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EC number: 234-858-4 | CAS number: 12037-47-7
- 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
Endpoint summary
Administrative data
Description of key information
Additional information
Silicon orthophosphate is an inorganic salt, which easily dissociates into silicon and phosphate ions after introducing into the aquatic environment (relevant pH values range from 4 – 9). The tetravalent silicon ion and the phosphate ion will then react with the media to form different silicon and phosphate species depending on the pH and redox potential of the media.
The dissociated silicon ion hydrolyses in water and exists predominantly as orthosilicic acid H4SiO4/Si(OH)4, which is also the main species when silicon dioxide is dissolved in water. The dissociation constants of orthosilicic acid are high (pKa 9.9, 11.8, 12 & 12 at 30 °C, Lide & Frederikse 1995). The sum of soluble silicate rapidly decreases when the pH is lowered to 9. Because of these, at environmental pH values of 6.5 – 8.5 large amounts of the soluble silicate ions might be removed from the aqueous solution gradually(OECD SIDS, 2004).
In the case of free aqueous phosphate, four forms are existent. PO34- predominates in strong basic conditions, whereas H3PO4 is the main form in strong acid conditions. In the normal aquatic environment (pH 4-9), H2PO4- and HPO42- are prevalent and show equilibrium, which is relatively stable and not significantly affected by the normal environmental pH conditions.
As inorganic substance, silicon orthophosphate is not amenable to photo- or biodegradation. For silicon orthophosphate as well as its products of dissociation, bioaccumulation is not expected. As an inorganic compound, silicon orthophosphate is insoluble in n-octanol, making determination of a log Kow not feasible.
If silicon orthophosphate is released into the environment, it is expected to combine indistinguishably with the soil or sediment, due to the similarity with inorganic soil/sediment matter and will be subjected to natural processes under environmental conditions (cation exchange, dissolution, sedimentation).
Of the elemental composition of the earth’s crust, silicon is the second most abundant element after oxygen, i.e. 28% (Salminen, 2012). Silicon oxides are the most abundant compounds in the earth’s crust mass (> 60%; Salminen, 2012). Compounds of silicon, oxygen and phosphorus are ubiquitous in the environment; they are present in inorganic matter, like minerals and soils as well as in organic matter, like plants, animals and man. By weathering of soil, rocks and sediments and by atmospheric deposition, silica is released into surface and ground waters from where it may be removed by precipitation and sedimentation or taken up by living organisms, espacially diatoms as normal process mainly related to structural function. Silica is found in all natural waters with an average concentration of 8 mg SiO2/L (Salminen, 2012).
References:
Lide, D. R. and Frederikse, H. P. R., editors (1995). Handbook of Chemistry and Physics, 76th Edition. CRS Press, Boca Raton.
OECD SIDS (2004). Synthetic amorphous silica and silicates, SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 19-22 October 2004.
Salminen R. (ed.) (2012): FOREGS: Geochemical Atlas of Europe. ISBN 951-690-913-2 (electronic version).
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