rotation, +0° 13' to +2° 30'. Solidifies to a crystalline mass at 5° to 10°. Adulteration of the oil is easily detected, the additions usually lowering the solidifying point and raising the specific gravity. Turpentine, the usual adulterant, and petroleum may be detected by the insolubility of the oil in 70 per cent. alcohol. Not more than 5 per cent. of the oil distils over below 200°; the remainder distils almost entirely between 215° and 232°.
Soluble in 70 per cent. alcohol (1 in 2 or 3), forming a clear solution.
Constituents.—The chief constituent of the oil is methyl nonyl ketone, C11H22O, of which the oil contains at least 90 per cent. It also contains methyl heptyl ketone and traces of methyl methyl-anthranilate. Lauric aldehyde, C12H25O, is supposed to be present, but absolute proof is wanting. The value of the oil depends on the amount of methyl nonyl ketone contained in it, and the solidifying point affords some indication of the amount of ketone present. The ketone may be separated from the oil by shaking with solution of sodium bisulphite, adding ether, and pressing the mixture. The solid cake is again treated with ether and pressed, and the operation repeated several times. The compressed cake is finally broken up and decomposed by an alkaline solution, the separated oil being purified by distilling in a current of steam. The specific gravity of the purified product is about 0.830. Boiling-point, 225°; melting-point, +15°. It is an oily liquid with a bluish fluorescence.
Action and Uses.—Oil of rue has properties resembling those of other volatile oils; it is employed principally as an antispasmodic in hysterical conditions, and as an emmenagogue in amenorrhoea. The oil may be administered on sugar, or in hot water.
Dose.—1 to 3 decimils (0.1 to 0.3 milliliters) (2 to 5 minims).