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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:
Testing was conducted between 30 September 2009 and 13 October 2009
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
EU Method A.6 (Water Solubility)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
Date of inspection: 2008-08-19 Date of Signature: 2009-03-04
Type of method:
flask method
Remarks:
The determination was carried out using the flask method, Method A6 Water Solubility of Commission Regulation (EC) No 440/2008 of 30 May 2008.
Water solubility:
> 23.8 - < 25.1 other: % w/w
Temp.:
20 °C
pH:
9.2
Details on results:
Please see section Remarks on results.

Preliminary test:

The sample concentrations and observations recorded on completion of each 24 hour equilibration period are shown in the following tables:

Observations after Equilibration at 30°C

Sample
Identity

Concentration
(% w/w)

Observations

1

5.1

Clear colourless solution, free from any excess, un-dissolved test material.

2

10.1

Clear colourless solution, free from any excess, un-dissolved test material.

3

15.2

Clear colourless solution, free from any excess, un-dissolved test material.

4

20.0

Clear colourless solution, free from any excess, un-dissolved test material.

5

25.1

Clear colourless solution, free from any excess, un-dissolved test material.

Observations after Equilibration at 20°C

Sample
Identity

Concentration
(% w/w)

Observations

1

5.1

Clear colourless solution, free from any excess, un-dissolved test material.

2

10.1

Clear colourless solution, free from any excess, un-dissolved test material.

3

15.2

Clear colourless solution, free from any excess, un-dissolved test material.

4

20.0

Clear colourless solution, free from any excess, un-dissolved test material.

5

25.1

Clear colourless solution containing a small quantity of crystallised excess, un-dissolved test material.

Observations after Equilibration at 10°C

Sample
Identity

Concentration
(% w/w)

Observations

1

5.1

Clear colourless solution, free from any excess, un-dissolved test material.

2

10.1

Clear colourless solution, free from any excess, un-dissolved test material.

3

15.2

Opaque solid containing no visible solution/liquid.

4

20.0

Opaque solid containing no visible solution/liquid.

5

25.1

Opaque solid containing no visible solution/liquid.

 


The solution pH’s on completion of the preliminary test are shown in the following table:

Sample
Identity

Concentration
(% w/w)

Solution pH

1

5.1

9.2

2

10.1

9.2

3

15.2

9.0

4

20.0[1]

*

5

25.1

*

Preliminary test result:     Solubility at 30.0°C: Greater than 25.1% w/w
                                     Solubility at 20.0°C: In the range 20.0 to 25.1% w/w
                                       Solubility at 10.0°C: In the range 10.1 to 15.2% w/w            

Definitive test:

The sample concentrations, observations recorded and solution pH on completion of the 24 hour equilibration period at their respective temperatures are shown in the following tables:

Observations for 30°C Samples

Sample
Identity

Concentration
(% w/w)

Observations

Solution pH

1

29.8

Clear colourless solution containing a quantity
 of crystalline, excess, un-dissolved test material.

9.2

2

35.1

Clear colourless solution containing a quantity
 of crystalline, excess, un-dissolved test material.

*

3

39.9

Small volume of a clear colourless solution and a quantity of excess, un-dissolved test material.

*

 

Observations for 20°C Samples

Sample
Identity

Concentration
(% w/w)

Observations

Solution pH

1

21.2

Clear colourless solution, free from any excess, un-dissolved test material.

9.1

2

21.8

Clear colourless solution, free from any excess, un-dissolved test material.

9.2

3

22.8

Clear colourless solution, free from any excess, un-dissolved test material.

9.1

4

23.8

Clear colourless solution, free from any excess, un-dissolved test material.

9.1

Observations for 10°C Samples

Sample
Identity

Concentration
(% w/w)

Observations

Solution pH

1

11.0

Clear colourless solution, free from any excess, un-dissolved test material.

9.2

2

12.0

Clear colourless solution, free from any excess, un-dissolved test material.

9.2

3

13.0

Clear colourless solution, containing a quantity of un-dissolved gelatinous material

9.0

4

14.0

Clear colourless solution, free from any excess, un-dissolved test material.

