[Footnote 1: Read at an evening meeting of the Pharmaceutical
Society of Great Britain, Feb, 4, 1885.]
By ROBERT H. DAVIES, F.I.C., F.C.S., General Superintendent
of Apothecaries' Hall.
The three oils that form the subject of the examination detailed in
this paper were consigned to a London broker, with a view to their
being regularly exported from China if a market could be found for
them here: it was, therefore, necessary to ascertain what commercial
oils they resembled in character, so as to estimate to what uses they
might be applied.
TEA OIL (_Camellia oleifera_).
In color, transparency, and mobility, this oil considerably resembles
olive oil. The odor and taste, though characteristic, are not easy to
describe.
(1.) _Specific Gravity._--The specific gravity at 60° F. is 917.5),
water at 60° F. being taken as 1,000.
(2.) _Action of Cold._--On subjecting to the cold produced by a
mixture of pounded ice and salt, some solid fatty matter, probably
stearine, separates, adhering to the side of the tube. It takes a
longer exposure and a lower temperature than is necessary with olive
oil. I did not succeed in solidifying it, but only in causing some
deposit. Olive oil became solid, while almond and castor oil on the
other hand did not deposit at all under similar circumstances. The
lowest temperature observed was -13.3° C. (8° F.), the thermometer
bulb being immersed in the oil.
A few qualitative tests, viz., the action of sulphuric acid, nitric
acid (sp. gr. 1.42), and digestion, with more dilute nitric acid (1.2
sp. gr.) and a globule of mercury, were first tried.
When one drop of sulphuric acid is added to eight or ten drops of tea
oil on a white plate, the change of color observed is more like that
when almond oil is similarly treated than with any other oil, olive
oil coming next in order of similarity.
When a few drops of tea oil are boiled with thirty drops or so of
nitric acid in a small tube, the layer of oily matter, when the brisk
action has moderated, is of a light yellow color, similar in tint to
that produced from almond and olive oil under similar circumstances.
When the oil is digested with an equal volume of nitric acid (1.2 sp.
gr.), and a globule of mercury added, the whole becomes converted
into a mass of elaidin in about two hours, of the same tint as that
produced from almond oil when similarly treated.
These tests point to the fact that the oil may be considered as
resembling almond or olive oil in composition, a conclusion which is
borne out by the subsequent experiments.
(3.) _Free Acidity of Oil._--The oil was found to contain free acid
in small quantity, which was estimated by agitating a weighed quantity
with alcohol, in which the free acid dissolves while the neutral fat
does not, and titrating the alcoholic liquid with decinormal alkali,
using solution of phenol-phthalein as an indicator.
It was thus found that 100 grammes of the oil require 0.34 gramme of
caustic potash to neutralize the free acid. Mr. W. H. Deering (_Journ.
Soc. of Chem. Industry_, Nov., 1884) states that in seven samples of
olive oil examined by him, the minimum number for acidity was 0.86 per
cent., and the maximum 1.64 per cent., the mean being 1.28 per cent.
Tea oil compares favorably with olive oil, therefore, in respect of
acidity, a quality of which note has to be taken when considering the
employment of oil as a lubricating agent.
(4.) _Saponification of the Oil._--Considerable light is thrown on the
composition of a fixed oil by ascertaining how much alkali is required
to saponify it. In order to estimate this, a known excess of alcoholic
solution of potash is added to a weighed quantity of the oil,
contained in a stout, well-closed bottle (an India-rubber stopper is
the most convenient), which is then heated in a water oven until
the liquid is clear, no oil bubbles being visible. Phenol-phthalein
solution being added, the excess of potash is estimated by carefully
titrating with standard hydrochloric acid solution.
It was thus found that 1,000 grammes of oil would require 195.5
grammes of caustic potash to convert it entirely into potash soap.
Koettstorfer, to whom this method of analysis is due, gives 191.8, and
Messrs. F. W. and A. F. Stoddart the numbers 191 to 196, as the amounts
of caustic potash required by 1,000 parts of olive oil. The numbers
given by niger seed, cotton seed, and linseed oils are very similar to
these. These oils differ from olive and tea oil, however, in having a
higher specific gravity, and in the property they possess of drying to
a greater or less extent on exposure to air.
(5.) _The Fatty Acids Produced._--A solution of the potash soap was
treated with excess of hydrochloric acid, and after being well washed
with hot water, the cake of fatty acids was dried thoroughly and
weighed. These, insoluble in water, amounted to 93.94 per cent, of the
fat taken. The proportion dissolved in the water used for washing was
estimated by titration with alkali; the quantity of KOH required was
insignificant, equaling 0.71 per cent, of the fat originally used.
