Saponification is the hydrolysis of an ester under basic conditions to form an alcohol and the salt of the acid.

Saponification is commonly used to refer to the reaction of a metallic alkali (base) with a fat or oil to form 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) R=(CH₂)₁₄CH₃ (for example)

Sodium chloride is added to precipitate the soap.

Lye is a form of sodium hydroxide which is a caustic base. If NaOH is used a hard soap is formed, whereas a soft soap is formed when KOH is used.

Vegetable oils and animal fats are fatty esters in the form of triacylglycerols . The alkali breaks the ester bond and releases the fatty acid and glycerol.

The soap is salted out by precipitating it with sodium chloride.

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

Fire extinguishers

Fires involving cooking fats and oils 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 also has a cooling effect, and suppresses the flames with steam.

See Wet Chemical Extinguisher

External links:

• Glossary for the Modern Soap Maker - A collection of terms, definitions and acronyms for today's soap maker.
• Adipocere - A collection of resources on soap mummies and adipocere formation.