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Physical & Chemical properties

Water solubility

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Reference
Endpoint:
water solubility
Type of information:
experimental study
Adequacy of study:
key study
Study period:
November 2011 to February 2012
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other:
Remarks:
Valid without restriction; comparable to guideline study
Qualifier:
equivalent or similar to guideline
Guideline:
other: OECD Guideline for testing of chemicals - draft proposal - February 2001. Transformation dissolution of metals and metal compounds in aqueous media
Qualifier:
equivalent or similar to guideline
Guideline:
other: The Standard Operating Procedure for the Transformation/Dissolution of Metals and Sparingly Soluble Metal Compounds, Version February 2004; proposed by CANMET and LISEC
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: Transformation/Dissolution Test
Water solubility:
76 µg/L
Temp.:
19.6 °C
pH:
6.1
Remarks on result:
other: total dissolved W, pH screening test, time point 0 h, 100 mg/L loading
Water solubility:
567 µg/L
Temp.:
21.5 °C
pH:
6.07
Remarks on result:
other: total dissolved W, pH screening test, time point 24 h, 100 mg/L loading
Water solubility:
72 µg/L
Temp.:
21.4 °C
pH:
7.03
Remarks on result:
other: total dissolved W, pH screening test, time point 0 h, 100 mg/L loading
Water solubility:
635 µg/L
Temp.:
21.5 °C
pH:
7.01
Remarks on result:
other: total dissolved W, pH screening test, time point 24 h, 100 mg/L loading
Water solubility:
57 µg/L
Temp.:
20.1 °C
pH:
7.83
Remarks on result:
other: total dissolved W, pH screening test, time point 0 h, 100 mg/L loading
Water solubility:
780 µg/L
Temp.:
20.9 °C
pH:
7.87
Remarks on result:
other: total dissolved W, pH screening test, time point 24 h, 100 mg/L loading
Water solubility:
33 µg/L
Temp.:
22.6 °C
pH:
7.98
Remarks on result:
other: total dissolved W, 7 day full T/D-test, 1 mg/L loading
Water solubility:
239 µg/L
Temp.:
22.8 °C
pH:
7.8
Remarks on result:
other: total dissolved W, 7 day full T/D-test, 10 mg/L loading
Water solubility:
4 225 µg/L
Temp.:
23.5 °C
pH:
7.8
Remarks on result:
other: total dissolved W, 7 day full T/D-test, 100 mg/L loading
Water solubility:
106 µg/L
Temp.:
22.6 °C
pH:
7.8
Remarks on result:
other: total dissolved W, 28 day full T/D-test, 1 mg/L loading
Details on results:
Transformation / dissolution screening test of tungsten dioxide, showed a maximum tungsten release of 780 μg/L at pH 8, after 24 hours of incubation in OECD medium. A full transformation / dissolution study was performed at pH 8 with sample loadings of 1, 10 and 100 mg/L. A direct relationship between sample loading and metal released to the media, after seven days of T/D, with values of 33, 239 and 4225 μg/L for 1, 10 and 100 mg/L loading, respectively, could be observed.
The W-concentrations measured in the controls (blanks) were below detection limit.
Conclusions:
Interpretation of results (migrated information): slightly soluble (0.1-100 mg/L)
The test substance was found to be most soluble at a pH of 8. The respective W-concentrations of about 4.2 mg/L for the 7 day, 100 mg/L loadings at pH 8 indicate that the substance is slightly soluble.
Executive summary:

A transformation / dissolution (T/D) test equivalent to "OECD Guideline for testing of chemicals: Transformation dissolution of metals and metal compounds in aqueous media (2001)" was carried out to study the potential of tungsten dioxide to release metal to the environment. A 24 hour screening test to determine the pH of maximum tungsten release was performed at pHs of 6, 7 and 8 with a sample loading of 100 mg/L. An increasing release of metal as the pH goes from 6 to 8 was measured, 567 and 780 μg/L, respectively. Accordingly pH 8 was chosen to perform the full T/D test. The acute endpoint (7 days), was performed at a sample loading of 1, 10 and 100 mg/L; chronic endpoint was determined from the extension of the 1 mg/L loading test to 28 days. The results of the study indicate a direct relationship between sample loading and metal released to the media, after seven days of T/D, with values of 33, 239 and 4225 μg/L for 1, 10 and 100 mg/L loading, respectively. After 28 days a release of 106 µg/ml was measured with a sample loading of 1 mg/L.

Description of key information

A transformation/dissolution test equivalent to the OECD guideline for testing of chemicals on transformation dissolution of metals and metal compounds in aqueous media is available showing that tungsten dioxide is slightly soluble in water.

Key value for chemical safety assessment

Water solubility:
4.2 mg/L
at the temperature of:
23.5 °C

Additional information

Tungsten dioxide was found to be most soluble at a pH of 8. The respective tungsten concentrations of about 4.2 mg/L for the 7 day, 100 mg/L loadings at pH 8 indicate that the substance is slightly soluble (0.1–100 mg/L).