- Saponification
Saponification is a chemical reaction that occurs when an alkali (like potassium salts in a wet chemical extinguisher) comes into contact with a fat or oil. In fire safety, this reaction is crucial for fighting Class F fires.
When applied to a burning cooking oil or fat, the wet chemical reacts with the fat to form a soapy, foam-like substance. This layer cools the surface and seals it from oxygen, which smothers the fire and prevents it from re-igniting.
In essence, saponification transforms the burning oil into a harmless soap layer, making it an essential function in the operation of wet chemical fire extinguishers.
Typical chemical reaction
Fat or Oil (Triglyceride) + Potassium Hydroxide (KOH) → Glycerol + Potassium Soap
Chemical Equation:
C₃H₅(OOCR)₃ + 3 KOH → C₃H₅(OH)₃ + 3 RCOOK
- C₃H₅(OOCR)₃ = A triglyceride (fat or cooking oil)
- KOH = Potassium hydroxide (the wet chemical)
- C₃H₅(OH)₃ = Glycerol (a non-flammable by-product)
- RCOOK = Potassium salts of fatty acids (soap)
Explanation
- The wet chemical (KOH) in the extinguisher is discharged onto the superheated burning oil or fat;
- A cooling effect occurs, dropping the temperature.
- The chemical reaction converts the oil into soap.
- The soap forms a stable foam blanket, cutting off oxygen and preventing re-ignition.