Registration Dossier

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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Administrative data

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

Data source

Materials and methods

Test material

Constituent 1
Chemical structure
Reference substance name:
Sulphur dioxide
EC Number:
EC Name:
Sulphur dioxide
Cas Number:
Molecular formula:
Sulphur dioxide generated from sulphur by combustion

Results and discussion

Applicant's summary and conclusion

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).