Knowledge

Difference Between Sodium Bisulfite and Sodium Metabisulfite

• Chemical Formula:
  
  • Sodium Bisulfite: NaHSO₃
  • Sodium Metabisulfite: Na₂S₂O₅
• Structure:
  
  • Sodium bisulfite contains one sodium ion and one bisulfite ion.
  • Sodium metabisulfite contains two sodium ions bonded to a disulfite (S₂O₅^2–) group.
• Usage:
  
  • Both are used as preservatives and antioxidants, but sodium metabisulfite is more common in industrial applications.
• Properties:
  
  • Sodium bisulfite is generally more reactive in solution.
  • Sodium metabisulfite can release sulfur dioxide (SO₂) when dissolved in water.
• Interconversion:
  
  • Sodium metabisulfite produces sodium bisulfite when mixed with water:
  • Na₂S₂O₅ + H₂O → 2 NaHSO₃

Summary: Sodium bisulfite and sodium metabisulfite are related but differ in structure, chemical formula, and some chemical properties. Sodium metabisulfite is commonly used as a source of sodium bisulfite in aqueous solutions.