This primitive Elemi is in our opinion identical with a peculiar sort of olibanum known as Luban Meyeti, afforded by Boswellia Frereana Birdwood ([p. 135]). It has a remarkable resemblance both in external appearance and in odour to the substance in after-times imported from America, and which were likened to the elemi and animi of the Old World. The description of “gummi elemnia” given by Valerius Cordus,[598] the most careful observer of his period, could in our opinion well apply to Luban Meyeti. ([See p. 153] further on.)
The first reference to Elemi as a production of America comes from the pen of Monardes[599] who has a chapter on Animi and Copal. He describes animi as of a more oily nature than copal, of a very agreeable odour, and in grains resembling olibanum but of larger size, and adds that it differs from the animi of the Old World in being less white and clear.
At a somewhat later period this resin and some similar substances began to be substituted for Elemi which had become scarce.[600] Pomet,[601] who as a dealer in drugs was a man of practical knowledge, laments that this American drug was being sold by some as Elemi, and by others as Animi or as Tacamaca. It was however introduced in great plenty, and at length took the place of the original elemi which became completely forgotten.
American Elemi was in turn discarded in favour of another sort imported from the Philippines. The first mention of this substance is to be found among the descriptions accompanied by drawings sent by Father Camellus to Petiver of London, of the shrubs and trees of Luzon,[602] in the year 1701. Camellus states that the tree, which from his drawing preserved in the British Museum appears to us to be a species of Canarium, is very tall and large, that it is called by the Spaniards Arbol de la brea, and that it yields an abundance of odorous resin which is commonly used for pitching boats. Living specimens of the tree together with samples of the resin were brought to Paris from Manila by the traveller Perrottet about the year 1820. For the last twenty years the resin has been common, and is now imported in large quantities[603] for use in the arts, so displacing all other kinds. It has been adopted as the Elemi of the British Pharmacopœia (1867), and is in fact the only variety of elemi now found in English commerce.
Description—Manila elemi is a soft, resinous substance, of granular consistence not unlike old honey, and when recent and quite pure is colourless; more often it is found contaminated with carbonaceous matter which renders it grey or blackish, and it is besides mixed with chips and similar impurities. By exposure to the air it becomes harder and acquires a yellow tint. It has a strong and pleasant odour suggestive of fennel and lemon, yet withal somewhat terebinthinous. When moistened with spirit of wine, it disintegrates, and examined under the microscope is seen to consist partly of acicular crystals. At the heat of boiling water the hardened drug softens, and at a somewhat higher temperature fuses into a clear resin.
Chemical Composition—Manila elemi is rich in essential oil. On submitting 28 lb. of it to distillation with water, we obtained 2 lb. 13 oz. (equivalent to 10 per cent.) of a fragrant, colourless, neutral oil, of sp. gr. 0·861 at 15° C. Observed in Wild’s polaristrobometer we found it to be strongly dextrogyre.[604] H. Sainte Claire Deville[605] on the other hand has examined an oil of elemi that was strongly levogyre. This discrepancy shows that there are among the oils of various kinds of elemi, differences similar to those existing in the oils of turpentine and copaiba. By the action of dry hydrochloric acid gas, Deville obtained from his oil of elemi a solid crystalline substance, C₁₀H₁₆ + 2 HCl. We failed to produce any such compound from the oil of Manila elemi. Our oil of elemi dissolves in bisulphide of carbon; when mixed with concentrated sulphuric acid, it becomes thick and assumes a deep orange colour.
By submitting the crude oil to fractional distillation, we separated it into six portions, of which the first five were dextrogyre in gradually diminishing degree, while the sixth displayed a weak deviation to the left.[606] The first portion having been dissolved in four times its weight of strong sulphuric acid, washed and again distilled, exhibit a deviation to the left.[607]
If the essential oil of elemi (8 parts) is shaken with alcohol, 0·816 sp. gr. (2 parts), nitric acid, 1·2 sp. gr. (1 part) and water (5 parts), the mixture, on exposure to air in a shallow capsule soon yields large crystals, which were found to agree crystallographically[608] perfectly with terpin, C₁₀H₂₀O₂ + OH₂ from oil of turpentine.
Maujean,[609] a French pharmacien, examined Manila elemi as long ago as 1821 and proved it to contain two resins, the one soluble in cold, the other only in hot spirit of wine. The former, which appears to constitute by far the prevailing part of all varieties of elemi, has not yet been satisfactorily examined. Bonastre[610] a little latter made a more complete analysis, showing that the less soluble resin which he obtained to the extent of 25 per cent. is easily crystallizable, and apparently identical with a substance obtainable in a similar manner from what he regarded as true elemi, which the Manila resin was not then held to be. Baup (1851) gave it the name of Amyrin. According to our experiments, it is readily isolated to the extent of 20 per cent. when Manila elemi is treated with cold spirit of wine, in which the crystals of amyrin are but slightly soluble. If the elemi is pure, the amyrin may be thus obtained (by washing with spirit and pressure between bibulous paper) in a cake of snowy whiteness, which may be further purified by crystallization from boiling alcohol. The fusing point of the crystals is 177° C.; their composition has been ascertained by Buri[611] to agree with the formula C₂₅H₄₂O, which may be written thus: (C₅H₈)₅ OH₂. Amyrin at 16° C. dissolves in 27·5 parts of alcohol 0·816 sp. gr., being readily soluble also in all the usual solvents for resins. The alcoholic solution is slightly dextrogyre. Amyrin is a neutral substance, and may be sublimed in small quantities by very carefully heating it.
By heating amyrin with zinc dust Ciamician[612] obtained chiefly toluol, methyl-ethyl-benzol and ethyl-naphtalin.