Na₂SO₃ can be prepared by:

The process prepared :

${\mathrm{Na}}_2{\mathrm{SO}}_3\text{ solution }+\mathrm{S}\text{ (powder) }\stackrel{\text{ Boiled }}{⟶}$

$\mathrm{S}+\mathrm{NaOH}⟶$

${\mathrm{Na}}_2\mathrm{S}+{\mathrm{Na}}_2{\mathrm{CO}}_3+{\mathrm{SO}}_2⟶$

By treating a sodium hydroxide solution with sulphur dioxide, sodium sulfite can be created. When in warm water, the Na₂SO₃ first crystallizes as a yellow solid. More SO₂ is used to dissolve the solid, resulting in the formation of disulfite, which crystallizes as it cools.