Sodium Sulphite - Overview

Sodium sulphite is widely used as a food preservative to prevent fresh produce and meat from discolouring. It is used in flue-gas desulfurization process. It is widely used in paper and pulp industry as an agent to avoid corrosion problems. A solution of sodium sulphite is of pH 9 and when the solution is exposed to air they are oxidised to sodium sulphate.

Manufacturing Process

Sulphur dioxide and sodium hydroxide when reacted together under laboratory conditions, produce sodium sulphite. 2 NaOH + SO2 → Na2SO3 + H2O In industrial level, sodium sulphite is produced by making sodium carbonate react with sulphur dioxide. SO2 + Na2CO3 → Na2SO3 + CO2

The Uses of Sodium Sulphite

Sodium sulphite is widely used as food preservative. It is added to fresh produce, canned foods, processed foods, dry fruits to prven from discolouring and unwanted oxidation.
Chemical Industry
Widely used in water treatment as an oxygen scavenger agent to treat water being fed to steam boilers to avoid corrosion problems. It is also used in the textile industry as a bleaching, desulfurizing and dechlorinating agent and in the leather trade for the sulphonation of tanning extracts.
It is used in the purification of TNT for military use. It is used in chemical manufacturing as a sulfonation and sulfomethylation agent. It is used in the production of sodium thiosulfate. It is used in other applications, including froth flotation of ores, oil recovery, food preservatives, and making dyes.


Chemical FormulaNa2SO3
SynonymSodium sulphite
H.S. Code28301000
CAS No.7757-83-7
Molecular Weight126.037 g/mol


PropertyUnits Value
Melting PointCDecomposes
Boiling PointCDecomposes
AppearanceWhite Powder
SolubilitySoluble in Water