Registration Dossier
Registration Dossier
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EC number: 273-761-1 | CAS number: 69012-64-2 Amorphous silicon dioxide particles from the volatilization and vaporization of furnace feed materials in the manufacture of ferrosilicon and silicon.
Dissociation constant
Administrative data
- Endpoint:
- dissociation constant
- Type of information:
- migrated information: read-across based on grouping of substances (category approach)
- Adequacy of study:
- key study
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- other: Study based on accepted scientific principles, conducted as part of a comprehensive testing programme, basic data given, in accordance with published data
Data source
Reference
- Reference Type:
- publication
- Title:
- Current considerations for the dissolution kinetics of solid oxides with silica
- Author:
- Löbbus M, Vogelsberger W, Sonnefeld J, Seidel A
- Year:
- 1 998
- Bibliographic source:
- Langmuir 14(16), 4386-4396 (American Chem. Society)
Materials and methods
Test guideline
- Qualifier:
- no guideline available
- Principles of method if other than guideline:
- Experiments carried out with a well-defined amorphous silica, Monospher 250 (Merck Darmstadt), included dependence on pH and NaCl concentration at 40 °C. pK determination was based on calculations combined with experimental studies.
- GLP compliance:
- no
Test material
- Reference substance name:
- Automatically generated during migration to IUCLID 6, no data available
- IUPAC Name:
- Automatically generated during migration to IUCLID 6, no data available
- Details on test material:
- Synthetic amorphous silicas:
CAS-No. 112945-52-5, CAS-Name: Silica, amorphous, fumed, crystalline-free;
CAS-No. 112926-00-8, CAS-Name: Silica gel, precipitated, crystalline-free.
Constituent 1
Results and discussion
- Dissociating properties:
- yes
Dissociation constantopen allclose all
- No.:
- #1
- pKa:
- 6
- Temp.:
- 40 °C
- Remarks on result:
- other: for silanol groups: mean value of 4 (+-0.08) at 0.1 mol NaCl/L
- No.:
- #2
- pKa:
- 6.42
- Temp.:
- 40 °C
- Remarks on result:
- other: for silanol groups: mean value of 4 (+-0.10) at 0.01 mol NaCl/L
- No.:
- #3
- pKa:
- 6.65
- Temp.:
- 40 °C
- Remarks on result:
- other: for silanol groups: mean value of 4 (+-0.11) at 0.001 mol NaCl/L
Any other information on results incl. tables
According to the authors (publication, p. 4391 - 4393, Tab. 2), the data are largely consistent with others given in the literature:
pKa = 6.8 (titrated in 0.1 molNaClO4/L, 25 °C) [Schindler P, Kamber HR: Helv. Chim. Acta 51 (1968), 1781]
(Note:NaClO4iscorrect.)
pKa = 6.13 - 6.24 (0.1 mol NaCl/L, 25 °C) [Sonnefeld J: J. Colloid Interface Sci. 183 (1996), 597]
Note: The pKa for the dissolved ortho (mono-) silicic acid is higher: pKa = 9.8
(based on data given by Iler RK;: The Chemistry of Silica. John Wiley & Sons, N.Y., 1979)
Applicant's summary and conclusion
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