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EC number: 215-628-2 | CAS number: 1335-30-4
- 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
Particle size distribution (Granulometry)
Administrative data
Link to relevant study record(s)
Description of key information
73.055 µm (mean particle size)
Additional information
The particle size distribution of a silica aerosol is mainly influenced by the shear forces acting upon the starting material.
Under normal handling and use of commercial products, the silicates tend to form agglomerates of high mass median aerodynamic diameters that are not respirable (MMAD >> 10 µm; for Silicic acid, aluminium salt about 200 to 400 µm). The respirable fraction (=< 10 µm) comprises of less than 1 wt% (Barthel 1998/Stintz 2001; Stintz 2003).
Under experimental conditions and in measurements with destructive techniques (e.g. dispersion), the MMADs may range significantly below 10 µm.
Particle Size, Definition and Dynamic Interactions (modified after ECETOC 2006):
With respect to particle size, the German standard DIN 53206 (1972) distinguishes between primary particles, aggregates and agglomerates.
- Primary particles are recognisable by electron (transmission, scanning) microscopy as sub-units of pyrogenic and precipitated SAS (synthetic amorphous silica) or individual particles in SAS sols. For SAS gels, primary particles are not visible: nucleation and condensation give rise to further particle growth. Primary particles in the case of pyrogenic or precipitated SAS do not exist in isolation.
- Aggregates are assemblies of primary particles which are grown together face-to-face in the form of chains or clusters. The aggregates are formed by the collision of primary particles during particle growth and/or by the further deposition of silica onto these aggregates.
SAS aggregates represent the smallest, stable, non-dispersible particle units of three-dimensional structure, with a size ranging from 100 to 1,000 nm for pyrogenic and precipitated SASs. These aggregates can be found at infinite dilution or after blending in a polymer matrix, e.g. composites. For SAS gels, aggregates form macroscopic structures. SAS sols consist of primary particles and aggregates only in a fluid like water, organic solvent or a polymeric matrix but typically agglomerate irreversibly under drying.
- Agglomerates are assemblies of aggregates, held together by strong physical adhesion forces.
By adjusting certain process parameters, the mean particle size, particle size distribution and degree of aggregation and/or
agglomeration can be varied over relatively broad ranges. However, the smallest particles in precipitated and pyrogenic SAS remain the corresponding aggregates, not the primary particles.
Shear forces cause a breakdown of agglomerates as well as dilution tends to prevent the formation of larger agglomerates due to the larger interparticle distances and low collision frequencies. Under the technical conditions of inhalation exposure of experimental animals, in general high shear forces dominate that form aerosols of small particle sizes with a high fraction of respirable particles. This is in marked contrast to the largely stressless settling conditions that prevail under normal handling and use of these materials.
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.
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