_Crude or Common Turpentine_; F. _Térebenthine commune_; G. _Gemeiner
Terpenthin_.
=Botanical Origin=—The trees which yield Common Turpentine may be
considered in two groups, namely, European and American.
1. _European_—In Finland and Russia Proper, the Scotch Pine, _Pinus
sivestris_ L.; in Austria and Corsica, _P. Laricio_ Poiret; and in
South-western France, _P. Pinaster_ Solander (_P. maritima_ Poiret),
extensively cultivated as the _Pin maritime_, yield turpentine in their
respective countries.
2. _American_—In the United States, the conifers most important for
terebinthinous products are the Swamp Pine, _Pinus australis_ Michaux
(_P. palustris_ Mill.), and the Loblolly Pine, _P. Tæda_ L.
=History=—The resin of pines and firs was well known to the ancients,
who obtained it in much the same manner as that practised at the
present day. The turpentine used in this country has for many years
past been derived from North America. Up to the last century, both
it and the substance called _Common Frankincense_ were imported from
France. The late civil war in the United States and the blockade of the
Southern ports, occasioned a great scarcity of American turpentine; and
terebinthinous substances from all other countries were poured into the
London market. The actual supplies, however, were mainly furnished by
France.
Kopp[2271] quotes a passage showing that the essential oil of
turpentine was known to Marcus Græcus, who termed it _Aqua ardens_.
This almost unknown personage is the reputed inventor of _Greek Fire_,
a dreaded engine of destruction in mediæval warfare.
=Secretion=—The primary formation of resin-ducts in the bark of
coniferous trees has been explained by Dippel,[2272] Müller,[2273] and
Frank.[2274] The subsequent diffusion of the resinous juice through
the heartwood, sapwood, and bark, has been elaborately investigated by
Hugo von Mohl.[2275] From the various forms under which this diffusion
exists in the different species have arisen the diverse methods of
obtaining the terebinthinous resins.
[2271] _Geschichte der Chemie_, iv. (1847) 392.
[2272] _Botanische Zeitung_, 1863.
[2273] Pringsheim, _Jahrb. für wissenschaftl. Botanik._ 1866.
[2274] _Beiträge zur Pflanzenphysiologie_, Leipzig, 1868. 119.
[2275] _Botanische Zeitung_, 1859. 329.
Thus in the wood of the Silver Fir (_Pinua Picea_ L.) resin-ducts are
altogether wanting;—and led by experience, the Alpine peasant collects
the turpentine of this tree by simply puncturing the little cavities
which form under its bark. In the Scotch Pine (_P. silvestris_ L.),
they are more abundant in the wood than in the bark, a fact which
might be anticipated by observing how rarely this tree exudes resin
spontaneously.
Oil of turpentine, like volatile oils in general, undergoes on
exposure to the air certain alterations giving rise to what is called
_resinification_. The formic acid which is produced in small quantity
during this change characterizes it as one of oxidation; the chief
products however are not exactly known, and not one of them has
been proved identical with any natural resin. The common assumption
that resins are produced from volatile oils by simple oxidation, is
consequently not yet entirely justified.
=Extraction=—In the United States[2276] turpentine is obtained to the
largest extent from _Pinus australis_, of which tree there are vast
forests, the piny woods or pine-barrens, extending from Virginia to the
Mexican Gulf, especially through North and South Carolina, Georgia and
Alabama. But it is in North Carolina that the extraction of turpentine
is principally carried on.
In the winter, _i.e._ from November to March, the negroes in a
_Turpentine Orchard_, as the district of forest to be worked is called,
are occupied in making in the trunks of the trees, cavities which
are technically known as _boxes_. For this purpose a long narrow axe
is used, and some skill is required to wield it properly. The boxes
are made from 6 to 12 inches above the ground, and are shaped like a
distended waistcoat-pocket, the bottom being about 4 inches below the
lower lip, and 8 or 10 below the upper. On a tree of medium size, a box
should be made to hold a quart. The less the axe approaches the centre
of the tree the better, as vitality is the less endangered. An expert
workman will make a box in less than 10 minutes. From one to four boxes
are made in each tree, a few inches of bark being left between them.
The greater number of trees from which turpentine is now obtained, are
from 12 to 18 inches in diameter, and have three boxes each.
The boxes having been made, the bark and a little of the wood
immediately beneath it, which are above the box, are _hacked_; and from
this excoriation, the sap begins to flow about the middle of March,
gradually filling the box. Each tree requires to be freshly hacked
every 8 or 10 days, a very slight wound above the last being all that
is needed. The hacking is carried on year after year, until it reaches
12 to 15 feet or more, ladders being used. The turpentine, which is
called _dip_, is removed from the boxes by a spoon or ladle of peculiar
form, and collected into barrels, which are made on the spot and are of
very rude construction. The first year’s flow of a new tree, having but
a small surface to traverse before it reaches the box, is of special
goodness and is termed _Virgin dip_.
