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Diss Factsheets
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EC number: 215-710-8 | CAS number: 1344-95-2
- Life Cycle description
- Uses advised against
- Endpoint summary
- Appearance / physical state / colour
- Melting point / freezing point
- Boiling point
- Density
- Particle size distribution (Granulometry)
- Vapour pressure
- Partition coefficient
- Water solubility
- Solubility in organic solvents / fat solubility
- Surface tension
- Flash point
- Auto flammability
- Flammability
- Explosiveness
- Oxidising properties
- Oxidation reduction potential
- Stability in organic solvents and identity of relevant degradation products
- Storage stability and reactivity towards container material
- Stability: thermal, sunlight, metals
- pH
- Dissociation constant
- Viscosity
- Additional physico-chemical information
- Additional physico-chemical properties of nanomaterials
- Nanomaterial agglomeration / aggregation
- Nanomaterial crystalline phase
- Nanomaterial crystallite and grain size
- Nanomaterial aspect ratio / shape
- Nanomaterial specific surface area
- Nanomaterial Zeta potential
- Nanomaterial surface chemistry
- Nanomaterial dustiness
- Nanomaterial porosity
- Nanomaterial pour density
- Nanomaterial photocatalytic activity
- Nanomaterial radical formation potential
- Nanomaterial catalytic activity
- Endpoint summary
- Stability
- Biodegradation
- Bioaccumulation
- Transport and distribution
- Environmental data
- Additional information on environmental fate and behaviour
- Ecotoxicological Summary
- Aquatic toxicity
- Endpoint summary
- Short-term toxicity to fish
- Long-term toxicity to fish
- Short-term toxicity to aquatic invertebrates
- Long-term toxicity to aquatic invertebrates
- Toxicity to aquatic algae and cyanobacteria
- Toxicity to aquatic plants other than algae
- Toxicity to microorganisms
- Endocrine disrupter testing in aquatic vertebrates – in vivo
- Toxicity to other aquatic organisms
- Sediment toxicity
- Terrestrial toxicity
- Biological effects monitoring
- Biotransformation and kinetics
- Additional ecotoxological information
- Toxicological Summary
- Toxicokinetics, metabolism and distribution
- Acute Toxicity
- Irritation / corrosion
- Sensitisation
- Repeated dose toxicity
- Genetic toxicity
- Carcinogenicity
- Toxicity to reproduction
- Specific investigations
- Exposure related observations in humans
- Toxic effects on livestock and pets
- Additional toxicological data
Hydrolysis
Administrative data
Link to relevant study record(s)
- Endpoint:
- hydrolysis
- Type of information:
- other: Well documented publication
- Adequacy of study:
- key study
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- other: Study based on accepted scientific principles, well documented publication
- Reason / purpose for cross-reference:
- reference to same study
- Reason / purpose for cross-reference:
- reference to other study
- Qualifier:
- equivalent or similar to guideline
- Guideline:
- other: OECD 105 (water solubility)
- Principles of method if other than guideline:
- Development of a dissolution model for silicon oxides, taking into account Si-O bond cleavage and formation as well as protolysis of silanol groups. Three different models, pH dependent surface potential, diffuse double layer, and gel layer, are investigated.
Experiments carried out with a well-defined amorphous silica (Monospher 250 (Merck Darmstadt) included dependence on pH and NaCl concentration at 40 °C. - GLP compliance:
- no
- Analytical monitoring:
- yes
- Preliminary study:
- Not relevant
- Transformation products:
- yes
- No.:
- #1
- Details on hydrolysis and appearance of transformation product(s):
- See Report, Table 1 and Fig. 4 (see below: AD under attached background material)
- Key result
- Remarks on result:
- other: see remarks
- Remarks:
- The experimental part showed that there was a distinct pH dependence in the rate of dissolution, increasing with the pH increasing. However, the free dissolved SiO2 reached a maximum independent of the pH (Report, Table 1, Fig.. 4). It is concluded that the total amount of silica dissolved is relatively constant in a broad range of pH (1.1 < pH < 8.9) (p. 4393).
- Validity criteria fulfilled:
- yes
- Conclusions:
- Based on the results of the study performed with silicon dioxide, it can be stated that although ion exchange processes are possible, depending on the surrounding environment, the degree of hydrolysis involved in the dissolution of silicates in water is very limited and not quantifiable.
Reference
The surface of silica may be covered by a partial hydrolysed gel layer when in contact with water (p. 4389). This layer is in equilibrium with the outer aqueous phase and constitutes a diffusion barrier for ions and water.
It is known and generally recognised that proton and hydroxide ion promoted dissolution plays a more prevailing role in the dissolution process than a simple hydrolysis of siloxane bridges (p. 4390).
The experimental part showed that there was a distinct pH dependence in the rate of dissolution, increasing with the pH increasing. However, the free dissolved SiO2 reached a maximum independent of the pH (Report, Table 1, Fig.. 4). It is concluded that the total amount of silica dissolved is relatively constant in a broad range of pH (1.1 < pH < 8.9) (p. 4393).
The level of maximum solubility was about 2.7 mmol SiO2/L (here: Monosphere, see also 4.8 Water solubility).
The degree of hydrolysis that may be involved in the dissolution process could not yet be solved.
Description of key information
It is not possible to quantify the very limited hydrolysis involved in the dissolution of silicates in water.
Key value for chemical safety assessment
Additional information
Based on the results of the study performed with silicon dioxide, it can be stated that although ion exchange processes are possible, depending on the surrounding environment, the degree of hydrolysis involved in the dissolution of silicates in water is very limited and not quantifiable.
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