AskDefine | Define saponification

Dictionary Definition

saponification n : a chemical reaction in which an ester is heated with an alkali (especially the alkaline hydrolysis of a fat or oil to make soap)

User Contributed Dictionary



  1. The hydrolysis of an ester under basic conditions to form an alcohol and the salt of the acid.
  2. The reaction of a metallic alkali (base) with a fat or oil to form soap.


  • Greek: σαπωνοποίηση
  • Italian: saponificazione

Extensive Definition

Saponification is the hydrolysis of an ester under basic conditions to form an alcohol and the salt of a carboxylic acid. Saponification is commonly used to refer to the reaction of a metallic alkali (base) with a fat or oil to form soap. Saponifiable substances are those that can be converted into soap.
CH2-OOC-R - CH-OOC-R - CH2-OOC-R (fat) + 3 NaOH ( or KOH)
both heated →
CH2-OH -CH-OH - CH2-OH (glycerol) + 3 R-CO2-Na (soap)
where R=(CH2)14CH3 in the example (right)
Sodium hydroxide (NaOH) is a caustic base. If NaOH is used a hard soap is formed, whereas when potassium hydroxide (KOH) is used, a soft soap is formed. Vegetable oils and animal fats are fatty esters in the form of triglycerides. The alkali breaks the ester bond and releases the fatty acid and glycerol. If necessary, soaps may be precipitated by salting it out with saturated sodium chloride.


Saponification can also refer to the other soft tissue in a conversion of the fat of a corpse into adipocere, often called "grave wax." This process is more common where the amount of fatty tissue is high, the agents of decomposition are absent or only minutely present, and the burial ground is particularly alkaline.

Fire extinguishers

Fires involving cooking fats and oils (classified as Class K) burn hotter than other typical combustible liquids, rendering a standard class B extinguisher ineffective. Such fires should be extinguished with a wet chemical extinguisher. Extinguishers of this type are designed to extinguish cooking fats and oils through saponification. The extinguishing agent rapidly converts the burning substance to a non-combustible soap. This process is endothermic, meaning it absorbs energy (in this case, thermal energy) from its surroundings, decreasing the temperature and eliminating the fire.

External links

saponification in Danish: Forsæbning
saponification in German: Verseifung
saponification in Modern Greek (1453-): Σαπωνοποίηση
saponification in Spanish: Saponificación
saponification in Esperanto: Sapiĝo
saponification in French: Saponification
saponification in Indonesian: Saponifikasi
saponification in Italian: Saponificazione
saponification in Latvian: Pārziepošana
saponification in Dutch: Verzeping
saponification in Japanese: 鹸化
saponification in Polish: Zmydlanie
saponification in Portuguese: Saponificação
saponification in Slovenian: Saponifikacija
saponification in Chinese: 皂化反应
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