Extraction—A recent account of the production of this drug is found in the Reports of the Jury of the Madras Exhibition of 1855. It is there stated that Wood Oil, as the balsam is commonly called, is obtained for the most part from the coast of Burma and the Straits, and is procured by tapping the trees about the end of the dry season. Several deep incisions are made with an axe into the trunk of the tree and a good-sized cavity scooped out. In this, fire is placed, and kept burning until the wood is somewhat scorched, when the balsam begins to exude, and is then led away into a vessel of bamboo. It is afterwards allowed to settle, when a clear liquid separates from a thick portion called the “guad.” The oil is extracted year after year, and sometimes there are two or three holes in the same tree. It is produced in extraordinary abundance; from 30 to 40 gallons according to Roxburgh may sometimes be obtained from a single tree in the course of a season, during which it is necessary to remove from time to time the old charred surface of the wood and burn afresh.
If a growing tree is felled and cut into piece, the oleo-resin exudes and concretes on the wood, very much, it is said, resembling camphor (?) and having an aromatic smell.
Description—As Gurjun balsam is the produce of different trees as well as of different countries, it is not surprising to find that it varies considerably in its properties.
The following observations refer to a balsam of which 400 lb. were recently imported from Moulmein for a London drug firm. It is a thick and viscid fluid, exhibiting a remarkable fluorescence, so that when seen by reflected light it appears opaque and of dingy greenish grey; yet when placed between the observer and strong daylight it is seen to be perfectly transparent and of a dark reddish-brown.[365] It has a weak aromatic copaiba-like odour and a bitterish aromatic taste without the persistent acridity of copaiba. Its sp. gr. at 16·9° C. is 0·964.
With the following liquids Gurjun affords perfectly clear solutions which are more or less fluorescent, namely pure benzol (from benzoate of calcium), cumol, chloroform, sulphide of carbon, essential oils. On the other hand, it is not entirely soluble in methylic, ethylic, or amylic alcohol; in ether, acetic ether, glacial acetic acid, acetone, phenol (carbolic acid), or in caustic potash dissolved in absolute alcohol. Many samples of commercial benzin also are not capable of dissolving the oleo-resin perfectly, but we have not ascertained on what constituent of such benzin this depends. We have further noticed that that portion of petroleum which is known as Petroleum Ether, containing the most volatile hydrocarbons, does not wholly dissolve the oleo-resin. One hundred parts of the balsam warmed and shaken with 1000 parts of absolute alcohol yielded on cooling a precipitate of resin amounting when dried to 18·5 parts. All concentrated solutions of the balsam are precipitated by amylic alcohol.
If the balsam is kept for a long time in a stoppered vessel at 100° C. it simply becomes a little turbid; but about 130° C. it is transformed into a jelly, and on cooling does not resume its former fluidity. Balsam of copaiba heated in a closed glass tube to 220° C. does not at all lose its fluidity, whereas Gurjun balsam becomes an almost solid mass.
Chemical Composition—Of the balsam 6·99 grammes dissolved in benzol and kept in a water bath until the residue ceased to lose weight, yielded 3·80 grammes of a dry, transparent, semi-fluid resin, corresponding to 54·44 per cent., and 45·56 of volatile matters expelled by evaporation. But another sample afforded us much less residue. By submitting larger quantities of the above balsam to the usual process of distillation with water in a large copper still, 37 per cent. of volatile oil were easily obtained. The water passing over at the same time did not redden litmus paper. A dark, viscid, liquid resin remained in the still.
The essential oil is of a pale straw-colour and less odorous than most other volatile oils. Treated with chloride of calcium and again distilled, it begins to boil at 210° C. and passes over at 255°-260° C., acquiring a somewhat empyreumatic smell and light yellowish tint. The purified oil has a sp. gr. of 0·915;[366] it is but sparingly soluble in absolute alcohol or glacial acetic acid, but mixes readily with amylic alcohol.
According to Werner (1862) this oil has the composition C₂₀H₃₂ like that of copaiba. He says it deviates the ray of polarized light to the left, but that prepared by one of us deviated strongly to the right, the residual resin dissolved in benzol being wholly inactive. The oil does not form a crystalline compound with dry hydrochloric acid, which colours it of a beautiful blue.[367] De Vry[368] states that the essential oil after this treatment deviates the ray to the right.
The resin contains, like that of copaiba, a small proportion of a crystallizable acid which may be removed by warming it with ammonia in weak alcohol. That part of the resin which is insoluble even in absolute alcohol,[369] we found to be uncrystallizable. The Gurgunic Acid, as the crystallized resinous acid is called by Werner,[370] but which it is more correct to write Gurjunic, may consequently be prepared by extracting the resin with alcohol (·838) and mixing the solution with ammonia. From the ammoniacal solution gurjunic acid is precipitated on addition of a mineral acid, and if it is again dissolved in ether and alcohol it may be procured in the form of small crystalline crusts. From the specimen under examination we were not successful in obtaining indubitable crystals.