Sperm oil

Sperm oil (see also: Spermaceti) is a waxy liquid obtained from sperm whales. It is a clear, yellowish liquid with a very faint odor. Sperm oil has a different composition from common whale oil, obtained from rendered blubber. Although it is traditionally called an "oil", it is technically a liquid wax. It is composed of wax esters with a small proportion of triglycerides, an ester of an unsaturated fatty acid, and a branched-chain fatty alcohol. It is a natural antioxidant and heat transfer agent. In the late-18th and early-19th centuries, sperm oil was prized as an illuminant for its bright, odorless flame and as a lubricant for its low viscosity and stability. It was supplanted in the late 19th century by less expensive alternatives such as kerosene and petroleum-based lubricants. With the 1987 international ban on whaling, sperm oil is no longer legally sold.

The oil from bottlenose whales was sometimes called "Arctic sperm oil." It was cheaper than but inferior to true sperm oil.

After killing a sperm whale, the whalers would pull the carcass alongside the ship, cut off the cranium and haul it on deck, whereupon they would cut a hole in it and bail out the matter inside with a bucket. The primary source of sperm oil was the spermaceti organ and the junk (or "melon"), the organs that serve to focus and modulate the animal's vocalizations. The matter from these organs was stored in casks to be processed on land; sometimes it was boiled first to prevent it going rancid. The blubber also contained smaller proportions of spermaceti, which was obtained by boiling the blubber on the ship itself.

On land, the casks of head-matter were allowed to chill during the winter, causing it to congeal into a spongy and viscous mass. The congealed matter was then loaded into wool sacks and placed in a press to squeeze out its liquid. This liquid was bottled and sold as "winter-strained sperm oil". This was the most valuable product: a lubricant that remained liquid in freezing winter temperatures. When spring came and the leftover solid matter melted a bit, the liquid was strained off and sold as "spring-strained sperm oil". In summer, the matter melted some more and the liquid was strained off to leave a fully solid wax. This wax, brown in color, was then bleached and sold as "spermaceti wax".

Sperm oil has a fairly low viscosity (roughly equal to coconut oil). It retains its viscosity in high temperatures better than most oils. It does not tend to become rancid, dry out, or corrode metals. Sperm oil cannot be easily hydrogenated, and thus could not be used to make soap or margarine. It is fairly resistant to oxidization.

Spermaceti is a liquid wax, composed mostly of wax esters (chiefly cetyl palmitate) and a smaller proportion of triglycerides, with oleic acid being the most common fatty acid. The proportion of wax esters in the spermaceti organ increases with the age of the whale: 38-51% in calves, 58-87% in adult females, and 71-94% in adult males. The blubber oil of the whale is about 66% wax. When cooled to below 30 °C (86 °F), the waxes in spermaceti begin to crystallize.

Winter-strained sperm oil is roughly two-thirds wax esters and one third triglycerides. Most of the carbon chains are unsaturated, with 18:1 being the most common. Unlike other toothed whales save the Amazon river dolphin, most of the carbon chains in the wax esters are relatively long (C₁₀-C₂₂).

Sperm oil was particularly prized as an illuminant in oil lamps, as it burned more brightly and cleanly than any other available oil and gave off no foul odor. It was replaced in the late-19th century by cheaper, more efficient kerosene.^{[citation needed]}