9.2

Definitive test result:        Solubility at 30.0°C: In the range 25.1 to 29.8% w/w
                                     Solubility at 20.0°C: In the range 23.8 to 25.1% w/w
                                       Solubility at 10.0°C: In the range 14.0 to 15.2% w/w


Conclusions:
Interpretation of results (migrated information): very soluble (> 10000 mg/L)
The water solubility of the test material was determined by visual assessment, using a flask method based on Method A6 Water Solubility of Commission Regulation (EC) No 440/2008 of 30 May 2008. The results are shown in the following table:

Test Temperature Water Solubility Typical Solution pH
30.0 ± 0.5°C In the range 25.1 to 29.8% w/w 9.2
20.0 ± 0.5°C In the range 23.8 to 25.1% w/w 9.2
10.0 ± 0.5°C In the range 14.0 to 15.2% w/w 9.2

The temperature range 10 to 30°C had a significant influence on the observed solubility of the test material. An assessment of the solubility of the test material over the environmentally relevant pH range of 4 to 9 was performed from water solubility data for the related test material sodium dihydrogenorthophosphate (sourced from Harlan Laboratories Ltd project numbers 2920/0001). From this data it could be concluded that the solubility of the test material would increase significantly as the pH decreased over the pH range of 9 to 4 (solubility in the range 50.2% to 52.0% w/w, 20°C, pH 3.6 to 4.0). However, it must be noted that such an increase would only be observed if significant buffering capacity was present which prevented the formation of an alkali solution as formed on dissolution of the test material.
This study is conducted according to an appropriate guideline and under the conditions of GLP and therefore the study is considered to be acceptable and to adequately satisfy both the guideline requirement and the regulatory requirement as a key study for this endpoint.
Executive summary:
The water solubility of the test material was determined by visual assessment, using a flask method based on Method A6 Water Solubility of Commission Regulation (EC) No 440/2008 of 30 May 2008.  The results are shown in the following table:

Test Temperature

Water Solubility

Typical Solution pH

30.0±0.5°C

In the range 25.1 to 29.8% w/w

9.2

20.0±0.5°C

In the range 23.8 to 25.1% w/w

9.2

10.0±0.5°C

In the range 14.0 to 15.2% w/w

9.2

The temperature range 10 to 30°C had a significant influence on the observed solubility of the test material. An assessment of the solubility of the test material over the environmentally relevant pH range of 4 to 9 was performed from water solubility data for the related test material sodium dihydrogenorthophosphate (sourced from Harlan Laboratories Ltd project numbers 2920/0001). From this data it could be concluded that the solubility of the test material would increase significantly as the pH decreased over the pH range of 9 to 4 (solubility in the range 50.2% to 52.0% w/w, 20°C, pH 3.6 to 4.0). However, it must be noted that such an increase would only be observed if significant buffering capacity was present which prevented the formation of an alkali solution as formed on dissolution of the test material.

Description of key information

The water solubility of disodium hydrogenorthophosphate was determined according to EU Method A.6 (Water solubility) and under the conditions of GLP. 

Key value for chemical safety assessment

Additional information

The water solubility of the test material was determined by visual assessment, using a flask method based on Method A6 Water Solubility of Commission Regulation (EC) No 440/2008 of 30 May 2008.  The results are shown in the following table:

Test Temperature

Water Solubility

Typical Solution pH

30.0±0.5°C

In the range 25.1 to 29.8% w/w

9.2

20.0±0.5°C

In the range 23.8 to 25.1% w/w

9.2

10.0±0.5°C

In the range 14.0 to 15.2% w/w

9.2

The temperature range 10 to 30°C had a significant influence on the observed solubility of the test material. An assessment of the solubility of the test material over the environmentally relevant pH range of 4 to 9 was performed from water solubility data for the related test material sodium dihydrogenorthophosphate (sourced from Harlan Laboratories Ltd project numbers 2920/0001). From this data it could be concluded that the solubility of the test material would increase significantly as the pH decreased over the pH range of 9 to 4 (solubility in the range 50.2% to 52.0% w/w, 20°C, pH 3.6 to 4.0). However, it must be noted that such an increase would only be observed if significant buffering capacity was present which prevented the formation of an alkali solution as formed on dissolution of the test material.