[Footnote 1: Read at a meeting of the Liverpool Chemists'
Association.]
By EDWARD DAVIES, F.C.S., F.I.C.
In treating this subject it is necessary to limit it within
comparatively narrow bounds, for bodies of the turpentine class are
exceedingly numerous and not well understood. In this definite class
turpentine means the exudation from various trees of the natural order
Coniferæ, consisting of a hydrocarbon, C10 H16, and a resin. The
constitution of the hydrocarbons in turpentine from different sources,
though identical chemically, varies physically, the boiling point
ranging from 156° C. to 163° C., the density from 0.855 to 0.880, and
the action on polarized light from -40.3 to +21.5. They are very
unstable bodies in their molecular constitution, heat, sulphuric acid,
and other reagents modifying their properties. The resins are also
very variable bodies formed probably by oxidation of the hydrocarbons,
and as this oxidation is more or less complete, mixtures are formed
very difficult to separate and study.
Turpentine as met with in commerce is mainly derived from _Pinus
maritima_, yielding French turpentine, and _Pinus australis_,
furnishing most of the American turpentine. The latter is obtained
from North and South Carolina, Georgia and Alabama. In Hanbury and
Fluckiger's Pharmacographia there is a full description of the manner
in which the trees are wounded to obtain the turpentine. Besides these
there are Venice turpentine from the larch, _Pinus Larix_, Strassburg
turpentine from _Abies pectinata_, and Canada balsam from _Pinus
balsamea_.
The crude American turpentine is a viscid liquid of about the
consistence of honey, but varying to a soft solid, known as gum, thus,
according to the amount of exposure which it has undergone, it
contains about 10 to 25 per cent. of "spirits," to which the name of
turpentine is commonly given, the rest being resin, or as it is
usually called, rosin.
In Liverpool almost all the spirits of turpentine comes from America,
so that it is almost impossible to get a sample of French.
The terpene from American turpentine is called austraterebenthene. It
possesses dextro-rotatory polarization of +21.5. Its density is 0.864.
Boiling point 156° C.
In taking the boiling point of a commercial sample of spirits it is
necessary to wait until the thermometer becomes steady. Not more than
5 per cent. should pass over before this takes place, and then there
is not more than two or three degrees of rise until almost all is
distilled over.
The liquids of lower boiling point do not appear to have been much
studied. In French spirits they seem to be of the same composition as
the main product, but with more action on polarized light.
French spirits of turpentine is mainly composed of terebenthene. The
boiling point and sp. gr. are the same as those of the austraterebenthene,
but the polarization is left handed and amounts to -40.5.
Isomeric modifications. Heated to 300° C. in a sealed tube for two
hours, it becomes an isomeric compound, boiling at 175° C., while the
density is lowered, being only 0.8586 at 0° C. The rotatory power is
only -9°. It oxidizes much more rapidly. It is called isoterebenthene
and has a smell of essential oil of lemons.
By the action of a small quantity of sulphuric acid, among other
products terebene is formed. It has the same boiling point and sp. gr.
as terebenthene, but is without action on polarized light.
Austraterebenthene forms similar if not identical bodies.
Polymers. One part of boron fluoride BF3 instantly converts 160
parts of terebenthene into polymers boiling above 300° C., and
optically inactive. H2 SO4 does the same on heating and forms
diterebene C20 H32.
Terchloride of antimony does the same, and also produces tetraterebene
C40H64, a solid brittle compound formed by the union of four
molecules of C10 H16. It does not boil below 350° C. and
decomposes on heating.
Compound with H2O. Terpin C10 H18 2HO is formed when 1 volume
of spirits of turpentine is mixed with 6 of nitric acid and 1 of
alcohol, and exposed to air for some weeks. Crystals are formed which
are pressed, decolorized by animal charcoal, and recrystallized from
boiling water.
Compounds with HCl. When a slow current of HCl is passed through
cooled spirits of turpentine, two isomeric compounds are formed, one
solid, and one liquid. The lower the temperature is kept, the more of
the solid body is produced. To obtain the solid body pure it is
pressed and recrystallized from ether or alcohol. It is volatile and
has the odor of camphor. It is called artificial camphor, and has the
composition C10 H16 HCl. There is also a compound with 2HCl.
Oxidation products. By passing air into spirits of turpentine oxygen
is absorbed. It was thought at one time that ozone was produced, but
Kingzett's view is that camphoric peroxide is formed C10 H14 O4,
and that in presence of water it decomposes into camphoric acid and
H2 O2. This liquid constitutes the disinfectant known as
"sanitas," which possesses the advantages of a pleasant smell and
non-poisonous properties. C10 H18 O2 may be obtained by
exposing spirits of turpentine in a flask full of oxygen with a little
water.
Camphor C16 H16 O has been made in small quantity by oxidizing spirits
of turpentine. Terebenthene belongs to the benzene or aromatic series,
which can be shown from its connection with cymene. Cymene is
methylpropyl-benzene, and can be made from terpenes by removing two
atoms of H. It has not yet been converted again into terpene, but the
connection is sufficiently proved. The presence of CH3 in terpenes is
shown by their yielding chloroform when distilled with bleaching
powder and water. The resin is imperfectly known. It was supposed to
consist of picric and sylvic acids. It is also stated to contain
abietic anhydride C44 H62 O4, but it is difficult to understand how a
compound containing C44 can be produced from C10 H16. The most
probable view is that it is the anhydride of sylvic acid, which is
probably C20 H30 O2.
The dark colored resin which is obtained when the turpentine is
distilled without water can be converted into a transparent slightly
yellow body by distillation with superheated steam. A small portion is
decomposed, but the greater part distills unchanged. It is used in
making soap which will lather with sea water.
When distilled alone, various hydrocarbons, resin oil and resin pitch,
are obtained.
I find that commercial spirits of turpentine varies in sp. gr. from
0.865 to 0.869 at 15° C. The higher sp. gr. appears to be connected
with the presence of resinous bodies, the result of oxidation. The
boiling point is very uniform, ranging from 155° C. to 157° C. at 760
mm. Taking these two points together, it is hardly possible to
adulterate spirits of turpentine without detection. I give the figures
for a few imitations or adulterations:
Sp. gr. B.P.
No. 1 0.821 137° C.
No. 2 0.884 165° C.
No. 3 0.815 150° C.
No. 4 0.895 156° C.
There is a considerable difference in the flashing point, no doubt due
to the longer or shorter exposure of the crude turpentine, by which
more or less of the volatile portion escapes.
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