Which of the following is left in the sodium hydroxide solution after removing the soap?

The correct answer is Glycerol.

Key Points

• Glycerol is a byproduct formed during the saponification process, which involves the reaction of fats/oils with sodium hydroxide to produce soap.
• After soap is removed from the sodium hydroxide solution, glycerol remains dissolved in the solution due to its high solubility in water.
• Glycerol is a trihydroxy alcohol (1,2,3-propanetriol) and is commonly used in pharmaceuticals, cosmetics, and food industries.
• It is separated from the solution after soap production through purification processes such as distillation or evaporation.
• Glycerol has hygroscopic properties, meaning it attracts water, which makes it beneficial for moisturizing applications.

Additional Information

• Saponification:
  • Saponification is the chemical process of soap production by reacting fats or oils with a strong alkali such as sodium hydroxide (NaOH).
  • The reaction produces soap and glycerol as its main products.
  • The fats/oils used are triglycerides, which are broken down into fatty acid salts (soap) and glycerol.
• Glycerol Applications:
  • Used as a humectant in cosmetics and skin care products.
  • Serves as a sweetener and preservative in food products.
  • Used in pharmaceutical formulations like cough syrups and suppositories.
• Sodium Hydroxide:
  • Sodium hydroxide (NaOH) is a strong alkali commonly used in soap production.
  • It reacts with triglycerides during saponification to create soap and glycerol.
  • NaOH is also used in various industries, including paper production and water purification.
• Separation Techniques:
  • Glycerol is separated from soap by processes like distillation or crystallization.
  • Purified glycerol is further refined for commercial use in multiple industries.