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Physical & Chemical properties

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
Study period:
NA to: 2009-08-25
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).
Reason / purpose:
reference to same study
Qualifier:
according to
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:
not specified
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. 6.615 mg/L
Element analysed:
Tungsten
Loading of aqueous phase:
100 mg/L
Incubation duration:
24 h
Test conditions:
21°C; pH=8.5
Key result
Type of test:
screening transformation/dissolution test - sparingly soluble metal compounds
Mean dissolved conc.:
ca. 9.118 mg/L
Element analysed:
Tungstate anion
Loading of aqueous phase:
100 mg/L
Incubation duration:
24 h
Test conditions:
21°C; pH=8.5
Key result
Type of test:
full transformation/dissolution test - metals and sparingly soluble metal compounds
Mean dissolved conc.:
0.145 mg/L
Element analysed:
Tungsten
Loading of aqueous phase:
1 mg/L
Incubation duration:
7 d
Test conditions:
21°C; pH=8.5
Key result
Type of test:
full transformation/dissolution test - metals and sparingly soluble metal compounds
Mean dissolved conc.:
ca. 188 mg/L
Element analysed:
Tungstate anion
Loading of aqueous phase:
1 mg/L
Incubation duration:
7 d
Test conditions:
21°C; pH=8.5
Key result
Type of test:
full transformation/dissolution test - metals and sparingly soluble metal compounds
Mean dissolved conc.:
ca. 3.774 mg/L
Element analysed:
Tungsten
Loading of aqueous phase:
10 mg/L
Incubation duration:
7 d
Test conditions:
21°C; pH=8.5
Key result
Type of test:
full transformation/dissolution test - metals and sparingly soluble metal compounds
Mean dissolved conc.:
ca. 4.984 mg/L
Element analysed:
Tungstate anion
Loading of aqueous phase:
10 mg/L
Incubation duration:
7 d
Test conditions:
21°C; pH=8.5
Key result
Type of test:
full transformation/dissolution test - metals and sparingly soluble metal compounds
Mean dissolved conc.:
ca. 48.644 mg/L
Element analysed:
Tungsten
Loading of aqueous phase:
100 mg/L
Incubation duration:
7 d
Test conditions:
21°C; pH=8.5
Key result
Type of test:
full transformation/dissolution test - metals and sparingly soluble metal compounds
Mean dissolved conc.:
ca. 65.081 mg/L
Element analysed:
Tungstate anion
Loading of aqueous phase:
100 mg/L
Incubation duration:
7 d
Test conditions:
21°C; pH=8.5
Key result
Type of test:
full transformation/dissolution test - metals and sparingly soluble metal compounds
Mean dissolved conc.:
ca. 0.201 mg/L
Element analysed:
Tungsten
Loading of aqueous phase:
1 mg/L
Incubation duration:
28 d
Test conditions:
21°C; pH=8.5
Key result
Type of test:
full transformation/dissolution test - metals and sparingly soluble metal compounds
Mean dissolved conc.:
0.265 mg/L
Element analysed:
Tungstate anion
Loading of aqueous phase:
1 mg/L
Incubation duration:
28 d
Test conditions:
21°C; pH=8.5
Details on results:
24-hr screening tests at pH 8.5:
The T/D data for the 24-hr screening tests of the 100 mg/L loadings, reveal 24-hr W and WO4--concentrations of 6.615 mg/L and 9.118 mg/L, respectively, with an attendant y value of 0.725 that indicates most of the W in solution as the WO4-- anion. These concentrations represent about 8% dissolution of the W content of the blue tungsten oxide.

Definitive seven- and 28-day tests at pH 8.5
The T/D data for the 1 mg/L loadings exhibit exponential formation behaviour over the first 336 hr followed by approaches to limiting W and WO4-- concentrations of 0.201 mg/L and 0.265 mg/L, respectively, at 672 hr, which correspond to about 25% dissolution of the W in the blue tungsten oxide. As per the 672-hr value of 0.757 for y, essentially all of the W dissolved as WO4--.

For the 10 mg/L loadings, the concentrations of W and WO4-- increase over the seven days to values of 3.774 mg/L (σ% = 4) and 4.984 mg/L (σ% = 5), respectively. For the 100 mg/L loadings, 48.644 mg/L (σ% = 10) and 65. 081 mg/L (σ% = 8) for W and WO4-- were measured, respectively. These concentrations represented about 60% dissolution of the blue tungsten oxide W content. The average value of 0.781 for y suggests that the WO4-- anion accounted for most of the W in solution.

The average temperature among all seven- and 28-day tests 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 for the T/DP. 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/DP.

Conclusions:
The respective W and WO4-- concentrations of about 49 and 65 mg/L for the 7 day, 100 mg/L loadings at pH 8.5 corresponding to about 60% dissolution. The seven-day y value of 0.781, which indicated that most W dissolved as the WO4-- anion.

Description of key information

The test substance was found to be more soluble at a pH of 8.5 than 6. The respective W and WO4 concentrations of about 49 and 65 mg/L for the 7-day, 100 mg/L loadings at pH 8.5 corresponding to about 60% dissolution. The seven-day y value of 0.781, which indicated that all W dissolved as the WO4-anion..

Key value for chemical safety assessment

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

Additional information