CHAPTER LVIII. FIXED OILS, FATS, AND SOAPS. FIXED oils and fats are obtained from both the vegetable and the animal kingdom. They are greasy to the touch, and leave a permanent oily stain on paper; they are insoluble in water, but dissolve in ether, chloroform, carbon disulphide, benzol, benzin, turpentine, and volatile oils; they usually mix with one another without separating. When pure, they are generally colorless or have a pale yellow color; they have a distinctive odor and taste, which is often caused by impurities with which they are associated, as the process of refining deprives them of odor and taste. When heated moderately, if solid they melt, or if liquid they become thinner; if heated strongly in air they are decomposed, evolve offensive vapors, and then burn with a sooty flame, much heat being generated. Their specific gravity varies from 0.870 to 0.985, thus being lighter than water. By exposure to air they acquire an acrid, disagreeable taste and become acid to litmus paper. This change, termed rancidity, is believed to be due to the presence of impurities (like albuminous substances), which act as ferments, induce decomposition, liberate the fatty acids, and produce volatile, odorous acids, like caproic, caprylic, butyric, and valerianic acids. Oils which have become rancid may often be purified by shaking them thoroughly with hot water and then with a cold solution of sodium carbonate, and subsequently washing them with cold water. Chemically, the fixed oils and fats are compound ethers of higher members of the fatty acids, the alcohol being glycerin and the radical glyceryl. In most cases they consist of two or three proximate principles, olein, palmitin, or stearin. These are sometimes termed the glycerides of oleic, palmitic, and stearic acids. Olein is liquid, and palmitin and stearin are both solid: hence the consistence of fixed oils and fats is due to the relative proportion of these principles: thus, almond oil, being composed principally of olein, is always liquid at ordinary temperatures, whilst tallow, being largely stearin, is solid. 18 Olein, CH,(CH3O2)3, is the oleate of the triad radical glyceryl, and constitutes the liquid principle of oils. It is extremely difficult to obtain it pure. Being in most oils associated with the solids stearin and palmitin, it has to be separated by pressure and other mechanical means, and this is not easily effected. As ordinarily procured, therefore, olein contains more or less of palmitin or stearin, or both. It is obtained either by the agency of alcohol or by expression. When one of the oils, olive oil, for example, is dissolved in boiling alcohol, the solution, on cooling, deposits the concrete principles, retaining the olein, which it yields upon evaporation. The other method consists in compressing one of the solid fats, or of the liquid oils rendered concrete by cold, between folds of bibulous paper, which absorb the olein, and give it up after wards by compression under water. Olein is a liquid of oily consistence, congealing at -6° C. (21.2° F.), colorless when pure, with little odor and a sweetish taste, insoluble in water, soluble in boiling alcohol and ether. Palmitin.-Palmitic acid occurs in the more liquid fats, such as palm oil and coco-nut oil, as glyceride; while in spermaceti and some forms of wax it is combined with monatomic alcohol radicals. Palmitin is the glyceride of palmitic acid or tripalmitate of glyceryl. Stearin.-This exists abundantly in tallow and other animal fats, and it is made on an immense scale for use in candles by cooling lard and tallow, and separating the olein by hydraulic pressure. It may be obtained pure by dissolving suet in hot oil of turpentine, allowing the solution to cool, submitting the solid matter to expression in unsized paper, repeating the treatment several times, and finally dissolving in hot ether, which deposits the stearin on cooling. This is white, opaque in mass, but of a pearly appearance as crystallized from ether, pulverizable, fusible at 66.5° C. (152° F.), soluble in boiling alcohol and ether, but nearly insoluble in those liquids cold, and quite insoluble in water. It consists of glyceryl and stearic acid, as a glyceride, CH,(CH3O2)39 and has been formed synthetically by heating a mixture of these two materials to 280°-300° C. 35 Margarin.