Praseodymium trinitrate

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2012-02-28

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

other: Preliminary estimate of solubility by visual judgement with an investigation of the influence of pH variations.

Key result

Water solubility:

> 1 320 - < 1 670 g/L

Temp.:

20 °C

pH:

ca. 1

Remarks on result:

other: The test item was completely dissolved at 1320 g/L while precipitation was observed at 1670 g/L.

Water solubility:

1 300 g/L

Temp.:

19.7 °C

pH:

4.9

Remarks on result:

other: The test item was completely dissolved at 1300 g/L, revealing no effect on solubility of a pH = ca. 5.

Water solubility:

1 300 g/L

Temp.:

20.4 °C

pH:

5.02

Remarks on result:

other: The test item was completely dissolved at 1300 g/L, revealing no effect on solubility of a pH = ca. 5.

Temp.:

24.2 °C

pH:

6.27

Remarks on result:

other: A significant impact of pH = ca. 7 was observed on solubility; the test item precipitating and giving a pasty solution. No maximum solubility could be determined.

Details on results:

Due to the high solubility observed during the assay without pH adjustment (i.e. pH = ca. 1), no definitive test was conducted. The experiments intended to investigate the pH effect were stopped after reaching the pH of 6.27 as it was not possible to reach a higher pH value due to the difficulty to homogenize the solution.

During the preliminary estimation it was found that the sample was completely miscible with water in the assays 1, 2, 3 and 5. The test item:water 5:1 ratio (assay 4) did not mix completely. The maximum water solubility is therefore estimated to be in the range of the concentrations prepared for assay 2 and 3 (between 1.32 and 1.67 g/mL).

The pH of assay 2, 3 and 5 were determined to be 2.0, 1.0 and 0.9, respectively. The other samples could not be measured due to insufficient sample material.

At pH 5 the substance stayed completely into solution. Taken the amount of sodium hydroxide added into account, the final concentration was calculated to be 1.30 g/mL.

The pH 7 could not be reached and the test was terminated at pH 6.27 where the solution became pasty and a greenish precipitate was observed. Although it can be concluded that increasing the pH will lower the water solubility, no maximum solubility could be determined at pH 7.

Conclusions:

The substance is concluded to be very soluble in water with a maximum solubility in the range of 1.32 to 1.67 kg/L, at 20°C and a pH of approx 1. The maximum solubility did not change when increasing the pH to approx 5, while above (i.e. pH=6.27, not possible to reach a pH>7) the test item precipitated and the solution became pasty.

Description of key information

In a GLP study according to the preliminary test as specified in test method EC A.6, praseodymium trinitrate was determined to be very soluble in water with a maximum solubility in the range of 1.32 to 1.67 kg/L, under ambient conditions (Demangel B, 2012). It is important to note that the solubility was significantly decreased when the pH was adjusted to environmental values (i.e. pH = 6.27) due to the precipitation of the test item. 

Key value for chemical safety assessment

Water solubility:

100 g/L

at the temperature of:

20 °C

Additional information

Although the maximum solubility in water was determined to be in the range of 1.32x10E3 g/L to 1.67x10E3 g/L, a bounded value of 100 g/L is used as the key value for chemical safety assessment, being the maximum value for water solubility as defined in the EUSES program. The maximum solubility did not change when increasing the pH to approx 5, while above (i.e. pH=6.27, not possible to reach a pH>7) the test item precipitated and the solution became pasty.