Sodium Thiosulfate CAS 7772-98-7, Sodium Thiosulfate, CAS 7772-98-7
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.
7772-98-7
Na2O3S2
158.11
231-867-5
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 | / |
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).
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.
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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