Knowledge

Reaction of Sodium Metabisulfite with Chlorine Compounds

Sodium metabisulfite (Na₂S₂O₅) is a strong reducing agent and is commonly used to remove chlorine compounds from solutions, especially in water treatment and laboratory processes.

Chemical Reaction with Chlorine (Cl₂)

When sodium metabisulfite reacts with chlorine, it effectively reduces chlorine to chloride ions while being oxidized itself. The main reaction is as follows:

Na₂S₂O₅ + 2 Cl₂ + 3 H₂O → 2 NaHSO₄ + 4 HCl

• Chlorine (Cl₂) is reduced to chloride ions (Cl^-).
• Sodium metabisulfite is oxidized to sodium bisulfate (NaHSO₄).

Reaction with Hypochlorite Compounds

Sodium metabisulfite can also react with hypochlorite ions (OCl^-), which are found in common bleach solutions. The reaction dechlorinates the solution:

Na₂S₂O₅ + 4 NaOCl + 2 H₂O → 4 NaCl + 2 NaHSO₄

• Hypochlorite is reduced to chloride ions.
• The process neutralizes active chlorine and produces sodium chloride and sodium bisulfate.

Summary

• Sodium metabisulfite is an effective dechlorinating agent.
• It reduces chlorine compounds (both Cl₂ and OCl^-) to harmless chloride ions.
• The main byproducts are sodium bisulfate (NaHSO₄) and sodium chloride (NaCl).