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Sodium dithionite



Sodium dithionite
General
Other names Dithionous acid, disodium salt
D-Ox
Hydrolin
Reductone
Sodium dithionite
Sodium dithionite hydrate
Sodium hydrosulfite
Sodium sulfoxylate
Sulfoxylate
Vatrolite
Virtex L
Molecular formula Na2O4S2
Molar mass 174.09714 g mol−1
Appearance White to grayish crystalline powder
CAS number [7775-14-6]
Properties
Density and phase 2.19 g cm−3, solid
Solubility in water soluble
Other solvents insoluble in alcohol
Melting point 52°C (325 K)
Boiling point Decomposes
Hazards
Toxicity LD 50: 5 g/kg (oral in rats)
Main hazards flammable solid
Flash Point 90 C (363 K)

Sodium dithionite (aka sodium hydrosulfite or sodium hydrosulphite) is a white crystalline powder with a weak sulfurous odor. It is stable under most conditions, although it will decompose in hot water and in acid solutions. It can be obtained by the following reaction:

2NaHSO3 + Zn → Na2S2O4 + Zn(OH)2

Additional recommended knowledge

Contents

Applications

Industry

This compound is a water-soluble salt, and can be used as a reducing agent in aqueous solutions. It is used as such in some industrial dying processes, where an otherwise water-insoluble dye can be reduced into a water-soluble alkali metal salt. The reduction properties of sodium dithionite also eliminate excess dye, residual oxide, and unintended pigments, thereby improving overall colour quality. It can also be used as a bleach, in, for instance, paper pulp, cotton, wool, and kaolin clay.

This chemical can also be used for water treatment, gas purification, cleaning, and stripping. It can also be used in industrial processes as a sulfonating agent or a sodium ion source. In addition to the textile industry, this compound is used in industries concerned with leather, foods, polymers, photography, and many others. Its wide use is attributable to its low toxicity LD 50 at 5 gms/kg., and hence its wide range of applications.

Biological sciences

Sodium dithionite is often used in physiology experiments as a means of lowering solutions' redox potential (Eo' ~ −420 mV at pH 7). Potassium ferricyanide is usually used as an oxidizing chemical in such experiments (Eo' ~ 436 mV at pH 7). In addition, sodium dithionite is often used in soil chemistry experiments to determine the amount of iron that is not incorporated in primary silicate minerals. Hence, iron extracted by sodium dithionite is also referred to as "free iron." The strong affinity of the dithionite ion for bi- and trivalent metal cations (M2+, M3+) allows it to enhance the solubility of iron, and therefore dithionite is a useful chelating agent.

See also

 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Sodium_dithionite". A list of authors is available in Wikipedia.
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