Wax ester in the context of "Waxes"

Waxes are a diverse class of organic compounds that are lipophilic solids that are malleable near ambient temperatures. They include higher alkanes and lipids, typically with melting points above about 40 °C (104 °F), melting to give low viscosity liquids. Waxes are insoluble in water but soluble in nonpolar organic solvents such as hexane, benzene and chloroform. Natural waxes of various types are produced by plants and animals and occur in petroleum.

Spermaceti /spərməˈsiːtiˌ -ˈsɛ-/ (see also: sperm oil) is a waxy substance found in the head cavities of the sperm whale (and, in smaller quantities, in the oils of other whales). Spermaceti is created in the spermaceti organ inside the whale's head. This organ may contain as much as 1,900 litres (500 US gal) of spermaceti. It has been extracted by whalers since the 17th century for human use in cosmetics, textiles, and candles.

Theories for the spermaceti organ's biological function suggest that it may control buoyancy, act as a focusing apparatus for the whale's sense of echolocation, or possibly both. Concrete evidence supports both theories. The buoyancy theory holds that the sperm whale is capable of heating the spermaceti, lowering its density and thus allowing the whale to float; for the whale to sink again, it must take water into its blowhole, which cools the spermaceti into a denser solid. This claim has been called into question by recent research that indicates a lack of biological structures to support this heat exchange, and the fact that the change in density is too small to be meaningful until the organ grows to a huge size. Measurement of the proportion of wax esters retained by a harvested sperm whale accurately described the age and future life expectancy of a given individual. The level 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.