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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.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: 241-034-8 | CAS number: 16961-83-4
Dissociation constant
Administrative data
Link to relevant study record(s)
- Endpoint:
- dissociation constant
- Type of information:
- experimental study
- Adequacy of study:
- weight of evidence
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- data from handbook or collection of data
- Remarks:
- Data taken from a published chemistry handbook
- Qualifier:
- no guideline followed
- Principles of method if other than guideline:
- Not reported
- Dissociating properties:
- yes
- No.:
- #1
- Remarks on result:
- other: The anhydrous substance dissociates totally to form SiF4 and HF.
- Conclusions:
- The anhydrous substance dissociates totally to form SiF4 and HF.
- Executive summary:
The anhydrous substance dissociates totally to form SiF4 and HF. For this reason, the substance contains HF to prevent dissociation and hydrolysis.
- Endpoint:
- dissociation constant
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- comparable to guideline study with acceptable restrictions
- Remarks:
- Publication
- Qualifier:
- no guideline followed
- Principles of method if other than guideline:
- No details
- Dissociating properties:
- yes
- No.:
- #1
- Remarks on result:
- other: Hexafluorosilicic acid is a strong acid with respect to loss of the first proton (complete dissociation) to form HSiF6- and H+.
- No.:
- #2
- pKa:
- >= 0.65 - <= 1.83
- Remarks on result:
- other: The second dissociation is limited (Ka of between 10e-0.65 to 10e-1.83), with the formation of SiF62- and H+.
- Conclusions:
- Hexafluorosilicic acid is a strong acid with respect to loss of the first proton (complete dissociation) to form HSiF6- and H+.
The second dissociation is limited (Ka of between 10e-0.65 to 10e-1.83), with the formation of SiF62- and H+. - Executive summary:
Hexafluorosilicic acid is a strong acid with respect to loss of the first proton (complete dissociation) to form HSiF6- and H+.
The second dissociation is limited (Ka of between 10e-0.65 to 10e-1.83), with the formation of SiF62- and H+.
- Endpoint:
- dissociation constant
- Type of information:
- experimental study
- Adequacy of study:
- weight of evidence
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- comparable to guideline study with acceptable restrictions
- Remarks:
- Published paper
- Qualifier:
- no guideline followed
- Principles of method if other than guideline:
- Report of the behaviour of fluorosilicic aicd in aqueous conditions
- GLP compliance:
- no
- Dissociating properties:
- yes
- Remarks on result:
- other: Under dilute aqueous conditions, the substance dissociates to form SiF4 and HF.
- Conclusions:
- Under dilute aqueous conditions, the substance dissociates to form SiF4 and HF; the SiF4 formed from this reaction undergoing hydrolysis to form HF and Si(OH)4; HF dissociates (under aqueous conditions) for form the fluoride and hydronium ions.
- Executive summary:
Under dilute aqueous conditions, the substance dissociates to form SiF4 and HF; the SiF4 formed from this reaction undergoing hydrolysis to form HF and Si(OH)4; HF dissociates (under aqueous conditions) for form the fluoride and hydronium ions. Soluble silicates engage in complex behaviour and will react further to form oxo and hydroxo species.
Referenceopen allclose all
The anhydrous substance dissociates completely to form SiF4 and HF.
Under dilute aqueous conditions, the substance dissociates to form SiF4 and HF; the SiF4 formed from this reaction undergoing hydrolysis to form HF and Si(OH)4; HF dissociates (under aqueous conditions) for form the fluoride and hydronium ions. Soluble silicates engage in complex behaviour and will react further to form oxo and hydroxo species.
Description of key information
The anhydrous substance dissociates totally to form SiF4 and HF. For this reason, the substance contains HF to prevent dissociation and hydrolysis. Under dilute aqueous conditions, the substance dissociates to form SiF4 and HF; the SiF4 formed from this reaction undergoing hydrolysis to form HF and Si(OH)4; HF dissociates (under aqueous conditions) for form the fluoride and hydronium ions. Soluble silicates engage in complex behaviour and will react further to form oxo and hydroxo species. Hexafluorosilicic acid is a strong acid with respect to loss of the first proton (complete dissociation) to form HSiF6- and H+.
Key value for chemical safety assessment
- pKa at 20°C:
- 1.83
Additional information
The anhydrous substance dissociates totally to form SiF4 and HF. For this reason, the substance contains HF to prevent dissociation and hydrolysis. Under dilute aqueous conditions, the substance dissociates to form SiF4 and HF; the SiF4 formed from this reaction undergoing hydrolysis to form HF and Si(OH)4; HF dissociates (under aqueous conditions) for form the fluoride and hydronium ions. Soluble silicates engage in complex behaviour and will react further to form oxo and hydroxo species. Hexafluorosilicic acid is a strong acid with respect to loss of the first proton (complete dissociation) to form HSiF6- and H+.
The second dissociation is limited (Ka of between 10e-0.65 to 10e-1.83), with the formation of SiF62- and H+.
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.
