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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:
2018-05-29 to 2018-05-29
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:
no
Type of method:
effusion method: Knudsen cell
Test no.:
#1
Temp.:
20 °C
Vapour pressure:
< 0 Pa
Key result
Test no.:
#2
Temp.:
25 °C
Vapour pressure:
< 0 Pa
Test no.:
#3
Temp.:
50 °C
Vapour pressure:
< 0 Pa

The vapour pressure was measured twice in the overall temperature range of 25 °C to 100 °C (the first measurement was performed from 25 °C to 90 °C and the second was measured with a fresh sample from 40 °C to 100 °C). Due to the ambiguous course of the first measurement the test item was kept for 6 h at 40 °C under vacuum to remove any volatile components. The measured vapour pressures at the corresponding temperatures are listed in below. After the measurement a mass loss of approx. 8 % (w/w) (both measurements) was determined.

 

Measured vapour pressures and corresponding temperatures

Temperature / °C

Vapour pressure / hPa

25

4.5 x 10E-4

40

4.9 x 10E-4

50

4.5 x 10E-4

60

3.8 x 10E-4

70

2.9 x 10E-4

80

2.0 x 10E-4

90

1.5 x 10E-4

70

2.5 x 10E-4

40*

2.6 x 10E-4

50*

2.7 x 10E-4

60*

2.8 x 10E-4

70*

2.5 x 10E-4

80*

2.0 x 10E-4

90*

1.5 x 10E-4

100*

1.3 x 10E-4

*Second measurement

 

Both measurements showed an unusual course. Therefore estimation was applied to obtain values for 20, 25 and 50 °C. 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. Handbock of Chemistry and Physics) are lower than -5000. Thus, for a conservative estimation of the vapour pressure of the test item at 20, 25 and 50 °C, a value of -5000 for constant Band a value of 273.15 for constant C, respectively, were used.

 

Subsequently, the vapour pressure at 20, 25 and 50 °C can be calculated with the Antoine equation as follows:

 

Calculated vapour pressure at 20, 25 and 50 °C

T/°C

p/hPa

p/Pa

20

2.9 x 10E-8

2.9 x 10E-6

25

5.5 x 10E-8

5.5 x 10E-6

50

1.1 x 10E-6

1.1 x 10E-4

 

This is a conservative estimation of the vapour pressure of the test item 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.

 

Final upper limit values for the vapour pressure at 20, 25 and 50 °C 

T/°C

p/hPa

p/Pa

20

< 1 x 10E-7

< 1 x 10E-7

25

< 1 x 10E-7

< 1 x 10E-5

50

< 1 x 10E-5

< 1 x 10E-3

 

Final results

Based on the measured vapour pressure at 100 °C (vapour pressure: effusion method), the following upper limit vapour pressure values for the test item were calculated:

T/°C

p/hPa

p/Pa

20

< 1 x 10E-7

< 1 x 10E-5

25

< 1 x 10E-7

< 1 x 10E-5

50

< 1 x 10E-5

< 1 x 10E-3

Conclusions:
The vapour pressure of the test item was determined to be < 1x10E-7 Pa at 20 °C, <1x10E-7 Pa at 25 °C and <1x10E-5 Pa at 50 °C, respectively.
Executive summary:

A study was conducted according to OECD TG 104 and Regulation (EC) No 440/2008 method A.4 to determine the vapour pressure of the test item using the effusion method: vapour pressure balance. The vapour pressure of the test item was determined at temperatures between 25 and 90 °C and a second run from 40 to 100 °C. Due to the ambiguous course of the first measurement the test item was kept for 6 h at 40 °C under vacuum to remove any volatile components. Both measurements showed an unusual course. Therefore estimation was applied to obtain values for 20, 25 and 50 °C. Based on the measured vapour pressure at 100 °C the upper limit vapour pressure values for the test item were calculated. The vapour pressure of the test item was determined to be < 1x10E-7 Pa at 20 °C, < 1x10E-7 Pa at 25 °C and < 1x10E-5 Pa at 50 °C, respectively.

Description of key information

The vapour pressure of the test item was determined to be < 1x10E-7 Pa at 20 °C, <1x10E-7 Pa at 25 °C and <1x10E-5 Pa at 50 °C, respectively (reference 4.6-1).

Key value for chemical safety assessment

Vapour pressure:
0 Pa
at the temperature of:
25 °C

Additional information

A study was conducted according to OECD TG 104 and Regulation (EC) No 440/2008 method A.4 to determine the vapour pressure of the test item using the effusion method: vapour pressure balance (reference 4.6-1). The vapour pressure of the test item was determined at temperatures between 25 and 90 °C and a second run from 40 to 100 °C. Due to the ambiguous course of the first measurement the test item was kept for 6 h at 40 °C under vacuum to remove any volatile components. Both measurements showed an unusual course. Therefore estimation was applied to obtain values for 20, 25 and 50 °C. Based on the measured vapour pressure at 100 °C the upper limit vapour pressure values for the test item were calculated. The vapour pressure of the test item was determined to be < 1x10E-7 Pa at 20 °C, < 1x10E-7 Pa at 25 °C and < 1x10E-5 Pa at 50 °C, respectively.