This portion was not further examined.
The insoluble fatty acids amounted, as last stated, to 93.94 per cent.
Pure olein, supposing none of the liberated acid to be dissolved in
water, would yield 95.7 per cent. of fatty acid.
The acid was evidently a mixture, and had no definite melting point.
It was solid at 9° C., and sufficiently soft to flow at 12° C., but
did not entirely liquefy under 22° C. To test its neutralizing power,
0.9575 gramme dissolved in alcohol was titrated with decinormal
alkali; it required 34.05 c.c. This amount of pure oleic acid would
require 33.95 c.c.; of pure stearic acid, which has almost the same
molecular weight as oleic acid, 33.71 c.c.; or of pure palmitic acid,
37.4 c.c. This, taken in conjunction with the way in which the acid
melted, makes it extremely probable that it is a mixture of oleic and
stearic acids.
Additional evidence of the large proportion of oleic acid was
furnished by forming the lead salt, and treating with ether, in which
lead oleate is soluble, the stearate and palmitate being insoluble. In
this way it was found that the oleic acid obtained from the ethereal
solution of the lead salt amounted to 83.15 per cent. of the oil.
This acid was proved to be oleic, by its saturating power and its
melting point, which were fairly concordant with those of the pure
acid.
CABBAGE OIL (_Brassica, sp._).
_Appearance, etc._--The sample was of a deep brown color, of a
fluidity intermediate between olive and castor oil, and possessed a
strong, rather disagreeable odor.
_The Specific Gravity at 60° Fahr._, 914.0.--The specific gravity of
rape oil and colza oil, both of which are obtained from species of the
genius _Brassica_, varies from 913.6 to 916.
_Exposure to Cold._--This oil by exposure to a temperature of -12°
C. (10° F.) becomes solidified in course of an hour, a bright
orange-yellow mass resulting.
_Qualitative Examination._--The three reagents before indicated were
applied to this oil.
_(a.) Sulphuric Acid._--The color produced was very marked and
characteristic; it differed considerably from any of the others
simultaneously tested, the nearest to it being olive end rape oil.
_(b.) Strong Nitric Acid._--The reaction was more violent than before,
the stratum of oil after cooling being darker in color than in the
three cases before mentioned. The reaction with rape oil was similar
in all respects.
_(c.) Elaidin Test._--The solid mass of elaidin formed was of a darker
color than that from olive, almond, and tea oil, but closely resembled
that from rape oil.
_Free Acidity._--This was estimated as above described. 100 grammes of
oil would require 0.125 gramme caustic potash. The samples of rape oil
examined by Deering (loc. cit.) were found to require from 0.21 to
0.78 KOH per 100 grammes oil.
_Saponification of the Oil._--Upon saponifying with alcoholic potash,
it was found that 1,000 grammes of oil required 175.2 grammes of
potash for complete saponification.
The number obtained by Koettstorfer for colza was 178.7, by Messrs.
Stoddart for rape oil, 175-179, and by Deering for rape oil,
170.8-175.5. The only other oil of which I can find figures resembling
these is castor oil, which requires 176-178 grammes per kilo (Messrs.
Stoddart). The difference in specific gravity between this (cabbage)
oil and castor oil and the solubility of the latter in alcohol point
to a wide distinction between them. Hence I think the numbers above
given conclusively demonstrate the resemblance between this oil and
rape oil in composition.
_The Fatty Acids._--The acids produced by adding HCl to the potash
soap were almost entirely insoluble in water. The actual amount of
potash required to neutralize the acid in the wash water equaled 0.20
per cent. of the oil originally taken.
The insoluble fatty acid amounted to 95.315 per cent. of the oil
taken. It was evidently a mixture of two or more fatty acids. On
trying to take its melting point, I found that it commenced to soften
at 17° C., was distinctly liquid at 19°, but not completely melted
until 22° C.
According to O. Bach (Year Book Pharm., 1884, p. 250), the fatty acids
from rape seed oil melt at 20.7° C., which is fairly concordant with
the result obtained for cabbage oil acids.
The neutralizing power of these acids was then tested. 0.698 gramme
dissolved in alcohol required 20.52 c.c. decinormal alkali. It is a
singular coincidence that brassic acid (C_{22}H_{42}O_{2}), which is a
characteristic acid of colza and rape oils, would have required almost
exactly this quantity of alkali for neutralization, 0.698 brassic
acid theoretically saturating 20.69 c.c. of decinormal alkali. I
am disposed to regard this as a coincidence, since a subsequent
experiment showed that the lead salts formed were partially soluble in
ether, whereas the lead salt of brassic acid is said to be insoluble
in this liquid.
