Thus this oil in its general characters bears a close resemblance to the essential oils of the cones of Pinus Picea L., and of the leaves of P. Pumilio Hänke, and to most of the French varieties of oil of turpentine, rather than to the American turpentine oils, which rotate to the right, and combine immediately with HCl to form a solid crystalline compound.
On the other hand, the resin of Canada balsam is dextrogyre: two parts of it, entirely deprived of essential oil and dissolved in one of benzol, deviating the ray 8·5° to the right. The optical powers of the two components (oil and resin) are therefore antagonistic.
The resin of Canada balsam consists however of two different bodies, 78·7 per cent. of it being soluble in boiling absolute alcohol, and 21·3 (in our specimen) remaining as an amorphous mass, readily soluble in ether. Neither the alcoholic nor the ethereal solution yields a crystalline residue if allowed to evaporate. They redden litmus, but we did not succeed in obtaining any crystallized resinous acid, crystals of which are formed if common turpentine or colophony is digested with dilute alcohol. Glacial acetic acid acts upon the resins like absolute alcohol. Caustic alkalis do not dissolve either the balsam or the resin; the former however is considerably thickened by incorporation with ⅕ of its weight of recently calcined magnesia. If the mixture, moistened with dilute alcohol, is kept at 93° C. for some days and frequently stirred, a mass of hard consistence, finally translucent, results. Caustic ammonia heated with the balsam in a closed bottle, forms a thick milky jelly, which does not afterwards separate.
Hence, according to our investigations, 100 parts of Canada turpentine consist of
| Essential oil, C₁₀H₁₆}, with a very small | |
| proportion of an oxygenated oil | 24 |
| Resin soluble in boiling alcohol | 60 |
| Resin soluble only in ether | 16 |
The result of Wirzen’s examination of Canada balsam[2293] are not in complete accordance with those here stated. He found 16 per cent. of oil and three different amorphous resins, one of which had the composition of abietic acid.
Production and Commerce—Canada balsam is obtained either by puncturing the vesicles which form under the suberous envelope of the trunk and branches, and collecting their fluid contents in a bottle, or by making incisions. It is obtained principally in Lower Canada, and is shipped from Montreal and Quebec, in kegs or large barrels. In the neighbourhood of Quebec, about 2000 gallons (20,000 lb.) used to be collected annually; but in 1868, owing to distress among the farmers, the quantity obtained was unusually large, and it was estimated that nearly 7000 gallons would be exported to England and the United States.[2294] During a recent scarcity (1872-73) a sort of balsam from Oregon has been substituted in the American market for true Canada balsam.[2295]
Uses—The medicinal properties of Canada balsam resemble those of copaiba and other terebinthinous oleo-resins, yet it is now rarely employed as a remedy. The balsam is much valued for mounting objects for the microscope, as it remains constantly transparent and uncrystalline. It is also used for making varnish.
TEREBINTHINA ARGENTORATENSIS.
Strassburg Turpentine; F. Térébenthine d’Alsace ou de Strasbourg, Térébenthine du sapin; G. Strassburger Terpenthin.