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Saponification

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.

Animal fat is a fatty ester in the form of triacylglycerol. The alkali breaks the ester bond and releases the fatty acid and glycerol.

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

Soap Mummies

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.

External links:

• - A collection of terms, definitions and acronyms for today's soap maker.
• - A collection of resources on soap mummies and adipocere formation.