CHEMISTRY: SOAPS AND DETERGENTS

About soaps

• Soaps are anionic surfactants used for washing and cleaning. Surfactants are wetting agents that lower the surface tension of a liquid

• Soaps consist of sodium or potassium salts of fatty acids.
  
• They are obtained by reacting common oils or fats with a strong alkaline solution
  
• The earliest recorded evidence for use of soap is from Babylon c. 2800 BC

Mode of action

• Soap molecules have both a hydrophilic end and a hydrophobic end
• The hydrophilic end dissolves in water, while the hydrophobic end dissolves dirt and oil molecules
• As a result, although water and oil don’t mix, soaps allow oil to dissolve in water, allowing them to be rinsed away
  
• Thus, soaps allow water to remove normally insoluble matter by emulsification

Detergents

• Detergents are surfactants other than soap
  
• Detergents are commonly used as industrial soaps, due to their heavy duty grease removal capabilities
  
• Soaps differs from detergents in that in the case of former, excess of fat is used to consume the alkali and the glycerine is not removed, leaving a naturally moisturising soap
  
• In general detergents are substances that have cleaning properties. By definition, even water is a detergent

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