Oleum Aethereum (U. S. P.)—Ethereal Oil.

A volatile liquid consisting of equal volumes of heavy oil of wine and ether"—(U. S. P.).

Preparation.—"Alcohol, one thousand cubic centimeters (1000 Cc.) [33 fl℥, 391♏]; sulphuric acid, one thousand cubic centimeters (1000 Cc.) [33 fl℥, 391♏], distilled water, twenty-five cubic centimeter (25 Cc.) [406♏]; ether, a sufficient quantity. Add the acid slowly to the alcohol, mix them thoroughly, and allow the mixture to stand in a closed flask, for 24 hours, or until the liquid is clear; then pour the clear liquid into a tubulated retort of such capacity that the mixture shall nearly fill it. Insert a thermometer through the tubulure, so that the bulb shall be deeply immersed in the liquid, and, having connected the retort with a well-cooled condenser, and also having connected with the receiver a bent glass tube for conducting the uncondensed gases into water, distill, by means of a sand-bath, at a temperature between 150° and 160° C. (302° and 320° F.), until oily drops cease to come over, or until a black froth, which forms on the surface, begins to rise in the retort. Separate the yellow ethereal liquid from the distillate, and expose it to the air for 24 hours, in a shallow capsule. Then transfer it to a wet filter, and when the watery portion has drained off, wash the oil which is left on the filter with the distilled water, which should be as cold as possible. When this also has drained off, transfer the oil to a graduated measure, and add to it an equal volume of ether. Keep the product in small, glass-stoppered vials, in a cool place"—(U. S. P.).

Description and Chemical Composition.—Ethereal oil is officially described as "a transparent, nearly colorless, volatile liquid, of a peculiar, aromatic, ethereal odor, a pungent, refreshing, bitterish taste, and neutral to dry litmus paper. Specific gravity, 0.910 at 15° C. (59° F.)"—(U. S. P.).

The chemical composition of this oil is tersely stated by Bruno Hirsch (Universal Pharmacopoeia, 1890, No. 2109) as follows: "The heavy oil of wine which constitutes one-half of the finished product, is to be considered a solution of solid aetherin and liquid aetherol, both of the empirical formula C2H4, in diethyl-sulphurous acid ([C2H5]2SO3) and diethyl-sulphuric acid ([C2H5]2SO4) in variable quantities, the proportions of which are not yet determined." (Also see Prof. J. M. Maisch, Amer. Jour. Pharm., 1865, p. 100; and Charles L. Diehl, ibid., p. 126.)

Uses.—This oil is used only for pharmaceutical purposes. It is a constituent of compound spirit of ether. In moderate doses ethereal oil stimulates the vasomotor centers, and if the dose be sufficiently large, this is followed by paralysis of the tunics of the blood vessels.

King's American Dispensatory, 1898, was written by Harvey Wickes Felter, M.D., and John Uri Lloyd, Phr. M., Ph. D.