Source: https://chestofbooks.com/health/aromatherapy/The-Volatile-Oils-Vol2/381-Rose-Geranium-Oil-Part-2.html
Timestamp: 2019-04-24 22:22:03+00:00

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According to estimate, Spain produces in Valencia and Andalusia about 600 to 1000 kg. of oil annually. Under favorable climatic conditions 2 to 3 harvests are possible.
Properties. Oil of rose geranium is a colorless, greenish or brownish liquid with a pleasant, rose-like odor: d15o0,89 to 0,907; aD - 6 to - 16°. With the exception of the Spanish oil, the several varieties are as a rule soluble in 2 to 3 vol. of 70 p. c. alcohol, forming a clear solution. However, the addition of more solvent usually produces turbidity due to the separation of paraffin. According to Jeancard and Satie4) the A. V. fluctuates between 1,5 and 12, increasing upon standing when the oil is kept in but partly filled bottles. The E. V. fluctuates between 34 and 99, corresponding to between 14,3 and 41,7 p. c. of geranyl tiglinate.
1) Berichte von Roure-Bertrand Fils April 1901, 17; October 1907, 36.
2) Ibidem October 1906, 28.
3) Jeancard and Satie, Bull. Soc. chim. III. 31 (1904), 43.
4) Bull. Soc. chim. III. 23 (1900), 37.
The several varieties of oil differ from each other more or less, a fact that finds a ready explanation, in part at least, in the different botanical source of the material distilled (compare under yield on p. 614).
1. Reunion geranium oil. d15o 0,888 to 0,896; aD - 7° 50' to - 13°50'; nD20o 1,462 to 1,468; A. V.1) 1,5 to 12; E. V. 50 to 78 = 21 to 33 p. c. geranyl tiglinate2); E. V. after acetylation 206 to 233 = 67 to 77,6 p. c. alcohol C10H18O; total alcohol including alcohol as ester (comp. vol. I, p. 576) 60 to 71 p. c.
14,3 to 29,5 p. c. tiglinate; E. V. after acetylation 203 to 230 = 66 to 76,4 p. c. alcohol C10Hl8O; total alcohol content including alcohol as ester 62 to 71,5 p. c.
3. French geranium oil. d15o0,896 to 0,905; aD - 7° 30' to -10° 15'; A. V. 6 to 10; E. V. 46 to 66 = 19,4 to 28 p. c. tiglinate; E. V. after acetylation 217 to 228 = 71,3 to 75,6 p. c. alcohol C10H18O. Citronellol content 37 to 40 p. c.3).
4. Spanish geranium oil. d15o 0,897 to 0,907; aD - 7° 30' to -11°; A. V. 3 to 11; E. V. 64 to 99 = 27 to 42 p.c. tiglinate; E. V. after acetylation 204 to 234 = 66 to 78 p.c. alcohol C10H18O.
5. Corsican oil. Of this variety only a few samples have been investigated. d15o0,896 to 0,901; aD - 8 to - 10° 30'; A. V. 3,6 to 5; E. V. 56 to 63 = 23,6 to 26,5 p.c. tiglinate.
6. The German oil4), which has been distilled occasionally, is not an article of commerce. Yield 0,16 p. c. d15o0,906; aD - 16°; tiglinate content 27,9 p.c; E. V. after acetylation 212 = 69,3 p. c. alcohol C10H18O.
1) The acid value of these oils has been determined according to the customary method (see vol. I, p. 572) and not according to the method proposed by Jeancard and Satie (footnote 4, p. 616). According to the latter, 10 cc. of half-normal potassium hydroxide solution are added to 3 g. of the oil and the excess of alkali is titrated back with acid. This method of procedure may result in a partial saponification of the ester, hence in too large an acid value.
2) For the computation of the geranyl tiglinate content the table on p. 631 of vol. I may be utilized.
3) The properties of the French oil have been studied in detail by Jeancard and Satie. Bull. Soc. chim. III. 31 (1904), 43.
4) Report of Schimmel & Co. April 1894, 33.
7. Oil from Palestine1) d15o896; aD--8°20'; A. V. 9,8; E. V. 68,6; citronellol content 45,7 p. c.
Transportation' in tin cans, in which geranium oil is mostly shipped, causes it to assume a brown color and an odor reminding of rotten eggs. The odor, however, is readily removed by exposing the oil for several days in shallow dishes to the air. Naturally, the oil should be transferred to glass containers as soon as possible.
Composition. The principal constituent of geranium oil is geraniol2), C10H180, common to all commercial varieties.
In addition to geraniol a second alcohol, C10H20O, citronellol, has been identified by F. Tiemann and R. Schmidt8). It is particularly abundant in the Reunion oil. Mixtures of these two alcohols were formerly regarded as definite chemical compounds. Such was the case with the "rhodinol de pelargonium" of P. Barbier and L. Bouveault4) and the "Reuniol" of Hesse5).
The relative amounts of geraniol and citronellol in the several commercial oils have been determined by Tiemann and Schmidt'). Of the 70 p.c. of total alcohols of Spanish geranium oil, 65 p.c. consist of geraniol and 35 p.c. of citronellol. Of the 75 p.c. of total alcohols of the African geranium oil, four-fifths are geraniol and one-fifth citronellol. Reunion geranium oil yields 80 p.c. of alcohols, consisting half and half of geraniol and citronellol respectively. In all of the oils the citronellol existed as a mixture of the dextrogate and lasvogyrate modifications.
The above results, however, cannot be regarded as exact, since according to recent investigations other alcohols are present, viz., linalool, borneol (?), terpineol, pheriylethyl alcohol, menthol and an amyl alcohol (?). According to Tiemann and Schmidt's assay method6) some of these are determined as geraniol, others as citronellol.
1) C. Satie, Americ. Perfumer 1 (1907), No. 12, p. 12.
2) Gintl, Jahresb. d. Chem. 1879, 941; J. Bertram and E. Gildemeister, Journ. f. prakt. Chem. 11. 49 (1894), 191.
s) Berl. Berichte 29 (1896), 924.
4) Compt. rend. 119 (1894), 281 and 334.
5) Journ. f. prakt. Chem. H. 50 (1894), 472 and 53 (1896), 238.
°) By treating the oil with phosphorus trichloride. This reagent converts citronellol (other alcohols likewise) into a phosphorous acid ester, and geraniol is converted into geranyl chloride and a hydrocarbon.
According to C. Satie1), French oil contains from 37 to 43 p.c. of citronellol, African likewise 37 to 43 p. c. and Reunion oil 50 to 65 p. c. These amounts were determined by means of the formylation method with formic acid (comp. vol. I, p. 580), without, however, paying any attention to the length of formylation. As was shown later, this factor is of great importance, hence the above data may have to be modified.

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