A DISCOVERY BEARING ON THE FLORA OF THE CARBONIFEROUS EPOCH AND THE
FORMATION OF PETROLEUM.
By A.B. GRIFFITHS, Ph.D., F.C.S. Membre de la Societe Chimique de
Paris, Medallist in Chemistry and Botany, etc.
Having found, in small quantities, alcohols of the C_{n}H_{2n-7}
series, last summer, in the stem, acicular leaves, and cones of _Pinus
sylvestris_, I wish in this paper to say a few words on the subject.
First of all, I took a number of cones, cut them up into small pieces,
and placed them in a large glass beaker, then nearly filled it with
distilled water, and heated to about 80° C., keeping the decoction at
this temperature for about half an hour, I occasionally stirred with a
glass rod, and then allowed it to cool, and filtered. This filtrate
was then evaporated nearly to dryness, when a small quantity of
six-sided prisms crystallized out, which subsequently were found to be
the hydrate of phenol (C_{6}H_{5}HO)_{2}H_{2}O. Its melting point was
found to be 17.2° C. Further, the crystals already referred to were
dissolved in ether, and then allowed to evaporate, when long colorless
needles were obtained, which, on being placed in a dry test tube and
the tube placed in a water bath kept at 42° C., were found to melt;
and on making a careful combustion analysis of these crystals, the
following composition was obtained:
Carbon 76.6
Hydrogen 6.4
Oxygen 17.0
-----
100.0
This gives C_{6}H_{6}O, which is the formula for phenol.
On dissolving some of these crystals in water (excess) and adding
ferric chloride, a beautiful violet color was imparted to the
solution. To another aqueous solution of the crystals was added
bromine water, and a white precipitate was obtained, consisting of
tribromophenol. An aqueous solution of the crystals immediately
coagulated albumen.
All these reactions show that the phenol occurs in the free state in
the cones of this plant. In the same manner I treated the acicular
leaves, and portions of the stem separately, both being previously cut
up into small pieces, and from both I obtained phenol.
I have ascertained the relative amount of phenol in each part of the
plant operated upon; by heating the stem with water at 80° C., and
filtering, and repeating this operation until the aqueous filtrate
gave no violet color with ferric chloride and no white precipitate
with bromine water.
I found various quantities according to the age of the stem. The older
portions yielding as much as 0.1021 per cent, while the young portions
only gave 0.0654 per cent. The leaves yielding according to their age,
0.0936 and 0.0315 per cent.; and the cones also gave varying amounts,
according to their maturity, the amounts varying between 0.0774 and
0.0293.
Two methods were used in the quantitative estimation of the amount of
phenol. The first was the new volumetric method of M. Chandelon
(_Bulletin de la Societe Chemique de Paris_, July 20, 1882; and
_Deutsch-Americanishe Apotheker Zeitung_, vol. iii., No. 12, September
1, 1882), which I have found to be very satisfactory. The process
depends on the precipitation of phenol by a dilute aqueous solution of
bromine as tribromophenol. The second method was to extract, as
already staled, a known weight of each part of the plant with water,
until the last extract gives _no_ violet color with ferric chloride,
and no white precipitate with the bromine test (which is capable of
detecting in a solution the 1/60000 part of phenol). The aqueous
extract is at this point evaporated, then ether is added, and finally
the ethereal solution is allowed to evaporate. The residue (phenol) is
weighed directly, and from this the percentage can be ascertained. By
this method of extraction, the oil of turpentine, resins, etc.,
contained in _Pinus sylvestris_ do not pass into solution, because
they are insoluble in water, even when boiling; what passes into
solution besides phenol is a little tannin, which is practically
insoluble in ether.
From this investigation it will be seen that phenol exists in various
proportions in the free state in the leaves, stem, and cones of _Pinus
sylvestris_, and as this compound is a product in the distillation of
coal, and as geologists have to a certain extent direct evidence that
the flora of the Carboniferous epoch was essentially crytogamous, the
only phænogamous plants which constituted any feature in "the coal
forests" being the coniferæ, and as coal is the fossil remains of that
gigantic flora which contained phenol, I think my discovery of phenol
in the coniferæ of the present day further supports, from a chemical
point of view, the views of geologists that the coniferæ existed so
far back in the world's history as the Carboniferous age.
I think this discovery also supports the theory that the origin of
petroleum in nature is produced by moderate heat on coal or similar
matter of a vegetable origin. For we know from the researches of
Freund and Pebal (_Ann. Chem. Pharm._, cxv. 19), that petroleum
contains phenol and its homologues, and as I have found this organic
compound in the coniferæ of to-day, it is probable that petroleum in
certain areas has been produced from the conifers and the flora
generally of some primæval forests. It is stated by numerous chemists
that "petroleum almost always contains solid paraffin" and similar
hydrocarbons. Professors Schorlemmer and Thorpe have found heptane in
Pinus, which heptane yielded primary heptyl-alcohol, and
methyl-pentyl-carbinol, exactly as the heptane obtained from petroleum
does (_Annalen de Chemie_, ccxvii., 139, and clxxxviii., 249; and
_Berichte der Deutschen Chemischen Gesellschaft_, viii., 1649); and,
further, petroleum contains a large number of hydrocarbons which are
found in coal. Again, Mendelejeff, Beilstein, and others (_Bulletin de
la Societe Chemique de Paris_, No. 1, July 5, 1883), have found
hydrocarbons of the--
C_{n}H_{2n2+}, C_{n}H_{2n-6},
also hydrocarbons of the C_{n}H_{2n} series in the petroleum of Baku,
American petroleum containing similar hydrocarbons.
I think all these facts give very great weight to the theory that
petroleum is of organic origin.
On the other hand, Berthelot, from his synthetic production of
hydrocarbons, believes that the interior of the globe contains
alkaline metals in the _free_ state, which yield acetylides in the
presence of carbonic anhydride, which are decomposed into acetylene by
aqueous vapor. But it has been already proved that acetylene may be
polymerized, so as to produce aromatic carbides, or the derivatives of
marsh gas, by the absorption of hydrogen. Berthelot's view, therefore,
is too imaginative; for the presence of _free_ alkaline metals in the
earth's interior is an unproved and very improbable hypothesis.
Byasson states that petroleum is formed by the action of water,
carbonic anhydride, and sulphureted hydrogen upon incandescent iron.
Mendelejeff thinks it is formed by the action of aqueous vapor upon
carbides of iron; and in his article, "Petroleum, the Light of the
Poor" (in this month's--February--number of _Good Words_), Sir Lyon
Playfair, K.C.B., F.R.S., etc., holds opinions similar to those of
Mendelejeff.
Taking in consideration the facts that solid paraffin is found in
petroleum and is also found in coal, and from my own work that phenol
exists in _Pinus sylvestris_, and has been found by others in coal
which is produced from the decomposition of a flora containing
numerous gigantic coniferæ allied to Pinus, and that petroleum
contains phenol, and each (i.e., petroleum and coal) contains a number
of hydrocarbons common to both, I am inclined to think that the
balance of evidence is in favor of the hypothesis that petroleum has
been produced in nature from a vegetable source in the interior of the
globe. Of course, there can be no practical or direct evidence as to
the origin of petroleum; therefore "theories are the only lights with
which we can penetrate the obscurity of the unknown, and they are to
be valued just as far as they illuminate our path."
In conclusion, I think that there is a connecting link between the old
pine and fir forest of bygone ages and the origin of petroleum in
nature.--_Chemical News._
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