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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:
15 December 2017 to 18 December 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 104 (Vapour Pressure Curve)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method A.4 (Vapour Pressure)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of method:
effusion method: Knudsen cell
Key result
Temp.:
20 °C
Vapour pressure:
< 0 Pa
Remarks on result:
other: Extrapolated upper limit value
Key result
Temp.:
25 °C
Vapour pressure:
< 0 Pa
Remarks on result:
other: Extrapolated upper limit value
Key result
Temp.:
50 °C
Vapour pressure:
0.001 Pa
Remarks on result:
other: Measured value

- The vapour pressure was measured in the temperature range of 30 to 100 °C. The measured vapour pressures at the corresponding temperatures are listed in Table 1. After the measurement a mass loss of approx. 0.1 % (w/w) was determined.

Table 1: Measured vapour pressures and corresponding temperatures

Temperature / °C

Vapour pressure / hPa

30

4.4 × 10 -7

40

7.8 × 10 -6*

50

1.1 × 10 -5

60

9.0 × 10 -6*

70

8.6 × 10 -6*

80

7.8 × 10 -6*

90

8.8 × 10 -6*

100

7.0 × 10 -6*

* = Below the recommended range for this method

- All measured vapour pressures were near or below the lower limit of the recommended range for this method of 10^-5 hPa. Furthermore, no linear dependency between temperature and vapour pressure was found.

- A vapour pressure at 50 °C could be measured but no extrapolation to 20 and 25 °C was possible because the test did not yield vapour pressures sufficiently high to extrapolate to 20 and 25 °C. Therefore, these values were estimated. According to the Antoine equation, the vapour pressure can be calculated according to:

log(p/hPa) = A + [B/ (C + (T/°C))]

p = Vapour pressure in hPa

T = Temperature in °C

A,B,C = Antoine constants

- For an extrapolation to lower temperatures a conservative assumption of the Antoine constant C is 273.15. This results in a linear dependency of log(p) of the inverse Temperature 1/T (in K). Values for the resulting slope of the Antoine equation (constant B) for substances of high molecular weight, which can be derived from literature values (e.g. Handbook of Chemistry and Physics) are lower than -5000. Thus, for a conservative estimation of the vapour pressure of the test mateial at 20 and 25 °C, a value of -5000 for constant B and a value of 273.15 for constant C, respectively, were used.

- The data point of the measurement at 50 °C was used as the starting point for the calculation. The measured vapour pressure at 50 °C was 1.1 x 10 ^-5 hPa.

- Based on this assumption, the constant A of the Antoine equation was calculated according to:

A = log(p/hPa) - [-5000 / (273.15 + (T/°C))] = 1.1log10^-5 - [-5000/ (273.15 + 50)] = 10.49

- Subsequently, the vapour pressure at 20 and 25 °C can be calculated with the Antoine equation as follows:

log(p/hPa) = 10.49 + [ -5000 / (273.15 + (T/°C))]

- The values for 20 and 25 °C are calculated in Table 2.

Table 2: Calculated vapour pressure at 20 and 25 °C

T / °C

p / hPa

p/Pa

20

<2.7× 10 -7

 <2.7× 10 -5

25

<5.3× 10-7

<5.3× 10 -5

- This is a conservative estimation of the vapour pressure of the test material for the listed temperatures. In order to further ensure a conservative approach the vapour pressures were rounded up to the next order of magnitude in order to obtain final upper limit values for the vapour pressure.

Table 3: Final upper limit values for the vapour pressure at 25 and 25 °C

T / °C

p / hPa

p / Pa

20

 <1× 10 -6

  <1× 10 -4

25

 <1× 10 -6

  <1× 10 -4

- The following vapour pressure values and upper limit vapour pressure values for the test material were derived from the experimental data:

Table 4: Final Results

T / °C

p / hPa

p / Pa

20

 <1× 10-6*

<1× 10-4*

25

  <1× 10-6*

<1× 10-4*

50

1.1× 10-5**

1.1× 10-3**

* Extrapolated upper limit value

** Measured value

Conclusions:
Under the conditions of this study, the vapour pressure of the test material was <1x10^-4, <1x10^-4 and 1.1x10^-3 Pa at 20, 25 and 50 °C, respectively.
Executive summary:

The vapour pressure of the test material was investigated in accordance with the standardised guidelines OECD 104 and EU Method A.4, under GLP conditions.

The vapour pressure was examined using the effusion method with the Knudsen cell. The vapour pressure was measured in the temperature range of 30 to 100 °C.

After the measurement a mass loss of approximately 0.1 % (w/w) was determined. A vapour pressure at 50 °C could be measured but no extrapolation to 20 and 25 °C was possible because the test did not yield vapour pressures sufficiently high to extrapolate to 20 and 25 °C. Therefore, these values were estimated according to the Antoine equation.

Under the conditions of this study, the vapour pressure of the test material was <1x10^-4, <1x10^-4 and 1.1x10^-3 Pa at 20, 25 and 50 °C, respectively.

Description of key information

Under the conditions of this study, the vapour pressure of the test material was <1x10^-4, <1x10^-4 and 1.1x10^-3 Pa at 20, 25 and 50 °C, respectively.

Key value for chemical safety assessment

Vapour pressure:
0.001 Pa
at the temperature of:
50 °C

Additional information

The vapour pressure of the test material was investigated in accordance with the standardised guidelines OECD 104 and EU Method A.4, under GLP conditions. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

The vapour pressure was examined using the effusion method with the Knudsen cell. The vapour pressure was measured in the temperature range of 30 to 100 °C.

After the measurement a mass loss of approximately 0.1 % (w/w) was determined. A vapour pressure at 50 °C could be measured but no extrapolation to 20 and 25 °C was possible because the test did not yield vapour pressures sufficiently high to extrapolate to 20 and 25 °C. Therefore, these values were estimated according to the Antoine equation.

Under the conditions of this study, the vapour pressure of the test material was <1x10^-4, <1x10^-4 and 1.1x10^-3 Pa at 20, 25 and 50 °C, respectively.