Registration Dossier
Registration Dossier
Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.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.
Use of this information is subject to copyright laws and may require the permission of the owner of the information, as described in the ECHA Legal Notice.
EC number: 232-259-2 | CAS number: 7803-49-8
Biodegradation in water: screening tests
Administrative data
Link to relevant study record(s)
Description of key information
Inorganic substance, therefore biodegradation testing not applicable. Hydroxylamine is a natural intermediate in biological nitrification under aerobic conditions.
Key value for chemical safety assessment
Additional information
Hydroxyl-ammonium ion and hydroxylamine (free base) are in equilibrium according to the following reaction scheme:
[NH3-OH] + < --> NH2-OH + H+
The estimated pKa for this reaction is 5.8. The amount of hydroxylammonium ion decreases rapidly at pH-values above 5. Only in very acidic environment, the substance is present as hydroxyl-ammonium ion. At pH 7, the amount of hydroxyl-ammonium ion is approximately 6 %, and at pH 8 nearly only the free base is present.
The free hydroxylamine base is very reactive and, at environmental conditions, is expected to decompose further by abiotic processes and nitrification. The expected ultimate degradation products are ammonia, nitrogen and water (Hollemann-Wiberg, 1995).
2NH2OH --> NH3+ HNO + H2O
2HNO --> N2O + H2O
NH2OH + HNO --> N2+ 2H2O
For several chemolithoautotrophic bacteria, such as Nitrosomas europea, Nitrosomas nitrosa and Nitrosococcus oceanus, mixotrophic growth on hydroxylamine in the presence of ammonia has been demonstrated (Böttcher and Koops 1994, de Brujin et al. 1995).
Reference:
Hollemann-Wiberg (1995): Lehrbuch der Anorganischen Chemie, de Gruyter, p. 702-704
Böttcher B, Koops HP (1994). Growth of lithotrophic ammonia-oxidizing bacteria on hydroxylamine. FEMS Microbiol Lett 122: 263-266
De Brujin P et al. (1995). Growth of Nitrosomonas europaea on hydroxylamine. FEMS Microbiol Lett 125: 179-184
ECB (2008). EU-RAR Draft, Bis-(hydroxylammonium)sulphate, CAS: 10039 -54 -0,14. May 2008
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.
Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
