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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:
2012-04-03 to 2012-07-11
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 105 (Water Solubility)
Deviations:
yes
Remarks:
, exclusion of CO2 and O2; two vessels were set up in a parallel design, each vessel was sampled several times instead of sampling one vessel at every point in time.
Qualifier:
according to guideline
Guideline:
EU Method A.6 (Water Solubility)
Deviations:
yes
Remarks:
, exclusion of CO2 and O2; two vessels were set up in a parallel design, each vessel was sampled several times instead of sampling one vessel at every point in time.
GLP compliance:
yes (incl. QA statement)
Remarks:
signed, 2011-02-07
Type of method:
flask method
Specific details on test material used for the study:
Based on experiences from previous tests and in agreement with the monitor approx. 100 g of the test item was heated under argon to 100 °C in a water bath for easier handling and homogenisation.
Key result
Water solubility:
45.84 mg/L
Conc. based on:
element
Remarks:
Zn
Loading of aqueous phase:
1 000 g/L
Incubation duration:
>= 33 - <= 35 d
Temp.:
20 °C
pH:
>= 6.3 - <= 6.9
Remarks on result:
other: St.dev.=± 0.93 mg Zn/L
Key result
Water solubility:
309.4 mg/L
Conc. based on:
test mat. (dissolved fraction)
Loading of aqueous phase:
1 000 g/L
Incubation duration:
>= 33 - <= 34 d
Temp.:
20 °C
pH:
>= 6.3 - <= 6.9
Remarks on result:
other: St.dev.: ± 6.3 mg/L
Details on results:
Observations
During the study, undissolved test material was observed at bottom and walls of the flasks. After centrifugation and filtration of samples, the solution was clear. In order to verify this, the turbidity was measured in the filtered samples.

Temperature
The temperature in the thermostatically controlled water bath was monitored by a thermo data logger. The mean temperature was 19.3 ± 0.3 °C.

Monitoring oxygen amount
During the experimental performance of the test, the oxygen concentration in the acrylic glass box was monitored with a MICRO IV oxygen sensor prior and after sampling. The oxygen values (in %) remained around 0 %. Slightly negative values, though impossible, are due to measurement uncertainties of the device at 0 % oxygen.

pH values
The pH in test vessels was in the range of 6.3 – 6.9 in vessel A and 6.3 – 6.8 in vessel B. Measured pH in method blanks was in the range of 5.8 – 6.8. The temperature measured by the pH meter is not within 20.0 ± 1.0 °C. Considering the pH values the pH meter is calibrated every workweek and verified every working day. A calibration of the temperature was not performed because a reference thermometer and a thermo data logger were applied during the test.

Turbidity measurements
The turbidity was measured after centrifugation and filtration to verify that only dissolved zinc concentrations would get measured. The turbidity was always <<1 NTU, indicating that no undissolved material was left after the filtration step.

ICP-OES measurement
Zinc levels of method blanks were below the limit of detection (< 5.3 - < 45 μg Zn/L). All samples were analysed within twelve days after sampling. Constant Zn concentrations according to the study guideline OECD 105 as well as the Regulation 440/2008/EC A.6 were measured after day 33.

Constant zinc concentrations could be measured after 33 days (792 hours). The calculated variations between the last three sampling points were less than 15 % and no increase of the water solubility was observed. Thus, the validity criteria as foreseen in OECD 105 and Regulation 440/2008/EC A.6 were fulfilled.

The mean concentration was calculated.

Mean dissolved zinc concentration day 33 – day 35:

Vessel A: 45.30 ± 1.05 mg Zn/L

Vessel B: 45.67 ± 0.84 mg Zn/L

The calculated amount of VP 112/18 dissolved was calculated by:

= mean of measured values * 100 % / 14.7 % [percentage of zinc in test item]

mean calculated VP 112/18 dissolved day 33 – day 35:

Vessel A: 308.1 ± 7.2 mg/L

Vessel B: 310.7 ± 5.7 mg/L

 

Final results:

Under the conditions of this test (under exclusion of CO2 and O2, under inert argon gas; flask method; loadings of 1.0000 g/L test item in vessel A and B, respectively), a solubility equilibrium was reached after 33 days. The mean amount of dissolved zinc during the test at 20.0 ± 1.0°C is 45.48 ± 0.93 mg Zn/L (determined as dissolved zinc, separated by centrifugation and filtration from undissolved test item). This corresponds to dissolve VP 112/18 of 309.4 ± 6.3 mg/L. The pH in test vessels was in the range of 6.3 – 6.9 in vessel A and 6.3 – 6.8 in vessel B.

Conclusions:
A solubility equilibrium was reached after 33 days. The mean amount of dissolved zinc during the test at 20.0 ± 1.0°C is 45.48 ± 0.93 mg Zn/L (determined as dissolved zinc, separated by centrifugation and filtration from undissolved test item). This corresponds to dissolved VP 112/18 of 309.4 ± 6.3 mg/L.

Description of key information

Naphthenic acids, zinc salts, basic has a water solubility of 309.4 ± 6.3 mg/L at 20 ± 1.0 °C and pH 6.3 – 6.9.

In the Transformation/dissolution test (OECD Series 29) with naphthenic acids, zinc salts, basic, dissolved zinc concentrations of 149 µg/L and 188 µg/L were measured at pH 6 after 7 and 28 days whereas 118 µg/L and 154 µg/L were measured at pH 8 after 7 and 28 days, respectively.

Key value for chemical safety assessment

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

Additional information

Under the conditions of this test (under exclusion of CO2 and O2, under inert argon gas; flask method; loadings of 1.0000 g/L test item in vessel A and B, respectively), a solubility equilibrium was reached after 33 days. The mean amount of dissolved zinc during the test at 20.0 ± 1.0°C is 45.48 ± 0.93 mg Zn/L (determined as dissolved zinc, separated by centrifugation and filtration from undissolved test item). This corresponds to dissolved VP 112/18 of 309.4 ± 6.3 mg/L. The pH in test vessels was in the range of 6.3 – 6.9 in vessel A and 6.3 – 6.8 in vessel B.