CAS 7772-98-7: Sodium Thiosulfate (Na2S2O3)

Identity

CAS Number	7772-98-7
Molecular Formula	Na2S2O3
IUPAC Name	disodium thiosulfate
Molecular Weight	158.11 g/mol
SMILES	`[O-]S(=O)(=S)[O-].[Na+].[Na+]`
Synonyms	sodium thiosulfate, sodium hyposulfite, hypo, photographic fixer, thiosulfuric acid disodium salt

2D Structure

Physical Properties

Density	1.667 g/mL at 25°C
Boiling Point	100.0°C
Melting Point	48.0°C
Flash Point	None°C
Vapor Pressure	0.0 kPa at 20°C
Refractive Index	nD = 1.49
Dielectric Constant	ε = 5.0

Safety & GHS Classification

Storage: Store in a cool, dry area. Pentahydrate form effloresces in dry air. Store in tightly sealed containers. Keep away from strong acids (decomposes to sulfur and SO2). Protect from light.