Zinc

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

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.