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Water solubility

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Reference
Endpoint:
transformation / dissolution of metals and inorganic metal compounds
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Well documented, scientifically sound study that determined the dissolution of the test substance according to the UN Guidance on transformation/dissolution (T/D) of metals and metal compounds (UN GHS Annex 10).
Qualifier:
according to guideline
Guideline:
other: UN Guidance on transformation/dissolution (T/D) of metals and metal compounds (UN GHS Annex 10)
Principles of method if other than guideline:
Standardized amounts of powdered solids are added to specified simulated aquatic media and amounts of the relevant soluble metal ion are measured after defined timepoints.
GLP compliance:
no
Type of method:
other: Guidance on transformation/dissolution (T/D) of metals and metal compounds (UN GHS Annex 10)
Key result
Type of test:
screening transformation/dissolution test - sparingly soluble metal compounds
Mean dissolved conc.:
65.47 mg/L
Element analysed:
Dissolved tungsten
Loading of aqueous phase:
100 mg/L
Incubation duration:
24 h
Test conditions:
pH=8.5; 21°C
Key result
Type of test:
screening transformation/dissolution test - sparingly soluble metal compounds
Mean dissolved conc.:
87.88 mg/L
Element analysed:
Tungstate anion (WO4=)
Loading of aqueous phase:
100 mg/L
Incubation duration:
24 h
Test conditions:
pH=8.5; 21°C
Details on results:
AMT was readily soluble, dissolving within a few minutes of contact with the pH 8.5 medium.

The W and WO4(2-) concentrations at 24 h for AMT were 65,467 ug/L (σ% = 2) and 87,880 ug/L (σ% = 7), respectively, which, at 91% dissolution, suggest that 100% AMT dissolution was essentially achieved. Moreover the y-value is 0.745, which indicates that most of the W dissolved as WO4(2-) .

The average temperature varied in the range 19.8 -22.0 °C, with 19.8 °C as the single value below 20.0 ° C, which was not expected to affect the reaction kinetics. With the maximum temperature of 22.0 °C, essentially all temperatures fell within the 20-23 °C proposed in the T/D guidance document. The average D.O. readings met or exceeded the >70% saturation criterion.

All target 8.5 pH levels in the W-series for the test substance lay in the range 8.3-8.7, which is the variability proposed from the T/D guidance.

Conclusions:
Ammonium metatungstate was readily soluble, dissolving within a few minutes of contact with the pH 8.5 medium. The W and WO4(2-) concentrations at 24 h for AMT were 65,467 ug/L (σ% = 2) and 87,880 ug/L (σ% = 7), respectively, which, at 91% dissolution, suggest that 100% AMT dissolution was essentially achieved. Moreover the y-value is 0.745, which indicates that most of the W dissolved as WO4(2-) .

Description of key information

Information on the water solubility of ammonium metatungstate is available from a Transformation/Dissolution (T/D) test, in which ammonium metatungstate yielded a release of 65.47 mg dissolved tungsten/L at 100 mg AMT/L loading and a pH of 8.5.

Key value for chemical safety assessment

Water solubility:
65.47 mg/L
at the temperature of:
21 °C

Additional information

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