On the other hand the product obtained by the distillation of 2500 kilos of roses with 1 kilo of geraniol8) cannot be differen1) E. Gildemeister and K. Stephan, Arch, der Pharm. 234 (1896), 321.
*) G. Panajotow, Berl. Berichte 24 (1891), 2700. - Report of Schimmel & Co. April 1892, 45. Comp. also Jedermann, Zeitschr. f. analyt. Chemie 36 (1897), 96 and Report of Schimmel & Co. April 1897, 34.
3) Report of Schimmel & Co. October 1896, 66.
tiated from the commercial Bulgarian oil of rose. Intensity of odor, congealing point and stearoptene content are identical.
In order to guard against crude adulterations, the specific gravity, angle of rotation, index of refraction, stearoptene content, saponification value and the content of alcoholic components should be determined.
If the results of such an investigation are in harmony with the constants of good average oils, and if the odor is delicate and of sufficient strength, the oil in question may be regarded without suspicion. However, no chemist can undertake to guarantee the purity of an oil on the strength of its physical and chemical examination.
Specific Gravity. Inasmuch as the oil is permeated with crystals at 15°, the density determination must be made at 20, 25 or 30°. The addition of palmarosa oil scarcely alters the density, that of alcohol lowers it. The presence of the latter may be indicated by taking the specific gravity before as well as after shaking the oil with water1). Sandalwood oil, used in the distillation of rose oil in India, is indicated by its greater density.
Optical Rotation. The optical rotation is scarcely influenced by the presence of geraniol or palmarosa oil, but by that of gurjunbalsam oil (for its detection see p. 575). It is noteworthy that the angle of rotation of the French oil is much greater than that of German or Bulgarian oil.
Congealing Point. The congealing point of oil of rose is that degree of temperature at which the first crystals appear when the oil is subjected to slow cooling. According to P. N. Raikow2), who defines the congealing point as the point of supersaturation of the eleoptene with the stearoptene, the determination is carried out in the following manner:
About 10 cc. of oil of rose are transferred to a test tube with a diameter of 15 mm. A thermometer is suspended in the oil in such a manner that it touches neither the bottom nor the sides. With the aid of the hand the contents of the test tube are warmed to a temperature 4 to 5° above the point of super1) Report of Schimmel & Co. October 1908, 108. 2) Chem. Ztg. 22 (1898), 149.
saturation and well shaken. The tube is then fastened to a support and allowed to stand and cool until the first crystals separate. The degree of temperature is read off on the thermometer, the oil is again warmed and well shaken and the congealing point determined once more.
As to good Bulgarian oils of commerce, the congealing point or the crystallization point1), as it has been aptly named, as a rule fluctuates between 18 and 23°, however, variations upwards as well as downwards have been observed. Formerly oil of rose was valued in accordance with its congealing point. Although the odorless paraffin is valueless, an oil was higher priced the higher its congealing point. Originally this conclusion was based on the correct assumption that the addition of palmarosa oil must bring about a lowering of the congealing point. When later the congealing point was raised artificially by the addition of spermaceti, this method lost in importance. It has already been pointed out that the genuine, normal Bulgarian oil of rose is much richer in stearoptene than the commercial oil.
Determination of the Stearoptene Content2). 50 g. of oil and 500 g. 75 p.c. alcohol are heated to from 70 to 80°. Upon cooling the solution to 0° the stearoptene separates well nigh quantitatively. It is removed by filtration and is treated in like manner with 200 g. of 75 p.c. alcohol. This operation is repeated until the stearoptene is odorless. As a rule two such treatments of the crude stearoptene are sufficient.
Determination of possible Spermaceti in the Stearoptene. From 3 to 5 g. of stearoptene are boiled with 20 to 25 g. of 5 p.c. alcoholic potassa for a short time in a flask connected with a reflux condenser. The alcohol is then evaporated and water is added to the residue. Upon cooling, the bulk of the stearoptene separates at the surface as a solid, crystalline mass. The alkaline liquid is poured off, the stearoptene melted with some hot water and again allowed to cool. The water is again poured off and the operation repeated until the wash water is neutral. The combined aqueous liquids are shaken out twice with ether in order to remove any suspended stearoptene. The alkaline solution separated from the ether is acidulated with dilute sulphuric acid and again shaken out with ether. Upon evaporation of the ether no residue of fatty acids should remain. For the purpose of control the recovered stearoptene is dried at 90° and weighed. Invariably a small loss will be observed due to volatilization while drying.
1) P. Siedler, Berichte d. deutsch. pharm. Ges. 22 (1912), 489. 2) Report of Schimmel & Co. April 1889, 37.
It is simpler to determine any spermaceti content by saponifying with half-normal potassium hydroxide solution and titrating back with half-normal sulphuric acid. The saponification value of spermaceti is 128 to 130, that of the natural rose oil stearoptene about 3 to 7.
Saponification. The ester value of good commercial oils fluctuates between 7 and 16, the acid value between 0,5 and 3. Palmarosa oil has an E. V. of from 12 to 50, the true geranium oils one of from 31 to 100. Hence the addition of these foreign oils may be indicated by an increase in the E. V.
Acetylation. For a complete analysis, rose oil should be acetylated in order to determine the alcohol (geraniol and citronellol) content. Naturally the amount of these alcohols is inversely proportional to the stearoptene content. Good oils of rose contain from 66 to 75 p.c. of alcohols computed as geraniol. Palmarosa oil contains from 75 to 95 p.c. of geraniol1).