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Physical & Chemical properties

Water solubility

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Endpoint:
water solubility
Type of information:
experimental study
Adequacy of study:
key study
Study period:
from 01 DEC 2005 to 30 MARCH 2006
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 105 (Water Solubility)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method A.6 (Water Solubility)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of method:
other: Preliminary test comprising stirring
Key result
Water solubility:
> 600 g/L
Remarks on result:
other: Although the temperature of measurement was not reported, ambient conditions are anticipated. The pH is not routinely measured during the preliminary test.

Water solubility of cerium trinitrate

Sample

Initial Weight of Test Item

Water
added

Volume of aqueous test item solution

Solubility in
water

Solubility in
water

Reported value

No.

[g]

[ml]

[ml]

[g/l]

[g/l]

1

2.09

2

about 4

> 500

2

5.16

5

about 10

> 500

3

6.02

5

about 10

> 600

> 600

Conclusions:
The water solubility was determined to be > 600 g/l. Although the temperature of measurement was not reported, ambient conditions are anticipated. The pH was not measured.
Executive summary:

The water solubility of cerium trinitrate was assessed according to OECD guideline 105. In such a study, a preliminary test is done to determine the appropriate method to apply. However, in the present case, the pre-test revealed that cerium trinitrate is totally soluble in water. As a result, no additional main test was performed, and the water solubility of cerium trinitrate was determined by visual judgment to be > 600 g/L at room temperature.

Endpoint:
water solubility
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
GLP compliance:
no
Type of method:
other: dissolution study
Water solubility:
120 µg/L
Conc. based on:
test mat.
Remarks:
Ce(NO3)3.6H2O
Loading of aqueous phase:
0.46 other: µM Ce
Incubation duration:
28 d
pH:
4
Water solubility:
>= 1 - <= 5 µg/L
Conc. based on:
test mat.
Remarks:
Ce(NO3)3.6H2O
Loading of aqueous phase:
0.46 other: µM Ce
Incubation duration:
28 d
pH:
>= 7 - <= 9
Details on results:
The solubility of Ce3+ appears to be higher at acidic pH which is anticipated to be at least partly explained by the low solubility of Ce hydroxides that are formed at higher pH. Furthermore, Ce3+ is considered more soluble than Ce4+ and hence the presence of oxygen to enable oxidation of Ce3+ also influences the water solubility.
In the presence of NaCl, the concentration at pH 4 test conditions is stable over time at approximately 60% of the nominal Ce concentration; at higher pH values initial concentrations were at approximately 10% of nominal and decreased to values around the limit of detection (not further specified).
In the presence of artificial soil solution, significantly higher solubilities are noted (90 to 100% of nominal at pH 4 and 7, but only at or around the limit of detection at pH 9). This highest solubility at pH 4 and 7 can be related to the formation of ion pairs with the components of the solution (Ce3+ with chloride, sulphate and nitrate).

Temperature of measurement was not reported; ambient conditions are anticipated.

It is thus postulated that the solubility of Ce3+ is closely related to the pH and oxygen availability, which determines the reduction and oxidation rates, and the solution matrix that determines the formation of ion pairs.

Based on available data it is estimated that the water solubility of Ce(NO3)3.6H2O in the presence of sodium chloride, is approximately 120 μg/L at pH 4. At pH 7 and 9 a decrease in concentration was observed in time; as no stable concentration was reached it is estimated that the water solubilty under these conditions is in the range of 1-5 μg/L, but could eventually be lower.
In the presence of artificial soil, no maximum water solubility could be extracted from the data at pH 4 and 7, as measured concentrations were at the nominal level. At pH 9 however initially high concentrations decreased from day 1 onwards; as no stable concentration was reached it is estimated that the water solubilty under these conditions is in the range of 1-5 μg/L, but could eventually be lower.
Conclusions:
In a dissolution test over 28 days and in the presence of sodium chloride, the water solubility of Ce(NO3)3.6H2O is estimated to be approximately 120 μg/L at pH 4. At pH 7 and 9 a decrease in concentration was observed over time; as no stable concentration was reached it is estimated that the water solubilty under these conditions is in the range of 1-5 μg/L, but could eventually be lower. In the presence of artificial soil, no maximum water solubility could be extracted from the data at pH 4 and 7, as measured concentrations were at the nominal level. At pH 9 however initially high concentrations decreased from day 1 onwards to approx 1-5 μg/L, but could eventually be lower.

Description of key information

The water solubility of cerium trinitrate was determined in a GLP study to be > 600 g/L at ambient conditions using a preliminary test with visual observations in accordance with EC test method A.6 (Weissenfeld, 2006).

Key value for chemical safety assessment

Water solubility:
600 g/L
at the temperature of:
20 °C

Additional information

Although the temperature of measurement was not reported in the GLP key study, ambient conditions are anticipated.

In a supporting dissolution study (Cornelis et al., 2011) performed over 28 days and in the presence of sodium chloride, the water solubility of Ce(NO3)3.6H2O was estimated to be approximately 120 μg/L at pH 4. At pH 7 and 9 a decrease in concentration was observed in time; hence it is estimated that the water solubility under these conditions is in the range of 1-5 μg/L, but could eventually be lower. In the presence of artificial soil, no maximum water solubility could be extracted from the data at pH 4 and 7, as measured concentrations were at the nominal level. At pH 9 however initially high concentrations decreased from day 1 onwards to approx 1-5 μg/L, but could eventually be lower. This supporting study thus revealed that the solubility of cerium trinintrate was very low under environmentally and physiologically relevant conditions.