[2276] The account here given is taken from F. L. Olmsted’s _Journey in
the Seaboard Slave States_, New York, 1856, p. 338, etc.
The turpentine which concretes upon the trunk is occasionally scraped
off and barrelled by itself, and is known in the market as _scrape_, or
by English druggists as _Common Frankincense_ or _Gum thus_.
Although a large amount of turpentine is shipped to the northern ports
for distillation, a still larger is distilled in the neighbourhood of
the turpentine orchards. Copper stills are used, capable of containing
5 to 20 barrels of turpentine. The turpentine is distilled without
water, the volatile oil as it flows from the worm being received in
the barrel in which it is afterwards sent to market. When all the oil
that can be profitably drawn off has been obtained, a spigot is removed
from an opening in the bottom of the still, and the residual _Rosin_,
appearing as a viscid fluid-like molasses, is allowed to flow out. Only
the first qualities of rosin, as that obtained from _Virgin dip_, are
generally considered worth saving, the less pure sorts being simply
allowed to run to waste. When it is intended to save the rosin, the
latter is drawn off into a vat of water, which separates the chips and
other rubbish, and the rosin is then placed in barrels for the market.
A North Carolina turpentine orchard will remain productive under
ordinary treatment for fifty years.
The collection of turpentine in the departments of the Landes and
Gironde in the south-west of France, is performed in a more rational
manner than in America, inasmuch as the plan of making deep cavities
in the tree for the purpose of receiving the resin, is avoided by
the simple expedient of placing a suitable vessel beneath the lowest
incision.[2277] The turpentine which concretes upon the stem is termed
in France _Galipot_ or _Barras_.
[2277] For further particulars, see Guibourt, _Hist. des drog._ ii.
(1869) 259, also Curie, _Produits résineux du Pin maritime_. Paris
1874. 24 pages, 1 plate; Matthieu, _Flore forestière_ 1860, p. 353.
=Description=—Common turpentine is chiefly of two varieties, namely,
_American_ and _Bordeaux_; the first alone is commonly found in the
English market.
_=American Turpentine=_—A viscid honey-like fluid, of yellowish colour,
somewhat opaque, but becoming transparent by exposure to the air; it
has an agreeable odour and warm bitterish taste. When long kept in a
bottle, it is seen to separate into two layers, the upper clear and
faintly fluorescent, the lower somewhat turbid or granular. When the
latter portion is examined under the microscope, it is found to consist
mainly of minute crystals of peculiar curved or bluntly elliptic form.
These crystals are abietic acid; when the turpentine is warmed, the
crystals are speedily dissolved.
_Bordeaux Turpentine_—in all essential particulars agrees with American
Turpentine; it appears to separate rather more readily than the latter
into two layers,—a transparent and an opaque or crystalline.
=Chemical Composition=—The turpentines are mixtures of resin and
essential oil. The latter, which amounts to from 15 to 30 per cent.,
consists for the greater part of various hydrocarbons, corresponding
to the formula C₁₀H₁₆. Many of the crude turpentine oils, and some of
them even after rectification, are energetically acted on by metallic
sodium. This reaction proves the presence of a certain quantity of
oxygenated oils, not one of which has thus far been isolated.
The turpentine oils, although agreeing in composition, exhibit a
series of physical differences according to their origin. One and the
same tree, indeed, yields from its several organs oils of different
properties. The boiling point varies between 152° and 172° C. The
sp. gr. at mean temperatures ranges from 0·856 to 0·870. Greater
differences are exhibited in the optical properties, some varieties
of the oil turning the plane of polarization to the right, others to
the left. This rotatory power differs in many cases from that of the
turpentine from which the oil was derived.[2278] The odour of oil of
turpentine varies with the species from which it has been obtained.
When crude turpentine is distilled with water, nearly the whole of
the oil passes over, while the resin remains. This resin is called
_Colophony_ or _Rosin_. When it still contains a little water, it is
distinguished in English trade as _Yellow Rosin_; when fully deprived
of water, it becomes what is called _Transparent Rosin_. That of deeper
colour acquired by a still longer application of heat, bears the name
of _Black Rosin_.
