In order to ascertain the oil content in the several stages of development and thus to learn the most favorable time for harvest and distillation, A.W. K. de Jong1) has made a series of investigations with Andropogon citratus. According to these the leaves are richest in oil. Moreover the leaf last formed contains relatively the most oil, and the oil content diminishes with the increasing age of the leaf. However, the citral content of the oil increases slightly with the age of the leaf, averaging 77 to 79 p. c. in the youngest and going as high as 83 p. c. in the oldest. The sheaths likewise contain oil, but much less than the leaves. The roots of Andropogon citratus also contain volatile oil. While the fibrous roots are devoid of oil, it is found in the thick tubers, of which the younger ones contain more (abt. 0,5 p. c.) than the older ones (abt. 0,35 p. c). Hence De Jong recommends that the roots be distilled with the grass. (Concerning the properties of this root oil see p. 207). It is said not to be advisable to postpone the distillation after the formation of the 4th or 5th leaf.
In Java, according to P. Serre2), lemongrass oil is distilled principally in Tjitjoeroek, Kediri and Tjiaoei, the yield amounting to about 0,33 p. c.
1) Teysmannia 1907, No. 8; Report of Schimmel & Co. October 1908, 81. 2) Journ. d' Agriculture tropicale 5 (1905), 42; Report of Schimmel & Co. October 1905, 46.
Experimental distillation with lemongrass has also been made in one of the agricultural chemical experiment stations of Cochinchina1). These experiments showed that the oil content is much greater during the dry season, and that the upper third of the plant is much more aromatic than are the lower two-thirds. From thoroughly dried leaves that had lost 70 p. c. of their original weight, 8 to 8,5 p. c. of oil were obtained. Leaves distilled immediately after cutting yielded 2 p. c. in the rainy season, and 5,5 p. c. in the dry season.
According to a communication to the Imperial Institute-), cultural experiments with lemongrass have been made in the Seychelles. Grass that had been imported a long time ago from Mauritius yielded 0,23 p. c. of oil, grass imported as recently as 1903 from Ceylon yielded 0,34 p. c. of oil.
According to R. F. Bacon 3), there is in the Philippines a lemongrass which, to judge by the oil obtained therefrom, may be regarded as Andropogon citratus, DC. It occurs all over the group of islands, either wild or as a garden plant. It grows abundantly in the uplands of the province of Benguet. However, it is cultivated to a slight extent only. In the language-of the Tagali the oil grass is designated by the name given to it by its first investigator, the Spanish Jesuit juan Eusebius Nuremberg, in 1635: tang/at, or more correctly tanglad. Other native designations are salai and balyoco. The Spanish name is Paja de Meca. The grass is not distilled for commercial purposes. Bacon correctly points out that under the present market conditions, the cultivation of lemongrass would not be remunerative in spite of quick and abundant returns. He, therefore, recommends it for intermediate cultivation only until other crops can yield a sufficient harvest. The distillation of a grass 5 months old, 2 days after it had been cut, yielded 0,2 p. c. of oil with the following properties: d30/4o 0,894; aD30o + 8,1°; nD80o 1,4857; citral content 79 p. c; complies with Schimmel's test i. e. soluble in 1 to 2 vols, and 10 vol. of 80 p. c. alcohol (apparently a con1) Bull, de la Chambre d' Agriculture de la Cochinchine 11 (1908), Nr. 98, p. 218; Report of Schimmel & Co. October 1908, 82. fusion with the test for citronella oil). The same plants cut again 4 months later yielded 0,2 p. c. of oil with the following constants: d30/4o 0,8841; aD80o + 2,1°; nD80o 1,4765; citral content 77 p.c. Grass 7 months old, from another planting, yielded, when distilled immediately after having been cut, 0,21 p.c. of oil with the following constants: d30/4o 0,891; aD30o +7,76°; nD80.1,4812; citral content 78 p. c. Basing his computations on the amount of grass harvested and assuming that these cuts can be made each year, Bacon points out that 240 to 300 kg. of oil per hectare per year can be expected. Inasmuch as the plant exhausts the soil, a transplanting must take place after three years.
2) Bull. Imp. Inst. 6 (1908), 108; Report of Schimmel & Co. October 1908, 82.
3) Philippine Journ. of Sc. 4 (1909), A, 111.
Composition. Of the constituents of the West Indian lemon-grass oil, the most important, the citral, only is known. Whether aldehydes other than citral are present has not yet been established, neither is it known what substances make the oil so difficultly soluble. When fractionated, the oil behaves very differently from the East Indian oil. According to the investigations of Umney and Bennett1) the former contains fewer low boiling substances than the latter. Whereas the East Indian oil began to distil at 210°, as much as 23 p.c. of the West Indian oil had passed over at this temperature. Furthermore, a comparative distillation under diminished pressure, in which the oils were resolved into fractions of 20 p. c. of the original oil, yielded appreciable differences of the respective fractions. Whereas the fractions of the West Indian oil were all inactive, those of the East Indian oil deviated between - 12 and - 2°.
Noteworthy is likewise the fact that the first 20 p. c. of the West Indian oil had a density of 0,821, as opposed to 0,882 of the East Indian oil.
This would seem to indicate an olefinic terpene. In harmony with this assumption is the behavior of the oil to dissolve in 2 vol. of 70 p. c. alcohol when freshly distilled, but to loose this property after a few days'2). A similar behavior is revealed by oil of bay, in which case the loss of solubility is attributed to the polymerization of the myrcene contained therein.
1) Chemist and Druggist 70 (1907), 138.
2) De Jong, Teysmannia 1907, No. 8; Report of Schimmel & Co. Oct. 1908, 81. - Watts and Tempany, West Indian Bulletin 9 (1908) 265; Report of Schimmel & Co. April 1909, 63.
Properties. d15.0,870 to 0,912; aD - 1° to + 0°12'; nD20o 1,482 to 1,489. The solubility varies according to age and manner of storage. The old oils do not form a clear solution with 70 p. c. alcohol1); individual oils are soluble in several vol. of 80 p.c. alcohol, but the solution becomes turbid upon the addition of more alcohol. It is miscible with absolute alcohol in all proportions, but whereas some oils produce turbid solutions, others form clear solutions.
The citral content, determined according to the bisulphite method, varies between 53 and 83 p. c.