How Sodium Metabisulfite is Made

Sodium metabisulfite (Na₂S₂O₅) is an inorganic compound commonly used as a disinfectant, antioxidant, and preservative. The manufacturing process typically involves the reaction of sodium carbonate (soda ash) with sulfur dioxide.

Manufacturing Process

• Step 1: Preparation of Sodium Sulfite
  

  Sulfur dioxide (SO₂) is bubbled through a solution of sodium carbonate (Na₂CO₃) in water. This produces sodium sulfite (Na₂SO₃) and carbon dioxide.

  Na₂CO₃ + SO₂ → Na₂SO₃ + CO₂

• Step 2: Formation of Sodium Metabisulfite
  

  More sulfur dioxide is added to the sodium sulfite solution, resulting in the formation of sodium metabisulfite.

  Na₂SO₃ + SO₂ → Na₂S₂O₅

  The solution is then evaporated to obtain sodium metabisulfite crystals.

Summary

• Sodium metabisulfite is made by reacting sodium carbonate with sulfur dioxide.
• The intermediate product, sodium sulfite, reacts with additional sulfur dioxide to produce sodium metabisulfite.
• Crystallization occurs as the final step to separate and purify the compound.