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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+.
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