Registration Dossier

Administrative data

Endpoint:
dissociation constant
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
other:

Data source

Materials and methods

Test material

Constituent 1
Chemical structure
Reference substance name:
Sulphur dioxide
EC Number:
231-195-2
EC Name:
Sulphur dioxide
Cas Number:
7446-09-5
Molecular formula:
SO2
IUPAC Name:
Sulphur dioxide generated from sulphur by combustion

Results and discussion

Applicant's summary and conclusion

Conclusions:
Sulphur dioxide will not dissociate into two or more chemical species, instead sulphur dioxide reacts reversible with water to form sulfurous acid (H2SO3), with a equilibrium constant K <<< 10-9 (Hollemann & Wiberg, Lehrbuch der Anorganischen Chemie, 101. Auflage, Walter de Gruyter, Berlin/New York, 1995).
Sulfurous acid (H2SO3) further dissociates with dissociation constants Ka1 of 1.6.10-2 and Ka2 of 1.0.10-7 at 25 °C (Barbera, Sulfites, Thiosulfates, and Dithionites. In: Ullmann´s Encyclopedia of Industrial Chemistry. Wiley-VCH Verlag GmbH & Co KGaA. June 15, 2000.(2000).