Octanoic acid, 6,8-dimercapto-

Surface tension

Link to relevant study record(s)

Reference

Endpoint:

surface tension

Type of information:

experimental study

Adequacy of study:

key study

Study period:

28.09.2000 - 19.10.2000

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method A.5 (Surface Tension)

Deviations:

yes

Remarks:

, see "Principles of method if other than guideline"

Qualifier:

according to guideline

Guideline:

other: ISO 304

Principles of method if other than guideline:

The surface tension was not corrected using the Harkins-Jordan correction table as the correction is not applicable to the apparatus used. Once calibrated, the balance and ring assembly used in this test give a direct reading for surface tension that is within the required accuracy (+/- 0.5 mN/m); this as a result of the reduced ring dimensions.

GLP compliance:

yes (incl. QA statement)

Type of method:

ring method

Key result

Surface tension:

53.6 mN/m

Temp.:

21 °C

Conc.:

1.02 g/L

1) Calibration factor

The readings, temperatures and the corresponding calibration factors for glass double-distilled water are shown in table 1.

Table 1: readings, temperature and the corresponding calibration factor for glass double-distilled water.

Reading (mN/m)	Temperature (°C)	Literature Value (mN/m)	Calibration factor
72.5	21.0	72.60	1.001
72.5	21.0	72.60	1.001
72.5	21.0	72.60	1.001
72.5	21.0	72.60	1.001
72.5	21.0	72.60	1.001
72.5	21.0	72.60	1.001
72.5	21.0	72.60	1.001
Mean Calibration Factor = 1.001

2) Sample solution readings

The reading, times and temperatures for the sample solution are shown in table 2.

Table 2: readings, times and temperatures for the sample solution.

Time (min)	Reading (mN/m)	Temperature (°C)
75	53.5	21.0
81	53.5	21.0
87	53.5	21.0
95	54.0	21.0
101	53.5	21.0
105	53.5	21.0

Mean reading = 53.6 mN/m

Surface tension = reading x calibration factor

= 53.6 mN/m x 1.001 = 53.6 mN/m

3) Discussion

Substances having a surface tension below 60 mN/m are regarded as being surface-active.

The structure of the test material shows characteristics of a classic surfactant molecule, ie polar "head" with a carbon "tail".

Upon shaking of a 1.04 g/L solution of test material in octanol satured water with an equal volume of water satured octanol, slight emulsification was observed at the phase boundary, indicating the possibility of surfactant behaviour.

Conclusions:

Using a ring method based on ISO 304 and Method A5 of Commission Directive 92/69/EEC the surface tension of Dihydrolipoic Acid was determined to be 53.6 mN/m (1.02 g/L solution) at 21 °C +/- 0.5 °C. Therefore the test material is considered to be a surface-active material.

Executive summary:

Using a ring method based on ISO 304 and Method A5 of Commission Directive 92/69/EEC the surface tension of Dihydrolipoic Acid was determined to be 53.6 mN/m (1.02 g/L solution) at 21 °C +/- 0.5 °C. Therefore Dihydrolipoic Acid is considered to be a surface-active material.

Description of key information

Using a ring method based on ISO 304 and Method A5 of Commission Directive

92/69/EEC the surface tension of Dihydrolipoic Acid was determined to be 53.6 mN/m (1.02 g/L solution) at 21 °C +/- 0.5 °C. Therefore the test material is considered to be a surface-active material.

Key value for chemical safety assessment

Surface tension:

53.6

in mN/m at 20°C and concentration in mg/L:

1 020

Additional information

Using a ring method based on ISO 304 and Method A5 of Commission Directive 92/69/EEC the surface tension of Dihydrolipoic Acid was determined to be 53.6 mN/m (1.02 g/L solution) at 21 °C +/- 0.5 °C. Therefore Dihydrolipoic Acid is considered to be a surface-active material.