NOTES ON THREE NEW CHINESE FIXED OILS.1

NOTES ON THREE NEW CHINESE FIXED OILS.¹

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 O.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 (C₂₂H₄₂O₂), which is a characteristic acid of colza and rape oils, would have required almost exactly this quantity of alkali for neutralization, O.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."