"A fixed oil expressed from the seed of Gossypium herbaceum, Linné, and of other species of Gossypium (Nat. Ord.—Malvaceae), and subsequently purified. It should be kept in well-closed vessels"—(U. S. P.).
SYNONYMS: Oleum gossypii, Oil of cotton, Cotton oil.
Source and Preparation.—Cleaned cotton seeds are about 1/3 inch long and 1/6 inch wide, irregularly ovoid, covered with a hard, somewhat fragile, brown testa marked with a conspicuous raphè. Internally, the cotyledons are folded, and, imbedded throughout their substance are a number of resin-glands of a blackish color. The embryo is whitish. To obtain the oil, of which 2 gallons are yielded by 1 bushel of the seeds, the testa is crushed by machines especially designed for this purpose, the fragments winnowed out, the kernel ground, placed in bags, and expressed by powerful hydraulic pressure.
Purification.—Cotton-seed oil, when freshly expressed, is thick, turbid, of a ruby-red to dark-brown color, and contains much albuminous matter. Upon standing it deposits a considerable quantity of its impurities, leaving the oil as a clear orange-yellow liquid. This is known as clarified oil. The albuminous constituents may be coagulated by heating the oil by means of boiling water. Another method of purifying the crude oil consists in agitating the oil in the cold with a weak solution of caustic soda, which removes the characteristic coloring matter of the oil (see Chemical Composition), and forms with part of the oil a soap which settles upon standing, in the form of a black deposit. Thus the oil becomes of a much lighter color and constitutes refined oil. The loss by this process is about 4 to 7 per cent, sometimes considerably more. Bleaching agents are also frequently employed in the refining of cotton-seed oil.
Description and Tests.—This oil is officially described as "a pale yellow, oily liquid, without odor, and having a bland, nut-like taste. Specific gravity, 0.920 to 0.930 at 15° C. (59° F.). Very sparingly soluble in alcohol, but readily soluble in ether, chloroform, or carbon disulphide. On cooling the oil to a temperature below 12° C. (53.6° F.), particles of solid fat will separate. At about 0° to -5° C. (32° to 23° F.), the oil solidifies"—(U. S. P.).
This oil stands intermediate between the non-drying and drying oils; it thickens upon exposure, but does not become solid. Strong solutions of alkalies readily saponify cotton-seed oil. Purified cotton-seed oil is largely employed for culinary purposes, e. g., as salad oil, as a butter substitute, one of its chief uses being to adulterate other oils, especially olive oil. It also serves in the manufacture of soap, in the preparation of woolen and Morocco leather goods, and has taken a prominent place in pharmaceutical preparations, displacing, in a measure, olive and almond oils. The crude oil may be easily recognized by the beautiful purple or violet coloration (cotton-seed blue) which the soap prepared from it assumes upon exposure to the air. For the purified cotton-seed oil there are several color tests, in addition to the requirements of specific gravity and other physical constants. A red color is observed upon treating the oil with strong solution of lead acetate and allowing it to stand; S. S. Bradford (Amer. Jour. Pharm., 1882, p. 481) regards it an easy test for the detection of this oil as an adulterant of olive oil. The U. S. P. tests are as follows: "When the oil is brought in contact with concentrated sulphuric acid, a dark reddish-brown color is instantly produced. If 6 Gm. of the oil be thoroughly shaken, in a test-tube, for about 2 minutes, with a mixture of 1.5 Gm. of nitric acid and 0.5 Gm. of water, then heated in a bath of boiling water for not more than 15 minutes, the oil will assume an orange or reddish-brown color, and, after standing for 12 hours at the ordinary temperature, will form a semisolid mass. If 5 Cc. of the oil be thoroughly shaken, in a test-tube, with 5 Cc. of an alcoholic solution of silver nitrate (made by dissolving 0.1 Gm. of silver nitrate in 10 Cc. of deodorized alcohol and adding 2 drops of nitric acid), and the mixture heated for about 5 minutes in a water-bath, the oil will assume a red or reddish-brown color."—(U. S. P.). The second of these includes the elaïdin test; the third is Becchi's test. Halphen's test, introduced in 1897, seems to be very delicate. According to A. H. Allen (Commercial Organic Analysis, Vol. II, Part I, 3d ed., 1889, p. 143), it is executed as follows: Carbon disulphide, containing about 1 per cent of sulphur in solution, is mixed with an equal volume of pentyl (amyl) alcohol. Equal volumes of this reagent and the sample—about 3 Cc. of each—are mixed and heated in a bath of boiling brine for 15 minutes. A red or orange tint is produced when cotton-seed oil is present. If the color is not produced, 1 Cc. more of the reagent is added, and heating continued for 5 or 10 minutes longer; in the absence of color, the addition is repeated once more.
