Sodium sulfite

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Sodium sulfite
Names
IUPAC name
Sodium sulfite
Other names
Disodium sulfite
E221
Hypo clear (photography)
Sodium sulphite
Sulfurous acid, sodium salt
Properties
Na2SO3
Molar mass 126.043 g/mol
Appearance White solid
Odor Odorless
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)
Boiling point Decomposes
27.0 g/100 mL water (20 °C)
Solubility Soluble in glycerol
Insoluble in ammonia, chlorine, ethanol
Acidity (pKa) ~9 (heptahydrate)
Hazards
Safety data sheet FisherScientific
Flash point Non-flammable
Related compounds
Related compounds
Potassium sulfite
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Sodium sulfite is a chemical compound with the formula Na2SO3, used as a reducing agent.

Properties

Chemical

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.

Physical

Sodium sulfite is an odorless white crystalline solid, soluble in water and glycerol.

Availability

Sodium sulfite can be purchased from various food retailers as antioxidant for foods. It can also be purchased from chemical suppliers.

Preparation

Can be made by bubbling sulfur dioxide in a solution of sodium hydroxide.

Projects

  • Reducing agent
  • Etard reaction
  • Neutralize bleach
  • Bucherer reaction
  • Corrosion inhibitor

Handling

Safety

Sodium sulfite is irritant and should be handled with care.

Storage

Sodium sulfite should be kept in closed bottles, away from air.

Disposal

Neutralization is not always necessary, but it can be destroyed with bleach.

References

Relevant Sciencemadness threads