True hemlock oil is the distillate from the young twigs of Abies canadensis, Michx. (Tsuga canadensis, Carr.; Ger. Spruce-, Hemlock-, or Schierlings-lanne) which is widely distributed over the American continent from Canada to Alabama and westward to the Pacific. With the hemlock there are frequently distilled the twigs of either the white spruce Picea alba, Lk. or the black spruce Picea nigra, Lk., or both. These two species with the hemlock constitute large forests, hence the twigs of all three species are, no doubt, frequently mixed, though but accidentally. Because of assumed identity the oils of the three species enter commerce under the common names of hemlock oil or spruce oil. Inasmuch as these oils agree largely, not only qualitatively but quantitatively, their common use may be of no disadvantage.
Properties and Composition. Hemlock oil is colorless, of pleasant balsamic odor; specific gravity 0,907 to 0,9132); aD-20°54'3) to - 23° 55'4). Fractional distillation yielded 11 p.c. between 150 and 170°, and 37 p.c. between 170 and 185°. Above this temperature decomposition set in with the liberation of acetic acid.
1) Report of Schimmel & Co. April 1906, 57.
2) Hanson and Babcock [Journ. Americ. chem. Soc. 28 (1906), 1198] observed d15° 0,9238 to 0,9273 for oils distilled from the needles and branches. 3) Bertram and Walbaum, Arch, der Pharm. 231 (1893), 294. 4) Power, Descriptive catalogue of essential oils. New York 1894, p. 58.
C. G. Hunkel1) examined an oil that was distilled from fresh twigs of Abies canadensis, Michx. collected by himself in September. The oil had a sp. gr. of 0,9288 at 20°; [a]D20o - 18,399°; /-bornyl acetate content 51,5 to 52 p.c. /-a-Pinene was identified by means of its nitrolbenzylamine base (m. p. 122°).