| IUPAC name
| Systematic IUPAC name
| Other names
|Molar mass|| 174.107 g/mol (anhydrous)|
210.146 g/mol (dihydrate)
|Appearance||White to grayish crystalline solid|
|Odor||Faint sulfurous odor|
|Density|| 2.38 g/cm3 (anhydrous)|
1.58 g/cm3 (dihydrate)
|Melting point||52 °C (126 °F; 325 K)|
18.2 g/100 ml (20 °C)
21.9 g/100 ml (20 °C)
|Solubility||Slightly soluble in ethanol, methanol|
|Safety data sheet||Sigma-Aldrich|
|Flash point||100 °C (212 °F; 373 K)|
| Sodium metabisulfite|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Sodium dithionite or sodium hydrosulfite is a white crystalline powder with a weak sulfurous odor, used as reducing agent.
Sodium dithionite reacts with oxygen in the presence of moisture:
- Na2S2O4 + O2 + H2O → NaHSO4 + NaHSO3
Sodium dithionite is stable when dry, but aqueous solutions deteriorate due to the following reaction:
- 2 S2O42− + H2O → S2O32− + 2 HSO3−
Anhydrous sodium dithionite decomposes to sodium sulfate and sulfur dioxide above 90 °C in air. In absence of air, it decomposes quickly if heated above 150 °C to sodium sulfite, sodium thiosulfate, sulfur dioxide and trace amount of sulfur.
Sodium dithionite is a reducing agent. At pH = 7, the potential is -0.66 V vs NHE. Redox occurs with formation of sulfite.
Sodium dithionite is a white-grayish solid, with a weak sulfurous odor.
It is sold by chemical suppliers.
The preparation of this compound is relative complicated, due to its sensitivity to air, and you might need an inert atmosphere to prevent the loss of product. It's cheaper to simply purchase it if you need significant amounts of it.
- Reducing agent
- Bleach paper
Contact with this substance may produce irritations or burns.
Sodium hydrosulfite spontaneously heats on contact with air and moisture. The heat generated may be sufficient to ignite surrounding combustible materials.
In closed air-tight bottles, away from moisture.
Can be neutralized with bleach or hydrogen peroxide.
Relevant Sciencemadness threads
- Interest Check: Sodium Dithionite, Na2S2O4 (Sodium Hydrosulfite)
- Sodum dithionite synthesis
- OTC source of sodium dithionite and synthesis
- Sodium dithionite
- Info on sodium dithionite please
- thoughts on practical reduction with dithionite
- how can I separate Sodium hydrosulfite and sodium bisulfite mixture?
- Dithionite Reductions