-What was long known under this name was shown by Heintz, in 1852, to be a mixture of stearin and palmitin. The true margaric acid, C17H3O2, has been obtained by synthesis, and according to Ebert is found in adipocere, a waxy substance formed in the tissues of dead animals. 17 Stearic acid, CH6O2, is a firm white solid, like wax, fusible at 69.2° C. (157° F.), greasy to the touch, pulverizable, soluble in alcohol, very soluble in ether, but insoluble in water. In the impure state it is used as a substitute for wax in making wax candles. (See Acidum Stearicum). Palmitic acid, CH2O2, forms a white scaly mass, and melts at 62° C. (143.6° F.). Oleic acid, CHO, is an oily liquid, insoluble in water, soluble in alcohol and ether, lighter than water, crystallizable in needles a little below 0° C. (32° F.), and having a slight smell and a pungent taste. (See Acidum Oleicum.) Glycerin is described under a separate head. (See Glycerina.) AMYGDALA DULCIS. U.S. Sweet Almond. The seed of Prunus Amygdalus var. dulcis De Candolle (nat. ord. Rosaceœ). Sweet almond contains about 40 per cent. of fixed oils, protein compounds (conglutin and amandin), sugar, mucilage, etc. Tannin is present in the integuments. The protein compounds aid in emulsionizing the fixed oil which is present, and simple trituration is all that is necessary to form a mixture. Official Preparations. Emulsum Amygdala.. Made by blanching 60 Gm. of sweet almond, adding 10 Gm. of Emulsion of Almond. acacia and 30 Gm. of sugar, and triturating with 1000 C.c. of distilled water (see page 316). Dose, two to eight fluid ounces (59 to 236 C.c.). Syrupus Amygdala.. Made from 140 Gm. of sweet almond, 40 Gm. of bitter almond, 200 Gm. of sugar, 100 C.c. of orange flower water, and water and syrup to make 1000 C.c. (see page 302). Dose, one to two fluidounces (29 to 59 C.c.). OLEUM AMYGDALÆ EXPRESSUM. U.S. Expressed Oil of Almond. A fixed oil expressed from Bitter or Sweet Almond. Preparation. This oil is obtained equally pure from sweet and bitter almonds. The almonds, having been deprived of a reddish-brown powder adhering to their surface, by being rubbed together in a piece of coarse linen, are ground in a mill, and then pressed in canvas sacks between plates of steel slightly heated. The oil, which is at first turbid, is clarified by rest and filtration. Sweet almond yields about 40 per cent. and bitter almond 35 per cent. of fixed oil. A colorless oil may be obtained by expressing almonds which have been blanched,―i.e., deprived of their testa by soaking them in hot water and slightly pressing them, and afterwards drying in a stove to evaporate the water. Oleum Amygdala Expressum. U.S. A clear, pale straw-colored, or colorless, oily liquid. Sp. gr. 0.915 to 0.920 at 15° C. (59° F.). It remains clear at -10° C. (14° F.), and does not congeal until cooled to near-20° C. (—4° F.). TESTS FOR IDENTITY. If 10 C.c. of the Oil be mixed with 15 C.c. of a 15-per-cent. solution of sodium hydrate and 10 C.c. of alcohol, the mixture allowed to stand at a temperature of 35° to 40° C. (95° to 104° F.), with occasional agitation, until it becomes clear, and then be diluted with 100 C.c. of water, the clear solution thus obtained, upon the subsequent addition of an excess of hydrochloric acid, will set free a layer of oleic acid. This, when separated from the aqueous liquid, washed with warm water, and clarified in a waterbath, will remain liquid at 15° C. (59° F.), although sometimes depositing particles of solid matter and becoming turbid. IMPURITIES. Fixed Oils of Apricot Olive, Arachis, Cotton Slightly. In all propor tions in ether and chloroform. TESTS FOR IMPURITIES. If 2 C.c. of the Oil be vigorously shaken with 1 C.c. of fuming nitric acid and 1 C.c. of water, a whitish, not red or brownish, mixture should be formed, which, after standing for some hours at about 10° C. (50° F.), should separate into a solid, white mass, and a scarcely colored liquid. One part of this oleic acid, when mixed with 1 volume of alcohol, should give a clear solution, which at 15° C. (59° F.) should not deposit any fatty acids, nor become turbid on the further addition of 1 volume of alcohol. Uses. Expressed oil of almond, or oil of sweet almonds, as it is usually called, is used as an emollient, and an ingredient in "cold cream" and phosphorated oil. OLEUM OLIVÆ. U. S. Olive Oil. A fixed oil expressed from the ripe fruit of Olea europœa Linné (nat. ord. Oleaceœ). Preparation.