Oleum Cetacei. Sperm Oil.
Related entries: Spermaceti
Sperm oil is obtained from the blubber of the sperm whale or cachalot, Physeter macrocephalus, Linn. (Order Cetacea). The fresh blubber separates on standing in the cold into a liquid and a solid portion, the former being the sperm oil, which may be obtained by filtration or expression. It occurs as a thin yellow liquid, almost free from odour when of good quality, but often having a slightly unpleasant fishy odour. Specific gravity, 0.875 to 0.884. Saponification value, 123 to 147. Iodine value, 79.5 to 84. On cooling the oil, spermaceti separates in crystalline scales, and stearin at a lower temperature. Sperm oil may be adulterated with mineral oils, shark liver oil, African fish oil; these are considered the only possible adulterants. The genuine oil gives a brown colouration with sulphuric acid, becoming, on stirring, somewhat darker with a tinge of violet. Shark oil gives by the same treatment a well-marked violet colour, the tint changing to red or reddish-brown on stirring.
Soluble in all proportions of ether, chloroform or petroleum ether; insoluble in absolute alcohol.
Constituents.—The oil consists wholly of the esters of fatty acids and monovalent alcohols, and contains no glycerides, or only traces. When saponified with potassium hydroxide, it forms potassium oleate and dodecatyl alcohol, and some allied bodies. On shaking the aqueous solution of the resulting soap with ether, the higher alcohols are dissolved and may be obtained by evaporating the solvent. The fatty acids are isolated by acidifying the soap solution. These latter have all the characters of a mixture of one acid of the oleic series with one of the stearic series.
Uses.—Sperm oil has only a slight tendency to become rancid, and for this and other reasons is much valued as a lubricant for light machinery. It is also used for hardening steel, and as a lamp oil.