Oleum Sinapis Volatile (U. S. P.)—Volatile Oil of Mustard.

Related entries: Sinapis Alba (U. S. P.)—White Mustard. Sinapis Nigra (U. S. P.)—Black Mustard

"A volatile oil obtained from Black mustard by maceration with water, and subsequent distillation. It should be carefully kept in well-stoppered bottles, in a cool place, protected from light"—(U. S. P.).
SYNONYMS: Oil of mustard, Oleum sinapis aethereum.

Preparation and Description.—Volatile oil of mustard does not pre-exist in black mustard seed, but is formed in the decomposition of its glucosid sinigrin by a process of fermentation (see Chemical Composition). The fixed oil is first removed by hydraulic pressure, the press-cake is crushed, digested with water at a temperature not exceeding 70° C. (158° F.), and the volatile oil of mustard is then distilled off with steam. The yield is about 0.5 to 0.75 per cent. White mustard seed does not yield a volatile oil when thus treated (see Sinapis).

The volatile oil of mustard thus obtained is "a colorless or pale-yellow, limpid, and strongly refractive liquid, having a very pungent and acrid odor and taste, Specific gravity, 1.018 to 1.029 at 15° C. (59° F.). Boiling point, 148° to 150° C. (298.4° to 302° F.). Freely soluble in alcohol, ether, or carbon disulphide, the solutions being neutral to litmus paper"—(U. S. P.). The oil is soluble in from 160 to 300 parts of water, and in 10 parts of 70 per cent by volume of alcohol. Exposed to light, volatile oil of mustard decomposes, turning reddish-brown, and depositing a thin brown film on the walls of its containing vessel.

Chemical Composition.—The principal constituent of volatile oil of mustard is allyl-isothiocyanate (allyl-mustard oil, S:C:N.C3H5), with small amounts of allyl cyanide (CN.C3H5) and carbon disulphide (CS2), the latter being of somewhat obscure origin. Allyl-cyanide is formed by decomposition of allyl-mustard oil, which takes place, for example, when the oil is in prolonged contact with the copper of the still, thus: SCNC3H5 + Cu = CuS + CNC3H5. Notable quantities of this compound, which has the specific gravity 0.835, may render the volatile oil of mustard lighter than water (Will, 1863).

ALLYL-ISOTHIOCYANIDE is formed by the decomposition of the glucosid sinigrin (or potassium myronate C10H16NS2KO9), under the influence of the albuminous ferment myrosin, both being constituents of black mustard seed. The reaction, as elucidated by J. Gadamer and his predecessors (see Archiv der Pharm., 1897, p. 44), takes place as follows: C10H16NS2KO9 (sinigrin) + H2O = SCNC3H5 (allyl-mustard oil) + C6H12O6 (dextrose) + KHSO4 (acid potassium sulphate). It may also be prepared synthetically by the interaction of potassium sulphocyanide (NCSK), and allyl iodide (C3H5I) in alcoholic solution, whereby a molecular rearrangement from N:C.S.C3H5 (allyl-thio-cyanide) to S:C:N.C3H5 (allyl-isothiocyanide) takes place

Tests and Assay.—The U. S. P. directs the following tests for the volatile oil of mustard: "If to 3 Gm. of the oil 6 Gm. of sulphuric acid be gradually added, the liquid being kept cool, the mixture, upon subsequent addition, will evolve sulphur dioxide, but will remain of a light-yellow color, and at first perfectly clear, becoming afterward thick, and occasionally crystalline, while the pungent odor of the oil will disappear"—(U. S. P.). The final product in this reaction is sulphate of allylamine (C3H5NH2).

"If a portion of the oil be heated in a flask connected with a well-cooled condenser, it should distill completely between 148° and 150° C. (298.4° and 302° F.), and both the first and the last portion of the distillate should have the same specific gravity as the original oil (absence of alcohol, chloroform, carbon disulphide, petroleum, or fatty oils). If a small portion of the oil be diluted with 5 times its volume of alcohol, and a drop of ferric chloride T.S. be added, no blue or violet color should be produced (absence of phenols). If a mixture of 3 Gm. of the oil and 3 Gm. of alcohol be shaken, in a small flask, with 6 Gm. of ammonia water, it will become clear after standing for some hours, or rapidly when warmed to 50° C. (122° F.), and usually deposit, without becoming colored, crystals of thiosinamine (allyl-thio urea, CS.N2H3[C3H5]). To determine the proportion of thiosinamine obtainable from the oil, decant the mother water from the crystals, and evaporate it gradually in a tared capsule, on a water-bath, adding fresh portions only after the ammoniacal odor of each preceding portion has disappeared. Then add the crystals from the flask to those in the capsule, rinsing them out of the flask with a little alcohol, and heat the capsule on a water-bath until its weight remains constant. The amount of thiosinamine thus obtained from 3 Gm. of the oil should be not less than 3.25 Gm., nor more than 3.5 Gm. After cooling, thiosinamine forms a brownish, crystalline mass, fusing at 70° C. (158° F.), and having a leek-like, but no pungent odor. The mass should be soluble in 2 parts of warm water, forming a solution which should not redden blue litmus paper, and which possesses a somewhat bitter, not persistent taste"—(U. S. P.).

Action, Medical Uses, and Dosage.—(See Sinapis.)

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