Sodium Sulfite

Sodium sulphite or Sodium sulfite is a soluble sodium salt of H2SO3 (sulfurous acid). The chemical formula of Sodium Sulfite is Na2SO3. It is widely used as a preservative for meat, used in the conversion of elemental halogens to hydrohalic acids. It is a byproduct of sulfur dioxide (SO2).


The molecular Weight of Na2SO3 is 103.047 g/mol and the exact mass is equal to 102.947 g/mol. The number of hydrogen bond acceptor equals to four whereas the number of hydrogen bond donor equals to zero. Its complexity is 28.4 and has a formal charge of -1. The number of covalently bonded unit is equal to two.

Preparation of Sodium Sulfite

Laboratory level:

In laboratories, sodium sulfite can be prepared by reacting sodium hydroxide (NaOH) solution with sulfur dioxide (SO2) gas. The reaction is given below:

2 NaOH + SO2 → Na2SO3 + H2O

Development of SO2 by adding a few drops of concentrated hydrochloric acid (HCl) designates if sodium hydroxide (NaOH) is gone or turned into aqueous sodium sulfite. The reaction is as follows:

Na2SO3 + 2 HCl → 2 NaCl + SO2 + H2O

Industry level:

At an industrial level, sodium sulfite is prepared by reacting sulfur dioxide (SO2) with a solution of sodium carbonate (Na2CO3). The beginning combination produces sodium bisulfite (NaHSO3), which is further converted to sulfite by the reaction of sodium carbonate or sodium hydroxide.

The reaction is as follows:

SO2 + Na2CO3 → Na2SO3 + CO2

Applications of Sodium Sulfite

  1. Sodium sulfite is widely used in the pulp and paper industries.
  2. It is used as an oxygen scavenger in water treatment.
  3. It is used to avoid corrosion problems in steam boilers.
  4. As a  bleaching agent in the textile industry.
  5. As a dechlorinating and desulfurizing agent as well as in the leather trade.
  6. In the purification of TNT military use.
  7. As a sulfonation agent in the manufacturing of chemicals.
  8. Used to produce sodium thiosulfate.
  9. It is used in froth flotation of ores.
  10. In the recovery of oil.
  11. Used in food preservatives.
  12. Production of dyes.

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