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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:
From October 18, 2017 to November 22, 2017
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Reason / purpose:
reference to same study
Qualifier:
according to
Guideline:
other: OECD 115
Version / remarks:
27 July 1995
Deviations:
no
Qualifier:
according to
Guideline:
other: EU Method A5
Version / remarks:
30 May 2008
Deviations:
no
Principles of method if other than guideline:
Below the CMC, a surfactant is considered to be thermodynamically soluble in the water; whereas above the CMC, the solubility of a surfactant in water has been exceeded and the excess surfactant aggregates to form micelles. These micelles have significantly less effect on the surface tension of a solution and are considered not to be in solution. Thus, the water solubility of a surfactant may be expressed in terms of the CMC.
GLP compliance:
no
Remarks:
The study was conducted in a facility which operates in accordance with Good Laboratory Practice principles; however no claim of GLP compliance was intended nor is made for this study
Type of method:
other: by determining the surface tension of a range of aqueous sample solutions of differing concentration
Key result
Water solubility:
ca. 25 mg/L
Conc. based on:
test mat.
Incubation duration:
ca. 23 h
Temp.:
20 °C
pH:
ca. 6.24
Remarks on result:
other: CMC - water solubility equivalent for surfactants
Details on results:
Please see below table.

The readings and temperatures for the sample solutions are shown in the following table:

Table1

Concentration (mg/L)

Reading (mN/m)

Temperature (°C)

1.015 x 103

30.0

20.0

30.0

20.0

30.0

20.0

304.4

30.5

20.0

30.5

20.0

30.5

20.0

101.5

31.5

20.0

31.5

20.0

31.5

20.0

30.44

33.5

20.0

34.5

20.0

34.5

20.0

34.5

20.0

15.22

37.0

20.0

39.0

20.0

39.0

20.0

39.0

20.0

10.15

38.5

20.0

41.0

20.0

41.0

20.0

43.0

20.0

43.0

20.0

43.0

20.0

5.074

45.0

20.0

49.0

20.0

49.0

20.0

51.0

20.0

51.0

20.0

52.5

20.0

52.5

20.0

54.0

20.0

54.0

20.0

54.0

20.0

Concentration (mg/L)

Reading (mN/m)

Temperature (°C)

3.044

49.5

20.0

54.0

20.0

54.0

20.0

57.0

20.0

58.0

20.0

59.0

20.0

59.0

20.0

59.0

20.0

2.030

56.5

20.0

60.0

20.0

61.0

20.0

63.5

20.0

63.5

20.0

64.5

20.0

64.5

20.0

64.5

20.0

1.015

65.0

20.0

68.0

20.0

69.0

20.0

70.5

20.0

70.5

20.0

70.5

20.0

Mean surface tension values were based on the last three readings for a particular concentration which were considered to be constant.

Theconcentration (mg/L), log10[concentration (mg/L)] and mean surface tension values for the sample solutions are shown in the following table:

Table2

Concentration
(mg/L)

Log10Concentration

Mean Surface Tension (mN/m)

Solution pH

1.015 x 103

3.006

30.0

8.40

304.4

2.483

30.5

7.91

101.5

2.006

31.5

7.54

30.44

1.483

34.5

5.95

15.22

1.182

39.0

5.69

10.15

1.006

43.0

5.84

5.074

0.705

54.0

5.31

3.044

0.483

59.0

5.59

2.030

0.307

64.5

5.36

1.015

0.006

70.5

5.67

The plot of log10[concentration (mg/L)] versus surface tension (mN/m) can be found under 'Attached background materials' :

In this graph, line 1(red) was generated from linear regression of 5 sample solution concentrations for which the surface tension was shown to be concentration dependent and line 2 (green) was generated from linear regression of 3 sample solution concentrations for which the surface tension was observed to be essentially independent of concentration. 

The intersection of these two lines gave the critical micelle concentration and was calculated by solving the two equations:

Line 1 equation:         y =-29.6x +73.7
Line 2 equation:         y =-1.49x +34.4

The sample solution at30.44 mg/L was not used in generating the two lines. At this concentration the surface tension appeared to be transitioning to Line 2 at a shallower gradient than Line 1.

The sample solution at1.015 mg/L was not used in generating the two lines. At this concentration the surface tension was only slightly affected and was approaching that of purified water.

The CMC was determined to be25.0mg/L.

Conclusions:
Under the study conditions, the the CMC or water solubility of the test substance was determined to be 25 mg/L at 20.0 ± 0.5°C.
Executive summary:

A study was conducted to determined the water solubility of the test substance, C10-12 and C18-unsatd. DEA, based on critical micelle concentration (CMC), according to OECD Guideline 115 and EU Method A.5, in compliance with GLP. Due to the surface activity of the test substance, the CMC value was considered as a water soluibility equivalent in accordance with the ECHA R.7a Guidance. Under study conditions, the CMC of the test substance was determined to be 25 mg/L at 20.0 ± 0.5°C (Envigo, 2018).

Description of key information

The water solubility of the test substance was determined based on the critical micelle concentration (a water solubility equivalent of surfactant), according to OECD Guideline 115 and EU Method A.5 (Envigo, 2018).

Key value for chemical safety assessment

Water solubility:
25 mg/L
at the temperature of:
20 °C

Additional information

(based on CMC)