WOOD OIL (_Elæococcus cordata_).
_Appearance, etc._--This oil has a decided brown color and a
persistent and disagreeable odor. It is rather more fluid than castor
oil. Glass vessels containing it soon show a film of apparently
resinous material, which forms whenever a portion of the oil flows
from the lip or edge down the outside of the vessel, and is thus
exposed to the air in a thin stream. This drying power is one of its
most prominent characters. If a few drops be exposed in a flat dish,
in the water oven, the oil dries rapidly, so that in two hours the
gain in weight will be appreciable, and in four hours the whole will
have become solid.
_The Specific Gravity at 60° Fahr._, 940.15.--This is an unusually
high gravity for a fixed oil. The only two which exceed it are castor
oil, which is 960, about, and croton oil, which is very similar to
this, 942 to 943 (A. H. Allen). It is interesting to note that both
these oils are yielded by plants of the natural order _Euphorbiaceæ_,
to which the plant yielding so-called wood oil belongs.
_Exposure to Cold._--This oil is apparently unaffected by exposure to
a temperature of -13.3° C. (8° F).
_Qualitative Examination._--The action of sulphuric acid is
remarkable. When a drop comes in contact with the oil, the latter
apparently solidifies round the drop of acid, forming a black envelope
which grows in size and gradually absorbs and acts upon so much of the
surrounding oil as to assume the appearance of a large dried currant
of somewhat irregular shape.
When a drop of the oil is added to nitric acid, it solidifies, and
on heating very readily changes into an orange yellow solid, which
appears to soften, though not to liquefy, at the temperature of
boiling water. This substance is readily soluble in hot solution of
potash or soda, producing a deep brown liquid, from which it is again
deposited in flocks on acidifying. I have not yet found any solvent
for it. The action of nitric acid with linseed oil is more similar to
this than that with any other oil I have tried, but the nitro products
of the two, if I may so call them, are quite different from one
another. That from linseed oil produced as indicated remains liquid at
ordinary temperatures, as does the oil upon its addition to the acid.
_Elaidin Test._--By the action of nitric acid in presence of mercury,
a semi-solid mass is produced of a much deeper color than in the
preceding cases. A portion of the oil remains in the liquid state, as
is usually the case with drying oils.
_Free Acidity._--By the method indicated, it was found that 100
grammes of oil required 0.39 grammes caustic potash to neutralize the
acid occurring in a free state.
_Saponification of the Oil._--The oil saponifies readily on being
heated with potash in presence of alcohol, and the amount required to
convert it entirely into potash soap was 211 grammes of caustic potash
per thousand grammes of oil. There are no saponification numbers for
oils that can be considered close to this. I can find no record of
any having been obtained between 197 and 221, so that the further
examination on which I am now engaged may show this unusual number to
be due to this oil containing some new fatty acid in combination.
_The Fatty Acid._--The acids produced by adding acid to the potash
soap formed in this case a cake on cooling, of a much deeper color
than I have before obtained. After washing well they amounted to 94.10
per cent. of the oil. The amount dissolved by the water in washing
was in this case also very small, the potash required for neutralizing
equaling 1.02 per cent. of the weight of oil.
I found that the cakes of acids were solid at 36° C., and were
completely melted at 39°.
On solution in alcohol, and digestion for two days with animal
charcoal, the color was much diminished, and on the liquid being
filtered and cooled to 0° C., an abundance of small white crystalline
plates separated out, which, when dried, melted at 67° C.
The crude fatty acids turn black with sulphuric acid, as the oil
does, and yield a similar substance with nitric acid. It is similar
in appearance, but differs in that it melts at about 50° C., and
is soluble in glacial acetic acid, which is not the case with the
substance from the oil.
These fatty acids crystallize on cooling, in a most characteristic and
beautiful way, forming wavy circular plates totally unlike any that I
have seen before.
The above experiments may, I think, be taken as conclusive as to
the nature of tea oil and cabbage oil. The former may certainly
be considered a useful lubricating agent for the finer kinds of
machinery. The work upon wood oil is not yet sufficiently complete to
show us the nature of its proximate constituents. I am continuing the
examination of this oil. Perhaps I need scarcely add that there is no
connection between this "wood oil" and the Gurgun balsam, the product
of _Dipterocarpus turbinatus_, which is also known as "wood oil."
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