But it is only in very recent times that the volatile oils of these plants have become objects of commerce with Europe. Lemon grass oil is mentioned by Roxburgh in 1820 as being distilled in the Moluccas; and it was first imported into London about the year 1832. Citronella oil is of much more recent introduction. Ginger grass oil, called in Hindustani Rúsa ka tel, is stated by Waring[2708] to have been first brought to notice by Dr. N. Maxwell in 1825.
Production—Citronella and Lemon grass are cultivated about Galle and at Singapore, the same estate often producing both. The grasses are distilled separately, the essential oils being regarded as entirely distinct, and having different market values. In Ceylon they are cut for distillation at any time of year, but mostly in December and January.
On the Perseverance Estate at Gaylang, Singapore, belonging to Mr. John Fisher, an area of 950 acres is cultivated with aromatic grasses and other plants, for the production of essential oils. The manufacture was tried on a small scale in 1865, and has been so successful that an aggregate of 200 lb. of various essential oils is now produced daily. These oils are stated to be Citronella, Lemon Grass, Patchouly, Nutmeg, Mace, Pepper, and Oman ([p. 302]): and mint is now being cultivated.[2709]
Ginger grass oil is distilled in the collectorate of Khandesh in the Bombay Presidency. That produced in the district of Namár in the valley of the Nerbudda, is sometimes called Grass Oil of Namar. We have no particulars of the distillation, which however must be carried on extensively.
Description—The Indian grass oils are lighter than water, devoid of rotatory power when examined by polarized light, and do not alter litmus paper. They are all extremely fragrant, having an odour like a mixture of lemon and rose. Lemon grass, which in colour is a deep golden brown, has an odour resembling that of the sweet-scented verbena of the gardens, Lippia citriodora H.B.K. Ginger grass oil, the colour of which varies from pale greenish yellow to yellowish-brown, has the odour of Pelargonium Radula Aiton. The colour of citronella oil is a light greenish yellow. The manufacture of Winter of Ceylon, and of Fisher of Singapore, have a reputation for excellence, and are generally indicated by name in drug sale catalogues.
Chemical Composition—Stenhouse[2710] examined in 1844 oil of ginger grass given to him by Christison as Oil of Namur (or Nimar). The sample was of deep yellow, and apparently old, for when mixed with water and subjected to distillation, it left nearly one half its bulk of a fluid resin, the oil which passed over being colourless. After rectification from chloride of calcium, it was shown to consist of a hydrocarbon mixed with a small proportion of an oxygenated oil. The latter having been decomposed by sodium, and the oil again rectified, a second analysis was made which proved it isomeric with oil of turpentine.
A genuine grass oil from Khandesh, derived as we suppose from the same species, which was examined by one of us (F.), yielded nothing crystalline when saturated with dry hydrochloric acid; but when the liquid was afterwards treated with fuming nitric acid, crystals of the compound, C₁₀H₁₆, HCl, sublimed into the upper part of the vessel. We have observed that the oils both of lemon grass and citronella yield solid compounds, if shaken with a saturated solution of bisulphite of sodium.
Citronella oil was found by Gladstone (1872) to be composed chiefly of an oxidized oil, which he called Citronellol, and which he separated by fractional distillation into two portions, the one boiling at 202-205° C., the other 199-202° C. The composition of each portion is indicated by the formula C₁₀H₁₆O.
Wright’s researches (1874) tend rather to show the prevailing part of citronella oil to consist of the liquid C₁₀H₁₈O, boiling near 210°, which he calls Citronellol. It unites with bromine, and the resulting compound, upon heating, breaks up according to the following equation:—
| C₁₀H₁₈OBr₂ = | OH₂ · 2 HBr · C₁₀H₁₄. |
| Cymene. |