1911 Encyclopædia Britannica/Oleic Acid

OLEIC ACID, C₁₃H₃₄O₂ or C₈H₁₇·CH:CH·[CH₂]₇·CO₂H, an organic acid occurring as a glyceride, triolein, in nearly all fats, and in many oils—olive, almond, cod-liver, &c. (see Oils). It appears as a by-product in the manufacture of candles. To prepare it olive oil is saponified with potash, and lead acetate added; the lead salts are separated, dried, and extracted with ether, which dissolves the lead oleate; the solution is then treated with hydrochloric acid, the lead chloride filtered off, the liquid concentrated, and finally distilled under diminished pressure. Oleic acid is a colourless, odourless solid, melting at 14° and boiling at 223° (10 mm.). On exposure it turns yellow, becoming rancid. Nitric acid oxidizes it to all the fatty acids from acetic to capric. Nitrous acid gives the isomeric elaidic acid, C₈H₁₇·CH:CH·[CH₂]₇·CO₂H, which is crystalline and melts at 51°. Hydriodic acid reduces both oleic and elaidic acids to stearic acid.

Erucic acid, C₈H₁₇·CH:CH·[CH₂]₁₁·COH, and the isomeric brassidic acid, belong to the oleic acid series. They occur as glycerides in rape-seed oil, in the fatty oil of mustard, and in the oil of grape seeds. Linoleic acid, C₁₈H₃₂O₂, found as glyceride in drying oils, and ricinoleic acid, C₁₈H₃₃(OH)O₂, found as glyceride in castor oil, closely resemble oleic acid.