It is also suitable for the softening of lignin in the pulping and refining processes of wood and lignocellulosic materials.

[3] The overall reaction is: Sodium sulfite is primarily used in the pulp and paper industry.

[4] It has been also applied in the thermomechanical conversion of wood to fibres (defibration) for producing medium density fibreboards (MDF).

[5] As an oxygen scavenger agent, it is used to treat water being fed to steam boilers to avoid corrosion problems,[6] in the photographic industry, it protects developer solutions from oxidation and (as hypo clear solution) to wash fixer (sodium thiosulfate) from film and photo-paper emulsions.

According to X-ray crystallography sodium sulfite heptahydrate features pyramidal SO32- centers.