Sodium Hydrosulfite (Sodium Dithionite) – CAS No. 7775-14-6

Sodium Hydrosulfite, chemically known as Na₂S₂O₄ and CAS Number 7775-14-6, is a powerful reducing agent widely applied in textile dyeing, paper manufacturing, and water treatment for its ability to decolorize and bleach without damaging fibers. This white crystalline powder, often supplied as a 85-90% active formulation, exhibits high solubility in water (up to 250 g/L at 20°C) and a neutral pH (6.0-8.0 in solution), enabling selective reduction of vat dyes and removal of impurities like lignin and heavy metals.

Specification Standard Result
Purity(wt%) 88min 88.78
Na2CO3(wt%) 2.5­3.0 2.72
Na2S2O3(wt%) 0.5­1 0.56
Na2S2O5(wt%) 5 ­ 7 6.68
Na2SO3(wt%) 0.5­1.5 0.63
Fe(ppm) 20ppm max 16ppm
Water lnsoluble 0.1 0.04
Total other heavy metals 10ppm max 8ppm

Applications

Textile and Dyeing Industry

  • Vat Dye Reduction: Dissolved at 1-3 g/L in alkaline baths to solubilize indigo and sulfur dyes, ensuring deep penetration and even fixation on cotton and wool.
  • Bleaching Aid: 0.5-1.5% in scouring to remove impurities, improving whiteness index by 20-30% without fiber degradation.

Paper and Pulp Processing

  • Lignin Removal: Added at 0.2-0.8% during bleaching stages to reduce color bodies, enhancing brightness and reducing chlorine demand in ECF sequences.
  • Effluent Treatment: 50-200 ppm to decolorize dyes and organics in wastewater, achieving 80% COD reduction.

Other Industrial Uses

  • Food and Beverage: Antioxidant in sugar refining at 10-50 ppm to prevent browning and maintain clarity.
  • Water Treatment: Reducer for hexavalent chromium to trivalent at 100-500 ppm, facilitating safe disposal.

Why Choose Our Sodium Hydrosulfite?

Our Sodium Hydrosulfite is zinc-free and stabilized for extended shelf life (>12 months), with sulfite <0.5% and heavy metals <10 ppm, guaranteeing odorless performance and minimal decomposition. Textile dyers report 15% faster reduction times and improved color fastness. Available in powder (88%), granular, and liquid forms, packaged in 50kg drums or 1000kg IBCs, with technical/textile grades and certifications like REACH and ISO 9001 for seamless integration.

Frequently Asked Questions (FAQs)

What is Sodium Hydrosulfite?

Sodium Hydrosulfite, or Sodium Dithionite, is a reducing salt with formula Na₂S₂O₄ and CAS 7775-14-6, used for decolorization and bleaching. It’s a white powder that selectively reduces dyes and impurities in textiles and paper.

How is Sodium Hydrosulfite used in textile dyeing?

Dissolve 1-2 g/L in 50-60°C water with NaOH; add to dye bath for 20-30 minutes to activate leuco form, then oxidize with air or persulfate for fixation.

Is Sodium Hydrosulfite safe for wastewater discharge?

Yes, at treated levels (<50 mg/L), it complies with EPA limits; it decomposes to sulfates and thiosulfates, non-toxic after aeration.

What is the shelf life of Sodium Hydrosulfite?

In moisture-proof packaging at <25°C, it retains >90% activity for 6-12 months; avoid air exposure to prevent oxidation.

Can Sodium Hydrosulfite be combined with other reducers?

It synergizes with sodium formaldehyde sulfoxylate at 1:1 ratios for deeper reductions but incompatible with oxidants like H₂O₂—test bath stability.

Does Sodium Hydrosulfite affect pH in applications?

Its neutral pH maintains system balance, but reactions may lower pH slightly—buffer with alkali for consistent dyeing.

What packaging options are available for Sodium Hydrosulfite?

We supply 50kg fiber drums, 25kg bags, and 1000kg supersacks, all lined with PE for humidity protection and UN 1384 compliance.

For reduction protocols, stability tests, or bulk supply, our technical team offers tailored advice.

Contact Us

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