Oil of Palm.
Oil of Palm. Palm Oil. Huile (Beurre) de Palme, Fr. Palmöl, Palmbutter, G.—This highly valuable fixed oil is the product of Eloeis guineensis Jacq., a palm growing on the western coast of Africa, and cultivated in the West Indies and South America. It is among the handsomest trees of its graceful family which flourish in the tropical regions of Africa. The oil is obtained by expression from the fruit. It is brought to this country chiefly from Liberia and other places on the African coast, although prepared also in the West Indies, Cayenne, and Brazil. It is not improbable that various species of Palmaceae contribute to the supply of this article of commerce. At present the chief ports for its shipment are Cape Palmas and Lagos, prima and secunda Lagos being the choicest varieties. The annual export from the African coast is about 50,000 tons, of which the bulk goes to England. The importation into the United States amounted in 1914 to 61,753,482 lbs., valued at $4,118,077, and in 1915 to 31,482,292 lbs., valued at $2,024,827.
Palm oil has the consistence of butter, a rich, orange-yellow color, a sweetish taste, and an agreeable odor, compared by some to that of violets, by others to that of the Florentine orris. By age and exposure it becomes rancid and of a pale yellow or nearly white color. It melts with the heat of the hand, and when perfectly fluid passes readily through blotting paper. Highly rectified. alcohol dissolves it at common temperatures, and in ether it is soluble in all proportions. Its constituents are tripalmitin and triolein, C3H5(C16H31O2)3 and C3H5(C18H33O2)3. The tripalmitin is converted into palmitic acid by superheated steam, with liberation of glycerin. It appears also that a considerable proportion of this acid, together with some glycerin, exists uncombined in the oil, as ascertained by Pelouze and Boudet; so that the changes which are effected in oils, through the agency of alkalies, in the process of saponification, take place, to a certain extent, spontaneously in palm oil. (J. P. C., xxiv, 389.) Hence it is more easily saponified than any other fixed oil. Preparatory to saponification, it may be bleached rapidly, according to J. J. Pohl, by heating it quickly to 240° C. (464° F.) and keeping it for ten minutes at that temperature. It loses for a time its peculiar odor by the process, acquiring an empyreumatic one; but this after a while ceases to be perceived, and the characteristic odor returns. (See A. J. P., xxvii, 346.) Englehart bleaches it in the following manner: 1000 lbs. of the oil are heated in a boiler to 62.2° C. (144° F.) and kept at that temperature until the next day, when it is decanted into a clean vessel, and cooled to a point between 36.6° C. (98° F.) and 40° C. (104° F.). In another vessel 15 lbs. of potassium dichromate are dissolved in 45 lbs. of boiling water, and, when the solution is partially cooled, 60 lbs. of hydrochloric acid are added. This solution is then mixed with the oil, and briskly agitated. In five minutes the color changes to green, through the reduction of the chromic acid, and, with a continuation of the agitation, the chromium oxide separates, and then nothing more is necessary than washing with water to get the oil colorless. (A. J. P., 1868, 333.) Palm oil is said to be frequently imitated by a mixture of lard and suet, colored with turmeric, and scented with Florentine orris. It is much employed in the manufacture of toilet soap, which retains its pleasant odor. Palm oil is emollient, and has sometimes been employed in friction or embrocation, though not superior for this purpose to many other oleaginous substances. It is sometimes used to impart a yellow color to mixtures of fats or manufactured products, such as oleomargarine. In the latter case it is considered as an artificial coloring matter which necessitates the payment of ten cents per lb. additional tax. It is detected in the presence of other fats by a color reaction developed when sulphuric acid is added to a mixture of the suspected oil and an equal volume of acetic anhydride. This is known as Crampton-Simons test for palm oil, but it has been attacked by A. G. Gill (J. I. & E. C., 1917, p. 136) as being fallacious, due not to a specific substance present in palm oil only, but to the presence of carotin, which is present in butter and some other constituents likely to be normally present in oleomargarine, to which this test is usually applied for the purpose of detecting the palm oil as an added coloring matter. The test as carried out is as follows: Preparation of Sample: The sample should be kept in a cool dark place until tested, as exposure to light and air or the presence of water, alcohol, ether or similar reagents, interferes with the tests. Immediately before testing, the sample is filtered as quickly as possible at a temperature not exceeding 70° C. (158° F.). First Method: Dissolve 100 mils of the fat in 300 mils of petroleum ether and shake out with 50 mils of a 0.5 per cent. potassium hydroxide solution. Draw off the aqueous layer, make distinctly acid with hydrochloric acid and shake out with 10 mils of pure carbon tetrachloride. Separate the carbon tetrachloride solution, transfer a portion to a porcelain crucible, add 2 mils of a mixture of one part colorless, crystallized phenol and two parts of carbon tetrachloride, then 5 drops of hydrobromic acid (sp. gr. 1.19) and mix by gentle agitation. The almost immediate development of a bluish-green color is indicative of palm oil.
Second Method (usually preferred): Shake out 10 mils of the melted and filtered fat with an equal volume of colorless, chemically pure, acetic anhydride, add 1 drop of sulphuric acid (sp. gr. 1.53) and shake the mixture for a few seconds longer.
If palm oil is present the lower layer, on settling, will be found to be colored blue with a tint of green. The color in this as well as in the preceding test is transient. Leach, p. 541-543.