-Although pure olive oil is still found occasionally, there is good reason to believe that the so-called olive oil is mainly cotton seed oil, or other similar substitution, judiciously flavored. Pure olive oil is made by expressing olives and clarifying the oil by subsidence; but the detection of admixtures of other fixed oils is attended with discouraging results. The exportation of over six million gallons of cotton seed oil annually to Mediterranean ports contiguous to the olive oil industry is a significant fact. The Pharmacopoeia furnishes the following tests. It is difficult to detect an admixture of a similar vegetable oil of less than 20 per cent. by any published test. Oleum Oliva. U.S. A pale yellow, or light greenish-yellow, oily liquid. When cooled to about 10° C. (50° F.), it begins to be somewhat cloudy from the separation of crystalline particles, and at 0° C. (32° F.) it forms a whitish, granular mass. Sp. gr. 0.915 to 0.918 at 15° C. (59° F.). TESTS. If 10 C.c. of the Oil be shaken fre- Odor, Taste, and Slight, peculiar odor; IMPURITIES. Appreciable quan- More than 5 per cent. of Cotton If 6 Gm. of the Oil be thoroughly shaken, in a test-tube, for about two 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 fifteen minutes, the Oil should retain a light yellow color, not becoming orange or reddish-brown, and, after standing at the ordinary temperature for about twelve hours, it should form a perfectly solid, light yellowish mass. If 5 C.c. of the Oil be thoroughly shaken, in a test-tube, with 5 C.c. of an alcoholic solution of silver nitrate (prepared by dissolving 0.1 Gm. of silver nitrate in 10 Č.c. of deodorized alcohol, and adding 2 drops of nitric acid), and the mixture heated for about five minutes in a water-bath, the Oil should retain its original pale yellow color, not becoming reddish or brown, nor should any dark color be produced at the line of contact of the two liquids. Uses.-Olive oil is used in making cerates, ointments, liniments, and plasters. It is a bland, agreeable oil, well suited for emollient purposes. OLEUM GOSSYPII SEMINIS. U. S. Cotton Seed Oil. A fixed oil expressed from the seed of Gossypium herbaceum Linné, and of other species of Gossypium (nat. ord. Malvaceœ), and subsequently purified. Preparation. This oil is made commercially in the southern part of the United States upon a very large scale. The seeds contain 15 per cent. of oil. The testa of the seeds is first separated, and the kernels are exposed to powerful expression in hydraulic presses. 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 two 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 fifteen minutes, the Oil will assume an orange or reddish-brown color, and, after standing for twelve hours at the ordinary temperature, will form a semi-solid mass. If 5 C.c. of the Oil be thoroughly shaken in a test-tube, with 5 C.c. of an alcoholic solution of silver nitrate (made by dissolving 0.1 Gm. of silver nitrate in 10 C.c. of deodorized alcohol and adding 2 drops of nitric acid), and the mixture heated for about five minutes in a water-bath, the Oil will assume a red or reddish-brown color. oleum seSAMI. U. S. Oil of Sesamum. [SESAME OIL. TEEL OIL. BENNÉ OIL.] A fixed oil expressed from the seed of Sesamum indicum Linné (nat. ord. Pedaliacea). This oil consists of olein (70 per cent.), palmitin, stearin, and myristicin. It is inodorous, of a bland, sweetish taste and a neutral reaction, and will keep long without becoming rancid. It is not a drying oil. At 15° C. (59° F.) it has the sp. gr. 0.919 to 0.923; and its point of congelation is -5° C. (23° F.). Concentrated sulphuric acid converts it into a brownish-red jelly. If 5 C.c. of the oil be shaken with an equal volume of concentrated hydrochloric acid, the latter will usually assume a bright emerald-green color, especially if the oil has been exposed for some time to the action of air and light; and, on the subsequent addition of about 0.5 Gm. of sugar, and again shaking the mixture, a blue color, changing to violet, and finally to deep crimson, will be produced. OLEUM LINI. U. S. Linseed Oil. [OIL OF FLAXSEED.] A fixed oil expressed from Linseed without the use of heat. Preparation. It will be noticed that the official description specifies an oil made without the use of heat: this would reject all the oil made on the large scale for use in the arts. Linseed oil is a drying oil, and consists mainly of linolein, which, by exposure, becomes linoxyn, C2H5O11; myristin and palmitin are also present. 32 54 |