How to Make 2 Sodium Metabisulfite

Here is a simple explanation for the preparation (laboratory method) of sodium metabisulfite (Na2S2O5):

Materials Needed

  • Sodium bisulfite (NaHSO3)
  • Heating apparatus (such as a beaker and Bunsen burner or hot plate)

Method

  • Take two moles of sodium bisulfite (2 NaHSO3).
  • Heat the sodium bisulfite gently.
  • The chemical reaction that occurs is:
    2 NaHSO3 → Na2S2O5 + H2O
  • Heat until the reaction is complete and water is driven off.
  • The residue left behind in the container is sodium metabisulfite.

Safety Precautions

  • Always wear gloves and safety goggles while handling chemicals.
  • Carry out this process in a well-ventilated area or fume hood, as SO2 gas may be produced in some side reactions.

Summary

To make sodium metabisulfite (Na2S2O5) in the laboratory: Gently heat two parts (moles) of sodium bisulfite (NaHSO3), and allow the water to escape. The resulting white powder is sodium metabisulfite.