5) Journ. f. prakt. Chem. II. 50 (1894), 472.
6) Berl. Berichte 29 (1896), 922.
It was discovered simultaneously by two investigators, though independently of each other, viz., by H. von Soden and W.Rojahn1) and by H. Walbaum2). In the so-called concrete oils obtained by the extraction of fresh or dried rose petals with ether or petroleum ether it occurs in much larger amounts8), likewise in the ethereal oil obtained from the rose pomades (abt. 46 p. c.)4) and in the oil extracted from rose water (abt. 35 p. c.)1).
An alcoholic constituent of minor importance is l-linalool5) (oxidation to citral; m. p. of naphthocinchoninic acid 197 to 199°). Essential as constituent is an odoriferous nonylic aldehyde (m. p. of pelargonic acid 252 to 253°) found by Schimmel & Co.5). Probably this is accompanied by higher and lower homologues. In this connection traces of citral were also found in oil of rose (m. p. of naphthocinchoninic acid 195 to 197°). In addition there should be mentioned eugenol6) which is present to the extent of about 1 p. c; also a primary sesquiterpene alcohol which combines with phthalic acid anhydride and which possibly is identical with farnesol7). Finally, nerol (m. p. of diphenyl urethane 52 to 53°) should be mentioned. According to von Soden and Treff6), rose oil contains from 5 to 10 p. c. of this alcohol.
The alcohols are contained in rose oil mostly as such. In small part only are they present as esters. The eleoptene of Bulgarian oil of rose contains about 90 p. c. of alcohols computed as C10H18O. Normal Bulgarian oil (including the stearoptene) contains, on the average, from 2,5 to 3,5 p. c. of esters computed as geranyl acetate, German oils from 1,6 to 3,6 p. c.
1) Berl. Berichte 33 (1900), 1720.
2) Ibidem 1903, 2299. - Walbaum and Stephan, ibidem 2302.
3) From the water left in the still after distillation of roses v. Soden and Rojahn separated an oil by means of ether extraction from which they isolated phenylethyl alcohol in the following manner: 200 g. of oil were shaken with 5 kg. of a 5p.c. solution of sodium hydroxide. In addition to the acids and phenols some of the phenylethyl alcohol went into solution and could be recovered in a very pure state by shaking out the clear solution with ether.
4) v. Soden and Rojahn, Berl. Berichte 33 (1900), 3063; 34 (1901), 2803.
5) Report of Schimmel & Co. October 1900, 54. 6) Berl. Berichte 37 (1904), 1094.
7) See vol. I, p. 399.
As becomes apparent from the investigations of Dupont and Guerlain1), the esters are more strongly optically active than is the mixture of the underlying alcohols. Whereas the liquid portions of a French oil of rose was laevorotatory to the extent of 10°30' before saponification, after saponification the angle was but, - 7°55'. The acids combined with the alcohols as esters have not yet been investigated. Dupont and Guerlain are of the opinion that the esters play an important role in the production of the perfume.
As shown by Fluckiger2), the stearoptenc of rose oil belongs to the hydrocarbons of the paraffin series C11H2n + 2. However, it does not consist of a single hydrocarbon but at least of two, and probably of a series of homologous paraffins. This becomes apparent from the fact that when larger amounts of rose oil stearoptene are treated properly, they can be separated into fractions melting at 22° and at from 40 to 41° 3).
According to Schimmel & Co.4) the ethyl alcohol, which was found by Eckart in rose oil, is formed only when the roses have become heated and begin to ferment during transportation to the still. If the floral leaves are distilled as soon as picked the oil contains no ethyl alcohol.
Examination. In connection with so costly a product as oil of rose the danger of adulteration is very great. Hence in the course of time numerous empirical methods of examination have been proposed. Most of these pertained to the detection of palmarosa oil, the so-called Turkish geranium oil. Even formerly these tests did not enjoy special confidence. This, however, was altogether shaken when it was shown that geraniol is the principal constituent of palmarosa oil as well as of rose oil. It is true, the possibility was not excluded that some minor constituent of the palmarosa oil might yield specific reactions with the reagents suggested and thus reveal the presence of the foreign oil. However, the investigation of palmarosa oil in this direction has yielded no tangible results1). Moreover, it should be remembered that the Bulgars treat the palmarosa oil before they use it as adulterant. Thus e.g. they attempt to impart to the palmarosa oil a more rose-like odor by shaking it with lemon juice and by exposing it to the sun.
1) Compt. rend 123 (1896), 750. 2) See footnote 2, p. 567.
3) Report of Schimmel & Co. October 1890, 54. - Eckart, Dupont and Guerlain, loc. cit.
4) Report of Schimmel & Co. October 1892, 41.
In addition to palmarosa oil, the genuine geranium oil, also its constituents geraniol and citronellol, come into consideration. If the adulteration has been made skillfully, not only do the various proposed color reactions with iodine, sulphuric acid2) and magenta sulphurous acid fail, but the more rational chemical and physical methods of investigation as well. This is partly due to the similarity between the chemical constituents of the oil of rose itself and those of its adulterant. Moreover, the character of oil of rose varies so considerably because of differences in climate, meteorological conditions, character of soil, and method of distillation. This is particularlytrue of its paraffin content; hence a comparison of the physical constants which, even in a normal oil, vary so considerably, do not always lead to the detection of an adulterant.
It is for this reason that it is impossible to state with any degree of certainty that the Bulgarian oil of rose of commerce is the pure distillate from roses. Various indications would seem to favor the doubt. First of all, the large importation of palmarosa oil into Bulgaria arouses suspicion. Its use seems to become apparent when one considers that, as a rule, the exportation of oil of rose from Bulgaria is greater than the production. (Comp. the curve on p. 576.) Moreover the differences between Bulgarian and German oil are too great to be explained away by climatic differences. It is also queer that especially fine oils, occasionally exhibited by Bulgarian distillers, reveal the greatest similarity with German oil as to odor, congealing point and stearoptene content.