The fragrance of the foliage having thus attracted the attention of the Dutch, probably suggested submitting the leaves to distillation. Rumphius narrates how the oil was obtained in very small quantities, and was regarded as a powerful sudorific.
In Europe it appears to have been first noticed by J. M. Lochner,[1062] of Nürnberg, physician to the German Emperor. About the same time (1717), a ship’s surgeon, returning from the east, sold a provision of the oil to the distinguished apothecary Johann Heinrich Link at Leipzig, who published a notice on it and sold it.[1063] It began then to be quoted in the tariffs of other German apothecaries,[1064] although it was still reputed a very rare article in 1726.[1065] Somewhat larger quantities appear to have been soon imported by Amsterdam druggists.[1066] In Germany the oil took the name of Oleum Wittnebianum, from the recommendations bestowed on it by M. von Wittneben, of Wolfenbüttel, who was much engaged in natural sciences and long resident in Batavia.[1067] In France and England, it was however scarcely known till the commencement of the present century, though it had a place in the Edinburgh Pharmacopœia of 1788. In the London Price Current, we do not find it quoted earlier than 1813, when the price given is 3s. to 3s. 6d. per ounce, with a duty of 2s. 4½d. per ounce.
Manufacture—In the island of Bouro, in the Molucca Sea, the leaves of the Kayu-puti or Aij-puti, i.e. White-wood trees, are submitted to distillation with water, the operation being conducted in the most primitive manner, as already witnessed, about the year 1792, by Labillardière in his celebrated voyage with Lapérouse. Bickmore,[1068] an American traveller who passed three months in the island in 1865, states that it produces about 8,000 bottles of the oil annually, and that this is almost its only export. The Trade Returns of the Straight Settlements published at Singapore, show that the largest quantity is shipped from Celebes, the great island lying west of Bouro.
Description—Oil of Cajuput is a transparent mobile fluid, of a light bluish-green hue, a fragrant camphoraceous odour, and bitterish aromatic taste. It has a sp. gr. of 0·926, and remains liquid even at (8°·6 F.)-13° C. It deviates the ray of polarized light to the left. On diluting it with bisulphide of carbon it becomes turbid.
Chemical Composition—The researches of Schmidl (1860) and of Gladstone (1872) have shown that cajuput oil consists chiefly of Hydrate of Cajuputene or Cajuputol, C₁₀H₁₆, H₂O, which may be obtained from the crude oil by fractional distillation at 174° C. If it is repeatedly distilled from anhydrous phosphoric acid, Cajuputene, C₁₀H₁₆, passes over at 160-165° C.; it has an agreeable odour of hyacinths. After the cajuputene, Isocajuputene distils at 177°, and Paracajuputene at 310-316°, both agreeing in composition with cajuputene.
Like most essential oils having the formula C₁₀H₁₆, crude cajuput oil is capable of forming the crystallized compound C₁₀H₁₆, 3OH₂. This we have abundantly obtained by mixing 4 parts of the oil with 1 of alcohol 0·830 sp. gr., and one part of nitric acid 1·20 sp. gr.; the mixture should be allowed to stand in shallow dishes. By adding 1 vol. of absolute alcohol to 3 vol. of cajuput oil, and saturating it with anhydrous hydrochloric gas, crystals of the compound C₁₀H₁₆(HCl)₂ may be obtained. By vapour of bromine the oil acquires a beautiful green colour.
If 1 part of iodine be gradually dissolved in cajuput oil, the temperature being maintained at 50° C., fine green crystals of (C₁₀H₁₆HI)₂OH₂ are formed. They may be recrystallized from very little glacial acetic acid, but will not keep for more than a few weeks.
The green tint of the oil is due to copper, a minute proportion of which metal is usually present in all that is imported. It may be made evident by agitating the oil with water acidulated by a little hydrochloric acid. The compounds of copper with inorganic acids being comparatively of a fainter colour than the cupric salts of organic acids, the aqueous solution of chloride of copper now formed displays no longer the fine green tint. To the solution, after it has been put into a platinum capsule, a little zinc should be added, when the copper will be immediately deposited on the platinum. The liquid may be then poured off and the copper dissolved and tested. When the oil is rectified, it is obtained colourless, but it readily becomes green if in contact for a short time with metallic copper. The presence of the metal in the oil may also be shown at once by a scrap of paper which has been impregnated with fresh tincture of guaiacum wood and dried. If it is then moistened with water containing 1 per cent. of sulphocyanate of potassium, the paper turns intensely blue by the contact with the oil provided the latter contains copper.
Guibourt[1069] has however proved by experiment that the volatile oil obtained by the distillation of the leaves of several species of Melaleuca, Metrosideros and Eucalyptus, has naturally a fine green hue. It is not improbable that this hue is transient, and that the contamination with copper is intentional in order to obtain a permanent green.
Commerce—The oil is imported from Singapore and Batavia, packed in glass beer or wine bottles. From official statements[1070] it appears that the imports into Singapore during 1871 were as under:—