_Balsamum Canadense_; _Canada Balsam_, _Canadian Turpentine_; F.
_Térébenthine ou Baume de Canada_; G. _Canada Balsam_.
=Botanical Origin=—_Pinus balsamea_ L. (_Abies balsamea_ Marshall), the
Balsam Fir or Balm of Gilead Fir, a handsome tree, 20 to 40 feet high,
with a trunk 6 to 12 inches in diameter, sometimes attaining still
larger dimensions, growing in profusion in the Northern and Western
United States of America, Nova Scotia and Canada, but not observed
beyond 62° N. lat. It resembles the Silver Fir of Europe (_Pinus Picea_
L.), but has the bracts short-pointed and the cones more acute at each
end.
Canada balsam is also furnished by _Pinus Fraseri_ Pursh, the
Small-fruited or Double Balsam Fir, a tree found on the mountains
of Pennsylvania, Virginia, and southward on the highest of the
Alleghanies.[2291]
_Pinus canadensis_ L. (_Abies canadensis_ Michx.), the Hemlock Spruce
or Pérusse, a large tree abundant in the same countries as _P.
balsamea_, and extending throughout British America to Alaska, is
said to yield a similar turpentine, which however has not yet been
sufficiently examined. The Hemlock Spruce is of considerable importance
on account of the resin collected from its trunk, and the essential oil
distilled from its foliage, the latter operation being performed on a
large scale in Madison County, New York. The inner bark of the tree is
a valuable material for tanning.
=History=—The French, in whose possession Canada remained until the
year 1763, were probably acquainted with Canada balsam long before
this period. Yet no mention of it is found in Pomet’s work, but in
1759 it was at Strassburg a current article of the pharmacy.[2292] As
to England, Lewis, in his _History of the Materia Medica_ published in
1761, says that “_an elegant balsam_,” obtained from the Canada Fir, is
sometimes brought into Europe under the name of _Balsamum Canadense_.
Canada balsam was first introduced into the London Pharmacopœia in
1788. From the books of a London druggist, J. Gurney Bevan, we find
that its wholesale price in 1776 was 4_s._, in 1788, 5_s._ per lb.
=Description=—Canada balsam is a transparent resin of honey-like
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.
[2291] Asa Gray, _Botany of the Northern United States_, New York,
1866. 422.
[2292] Flückiger, _Pharm. Journ._ vi. (1876), 1021.
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 _Balsamodendron_ growing in Arabia.
We found a good commercial balsam to have a sp. gr. of 0·998 at 14·5°
C., water at the same temperature being 1·000. 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 well as by spirit of wine
containing 70 to 75 per cent. of alcohol.
=Chemical Composition=—Like all analogous exudations of the _Coniferæ_,
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 different samples. The specimen
before mentioned 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
temperature 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, C₁₀H₁₆, 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 calcium. 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 5·6° to the left. The portion distilling at 160° does
not differ in this respect; but that passing over at 170°, deviates the
ray 7·2° to the left. The oil readily dissolves a large proportion of
glacial acetic acid; an equal weight of each mixes perfectly at about
54° C., but some acetic acid separates on cooling.
The essential oil of Canada balsam, saturated with dry hydrochloric
acid, does not yield a solid crystallizable compound; but this is
easily obtained on addition of fuming nitric acid and gently heating,
when the inside of the retort becomes covered by sublimed crystals of
C₁₀H₁₆ + HCl.
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.
[2293] _De balsamis et præsertim de Balsamo Canadense_, Helsingforsiæ,
1849,—abstracted in the _Jahresbericht_ of Wiggers for 1849. 38.
=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.