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Physical & Chemical properties

Vapour pressure

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Reference
Endpoint:
vapour pressure
Type of information:
experimental study
Adequacy of study:
key study
Study period:
from 2016-06-15 to 2016-07-08
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
Qualifier:
according to guideline
Guideline:
OECD Guideline 104 (Vapour Pressure Curve)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Remarks:
Siemens AG Prozess-Sicherheit, Industriepark Höchst, B 596 & B 598, 65926 Frankfurt am Main, Germany
Type of method:
effusion method: Knudsen cell
Key result
Temp.:
20 °C
Vapour pressure:
0.001 Pa
Temp.:
25 °C
Vapour pressure:
0.001 Pa
Temp.:
50 °C
Vapour pressure:
0.009 Pa

The vapour pressure was measured in a first run in the temperature range of 70 °C to 120 °C and a second measurement was performed in the temperature range of 30 °C to 60 °C. The measured vapour pressures at the corresponding temperatures are listed in Table 1 and 2.

Table 1: Measured vapour pressures and corresponding temperatures, 1st measurement

Temperature / °C

Vapour pressure / hPa

70

3.4 x 10-4

80

6.6 x 10-4

90

9.1 x 10-4

100

6.9 x 10-4

110

2.2 x 10-4

120

1.5 x 10-4

 

Table 2: Measured vapour pressures and corresponding temperatures, 2nd measurement

Temperature / °C

Vapour pressure / hPa

30

3.6 x 10-4

35

1.6 x 10-4

40

1.1 x 10-4

45

8.8 x 10-5

50

8.9 x 10-5

55

1.2 x 10-4

60

1.8 x 10-4

 

The measured vapour pressures showed an unusual behaviour. Below 50 °C and above 90 °C the measured vapour pressure decreased with increasing temperatures. These data points were not included in the linear regression. Taking into account the unusual course of the measured vapour pressures as a function of the temperature it can be assumed that the measured vapour pressure was influenced by moisture, release of water of crystallization or a decomposition under formation of sulfate.

The values for 20, 25 and 50 °C were calculated, using the Antoine equation with constants A, B and C as shown in Table 3.

 

Table 3: Antoine parameters and extrapolated vapour pressures

T / ° C

p / hPa

log (p/hPa) = A + B / (C+T [°C])

20

9.4 x 10-6

A = 5.52938

25

1.4 x 10-5

B= -3094.33

50

9.0 x 10-5

C = 273.15

 

The following vapour pressure values for the test item were extrapolated from the experimental data:

T /°C

p / hPa

p / Pa

20

9.4 x 10-6

9.4 x 10-4

25

1.4 x 10-5

1.4 x 10-3

50

9.0 x 10-5

9.0 x 10-3

 

Conclusions:
The vapour pressure at 20, 25 and 50 °C was extrapolated from the experimental data to be 9.4E-4, 1.4E-3 and 9.0E-3 Pa, respectively.
Executive summary:

A study was conducted according to OECD TG 104, Regulation (EC) No 440/2008 method A.4 and OPPTS 830.7950 to determine the vapour pressure of the test item. The vapour pressure of the test item was determined at two different temperature ranges (70 to 120 °C and 30 to 60 °C) using the effusion method (Knudsen cell). The measured values showed unusual behaviour.Below 50 °C and above 90 °C the measured vapour pressure decreased with increasing temperatures.The vapour pressure was calculated using the linear regression equation of the Log P versus 1/T function. The vapour pressure was calculated to be 0.00094 Pa at 20 °C and 0.0014 Pa at 25 °C respectively.

Description of key information

The vapour pressure at 20, 25 and 50 °C was extrapolated from the experimental data to be 9.4E-4, 1.4E-3 and 9.0E-3 Pa, respectively.

Key value for chemical safety assessment

Vapour pressure:
0.001 Pa
at the temperature of:
20 °C

Additional information

A study was conducted according to OECD TG 104, Regulation (EC) No 440/2008 method A.4 and OPPTS 830.7950 to determine the vapour pressure of the test item (reference 4.6-1). The vapour pressure of the test item was determined at two different temperature ranges (70 to 120 °C and 30 to 60 °C) using the effusion method (Knudsen cell). The measured values showed unusual behaviour. Below 50 °C and above 90 °C the measured vapour pressure decreased with increasing temperatures. The vapour pressure was calculated using the linear regression equation of the Log P versus 1/T function. The vapour pressure was calculated to be 0.00094 Pa at 20 °C and 0.0014 Pa at 25 °C respectively.