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Diss Factsheets

Administrative data

Endpoint:
hydrolysis
Type of information:
other: Hand Book Data
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)

Data source

Reference
Reference Type:
review article or handbook
Title:
Unnamed
Year:
2004
Report date:
2004

Materials and methods

Principles of method if other than guideline:
hand book data
GLP compliance:
no

Test material

Constituent 1
Chemical structure
Reference substance name:
Silicon dioxide
EC Number:
231-545-4
EC Name:
Silicon dioxide
Cas Number:
7631-86-9
Molecular formula:
O2Si
IUPAC Name:
Silicon dioxide
Test material form:
solid

Results and discussion

Preliminary study:
The basic consideration is that silica dissolves according to : SiO2 + H2O = Si(OH)4. At low concentrations most species are present as monomers, at higher concentrations polymerisation will occur.

Most soluble silicates are in the form:

M2O . mSiO2 . nH2O

where M = alkali metal, predominantly Na, but also K. The index m (molar ratio) ranges between 0.5 - 4, most commonly m = 3.3. Stability depends to a large extent on pH, above pH 10.6 the solutions are chemically stable. The increase of
ionic strength accelerates nucleation and deposition and decreases the SiO2 solubility. Coating of surfaces by organic matter may hamper dissolution, but at the same time Si(OH)4 may form complexes with organic matter, a process
which favours dissolution.
Transformation products:
not specified
Dissipation DT50 of parent compound
Key result
Remarks on result:
hydrolytically stable based on preliminary test

Any other information on results incl. tables

The basic consideration is that silica dissolves according to : SiO2 + H2O = Si(OH)4. At low concentrations most species are present as monomers, at higher concentrations polymerisation will occur.


Most soluble silicates are in the form:


M2O . mSiO2 . nH2O


where M = alkali metal, predominantly Na, but also K. The index m (molar ratio) ranges between 0.5 - 4, most commonly m = 3.3. Stability depends to a large extent on pH, above pH 10.6 the solutions are chemically stable. The increase of
ionic strength accelerates nucleation and deposition and decreases the SiO2 solubility. Coating of surfaces by organic matter may hamper dissolution, but at the same time Si(OH)4 may form complexes with organic matter, a process
which favours dissolution.


 

Applicant's summary and conclusion

Conclusions:
The basic consideration is that silica dissolves according to : SiO2 + H2O = Si(OH)4. At low concentrations most species are present as monomers, at higher concentrations polymerisation will occur.

Most soluble silicates are in the form:

M2O . mSiO2 . nH2O

where M = alkali metal, predominantly Na, but also K. The index m (molar ratio) ranges between 0.5 - 4, most commonly m = 3.3. Stability depends to a large extent on pH, above pH 10.6 the solutions are chemically stable. The increase of
ionic strength accelerates nucleation and deposition and decreases the SiO2 solubility. Coating of surfaces by organic matter may hamper dissolution, but at the same time Si(OH)4 may form complexes with organic matter, a process
which favours dissolution.