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Physical & Chemical properties

Water solubility

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Endpoint:
water solubility
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
2012
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
comparable to guideline study
Qualifier:
according to guideline
Guideline:
other: ISO 4311
Deviations:
not specified
Principles of method if other than guideline:
-
GLP compliance:
no
Type of method:
other: Determination of critical micelle concentration
Water solubility:
0.23 g/L
Temp.:
20 °C
pH:
6.4

The surface tension vs. concentration plot shows a minimum. In accordance with ISO 4311, the cmc is taken as the minimum. The standard error in the cmc is estimated from the uncertainty of the slope of the low concentration branch of the plot. The critical micelle concentration obtained is thus 0.23 ±0.07 g/L.

Conclusions:
Water solubility determined as critical micelle concentration: 0.23±0.07 g/L
Executive summary:

The critical micelle concentration of the test item was determined from a plot of surface tension versus concentration of the test item in water in a well reported study according to national testing guideline DIN ISO 4311. The critical micelle concentration is an appropriate parameter to fully describe the water solubility behaviour of surface active materials.

Endpoint:
water solubility
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
comparable to guideline study
Qualifier:
according to guideline
Guideline:
EU Method A.6 (Water Solubility)
Qualifier:
according to guideline
Guideline:
OECD Guideline 105 (Water Solubility)
GLP compliance:
no
Type of method:
flask method
Water solubility:
> 250 g/L
Temp.:
20 °C
pH:
8.03

The pre-test shows formation of gel with 4.0526 g of test item into 10 mL of water. Total weight of gel is then approx. 14.1 g. This is equivalent to 29 % (w/w) of test item in solution / gel.

As the density of the water will significantly increase with addition of the test item, it can be concluded that water solubility is about 290 g / L, resulting in a gel.

Due to the fact that the formation of the gel is a continuous process and no discrete point can be identifed at which dissolution in water switches to gelling, the water solubility can be approximated to > 250 g / L.

Description of key information

water solubility: > 250 g/L at 20 °C (EU A.6, flask method)
critical micelle concentration: 0.23 ±0.07 g/L at 20 °C (DIN ISO 4311, tensiometer)

Key value for chemical safety assessment

Additional information

Two studies are available, determining the water solubility of Sodium methyl cocoyl taurate. The first study (conducted according to OECD 105), a pre-test showed the formation of gel with 4.0526 g of test item into 10 mL of water. As the density of the water would significantly increase with addition of the test item, it was concluded that water solubility is about 290 g/L, resulting in a gel. Due to the fact that the formation of the gel is a continuous process and no discrete point can be identifed at which dissolution in water switches to gelling, the water solubility was approximated to be > 250 g/L.

The second test was performed according to ISO 4311, i.e. the critical micelle concentration of the test item was determined in water. The critical micelle concentration is an appropriate parameter to fully describe the water solubility behaviour of surface active materials. The CMC for Sodium cocoyl taurate was estimated as 0.23 g/L