Sodium Sulphite

Brief 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.

2NaOH + SO₂ → Na₂SO₃ + H₂O

In industrial level, sodium sulphite is produced by making sodium carbonate react with sulphur dioxide.  

SO₂ + Na₂CO₃ → Na₂SO₃ + CO₂

Food Industry 

Sodium sulphite is widely used as a food preservative. It is added to fresh produce, canned foods, processed foods, and dry fruits to prevent discolouring and unwanted oxidation.

Chemical Industry

Sodium sulphite is 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.

Other Applications 

Sodium sulphite is used in other applications, including froth flotation of ores, oil recovery, food preservatives, and making dyes. In chemical manufacturing, it is used as a sulfonation and sulfomethylation agent. Sodium sulphite is used in the purification of TNT for military use. It is also used in the production of sodium thiosulfate.