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Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

09 - 12 Apr 2018

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

water solubility based on measured phosphate concentration

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

GLP compliance:

no

Type of method:

flask method

Water solubility:

1 275 g/L

Conc. based on:

other: total phosphate

Temp.:

20 °C

pH:

12.3

Results and Discussion

Results of the preliminary visual estimation of the water solubility

Amount of test item (mg)	Added volume of dist. Water (g)	Total Volume (mL)	Appearance of the mixture
1008	0.5	0.9	Clear solution after 90 minutes shaking at 20°C
1009	1	1.4	Clear Solution after 10 minutes shaking at 20°C

 

According to the guideline method a preliminary visual estimation of the water solubility was conducted, which revealed a high water solubility of the test substance >1000 g/L. The quantity of the tests substance needed to saturate the desired volume of water was therefore estimated by a second, extended preliminary stirring test. However, the apparently extremely hydrophilic nature of the tests substance made the use of additional descriptors (apart from saturation) necessary. The viscosity related mixing problems is a particularly limiting factor.

Test No.	Amount of test item (g)	Added volume of dist. Water (mL)	Total Volume (mL)	Appearance of the mixture
1	5.16	2.05	4.15	homogenous/could be stirred
2	5.015	1.519	3.78	homogenous/very viscous >5000 mPas, but could be stirred after 30 minutes of standing
3	4.992	1.006	3.41	heterogeneous/could not be stirred
4	5.056	0.496	n.d.	heterogeneous/could not be stirred

 

According to this preliminary estimation, the water solubility of the test item was ≥ 1243 g/L (Test No. 1). Therefore the preferred method for further testing was the flask method.

	(solid substance ref.)	24 h experiment	48 h experiment	72 h experiment
Amount of test item (g)	-	4.961	5.055	5.100
Added volume of dist. Water (ml)	-	1.563	1.504	1.487
Sample Mass (g)	-	6.52	6.56	6.59
Mass fraction of the item in the mixture (%)	-	76.0%	77.1%	77.4%
Sample Volume (mL)	-	3.77	3.79	3.80
Stirring/equilibration time at 30 °C	-	24	48	72
Total Volume (mL)	-	3.77	3.79	3.80
Sample pH	-	12.3	12.3	12.3
Concentration of total phosphates measured (g/kg as PO4)	224	158	169.5	167
Theoretical concentration of phosphate upon 100% dissolution (g/kg as PO4)	-	170.33	172.64	173.43
Solubility (g/L)	-	1222	1311	1291

 

Based on these results, the average water solubility of the test item was determined to be 1275 g/L.

Conclusion

Water Solubility: 1275 g/L at 20°C and pH 12.3 (OECD 105, flask method)

 

Additional information: The water solubility of the substance is calculated based on the measured concentration of the total phosphate. The test is considered valid since the deviation of the three experiments is below 15%.

 

 

Key value for chemical safety assessment

Water solubility:

1 275 g/L

at the temperature of:

20 °C