Magnesium hydroxide sulfate (Mg6(OH)10(SO4)), hydrate (1:3)

Surface tension

Administrative data

Endpoint:

surface tension

Type of information:

experimental study

Adequacy of study:

key study

Study period:

29 June 2006 and 24 July 2006.

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2006

Report date:

2006

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

EU Method A.5 (Surface Tension)

Deviations:

yes

Remarks:

see below in principles of method

Principles of method if other than guideline:

The determination was carried out using a White Electrical Institute interfacial tension balance and a procedure based on the ISO 304 ring method. With the exception of the following deviation, the experimental procedure used complied with that specified in Method A5 of Commission Directive 92/69/EEC (which constitutes Annex V of Council Directive 67/548/EEC).
1) The surface tension result 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 is as a result of the reduced ring dimensions.

This deviation has been considered not to have affected the integrity of the study.

GLP compliance:

yes (incl. QA statement)

Remarks:

Date of inspection: 30/08/06; Date of signature: 04/09/2006

Type of method:

ring method

Test material

Test material information

Constituent 1

Reference substance name:

-

EC Number:

483-390-9

EC Name:

-

Cas Number:

12508-61-1

Molecular formula:

H16Mg6O17S

IUPAC Name:

hexamagnesium(2+) trihydrate decahydroxide sulfate

Results and discussion

Surface tension

Key result

Surface tension:

70.3 mN/m

Temp.:

22.5 °C

Conc.:

0.03 g/L

Any other information on results incl. tables

Sample solution concentration

The mean absorbances relating to the standard and sample solutions are shown in the following table:

Solution	Mean Absorbance
Standard 1.98 mg/l	0.344
Standard 1.58 mg/l	0.270
Standard 1.19 mg/l	0.239
Standard 0.396 mg/l	0.139
Standard 0.198 mg/l	7.945 x 10^-2
Standard 9.90 x 10^-2mg/l	6.650 x 10^-2
Sample A	0.145
Sample B	0.146
Mean sample solution concentration = 2.96 x 10^-2g/l (magnesium)

Calibration factor (f)

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

Table 6.2

Reading (mN/m)	Temperature (ºC)	Literature Value (mN/m)	Calibration Factor
72.5	22.4	72.35	0.998
72.5	22.4	72.35	0.998
72.5	22.4	72.35	0.998
72.0	22.4	72.35	1.005
72.0	22.6	72.32	1.004
72.5	22.6	72.32	0.998
Mean Calibration Factor = 1.000

Sample solution readings

The readings, times and temperatures for the sample solution are shown in the following table:

Table 6.3

Time (mins)	Reading (mN/m)	Temperature (ºC)
109	70.0	22.4
117	70.0	22.4
127	70.5	22.4
136	70.5	22.6
144	70.5	22.6

Mean reading                    :   70.3 mN/m
Surface tension                  = reading x calibration factor
                                         = 70.3 x 1.000
                                         = 70.3 mN/m
Temperature                      :   22.5 ± 0.5ºC
pH of sample solution        :   9.3

Discussion

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

As the test material was essentially insoluble in typical reverse phase solvents, it was deemed not possible to perform any analysis of the sulphate component within the test material.

Conclusion

The surface tension of a 2.96 x 10^-2 g/l (magnesium) solution of test material has been determined to be 70.3 mN/m at 22.5 ± 0.5°C. The test material is considered not to be a surface-active material.

Applicant's summary and conclusion

Conclusions:

The surface tension of a 2.96 x 10-2 g/l (magnesium) solution of test material has been determined to be 70.3 mN/m at 22.5 ± 0.5°C. The test material is considered not to be a surface-active material.

Executive summary:

For substance MOS-HIGE in project number 1456 -0064, the surface tension of a 2.96 x 10-2 g/l (magnesium) solution of test material has been determined to be 70.3 mN/m at 22.5 ± 0.5°C. The test material is considered not to be a surface-active material.

The determination was carried out using a White Electrical Institute interfacial tension balance and a procedure based on the ISO 304 ring method. With the exception of the following deviation, the experimental procedure used complied with that specified in Method A5 of Commission Directive 92/69/EEC (which constitutes Annex V of Council Directive 67/548/EEC). The surface tension result 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 is as a result of the reduced ring dimensions.

This deviation has been considered not to have affected the integrity of the study.