Saponification: The Chemistry of Soap Formation

Saponification is a chemical reaction that produces soap. Glycerol is a byproduct in this reaction. Soap can be precipitated out from glycerol in the form of salts by reacting with sodium chloride.

As soon as saponification starts, glycerol reacts with the long-chain fatty acids to produce triglycerides. Triglycerides are animal fat or vegetable oils. They react with the bases to produce salts of fatty acids known as soap and glycerol as a byproduct. The soap produced in this reaction is not pure. It can be refined by processing further.

Saponification reactions step by step

Saponification depends on the amount of the bases (sodium or potassium hydroxide) that are necessitated to saponify triglycerides into soap. This amount of alkali is known as the saponification value or the saponification number. For example, the number of milligrams of alkali (sodium or potassium hydroxide) used to saponify one gram of triglyceride.

Types of Saponification

These are the types of saponification depending on temperature during the process:

Saponification by cold process

This type of saponification continues for long periods of time such as 24 hours or more. Heating is not done during the process. The reactions between fats and bases occur at room temperature. That’s why they are very slow as compared to the hot process. This results in a crude soup that is moved for cooling and finishing.

Saponification by semi-boiled process

This type of reaction takes place at a temperature of 60 to 90 oC. This is a fast reaction as compared to the reactions in the cold process. The following are advantages of semi boiled process:

  • It allows altering the amount of soda or potash lye (sodium or potassium hydroxide). This can enhance the quality of soap.
  • Waste products obtained in the process can be recycled.
  • It allows the integration of additives materials (pigments, fragrances, etc) in better ways.

Saponification by complete-boiled process

This process is known as the hot process. The reaction takes place at the temperature of 100 oC. This is the most useful of all saponification types. Saponification in this way helps in producing different types of soap with better quality such as toilet soaps, simple soaps, laundry soaps, household soaps, etc.

Uses

  • It is used to produce hard and soft soap. Hard soap is the result of the reaction between fats and sodium hydroxide (NaOH). However, potassium hydroxide (KOH) is used to produce soft soap by the action of saponification.
  • It is used in fire extinguishers to control fire. There are wet chemicals (potassium carbonate and potassium citrate) used in a fire extinguisher that make foam of soap which ceases the fire.

Concepts Berg

What is an example of saponification?

Soaps are an example of saponification. There are different kinds of soaps that can be produced by the action of saponification.

Why is saponification important?

Saponification is the primary step in the industrial process to produce soap. This can be done under different conditions such as high or low temperatures.

What type of reaction is saponification?

Saponification is a hydration reaction. Free hydroxide ions are used to break the ester bond of triglycerides.

What is soap chemistry?

Soaps are the salts of fatty acids. They are produced by a chemical reaction known as saponification. Bases such as sodium or potassium hydroxide use to convert animal fats into soaps.

What is lye powder?

Sodium or potassium hydroxide is known as lye powder which is used as a base in the saponification reaction. Sodium hydroxide is called soda lye while potassium hydroxide is called potash lye.

What is the catalyst used in the saponification reaction?

Sodium hydroxide is used to produce hard soap while potassium hydroxide is used for the production of soft soap.

Is the saponification of ethyl acetate an endothermic or exothermic reaction?

Saponification of ethyl acetate is a mild exothermic reaction as this reaction releases the amount of heat from the system to its surroundings.

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