Sodium Thiosulfate Pentahydrate CAS 7772-98-7

Sodium Thiosulfate Pentahydrate – Versatile Reagent for Photography, Textile, and Water Treatment

Basic Information

• Product Name: Sodium thiosulfate pentahydrate

• CAS Number: 7772-98-7

• Molecular Formula: Na₂S₂O₃·5H₂O (corrected; the query listed Na₂S₂O₂·5H₂O)

• Molecular Weight: 248.17 g/mol

• Appearance: White crystalline powder or colorless crystals

• Solubility: Highly soluble in water; slightly soluble in alcohol

• Packaging: 25 kg or 50 kg polypropylene woven bags

Overview
Sodium thiosulfate pentahydrate is an important inorganic compound with a wide range of industrial and laboratory applications. Its reducing and complexing properties make it valuable in photography, textile processing, water treatment, and analytical chemistry. The pentahydrate form is the most common commercially available grade, known for its high solubility and stability.

Applications

• Photography: Used as a photographic fixer (hypo) to dissolve unexposed silver halides from photographic films and papers, making images permanent.

• Reducing agent: Employs its mild reducing properties in various chemical reactions and processes.

• Dechlorinating agent: Neutralizes residual chlorine in water treatment, making it safe for aquatic life and industrial use; commonly used in aquarium water conditioning.

• Sulfur dyes: Used in textile dyeing as a reducing agent for vat and sulfur dyes, enabling fixation on fibers.

• Disinfectant and bleaching: Applied in certain bleaching formulations and as a disinfectant in some industrial processes.

• Electrophoresis: Used in gel electrophoresis as a component of running buffers or for destaining.

• Leather processing: Employed in tanning and leather finishing operations.

• Analytical chemistry: Used as a titrant in iodometric titrations to determine oxidizing agents (e.g., iodine, chlorine, hydrogen peroxide).

Key Properties

• High water solubility – dissolves readily in aqueous solutions.

• Mild reducing properties – reduces halogens and other oxidizing agents.

• Stable under normal conditions but may decompose on prolonged heating.

• Non‑toxic and biodegradable under normal use conditions.

Recommended Use
Dosage depends on application. For water dechlorination, 1–5 mg/L of sodium thiosulfate is typically sufficient. In photography, fixer solutions typically contain 15–30% sodium thiosulfate. Optimize through specific application protocols.

Handling and Storage

• Store in a cool, dry, well‑ventilated area, away from acids and strong oxidizers.

• Keep containers tightly sealed to prevent caking and contamination.

• Use appropriate personal protective equipment (gloves, safety goggles, dust mask) when handling.

• Avoid prolonged contact with skin and eyes; wash thoroughly after handling.

Packaging
Available in 25 kg or 50 kg polypropylene woven bags, or custom packaging upon request.

Quality Assurance
Each batch is tested for purity, moisture, pH, and solubility to ensure consistent quality.