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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:
22 August 2016 07 September 2016
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:
static method
Key result
Temp.:
20 °C
Vapour pressure:
>= 17 - <= 35 Pa

The difference between the two results (run 1 and run 2) obtained was greater than expected. This can possibly be explained by the differences in the initial degassing time of the samples and the resulting initial starting pressures obtained. Although both samples were degassed over a period of time and under a vacuum that would normally be expected to remove any moisture present. It is still possible that varying amounts of water remained trapped in the solid. The test material is known to contain 8.2 % water. Small quantities of volatile components are known to affect the vapour pressure results by orders of magnitude; therefore the variation in results observed is possibly explained by the levels of water remaining in the sample. The result was therefore reported as a range of the values obtained.

Table 1. Vapour Pressure Test Results

Temp / °C

Temp / K

P / mbar

P / Pa

Run 1

20.0

293.15

0.35

35

20.4

293.55

0.3994

39.94

30.1

303.25

1.0685

106.85

40.1

313.25

2.5

250

50.0

323.15

9.2

920

Run 2

20.0

293.15

0.17

17

20.9

294.05

0.1922

19.22

30.1

303.25

0.4788

47.88

40.0

313.15

1.1

110

50.0

323.15

3.6

360

Conclusions:
Under the condition of the study, the vapour pressure of the test material was determined to be in the range of 17 to 35 Pa at 20 °C.
Executive summary:

The vapour pressure of the test material was investigated in a GLP study in accordance with the standardised guideline EU Method A.4.

The vapour pressure of the test substance was determined by the Static method. This method involved placing a quantity of test material in the sample chamber of the glassware and a suitable manometer liquid in the U-tube. The contents of the static glassware were connected to a vacuum system linked with pressure monitors to enable the reading of any pressure/ vacuum on the contents of the static glassware. The system was evacuated until optimum vacuum is observed. This process was to ensure that there were no residual gasses within the system other than that of the test material.

The glassware was then isolated from the vacuum system. This was immediately followed by isolation of the sample chamber of the glassware so that any gas evolved from the sample will cause a displacement of the manometer liquid. When this was observed the levels of the liquid in the manometer was balanced by introducing a positive pressure using an inert gas (typically nitrogen) or negative pressure (using vacuum). The total pressure on the sample after the levels of the liquid in the manometer was balanced was then registered on the display unit coupled with the pressure transducers.

The glassware was then positioned in the constant temperature bath set to a desired starting temperature. As the static apparatus and its contents approached temperature equilibrium in the bath, the levels of the manometer liquid were balanced using the positive or negative pressure depending on the direction of displacement. This procedure was repeated until the system achieved temperature and pressure equilibrium (i.e. no significant change in temperature or pressure was observed). The temperature and pressure displayed on the pressure monitors are then recorded. The temperature was subsequently set to a higher temperature (between 5-25 °C higher) and the procedure was repeated until enough data points were obtained.

The difference between the two results (run 1 and run 2) obtained was greater than expected. This can possibly be explained by the differences in the initial degassing time of the samples and the resulting initial starting pressures obtained. The result was therefore reported as a range of the values obtained.

Under the condition of the study, the vapour pressure of the test material was determined to be in the range of 17 to 35 Pa at 20 °C.

Description of key information

Under the condition of the study, the vapour pressure of the test material was determined to be in the range of 17 to 35 Pa at 20 °C.

Key value for chemical safety assessment

at the temperature of:
20 °C

Additional information

The vapour pressure of the test material was investigated in a GLP study in accordance with the standardised guideline EU Method A.4. The study was assigned a reliability score of 1 in accordance with the criteria for assessing data quality set forth by Klimisch et al. (1997).

The vapour pressure of the test substance was determined by the Static method. This method involved placing a quantity of test material in the sample chamber of the glassware and a suitable manometer liquid in the U-tube. The contents of the static glassware were connected to a vacuum system linked with pressure monitors to enable the reading of any pressure/ vacuum on the contents of the static glassware. The system was evacuated until optimum vacuum is observed. This process was to ensure that there were no residual gasses within the system other than that of the test material.

The glassware was then isolated from the vacuum system. This was immediately followed by isolation of the sample chamber of the glassware so that any gas evolved from the sample will cause a displacement of the manometer liquid. When this was observed the levels of the liquid in the manometer was balanced by introducing a positive pressure using an inert gas (typically nitrogen) or negative pressure (using vacuum). The total pressure on the sample after the levels of the liquid in the manometer was balanced was then registered on the display unit coupled with the pressure transducers.

The glassware was then positioned in the constant temperature bath set to a desired starting temperature. As the static apparatus and its contents approached temperature equilibrium in the bath, the levels of the manometer liquid were balanced using the positive or negative pressure depending on the direction of displacement. This procedure was repeated until the system achieved temperature and pressure equilibrium (i.e. no significant change in temperature or pressure was observed). The temperature and pressure displayed on the pressure monitors are then recorded. The temperature was subsequently set to a higher temperature (between 5-25 °C higher) and the procedure was repeated until enough data points were obtained.

The difference between the two results (run 1 and run 2) obtained was greater than expected. This can possibly be explained by the differences in the initial degassing time of the samples and the resulting initial starting pressures obtained. The result was therefore reported as a range of the values obtained.

Under the condition of the study, the vapour pressure of the test material was determined to be in the range of 17 to 35 Pa at 20 °C.