Sodium dithionite

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Sodium dithionite
Names
IUPAC name
Sodium dithionite
Systematic IUPAC name
Sodium dithionite
Other names
D-Ox
Hydrolin
Reductone
Sodium hydrosulfite
Sodium sulfoxylate
Sulfoxylate
Vatrolite
Virtex L
Properties
Na2S2O4
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)
Boiling point Decomposes
Anhydrous
18.2 g/100 ml (20 °C)
Dihydrate
21.9 g/100 ml (20 °C)
Solubility Slightly soluble in ethanol, methanol
Hazards
Safety data sheet Sigma-Aldrich
Flash point 100 °C (212 °F; 373 K)
Related compounds
Related compounds
Sodium metabisulfite
Sodium thiosulfate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Sodium dithionite or sodium hydrosulfite is a white crystalline powder with a weak sulfurous odor, used as reducing agent.

Properties

Chemical

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.

Physical

Sodium dithionite is a white-grayish solid, with a weak sulfurous odor.

Availability

It is sold by chemical suppliers.

Preparation

Can be prepared by reducing sulfur dioxide using various reducing agents, like zinc powder, sodium borohydride and formates.[1]

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.

Projects

  • Reducing agent
  • Bleach paper

Handling

Safety

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.

Storage

In closed air-tight bottles, away from moisture.

Disposal

Can be neutralized with bleach or hydrogen peroxide.

References

  1. https://onlinelibrary.wiley.com/doi/abs/10.1002/14356007.a25_477

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