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Physical & Chemical properties

Water solubility

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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:
test procedure in accordance with national standard methods
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.:
ca. 69.935 mg/L
Element analysed:
Total tungsten
Loading of aqueous phase:
100 mg/L
Incubation duration:
24 h
Test conditions:
21°C and pH=8.5
Key result
Type of test:
screening transformation/dissolution test - sparingly soluble metal compounds
Mean dissolved conc.:
ca. 75.585 mg/L
Element analysed:
Tungstate (WO42-)
Loading of aqueous phase:
100 mg/L
Incubation duration:
24 h
Test conditions:
21°C and pH=8.5
Details on results:
Sodium tungstate was readily soluble, dissolving within a few minutes of contact with the pH 8.5 medium.

The net 24-hr W concentration of 66,935 ug/L is about 20% greater than calculated for 100% dissolution. However, the corresponding WO4-- concentration of 75,585 ug/L is as expected for 101% dissolution. The 0.886 y value reflects the elevated W concentration.

The average temperature varied in the range 21.0-21.6 deg C, with 19.9 deg C as the single value below 20.0 deg C, which was not expected to affect the reaction kinetics. With the maximum temperature of 22.0 deg C, essentially all temperatures fell within the 20-23 deg 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:
Sodium tungstate was readily soluble, dissolving within a few minutes of contact with the pH 8.5 medium.

The net 24-hr W concentration of 66,935 ug/L is about 20% greater than calculated for 100% dissolution. However, the corresponding WO4-- concentration of 75,585 ug/L is as expected for 101% dissolution. The 0.886 y value reflects the elevated W concentration.
Endpoint:
water solubility
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Reason / purpose for cross-reference:
reference to same study
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 were chosen for inclusion in the handbook. Reference sources were not provided for this parameter, nor was the experimental method.
GLP compliance:
not specified
Key result
Water solubility:
ca. 0.575 g/cm³
Temp.:
0 °C
pH:
ca. 7
Key result
Water solubility:
ca. 0.732 g/cm³
Temp.:
21 °C
pH:
ca. 7
Key result
Water solubility:
ca. 0.969 g/cm³
Temp.:
100 °C
pH:
ca. 7

Description of key information

Sodium tungstate water solubility has been reported as 732 g/L @ 21 degrees C.  However, solubility is also assessed through Transformation-Dissolution testing, which yielded a release of 66.93 mg dissolved tungsten/L @ 100 mg sodium tungstate/L loading and a pH of 8.5.

Key value for chemical safety assessment

Water solubility:
73 200 mg/L
at the temperature of:
21 °C

Additional information