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.