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Vapour pressure

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Reference
Endpoint:
vapour pressure
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Experimental phase: 17 October 2017 to 23 March 2018.
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
EU Method A.4 (Vapour Pressure)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of method:
dynamic method
Remarks:
Ebulliometer
Key result
Test no.:
#1
Remarks on result:
not determinable
Remarks:
An attempt was made to experimentally determine the vapour pressure. Whilst initially increases in pressure correlated to increase in temperature as expected, this correlation dipped off after 77 mBar, suggesting true boil was not achieved above this point. Therefore, no further increased pressure measurements were taken above 105 mBar. Duplicate measurements were taken on reduced pressure and showed comparable temperature readings, suggesting no degradation had taken place. Due to the observed effects and lack of data points, a vapour pressure curve was not produced and a measurement of vapour pressure was not possible.

Results

The measured vapour pressure results are presented in the following table:

 Presure (mBar)  Temperature (°C)
 21  156.9
 41  170.1
 62  174.4
 77  175.8
 94  175.0
 105  174.6
 91  175.2
 81  175.4
 63  171.9
 44  167.8
 22  154.4

Whilst initially increases in pressure correlated to increase in temperature as expected, this correlation dipped off after 77 mBar, suggesting true boil was not achieved above this point. Therefore, no further increased pressure measurements were taken above 105 mBar. Duplicate measurements were taken on reduced pressure and showed comparable temperature readings, suggesting no degradation had taken place.

Due to the observed effects and lack of data points, a vapour pressure curve was not produced and a measurement of vapour pressure was considered to not be possible using this technique.

Conclusions:
A true boil was not achieved and due to the lack of data points, a vapour pressure curve was not produced and a measurement of vapour pressure was not possible.
Executive summary:

Introduction

The vapour pressure of the test substance was investigated using an Ebulliometer. The test method was designed to meet the requirements of the following guideline:

  • EU Method A4 (Vapour Pressure)

Method

Approximately 20 ml of the test item was added to the ebulliometer along with a magnetic stirrer bar and a few anti-banging granules. The system was sealed with a glass blanking rod. The system pressure was reduced to approximately 20 mBar and heating commenced. Measurements started at reduced pressure as per EC Test A4. The temperature stabilised at 156.9 °C at 21 mBar. Pressure was gradually increased, and temperature was recorded at various pressures up to 105 mBar. Duplicated measurements were taken on return to reduced pressure.

Results

Whilst initially increases in pressure correlated to increase in temperature as expected, this correlation dipped off after 77 mBar, suggesting true boil was not achieved above this point. Therefore, no further increased pressure measurements were taken above 105 mBar. Duplicate measurements were taken on reduced pressure and showed comparable temperature readings, suggesting no degradation had taken place. Due to these observed effects and lack of data points, a vapour pressure curve was not produced and a measurement of vapour pressure was considered to not be possible using this technique.

Conclusion

A true boil was not achieved and due to the lack of data points, a vapour pressure curve was not produced and a measurement of vapour pressure was not possible.

Description of key information

Default vapour pressure value used for risk assessment (It was not possible to determine experimentally a vapour pressure).

Key value for chemical safety assessment

Vapour pressure:
0.001 Pa

Additional information

The vapour pressure is a default value used for risk assessment as a vapour pressure could not be determined experimentally.