Sodium hydrosulphite is the sodium salt of dithionous acid and is also called as sodium dithionite. Sodium Hydrosulphite was discovered at the beginning of the 20th century and was first applied for textile printing. Due to structural changes in the textile industry, the importance of Sodium hydrosulphite for the application of the bleaching of wood pulp in the paper industry, increased continuously.
General properties of Sodium Hydrosulphite
- Sodium hydrosulphite is a white monoclinic crystalline powder with a weak sulphurous odour.
- Sodium hydrosulphite is a stable compound under all ambient dry conditions and is slowly oxidized by air. Thus solution of sodium dithionite cannot be stored for a long period of time.
- Sodium hydrosulphite can acts as a reductive bleaching agent and mainly used in the textile and paper industries.
- It will decompose in hot water and in acid solutions.
- Sodium hydrosulphite can act as a sulfonating agent and in a variety of chemical reactions.
- Sodium hydrosulphite does not undergo biodegradation, bioaccumulation & photo degradation.
- Sodium hydrosulphite is soluble in water and slightly soluble in ethanol.
- Sodium hydrosulphite can be used as a reducing agent in aqueous solutions.
- Aqueous solution of sodium hydrosulphite is acidic and the reactivity rate is higher under strong activity.
- Sodium hydrosulphite can also acts as a cation source in the chemical reaction.
Production of Sodium Hydrosulphite
Sodium hydrosulphite is obtained from the reaction mixture of Sodium bisulphite with zinc catalyst as a Zinc hydroxide as one of its by-product.
2 NaHSO3 + Zn -> Na2S2O4 + Zn(OH)2
- Paper Industry
- Photography Industry
- Textile Industry
- Chemical Industries
- Other applications
In paper and pulp industry, sodium hydrosulphite is used as an additive and reducing agent. It is used in the paper industry for bleaching, brightening and decolorization of recycled fiber.
Sodium hydrosulphite is used in the photography industry as a developing agent. It has unique features to reduce film speed and quickly fogs the image in the photographic industry.
In the textile industry, sodium hydrosulphite acts as a dyeing agent. It is used in the dyeing process as water-insoluble dye and it can be reduced into a water-soluble alkali metal salt.
Sodium hydrosulphite is used in chemical industries for various purposes such as water treatment, gas purification, cleaning and stripping. It can also be used in the chemical processes as a sulfonating agent for the preparation of various chemicals
Sodium hydrosulphite is used in chemical enhanced oil recovery to stabilize polyacrylamide polymers.It is also used in environmental applications in order to reduce pollutants such as Chromium.
Sodium hydrosulphite is used in the leather, food and polymer industry to reduce the low toxicity of the compound.It is used in physiology experiments for lowering the reduction potential and is used in soil chemistry experiments for the determination of iron in soil chemicatry experiments. In electrochemical industries it is used as an oxidizing agent.It can even be used as a chelating agent.
|Systematic Name||Disodium dithionite|
|SYNONYMS||Sodium dithionite, Disodium dithionate, Disodium dithionite, Dithionous acid, disodium salt, Sodium hypodisulfite,
Sodium hyposulfite, Reductone, Sodium sulfoxylate, Vatrolite and V-Brite B
Physical & Chemical Properties
|Physical State and Appearances||Solid (Solid Powder)|
|Odor||Faint Sulfurous (slight)|
|Molecular Mass/Weight|| 174.107 g/mol (anhydrous)
210.146 g/mol (dihydrate)
|Density|| 2.38 g/cm3 (anhydrous)
1.58 g/cm3 (dihydrate)
|Melting Point||52 °C, 325 K, 126 °F|
|FLASH Point||1000 °C|
|Solubility||Soluble in cold water, Slightly Soluble in Alcohol|
|Solubility in water|| 18.2 g / 100 ml (anhydrous, 20 °C)
21.9 g /100 ml (Dihydrate, 20 °C)
|pH||Acidic in Solution|
|NFPA 704||Reactivity – 1, Health – 2, Flammability – 3|
|Stability||Stable under ordinary condition (Decomposes in hot water and acid)|
|Appearance||White to grey crystalline powder, light-lemon colored flakes|
|Na2S2O4||85% OR 88% OR 90% min|
|Insoluble in Water||0.1% max|