Registration Dossier
Registration Dossier
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EC number: 201-083-8 | CAS number: 78-10-4
Dissociation constant
Administrative data
Link to relevant study record(s)
- Endpoint:
- dissociation constant
- Data waiving:
- study scientifically not necessary / other information available
- Justification for data waiving:
- the study does not need to be conducted because the substance is hydrolytically unstable (half-life less than 12 hours)
- Endpoint:
- dissociation constant
- Type of information:
- other: Data obtained from a handbook
- Adequacy of study:
- supporting study
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- data from handbook or collection of data
- Principles of method if other than guideline:
- Information on method and guideline not stated.
- GLP compliance:
- not specified
- Dissociating properties:
- yes
- No.:
- #1
- pKa:
- 9.9
- Temp.:
- 30 °C
- No.:
- #2
- pKa:
- 11.8
- Temp.:
- 30 °C
- No.:
- #3
- pKa:
- 12
- Temp.:
- 30 °C
- No.:
- #4
- pKa:
- 12
- Temp.:
- 30 °C
- Conclusions:
- Silicic acid was reported to have four dissociation constant values of pKa1 = 9.9, pKa2 = 11.8, pKa3 and pKa4 = 12 at 30°C in a secondary source which has been subject to peer review and in which the original sources are traceable.
Referenceopen allclose all
Description of key information
Dissociation constant [tetraethyl orthosilicate]: Not relevant because the substance hydrolyses very rapidly in contact with water.
Dissociation constant [silicic acid]: pKa1 = 9.9
Key value for chemical safety assessment
Additional information
The requirement to conduct a dissociation constant study for the substance is waived because in contact with water the substance hydrolyses very rapidly to form monosilicic acid (CAS 10193-36-9; EC No. 233-477-0) and ethanol (CAS 64-17-5; EC No. 200-578-6).
Monosilicic acid was reported to have dissociation constant values of pKa1 = 9.9, pKa2 = 11.8, pKa3 and pKa4 = 12 at 30°C in a secondary data source which has been subject to peer review and in which the original sources are traceable. Monosilicic acid is, therefore, an extremely weak acid. In neutral solution, the undissociated form will dominate.
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.
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