OLEIC ACID (Cs3lls303,H0), at temperatures above 57°, exists as a colorless limpid fluid, of an oily consistence, devoid of smell and taste, and (if it has not been exposed to air) exerting no action on vegetable colors. At 40° it solidifies into a firm, white, crys talline mass, and in this state it undergoes no change in the air; but when fluid it readily absorbs. oxygen, becomes yellow and rancid, and exhibits a strong acid reaction with litmus paper. It is not a volatile acid, and on the application of a strong heat it breaks up into several substances, such as caproic, caprylic, and sebacic acids—the last named being the most charactcrsitic product of the distillation. If oleic acid be exposed to the action of hyponitric acid it is converted into an isomeric, solid, fatty acid, termed elaidic acid. A very small quantity of hyponitric acid (1 part to 200 of oleic acid) is sufficient to effect this remarkable change, the nature of which is unknown. When distilled with moderately strong nitric acid, it is oxidized into a large number of products, including all the volatile fatty acids represented by the formula 0012,,04, from formic acid (C,11204) to capric acid (C2411,004), with six fixed dibasic acids of the formula C012,,-,04, viz., suceinie acid, lipic acid, adipic acid, pimelic acid, suberic acid, and anchoic (or lepargylic) acid. When heated with hydrated potash it breaks up into palmitic and acetic acids, as shown in the equation: Oleic Acid. Hydrated Potash. Pahnitate of Potash. Acetate of Potash.
C34113404 + 2(Ii0,110) = + 211 These decompositions and disintegrations seem to illustrate the facility with which, by the mere process of oxidation, which is perpetually at work in living structures, one organic acid can be converted into others.
Oleic acid is a constituent of oleine (q.v.), which exists in most of the fats and fatty oils of the animal and vegetable kingdoms, and most abundantly in the liquid fats or oils, and hence its name is derived. It is very difficult to obtain the acid in a state of purity, in consequence of the readiness with which it oxidizes; and we shall not enter into details. regarding the method of its preparation. It is obtained in a crude form, as a secondary product, in the manufacture of stearine candles, but almond oil is generally employed when the pure acid is required.
Oleic acid forms normal (or neutral) and acid salts; but the only compounds of this class that require notice are the normal salts of the alkalies. These are ill soluble, and by the evaporation of their aqueous solution form soaps. Olcate of potash forms a soft soap, which is the chief ingredient in Naples soap: while oleate of soda is a hard soap, which enters largely into the composition of Marseilles soap.
The oleates of the alkalies occur in the animal body, in the blood, chyle, lymph. and bile; they have also been found in pus, in pulmonary tubercles, and in the excrements, after the administration of purgatives.