Sodium hydrosulfite

Sodium hydrosulfite (Na₂S₂O₄), also known as sodium dithionite, is a white, crystalline powder with a slightly sulfurous odor. It is a powerful reducing agent widely used in various industrial and chemical applications. Due to its high reactivity, it is typically stored in airtight containers to prevent degradation from moisture and oxygen.

Uses

1. Textile Industry

• Bleaching Agent: Used for bleaching textiles like wool, cotton, and nylon without damaging fibers.
• Color Stripping: Removes unwanted dyes during fabric processing.
• Vat Dyes and Indigo Dyeing: Acts as a reducing agent to solubilize vat dyes for dyeing processes.

2. Paper and Pulp Industry

• Brightening Agent: Used to remove lignin and brighten recycled paper and pulp.

3. Mining and Metallurgy

• Ore Processing: Reduces metallic oxides in the extraction of minerals such as tin and tungsten.

4. Water Treatment

• Dechlorination: Removes excess chlorine from industrial and municipal water supplies.
• Heavy Metal Reduction: Converts metal ions into less toxic forms.

5. Chemical Synthesis

• Intermediate in Reactions: Used as a reducing agent in organic and inorganic chemical syntheses.
• Pharmaceuticals: Aids in synthesizing certain drugs and intermediates.

6. Food Industry

• Food Additive (E222): Sometimes used to preserve color in foods (though usage is regulated in many countries).

7. Photographic Industry

• Reducing Agent: Plays a role in the production of photographic films and prints.

8. Other Applications

• Leather Processing: Used in dyeing and as a reducing agent.
• Environmental Applications: Treats pollutants in industrial effluents.