Ammonium wolframate

Water solubility

Link to relevant study record(s)

Reference

Reference 1

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:

other: 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.:

67.21 mg/L

Element analysed:

Total 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.:

92.972 mg/L

Element analysed:

Tungstate anion (WO4-2)

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

pH=8.5; 21°C

Details on results:

Ammonium wolframate was readily soluble, dissolving within a few minutes of contact with the pH 8.5 medium.

The W and WO4-- concentrations at 24 hr for the ammonium wolframate were 67,210 ug/L (σ% = 2) and 92,972 ug/L (σ% = 13), respectively, which, at 95% and 98% dissolution, suggest essentially 100% ammonium wolframate dissolution. Moreover, y is 0.723, which indicates that most of the W dissolved as WO4-- .

The average temperature 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 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 paratungstate was readily soluble, dissolving within a few minutes of contact with the pH 8.5 medium.
The W and WO4-2- concentrations at 24 hr for the APT were 67,210 ug/L (σ% = 2) and 92,972 ug/L (σ% = 13), respectively, which, at 95% and 98% dissolution, suggest essentially 100% ammonium paratungstate dissolution. Moreover, y is 0.723, which indicates that most of the W dissolved as WO4-2- .

Reference 2

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

Remarks:

Data from peer-reviewed 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 was chosen for inclusion in the handbook. Reference sources were not provided for this parameter, nor was the experimental method.

GLP compliance:

no

Key result

Water solubility:

20 g/L

Conc. based on:

other: g WO3/L

Temp.:

20 °C

pH:

ca. 7

Remarks on result:

completely miscible

Key result

Water solubility:

60 g/L

Conc. based on:

other: g WO3/L

Temp.:

90 °C

pH:

ca. 7

Remarks on result:

completely miscible

Details on results:

Assumed to be tested at neutral pH as no pH data were reported.

Conclusions:

Ammonium paratungstate water solubility has been reported as 20 g WO3 equivalents/L at 20 °C.

Description of key information

Ammonium paratungstate (APT) water solubility has been reported as 20 g WO3 equivalents/L at 20 °C.  However solubility is also assessed through Transformation/Dissolution testing, which yielded a release of 67.21 mg dissolved tungsten/L at 100 mg APT/L loading and a pH of 8.5.

Key value for chemical safety assessment

Water solubility:

67.21 mg/L

at the temperature of:

21 °C