Botanical Origin—Pinus Picea L. (Abies pectinata DC.), the Silver Fir,[2296] a large handsome tree, growing in the mountainous parts of Middle and Southern Europe from the Pyrenees to the Caucasus, and extending under a slightly different form (var. β. cephalonica) into continental Greece and the islands of Eubœa and Cephalonia.
History—Belon in his treatise De Arboribus coniferis (1553) described this turpentine, which is also briefly yet accurately noticed by Samuel Dale,[2297] a learned apothecary of London and the friend of Sloane and Ray. It had a place in the London Pharmacopœia until 1788, when it was omitted from the materia medica.
Extraction—The oleo-resin of P. Picea, like that of P. balsamea, is contained in little swellings of the bark[2298] of young stems, and is extracted by the tedious process of puncturing them and receiving in a suitable vessel the one or two drops which exude from each. It is still collected near Mutzig and Barr, in the Vosges (1878), though only to a very small extent.
Description—An authentic sample collected for one of us by the Surveyor of Forests in the Bernese Jura, Switzerland, resembles very closely Canada balsam, but is devoid of any distinct fluorescence. It has a light yellow colour, a very fragrant odour,[2299] more agreeable than that of Canada balsam, and is devoid of the acrid bitterish taste of the latter.
We found our specimen to have sp. gr. of distilled water. It deviates a ray of polarized light 3° to the left, if examined either pure or diluted with a fourth of its weight of benzol, in the manner described at [p. 610]. Our drug is soluble in the same liquids as the Canadian, yet is miscible with glacial acetic acid, absolute alcohol and acetone, without leaving any considerable flocculent residue. It is even soluble in spirit of wine, the solution being but very little turbid. The solutions have an acid reaction.
Chemical Composition—After the complete desiccation of a small quantity, there remained 72·4 per cent. of a brittle, transparent resin, soluble in glacial acetic acid, but not entirely in absolute alcohol or in acetone. By submitting half a pound of the turpentine to distillation with water, we obtained 24 per cent. of essential oil, the remaining resin being when cold perfectly friable. The fresh oil, purified by sodium, deviates the ray of polarized light to the left, whereas the remaining resin, dissolved in half its weight of benzol, shows a weak dextrogyre rotation. The oil boils at 163° C. After having kept it for two years and a half in a well-stopped bottle, we find that it has become considerably thicker and now deviates to the right. If saturated with dry hydrochloric acid, the oil does not yield a solid compound.
This oil has nearly the same agreeable odour as the crude oleo-resin, yet the essential oil of the cones of the same tree is still more fragrant. The latter is one of the most powerfully deviating oils, the rotation being 51° to the left, and it is consequently extremely different from the oil obtained from the turpentine of the stem, though its composition is represented by the same formula, C₁₀H₁₆.
A peculiar sugar called Abietite, nearly related to mannite but having the composition C₁₂H₁₆O₆, has been detected by Rochleder[2300] in the leaves of the Silver Fir.
Uses—Strassburg turpentine possesses the properties of common turpentine, with the advantage of a very agreeable odour. It was formerly held in great esteem, but has now become nearly forgotten.