Sodium thiosulfate

Athanor · official

Na₂O₃S₂ · 158.11 g/mol

IUPAC name: disodium;dioxido-oxo-sulfanylidene-lambda6-sulfane

Also called hypo, photographic fixer, E539

Inorganic

Open in Athanor

Drawn from its SMILES with RDKit

Names and identifiers

IUPAC name: disodium;dioxido-oxo-sulfanylidene-lambda6-sulfane
Synonyms: hypo, photographic fixer, E539
+ 38 more
Sodium thiosulphate, Disodium thiosulfate, Hypo, Chlorine Control, Chlorine Cure, Sodium thiosulfate, anhydrous, Thiosulfuric acid, disodium salt, Sodium thiosulfate (Na2S2O3), Sodium thiosulphate (Na2S2O3), Sodium oxide sulfide (Na2S2O3), L0IYT1O31N, Thiosulfuric acid (H2S2O3), disodium salt, Ins no.539, Ins-539, Sodium thiosulphate, anhydrous, DTXSID9042417, CHEBI:132112, E-539, sulfothiorine, RefChem:6498, Cyanide Antidote Package, DTXCID7022417, Thiosulfate, Sodium, Pentahydrate, Sodium Nitrite and Sodium Thiosulfate, 231-867-5, Ametox, Db-020, HX1032V43M, Natrii thiosulfas, NSC-45624, NSC45624, PEDMARK, S-Hydril, Sodium hyposulfite, Sodium Thiosulfate Anhydrous, Sodium thiosulphate anhydrous, Sodothiol, Thiosulfuric Acid Disodium Salt
Molecular formula: Na₂O₃S₂
Empirical formula: Na₂O₃S₂
Molecular weight: 158.11 g/mol
Exact mass: 157.90842
CAS number: 7772-98-7
PubChem CID: 24477
Canonical SMILES: [O-]S(=O)(=S)[O-].[Na+].[Na+]
Isomeric SMILES: [O-]S(=O)(=S)[O-].[Na+].[Na+]
InChI: InChI=1S/2Na.H2O3S2/c;;1-5(2,3)4/h;;(H2,1,2,3,4)/q2*+1;/p-2
InChIKey: AKHNMLFCWUSKQB-UHFFFAOYSA-L
Molfile

Names, InChI and the identifiers from PubChem, retrieved 2026-10-14.

Physical properties

TemperaturePressureDensity

Appearance: CBI; Large Crystals; Wet Solid; Dry Powder; Liquid; Large Crystals; Liquid[1]
2 values
From EPA Chemical Data Reporting (CDR), the most authoritative source here.
Value As written Source
–shown CBI; Large Crystals; Wet Solid; Dry Powder; Liquid; Large Crystals; Liquid [1] EPA Chemical Data Reporting (CDR)
– COLOURLESS CRYSTALS. [2] ILO-WHO International Chemical Safety Cards (ICSCs)
Melting point: 48.5 °C[2]
Density: 1.7 g/cm³[2]
Solubility in water: Solubility in water, g/100ml at 20 °C: 20.9[2]
log P: -4.35 (calculated)[2]
Vapor pressure: Reported, but no value passed the checks.
The value and why
Vapor pressure at 20 °C: negligible (could not be read; source [2])

Value	As written	Source
–shown	CBI; Large Crystals; Wet Solid; Dry Powder; Liquid; Large Crystals; Liquid	[1] EPA Chemical Data Reporting (CDR)
–	COLOURLESS CRYSTALS.	[2] ILO-WHO International Chemical Safety Cards (ICSCs)

Each value as its source reports it, with the source's number after it (listed under References). Where several sources report a property, the row shows the value most of them agree on, the rule the app uses; open the values to see every one.

Calculated

Heavy atoms: 7
Rings: 0
Aromatic rings: 0
Fraction sp³ carbons (Fsp3): 0
H-bond donors: 0
H-bond acceptors: 4
Rotatable bonds: 0
TPSA (Å²): 63.2 computed here · PubChem 104
Formal charge: 0
Complexity: 82 PubChem
Stereocenters: None
Double-bond geometry: None specified
Point group: C3v of one 3D conformer with its hydrogens, by Athanor’s engine (as in the app)

Elemental analysis

Na29.08%
O30.36%
S40.56%

Isotope pattern

Each peak is a nominal mass with its abundance-weighted exact mass, as a percentage of the tallest, from IUPAC natural isotope abundances.

Computed from the structure with RDKit 2026.09 when this page was built, beside PubChem's own computed values from its record; where the two differ, both are shown.

Predicted

log P: -7 Crippen (Wildman and Crippen 1999)
log S (water solubility): 3.59 ESOL (Delaney 2004), log mol/L
Synthetic accessibility: 5.38 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

Molecular weight ≤ 500: 158.11
log P ≤ 5 (Crippen): -7
H-bond donors ≤ 5: 0
H-bond acceptors ≤ 10: 4

Passes all four rules.

Predictions, not measurements; each names its method. A measured log P, where a source reports one, is under Physical properties.

Safety

No GHS hazard classification was found in the sources.

First aid

Fresh air, rest.[2]
Rinse and then wash skin with water and soap.[2]
Rinse with plenty of water for several minutes (remove contact lenses if easily possible).[2]
Rinse mouth.[2]

Storage

Separated from strong oxidants.[2]

Safety data sheets on the supplier’s page: TargetMol, Sigma-Aldrich, AstaTech, Inc..

Always read the supplier’s safety data sheet before working with it.

Spectra

Experimental spectra held by these sources; each link opens the source's own record.

Literature

Reading PubChem, OpenAlex and GSRS…

Bioactivity

Reading ChEMBL…

References

[1]EPA Chemical Data Reporting (CDR) · Public domain (US EPA) · via PubChem · retrieved 2026-10-14
[2]ILO-WHO International Chemical Safety Cards (ICSCs) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
[3]Hazardous Substances Data Bank (HSDB) · Public domain (US NLM) · via PubChem · retrieved 2026-10-14
[4]European Chemicals Agency (ECHA) · ECHA legal notice: reuse with acknowledgement · via PubChem · retrieved 2026-10-14
[5]SpectraBase · Linked only · via PubChem · retrieved 2026-10-14
·Calculated values: computed by Athanor with RDKit 2026.09 from the structure.
·Literature on PubChem

Data last updated 2026-10-14.