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EC number: 234-733-4 | CAS number: 12028-48-7
- 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
Dissociation constant
Administrative data
Link to relevant study record(s)
- Endpoint:
- dissociation constant
- Type of 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:
- data from handbook or collection of data
- Remarks:
- Well documented, scientifically sound study that used appropriate instrumentation for quantifying effective dissociation constants.
- Justification for type of information:
- 1. HYPOTHESIS FOR THE CATEGORY APPROACH: The hypothesis is that properties are likely to be similar or follow a similar pattern because of the presence of a common metal ion, in this case tungstate.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES):
Source: Sodium metatungstate
Target: Ammonium metatungstate
3. CATEGORY APPROACH JUSTIFICATION: See Annex 3 in CSR
4. DATA MATRIX: See Annex 3 in CSR - Reason / purpose for cross-reference:
- read-across: supporting information
- Principles of method if other than guideline:
- The speciation and equilibria of sodium metatungstate was determined by a combination of 183W NMR spectroscopy and gravimetry over the pH range 4.5-10.0.
- GLP compliance:
- not specified
- Dissociating properties:
- yes
- No.:
- #1
- pKa:
- -118
- Temp.:
- 20 °C
- Remarks on result:
- other: See remarks on results for equation
- No.:
- #2
- pKa:
- -20
- Temp.:
- 20 °C
- Remarks on result:
- other: See remarks on results for equation
- No.:
- #3
- pKa:
- -195
- Temp.:
- 20 °C
- Remarks on result:
- other: See remarks on results for equation
- Conclusions:
- The major stable isopolytungstate species present, when sodium metatungstate solutions (pH 4.5-10) were measured via NMR, were WO4-–,(W7O24)6–, (H2W12O42)10- (as solid sodium salt) and (H2W12O40)6-.
- Executive summary:
Due to the similar chemical constituency and structure between the source substance (sodium metatungstate) and the target substance (ammonium metatungstate), the physico-chemical properties would be expected to be the same or sufficiently similar such that application of read-across is appropriate for this endpoint. For more details, refer to the read-across category approach description in the Category section of this IUCLID submission or Annex 3 of the CSR.
- Endpoint:
- dissociation constant
- Type of information:
- migrated information: read-across from supporting substance (structural analogue or surrogate)
- Adequacy of study:
- supporting study
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- data from handbook or collection of data
- Remarks:
- Data from peer-reviewed handbook or collection of data.
- Justification for type of information:
- 1. HYPOTHESIS FOR THE CATEGORY APPROACH: The hypothesis is that properties are likely to be similar or follow a similar pattern because of the presence of a common metal ion, in this case tungstate.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES):
Source: Ammonium
Target: Ammonium metatungstate
3. CATEGORY APPROACH JUSTIFICATION: See Annex 3 in CSR
4. DATA MATRIX: See Annex 3 in CSR - Principles of method if other than guideline:
- Data in this peer-reviewed publication were taken from many sources, including both compilations and primary literature. Where conflicts were found, the value deemed most reliable was chosen for inclusion in the handbook. Reference sources were not provided for this parameter, nor was the experimental method.
- GLP compliance:
- not specified
- Dissociating properties:
- yes
- pKa:
- 9.24
- Temp.:
- 25 °C
- Executive summary:
Ammonia is appropriate to use in assessing the dissociation of ammonium metatungstate as ammonia is one of the constituents of ammonium metatungstate and will affect the pKa for the substance such that application of read-across is appropriate for this endpoint. For more details, refer to the read-across category approach description in the Category section of this IUCLID submission or Annex 3 of the CSR.
Referenceopen allclose all
Reactions represented by pKas above:
No. | Reaction | log K | pKa |
1 | 12WO42- + 14H+= [H2W12O42]10–+ 6H2O |
118 | -118 |
2 | 7[H2W12O42]10–+ 2OH- = 12W7O246-+ 8H2O |
20 | -20 |
3 | 12W7O246-+ 30H+ = 7[H2W12O40]6 - + 8H2O |
195 | -195 |
The kinetics of equilibrium for the system were found to be slow, requiring up to 8 months to stabilize.
Sodium paratungstate B, Na10[H2W12O42].xH2O, which constituted a major component of this system, was found to be insoluble and precipitated as large, well-defined crystals. The solubility product for sodium paratungstate B ([H2W12O42]10–) was determined to be 6.89 (± 0.80) × 10–6
Metatungstate (H2W12O407-) is stable up to p[H] 7.5. Paratungstate B ([H2W12O42]10–
(as solid) is stable up to p[H] 9.6. The orthotungstate ion (WO42-)is stable above p[H] 6.4 and paratungstate A (W7O246-)has a stability range from p[H] 5.5 to 7.5.
NH3 + H2O = NH4 + + OH-
pKb = 4.76
Description of key information
The speciation of tungsten compounds in water is complex and several species exist coincidingly, depending on the pH of the system ammonium metatungstate is soluble and dissolution will occur at environmentally relevant pHs based on the Tranformation/Dissolution (T/D) testing (endpoint 4.8) conducted on ammonium metatungstate. Dean JA (ed.)(1985) indicates that the pKa for the ammonium constituent is 9.24. The major stable isopolytungstate species present, when sodium metatungstate solutions (pH 4.5-10) were measured via NMR, were WO4(2-), orthotungstate, W7O24(6-), paratungstate A, H2W12O42(10-), paratungstate B (as solid) and H2W12O40(6-), metatungstate (Smith and Patrick, 2000). Similar ionic species are expected to be present in solutions of ammonium metatungstate between these pHs. Other resources also support that dissociation would occur at environmentally relevant pHs.
Key value for chemical safety assessment
Additional information
No dissociation constant data are available for ammonium metatungstate (target substance). However, transformation/dissolution (T/D) data are available for ammonium metatungstate and sodium metatungstate, and pKa data are available for ammonium, which are used in a weight-of-evidence (WoE) approach for read-across. For more details, refer to the read-across category approach description in the Category section of this IUCLID submission or Annex 3 of the CSR.
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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