Sodium bisulfite solutions can be prepared by treating a solution of suitable base, such as sodium hydroxide or sodium bicarbonate with sulfur dioxide.
:SO  +  NaOH  →  NaHSO
:SO + NaHCO → NaHSO + CO
Attempts to crystallize the product yield sodium metabisulfite (also called sodium disulfite), NaSO.
Upon dissolution of the metabisulfite in water, bisulfite is regenerated:
:NaSO  +  HO   →   2 Na + 2 HSO
Sodium bisulfite is formed during the Wellman-Lord process.