Sodium Thiosulfate CAS 7772-98-7

Sodium Thiosulfate CAS 7772-98-7 Information

CAS	7772-98-7
Molecular formula	Na2O3S2
Molecular weight	158.11
EIENCS	231-867-5
Form	/
Melting point
boling point	/
Density	/
Solubility	Dissolves slowly in water to form a viscous solution; insoluble in ethanol and in ether.
PKA	/
Color	White to yellow powder
Storage temp	/

What is Sodium Thiosulfate CAS 7772-98-7?

Molecules and Structures

Molecular formula: Na₂S₂O₃ (anhydrous)/Na₂S₂O₃·5H₂O (pentahydrate)

Molecular weight: 158.11 (anhydrous) / 248.18 (pentahydrate)

Appearance: Colorless transparent monoclinic crystals (pentahydrate) or white crystalline powder (anhydrous), odorless and salty in taste.

Solubility: Readily soluble in water (solubility at 20℃ : 210 g/L), insoluble in ethanol and ether.

Key parameters

Melting point: 48℃ (the pentahydrate melts and dissolves in crystalline water).

Boiling point: 100℃ (Decomposition).

Density: 1.667 g/cm³ (anhydrous) / 1.69 g/cm³ (pentahydrate).

Stability

It is prone to efflorescence in dry air and deliquescent in humid air.

Decomposition in strong acids: generating elemental sulfur and SO₂ (Na₂S₂O₃ + 2HCl → 2NaCl + S↓ + SO₂↑ + H₂O).

Reducing property: Can be oxidized by oxidants (such as Cl₂, I₂)

Reaction with iodine: 2Na₂S₂O₃ + I₂ → Na₂S₄O₆ + 2NaI (iodometric principle).

Sodium Thiosulfate CAS 7772-98-7 Use

Medicine and detoxification

Cyanide poisoning antidote: Under the action of thiocyanase, it combines with cyanide ions to form non-toxic thiocyanates and is excreted from the body.

Cisplatin chemotherapy side effect prevention: Approved by the FDA for the prevention of hearing loss caused by cisplatin chemotherapy in children.

Skin disease treatment: 20% to 30% solution for external application to treat pityriasis versicolor (tinea versicolor).

Industry and Environmental Protection

Fixer: Dissolves unexposed silver bromide (AgBr + 2Na₂S₂O₃ → Na₃[Ag(S₂O₃)₂] + NaBr), used in photography and film industries.

Dechlorination agent

Residual chlorine (S₂O₃²⁻ + 4Cl₂ + 5H₂O → 2SO₄²⁻ + 8Cl⁻ + 10H⁺) is removed after bleaching in the textile/paper industry.

Removal of hydrogen chloride from industrial gases such as hydrogen and syngas.

Silver ore: with silver ions to form complex (2 S ₂ O ₃ squared ⁻ + Ag ⁺ - > [Ag (S ₂ O ₃) ₂] after ⁻).

Food and daily chemicals

Food additive: As an antioxidant and chelating agent, it is used for fruit juice preservation and preventing oil oxidation in nuts (national standard superior grade product).

Cosmetics and detergents: Dechlorination and stabilizing components in shampoos and disinfectants.

Sodium Thiosulfate CAS 7772-98-7 safety

Toxicity risk

Acute toxicity: Intraperitoneal injection of LD₅₀=5600 mg/kg in mice (low toxicity), but it is irritating to the eyes, skin and respiratory tract.

Decomposition risk: It releases SO₂ (highly toxic) when exposed to strong acids. Contact with acids and oxidants should be avoided.

Operation protection

Essential equipment: Dust mask, chemical goggles, nitrile gloves.

Leakage treatment: After the sand and soil are adsorbed, they should be incinerated as hazardous waste. Flushing is strictly prohibited (to prevent SO₂ diffusion).

Storage and Transportation

Conditions: Sealed, light-proof, cool and dry (humidity ≤60%), temperature ≤25℃.

Contraindications: Do not coexist with acids, oxidants, or halogens. Transport mark: UN 3263 (Corrosives).

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