(The greater portion of this paper was read before the Edinburgh Chemists' Assistants and Apprentices' Association, November 7, 1883.)
BY PETER MACEWAN.
During the past two or three years a demand has sprung up for oleum rusci, and considerable doubt has been expressed as to its nature and quality, articles of different characters having been supplied.
It would appear from the name that the article has some relation to butcher's broom (Ruscus aculeatus), but we learn from various sources that it is merely one of the synonyms of the empyreumatic oil of common birch (Betula alba). Thus the Danish Pharmacopoeia, 1805, has the oil under these names, "Oleum betulinum, oleum rusci, oleum brusci," the latter being another name for the butcher's broom. These names are quoted in the Norwegian Pharmacopoeia of 1854 under "Pix epidermidis betulae albae;" more recently we find that Hager uses the synonym for the birch tar oil, and the Dutch Society for the Advancement of Pharmacy have it as "Oleum betulae rectificatum, oleum rusci." (Pharm. Journ. , xiii, 10.)
I can find no explanation of the association of the words "Ruscus" and "Bruscus" with this birch product, and can offer none, unless "Brzoza" (Polish for birch) may have been corrupted into "Bruscus" and thence into "Ruscus." At all events it is beyond dispute that oleum rusci is birch tar oil.
The oil has been long known as that used in currying Russia leather, to which it imparts the peculiar odor and lasting properties that are so much admired; it is chiefly made in Russia and Poland. The bark, and sometimes the rootlets and twigs, are subjected to dry distillation, the retort being of clay and connected by wooden pipes to a receiver placed in the earth. Hager states that this oil is a thickish liquid of a reddish-brown or brown-black color, peculiar empyreumatic odor, and sparingly soluble in water, but soluble in alcohol and ether to a great extent. The re-distilled oil of the Dutch Society is said to be a red-brown volatile oil, sp. gr. 0.800-0.987, soluble in an equal weight of alcohol and imparting an acid reaction to water. Birch bark has a mildly fragrant odor, and by gentle heating yields a sublimate of birch camphor or betulin (C36H60O3). This body, as obtained from the bark by exhaustion with alcohol, is odorless and tasteless, but when subjected to a high temperature (about 258°C.) it gives off vapors smelling strongly like Russia leather. This change will very probably be effected in the distillation of the empyreumatic oil from the bark, thereby accounting for its distinctive odor. Independently of its use in currying, the oil is held in high esteem by the Russian peasantry as a household remedy for all diseases, as well as by the medical practitioners in the treatment of skin diseases, rheumatism and the like; it is similarly used in Germany, whence it is exported. Its reputation has traveled to this country, but I am afraid that the remedy has not accompanied the reputation.
Through the kindness of Mr. Holmes, Curator of the Museum of the Pharmaceutical Society, I have received a small portion of a veritable specimen brought from Russia by Mr. Greenish, of which Mr. Holmes gives me the following particulars:
"Specimen 511 b" (Museum Catalogue) "is a black empyreumatic fluid resembling in odor the liquid known as 'essence of smoke,' used for curing hams; after a mere trace of it has been rubbed on the hand an odor like Russia leather is perceptible. The fluid, when caused to cover the side of the bottle in thin layer, is black with a brown tinge. . . I believe the pyroligneous oil of birch is sometimes prescribed under the name of 'ol. rusci.' . . . Dr. Symes tells me that there is a brown oil of birch which he believes is only the dark oil redistilled."
There is no doubt whatever that oil similar to Mr. Greenish's is extremely rare in this country, although the oil mentioned by Dr. Symes is readily procurable; but there are others which can only be called substitutions and sophistications, and of these I append particulars I have only had small samples given me, and of these only No. 1 seems favorable for further investigation.
No. 1. Red-brown "re-distilled oil," sp. gr. 0.941. Exposed for fifteen minutes on a water bath it was reduced to half its original bulk. Residue resembled Mr. Greenish's specimen; betulin odor intensified, but more pyroligneous than the veritable specimen.
No. 2. Red-brown "re-distilled oil," sp. gr. .876. (This oil is more fragrant than the genuine or No. 1, and suggests "doctoring.") On a water bath, the greater part volatilized within ten minutes, leaving a small residue of an oily nature and strong pyroligneous odor.
No. 3. A thick tar, black and bituminous. Odor somewhat like huile de cade. This was not examined, Hager stating that very thick varieties should be rejected.
No. 4. An amber-colored oil, sp. gr. 0.891. Odor like that of common spirit of tar (ol. picis rect.). On the water bath a small quantity was vaporized within ten minutes, leaving a mere trace of resinous matter destitute of betulin odor.
Owing to my portion of Mr. Greenish's sample being extremely small, I have only been able to take its sp. gr. roughly and found it to be 0.943; this, however, requires verification. On the water bath it leaves a thick and tenacious black residue having the betulin odor. The only specimen which compares favorably with it is No. 1, which answers the description of the re-distilled oil of the Dutch Society. It is much thinner than the genuine oil, and the pyroligneous odor is stronger; but a trace of it, treated as directed by Mr. Holmes, gives a powerful betulin odor in the course of fifteen minutes. This variety is readily obtainable. From the behavior of No. 2 1 am inclined to think that it is a "made-up" oil, since the fragrance entirely disappears on the water bath. No. 4 is the "ol. rusci" which has been so largely supplied to pharmacists, and several eminent dermatologists have formed their opinions of the value of the remedy from their experience with this variety. It is not surprising, therefore, that they have reverted in some cases to old-fashioned remedies such as huile de cade. This is to be regretted, for ol. rusci has been found useful in the hands of continental practitioners, and if a demand were here made for the genuine oil, means would not be wanting for obtaining it.
I cannot conclude without expressing my thanks to Mr. Holmes for his assistance, and to Messrs. Crowden and Hill for specimens.—Phar. Jour. and Trans., Nov. 17, 1883.