Chemical Composition.—This oil is composed mainly of palmitin and olein. Cotton-seed blue (C17H24O4), an amorphous body, has been obtained by Kuhlmann (1861) as an oxidation product of a chromogene contained in the oil. Exposure to light and air bleaches the blue substance, while oxidizers wholly destroy it. It dissolves in strong sulphuric acid with a purple color, is also soluble in ether and alcohol, while chloroform and carbon disulphide sparingly dissolve it. It is insoluble in water, diluted acids, and alkalies. The chromogene body, according to J. Longmore, is a pungent, golden-yellow substance insoluble in water, soluble in alcohol and alkalies, insoluble in acids. It is a fast dye for wool and silk (see A. H. Allen, loc. cit.).
Action, Medical Uses, and Dosage.—This oil is a wholesome and digestible food, and is employed in pharmacy, medicine, and surgery, for many of the purposes for which olive oil is employed. Dose, 1 fluid drachm to 2 fluid ounces.
Related Oils.—OIL OF BRAZIL NUTS. The tree, whose seed yields this oil, is the handsome South American Berthollettia excelsa, of Humboldt and Bonpland (Nat. Ord.—Lecythidaceae). It is known to the Brazilians as castanhiero de Para, and the seeds are edible and an article of commerce under the names of Brazil or Para nuts. These nuts are the seeds of a large globular fruit nearly a foot in diameter, from 16 to 20 seeds being contained in 1 fruit. Brazil nuts are long (1 1/2 to 2 inches), triangular, convex on back, and have a rough, hard, brownish-gray testa, inclosing a kernel of a creamy white hue, and tasting somewhat like almonds. It is considerably used in making a cream-syrup for soda fountain uses. The kernels yield over 60 per cent of a fixed oil used by the natives as a burning fluid, as an adulterant of copaiba, and in unguents. It is a bland oil of a light-yellow color, readily becoming rancid. At 1° C. (30° F.) it congeals. It is composed chiefly of olein, palmitin, and stearin.
OIL OF SAPUCAYA NUTS.—An oil similar to Brazil-nut oil is obtained from the nuts (Sapucay nuts) of Lecythis Zabucajo, Aublet, a Brazilian tree.
OLEUM FAGI, Beech oil, Beech-nut oil.—The fruit of the beech tree of Europe (Fagus sylvatica, Linné (Nat. Ord.—Cupuliferae), yields a yellow oil, mild if prepared by cold expression, and acrid if heat be employed; in this case it becomes mild after a time. It is obtained from the kernels deprived of the integuments, the yield being about 22 per cent. Its specific gravity is 0.921 to 0.923; its congealing point near -17.5° C. (+.5° F.). A soft soap may be obtained from it by saponification. It does not readily become rancid. The oil contains stearin and palmitin, but is composed chiefly of olein. The press-cake, while eaten with impunity by fowls and swine, is said to produce untoward effects in horses or cattle. (See also interesting data on beech-nut oil by Charles H. La Wall, Amer. Jour. Pharm., 1896, p. 11.)
OIL OF MAIZE.—The germ alone of our Indian corn, or American maize, contains about 22 per cent of a rich golden-yellow oil of a characteristic, not unpleasant odor and taste. It is obtained largely as a by-product in preparing starch, glucose and alcohol. It is thickish and has a specific gravity of 0.916 at 15° C. (59° F.). At -10° C. (14° F.) it congeals. It is composed of olein, stearin, and palmitin, and easily becomes rancid.
King's American Dispensatory, 1898, was written by Harvey Wickes Felter, M.D., and John Uri Lloyd, Phr. M., Ph. D.