Colophony softens at 80° C., and melts completely at 100° into a clear
liquid. At about 150° it forms a somewhat darker liquid, but without
undergoing a loss in weight; at higher temperatures, it gradually
decomposes. Pure colophony has a sp. gr. of 1·07, and is homogeneous,
transparent, amorphous, and very brittle. At temperatures between 15°
and 20° C., it requires for solution 8 parts of dilute alcohol (0·883).
On addition of a caustic alkali, it dissolves in spirit much more
freely. It is plentifully soluble in acetone or benzol.
The composition of colophony agrees with the formula C₄₄H₆₂O₄. By
shaking coarsely powdered colophony with warm dilute alcohol, it is
converted into a crystalline body, _Abietic Acid_, C₄₄H₆₄O₅,—a result
due simply to hydration. Under such treatment, colophony yields 80 to
90 per cent. of abietic acid,[2279] and therefore consists chiefly of
the anhydride of that acid. This is probably the case with the resins
of other conifers. The living tree contains only the anhydride, for
the fresh resinous juice is clear and amorphous after the expulsion
of the oil; and when exposed to the air it loses oil, takes up water
and solidifies as the crystalline acid,—a change which may easily be
traced by the aid of the microscope, in drops taken direct from the
trunk. Amorphous colophony retains its transparency even in a moist
atmosphere, and appears to be capable of passing into the state of
abietic acid, only when the assumption of the needful molecule of
water is aided, in nature by the presence of the essential oil, or
artificially by that of alcohol.
[2278] For some particulars, see my notice in the _Jahresbericht_ of
Wiggers and Husemann for 1869, p. 36.—F. A. F.
[2279] Flückiger in _loc. cit._ 1867. 36.—Most chemists assign to this
acid the formula C₂₀H₃₀O₂, and call it _silvic acid_.
Colophony when boiled with alkaline solutions forms greasy salts of
abietic acid, the so-ccalled _resin-soaps_, which are used as additions
to other soaps.
Siewert’s _Silvic Acid_ is regarded by Maly (1864) as a product of the
decomposition of abietic acid; and the _Pimaric_, _Pinic_ and _Silvic
Acids_ of former investigators, as impure abietic acid. Pimaric acid
however, which is the chief constituent of _Galipot_, appears to be
decidedly different, so far as we can judge from the experiments of
Duvernoy (1865) and of one of ourselves (F.).
Abietic acid, as well as the unaltered coniferous resins, deviate
the ray of polarized light, whereas American colophony, dissolved in
acetone, is devoid of optical power.
=Commerce=—The supplies of turpentine are chiefly derived from the
United States, but the trade has undergone a great change, as shown by
the following figures, which represent the quantities imported in the
several years:—
1869 1870 1871 1872
60,468 cwt. 51,257 cwt. 2,231 cwt. 1,000 cwt.
This greatly diminished importation of the crude article is partially
explained by a larger importation of Oil of Turpentine and Rosin;
but the increase is by no means sufficient to account for the vast
diminution indicated by the above figures. The quantities of these
latter articles imported into the United Kingdom during the year 1872
were as follows:—_Oil of Turpentine_, 220,292 cwt., value £470,085,
six-sevenths being furnished by the United States of America and the
remainder chiefly by France. _Rosin_, 919,494 cwt., value £492,246; of
this quantity, the United States supplied nine-tenths, and France the
larger part of the remainder.[2280]
=Uses=—Turpentine, Common Frankincense and Colophony are ingredients
of certain plasters and ointments. Oil of turpentine is occasionally
administered internally as a vermifuge or diuretic, and applied
externally as a stimulant. But these substances are immeasurably less
important in medicine than in the arts.
Thus Americanum vel vulgare.
This substance, known among druggists as _Common Frankincense_ or _Gum
Thus_, is the resin which, as explained at p. 605, concretes upon the
stems of the pines in the American turpentine orchards, and is there
called _Scrape_. It corresponds to the _Galipot_ or _Barras_ of the
French, which in old times supplied its place.
It is a semi-opaque, softish resin, of a pale yellow colour, smelling
of turpentine; it is generally mixed with pine leaves, bits of wood
and other impurities, so that it requires straining before it is used.
By keeping, it becomes dry and brittle, of deeper colour and milder
odour. Under the microscope, it exhibits a crystalline structure due
to _Abietic Acid_, of which it chiefly consists. It is imported from
America in barrels, but in insignificant quantities and only for
the druggist’s use. Sometimes, however, it is distilled as common
turpentine.
Dry pine resin, of which Common Frankincense is the type, evolves when
heated an agreeable smell; hence in ancient times it was commonly used
in English churches in place of the more costly olibanum. At present it
is scarcely employed except in a few plasters.
[2280] _Annual Statement of the Trade of the U.K. for 1872._ pp. 53.
56. 60. 210.