Sources
Help build the largest human-edited directory on the web.
Submit a site - Become an editor
Wikipedia. Licensed under the GNU Free Documentation License.
Are you an expert in this subject? Join the discussion and share your knowledge at Wikipedia.org.
Sodium dithionite
From Wikipedia, the free encyclopedia
| 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
Contents |
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.
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.