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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
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 for cross-reference:
reference to same study
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:
Standardised 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 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 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 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 °C, with 19.9 °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 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

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