TEREBINTHINA CANADENSIS. 613 



consistence, and of a light straw-colour with a greenish tint. By keeping, 

 it slowly becomes thicker and of a somewhat darker hue, but always 

 retains its transparency. When carefully examined in direct sunlight, 

 it exhibits a slight greenish fluorescence in the same degree as other 

 turpentines or as copaiba ; this optical power appears to increase if the 

 balsam is exposed to a heat of about 200° C 



Canada balsam has a pleasant aromatic odour and bitterish, feebly 

 acrid, not disagreeable taste. On account of its flavour it is sometimes 

 called Balm of Gilead, but erroneously, as this latter is derived from a 

 tree of the genus Bahamodendron growing in Arabia. We found a 

 good commercial balsam to have a sp. gr. of 0998 at 14"5° C, water at 

 the same temperature being 1000. Four parts, mixed with one of 

 benzol and examined in a column of 50 mm. in length, deviated a ray 

 of polarized light 2° to the right. The balsam is perfectly soluble in any 

 proportion in chloroform, benzol, ether, or warm amylic alcohol ; and 

 the solution in each case reddens litmus. With sulphate of carbon it 

 mixes readily, but the mixture is somewhat turbid. Glacial acetic acid, 

 acetone or absolute alcohol dissolve the balsam partially, leaving, after 

 ebullition and cooling, a considerable amount of amorphous residue. 

 Colophony and Venice turpentine are completely dissolved by the 

 liquids in question, as weU as by spirit of wine containing 70 to 75 per 

 cent, of alcohol. 



Chemical Composition — Like all analogous exudationcs of the 

 Coniferoe, Canada turpentine is a mixture of resins with an essential oil. 

 If the latter is allowed to evaporate, the former are left as a transparent, 

 somewhat tough and elastic mass. The proportion of the components 

 is within certain limits, variable in difierent samples. The specimen 

 beforementioned lost after an exposure in a steam-bath during several 

 days, no less than 20 per cent of volatile oil, or even 24 per cent, if the 

 experiment was made on a very small scale, as with 20 grammes or less 

 in a thin layer. 



By distillation with water, it is not easy to obtain more than 17 to 

 18 per cent, of essential oil. The resin in this case is a tough, elastic, 

 non-transparent mass, retaining obstinately a large proportion of water, 

 which can only be removed by keeping it for some time at a tempera- 

 ture of 100°-176° C. 



The oil as obtained by distillation with water is colourless, and has 

 the odour of common oil of turpentine rather than the agreeable smell 

 of the balsam ; it consists of an oil, C^"H^^ mixed with an insignificant 

 proportion of an oxygenated oil, the presence of which may be proved 

 by the slight evolution of hydrogen on addition of metallic sodium, after 

 the oil has been freed from water by contact with fused chloride of cal- 

 cium. After this treatment, a small proportion begins to distil at about 

 160°, but by far the larger part boils at 167° C, a small portion only 

 distilling at last at 170° and above. The oil obtained at 167°, examined 

 under the conditions already mentioned, has a sp. gr. of 0*863, and the 

 power of rotating a ray of polarized light o'6° to the left. The portion 

 distilling at 160° does not difier in this respect; but that passing over 

 at 170°, deviates the ray 72° to the left. The oil readily dissolves a 

 large proportion of glacial acetic acid ; an equal weight of each mixes 

 l^erfectly at about 54° C, but some acetic acid sepaiutes on cooling. 



