Hexaammonium wolframate

Water solubility

Link to relevant study record(s)

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