Sodium Sulphite

Sodium sulfite reacts with aldehydes to yield a bisulfite adduct. However, sulfonic acids are produced from their reaction with ketones.

Solutions of sodium sulfite are oxidised by atmospheric oxygen, yielding sodium sulphate.

This compound is insoluble in ammonia and chlorine.

sodium sulphite is a white, water-soluble solid and used commercially as an antioxidant and preservative. It is also suitable for the softening of lignin in the pulping and refining processes of wood and lignocellulosic materials.

Sodium sulfite can be prepared by treating a solution of sodium hydroxide with sulfur dioxide. When conducted in warm water, Na2SO3 initially precipitates as a white solid. With more SO2, the solid dissolves to give the disulfite, which crystallizes upon cooling.

According to X-ray crystallography sodium sulfite heptahydrate features pyramidal SO32- centers. The S-O distances are 1.50 and the O-S-O angles are near 106º.