Sample of crystalline sodium sulfite
| IUPAC name
| Other names
Hypo clear (photography)
Sulfurous acid, sodium salt
|Molar mass||126.043 g/mol|
|Density|| 2.633 g/cm3 (anhydrous)|
1.561 g/cm3 (heptahydrate)
|Melting point|| 33.4 °C (92.1 °F; 306.5 K) (heptahydrate, decomposition)|
500 °C (932 °F; 773.15 K) (anhydrous, decomposes)
|27.0 g/100 mL water (20 °C)|
|Solubility|| Soluble in glycerol|
Insoluble in ammonia, chlorine, ethanol, isopropanol
|Acidity (pKa)||~9 (heptahydrate)|
|Safety data sheet||FisherScientific|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Sodium sulfite is a chemical compound with the formula Na2SO3, used as a reducing agent.
Sodium sulfite releases sulfur dioxide if a strong acid, such as hydrochloric acid, is added.
- Na2SO3 + 2 HCl → 2 NaCl + SO2 + H2O
Sodium sulfite will slowly oxidize in air to sodium sulfate.
Sodium sulfite is an odorless white crystalline solid, soluble in water and glycerol.
Sodium sulfite can be purchased from various food retailers as antioxidant for foods.
It can also be purchased from chemical suppliers.
Can be made by bubbling sulfur dioxide in a solution of sodium hydroxide, while maintaining the pH>7.
- Reducing agent
- Etard reaction
- Neutralize bleach
- Bucherer reaction
- Corrosion inhibitor
Sodium sulfite is irritant and should be handled with care.
Sodium sulfite should be kept in closed bottles, away from air.
Neutralization is not always necessary, but it can be destroyed with bleach.