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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
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
other: OECD environmental health and safety publications. Series on testing and assessments N° 29. Guidance document on transformation/dissolution of metals and metal compounds in aqueous media. July 2001.
GLP compliance:
not specified
Type of method:
other: transformation/dissolution test
Specific details on test material used for the study:
metallic zinc rods were mounted in epoxy holders to expose the cross-sectional surface to the solution.
Key result
Type of test:
full transformation/dissolution test - metals and sparingly soluble metal compounds
Mean dissolved conc.:
46.7 µg/L
Element analysed:
Zn
Loading of aqueous phase:
1 mg/L
Incubation duration:
168 h
Test conditions:
pH6
Remarks on result:
other: freshly poilished zinc surface tested
Key result
Type of test:
full transformation/dissolution test - metals and sparingly soluble metal compounds
Mean dissolved conc.:
338.7 µg/L
Element analysed:
Zn
Loading of aqueous phase:
10 mg/L
Incubation duration:
168 h
Test conditions:
pH 6
Remarks on result:
other: freshly polished zinc surface tested
Key result
Type of test:
full transformation/dissolution test - metals and sparingly soluble metal compounds
Mean dissolved conc.:
2 655.7 µg/L
Element analysed:
Zn
Loading of aqueous phase:
100 mg/L
Incubation duration:
168 h
Test conditions:
pH 6
Remarks on result:
other: freshly polished zinc surface tested
Key result
Type of test:
full transformation/dissolution test - metals and sparingly soluble metal compounds
Mean dissolved conc.:
185.7 µg/L
Element analysed:
Zn
Loading of aqueous phase:
1 mg/L
Incubation duration:
672 h
Test conditions:
pH 6
Remarks on result:
other: freshly polished zinc surface tested
Type of test:
full transformation/dissolution test - metals and sparingly soluble metal compounds
Mean dissolved conc.:
1 329 µg/L
Element analysed:
Zn
Loading of aqueous phase:
100 mg/L
Incubation duration:
168 h
Test conditions:
pH 6 after passivation of 3 days
Remarks on result:
other: zinc surface was passivated for 3 days in dry atmosphere before testing
Type of test:
full transformation/dissolution test - metals and sparingly soluble metal compounds
Mean dissolved conc.:
9.7 µg/L
Element analysed:
Zn
Loading of aqueous phase:
1 mg/L
Incubation duration:
168 h
Test conditions:
pH 8
Remarks on result:
other: freshly polished zinc surface tested
Type of test:
full transformation/dissolution test - metals and sparingly soluble metal compounds
Mean dissolved conc.:
95.7 µg/L
Element analysed:
Zn
Loading of aqueous phase:
10 mg/L
Incubation duration:
168 h
Test conditions:
pH 8
Remarks on result:
other: freshly polished zinc surface tested
Type of test:
full transformation/dissolution test - metals and sparingly soluble metal compounds
Mean dissolved conc.:
551 µg/L
Element analysed:
Zn
Loading of aqueous phase:
100 mg/L
Incubation duration:
168 h
Test conditions:
pH 8
Remarks on result:
other: freshly polished zinc surface tested
Type of test:
full transformation/dissolution test - metals and sparingly soluble metal compounds
Mean dissolved conc.:
25.7 µg/L
Element analysed:
Zn
Loading of aqueous phase:
1 mg/L
Incubation duration:
672 h
Test conditions:
pH 8
Remarks on result:
other: freshly polished zinc surface tested
Details on results:
Control at T= 0 of 8.3 µg Zn/L was subtracted from the results.
the repeatability of the results was sufficient, with coefficient of variation of 7-23% (168 h loading), and 24% (672 h loading)

Conclusions:
Standard TD test on metallic zinc, results useful for assessing dissollution of zinc ions from metallic zinc surface
Executive summary:

The dissolution of zinc ions from metallic zinc surface was studied by a standard TD test (OECD 29). Results obtained at pH 6 and pH 8 show the significantly higher dissolution of zinc at pH 6. Therefore, TD results obtained at pH 6 were used for classification.

Zinc dissolution results used for acute classification are those obtained after 168 h at pH 6: 46.7 µg Zn/L, 338.7 µg Zn/L, and 2655.7 µg Zn/L obtained after loading of 1, 10, and 100mg Zn surface, respectively. For the chronic classification, zinc dissolution of 185.7 µg Zn/L obtained after 672 h , was used.

Passivation of the zinc surface during the 7 days test was studied by drying the metallic surface after the test, keeping it for 3 days in dry atmosphere, and testing again. Zinc release from the metallic surface after passivation was 50% of the original release measured before passivation.

Description of key information

The dissolution of zinc ions from metallic zinc surface was studied by a standard TD test (OECD 29). Results obtained at pH 6 and pH 8 show the significantly higher dissolution of zinc at pH 6. Therefore, TD results obtained at pH 6 were used for classification.

Zinc dissolution results used for acute classification are those obtained after 168 h at pH 6: 46.7 µg Zn/L, 338.7 µg Zn/L, and 2655.7 µg Zn/L obtained after loading of 1, 10, and 100mg Zn surface, respectively. For the chronic classification, zinc dissolution of 185.7 µg Zn/L obtained after 672 h , was used.

Passivation of the zinc surface during the 7 days test was studied by drying the metallic surface after the test, keeping it for 3 days in dry atmosphere, and testing again. Zinc release from the metallic surface after passivation was 50% of the original release measured before passivation.

Key value for chemical safety assessment

Water solubility:
0.1 mg/L
at the temperature of:
20 °C

Additional information

The solubility of zinc metal powder at pH >6.93 - <8.57 was determined according to OECD 105. The solubility of the powder was 0.1mg/L. The solubility characteristics of zinc in massive form are to be assessed by the Transformation/Dissolution (TD) approach (OECD29). The solubility data obtained by classical "water solubility" testing are less relevant. Further details on the TD results see CIMM 2010.