Registration Dossier

Physical & Chemical properties

Endpoint summary

Administrative data

Description of key information

Sodium dithionite

- Appearance: grayish-white powder with a slight characteristic odour.

- Decomposition: 52 °C

- Relative density: 2.38

- Particle size distribution: D50= 107.1 µm, D10= 13.9 µm, D90= 314.4 µm

- Dustiness: 182.35 mg/g; MMAD (GSD): 24.46 µm (1.85)

- Water solubility: 241 g/L at 20 °C

- Self-ignition: Packaging group II of Division 4.2; Category 1 for self-heating substances; Signal Word "Danger" ; Hazard Statement "H251: Self-heating, may catch fire"; classified as auto flammable (R7).

- Flammability: non flammable solid

- Explosiveness: no explosive properties

Additional information

The majority of data on physico-chemical properties of sodium dithionite were taken from handbooks (including CRC Handbook of Chemistry and Physics and the Merck Index).

Studies conducted in accordance with EU guidelines are available for: particle size distribution, auto flammability, flammability and explosive properties.

Waivers are proposed for boiling point, vapour pressure, partition coefficient, surface tension, flash point, oxidising properties, stability in organic solvents, dissociation constant and viscosity, as well as for pyrophoric properties and flammability in contact with water.

Sodium dithionite (Na2S2O4, molecular weight 174.11 g/mol), CAS number 7775-14-6, EC number 231-890-0

Sodium dithionite appears as a grayish-white powder with a slight characteristic odour.

Melting point: decomposes at 52°C (reliable handbook data)

Relative density of sodium dithionite is 2.38. (reliable handbook data)

Particle size distribution and dustiness of a representative sample (experimental study results):

D50 = 107.1 µm

D10 = 13.9 µm

D90 = 314.4 µm

Dustiness: 182.35 mg/g; MMAD (GSD): 24.46 µm (1.85)

Water solubility: 241 g/L at 20°C (highly soluble, reliable handbook data)

Self-ignition: Sodium dithionite has to be assigned to Packaging group II of Division 4.2 according to the UN-Transport-regulation; and has to be assigned to Category 1 for self-heating substances according to EC 1272/2008 (CLP-Guideline) Annex 1: 2.11. The substance has to be labelled with the Signal Word "Danger" and the Hazard Statement "H251: Self-heating, may catch fire". (guideline study; according to EC A.16.). According to Directive 67/548/EECthe substance is classified as auto flammable (R7).

Flammability: non flammable solid (guideline study; according to EC A.10. - Flammable solids)

Explosiveness: sodium dithionite has no explosive properties (guideline study; according to EC A.14.)