Characters. - A yellowish, oily liquid, gradually becoming brown, rancid and acid, when exposed to the air; odourless, or nearly so, tasteless, and, when pure, of a neutral reaction. Sp. gr., 0.800 to 0.810.

Preparation. - It is obtained by adding lead oxide to almond oil, which forms an oleate of lead or lead soap, and decomposing this by hydrochloric acid. Or by decomposing palm oil by superheated steam, and separating from any solid fats by pressure (vide p. 566).

Solubility. - Oleic acid is insoluble in water, but completely soluble in alcohol, chloroform, benzin, benzene, oil of turpentine, and the fixed oils.

At 14° C. (57.2° F.) it becomes semi-solid, and remains so until cooled to 4° C. (39.2° F.), at which temperature it becomes a whitish mass of crystals.

Tests. - At a gentle heat the acid is completely saponified by carbonate of potassium. If the resulting soap be dissolved in water and exactly neutralised with acetic acid, the liquid will form a white precipitate with test-solution of acetate of lead. This precipitate, after being twice washed with boiling water, should be almost entirely soluble in ether (absence of more than traces of palmitic and stearic acids). Equal volumes of the acid and of alcohol, heated to 25° C. (77° F.) should give a clear solution, without separating oily drops upon the surface (fixed oils).

Uses. - Oleic acid is employed only for the preparation of oleates, which are not only elegant preparations, but appear to be more readily absorbed than other ointments.

Preparations. B.P.

Oleatum Hydrargyri (yellow oxide of mercury 1, oleic acid 9). This oleate may be prepared with half the above proportion of oleic acid, the remainder being added just before, or not long before, the oleate is dispensed.

oleatum Zinci (oxide of zinc 1, oleic acid 9).

Unguentum Zinci Oleati (oleate of zinc 1, soft paraffin 1).

U.S.P.

amount used.

Oleum Hydrargyri. Oleate of Mercury (Hydrargyri Oxidum Flavum, 1 part; Acidum Oleicum, 9 parts)......

10 min., externally.

Oleatum Veratrinae. (Veratrinum, 2 parts; Acidum

Oleicum, 98 parts).........................................................

6 25 gr., externally.

Acidum Arseniosum. - Vide p. 719. Acidum Benzoicum. - Vide p. 964. Acidum Carbolicum. - Vide p. 813. Acidum Chrysophanicum. - Vide p. 909. Acidum Gallicum. - Vide p. 1033. Acidum Meconicum. - Vide p. 846. Acidum Pyrogallicum. - Vide p. 819. Acidum Salicylicum. - Vide p. 819. Acidum Tannicum. - Vide p. 1031.