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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:
May 25, 2018 - May 27, 2018
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: by loss of weight or by trapping vaporisate
Key result
Test no.:
#1
Temp.:
20 °C
Vapour pressure:
< 0 Pa
Key result
Test no.:
#2
Temp.:
25 °C
Vapour pressure:
< 0 Pa

The vapour pressure was measured in the temperature range of 70 °C to 120 °C. The measured vapour pressures at the corresponding temperatures are listed in Table 1. Due to the high water content of the test item of 13.5 % (w/w) the test item was degassed at 50 °C for 8 h before the measurement. After the measurement a mass loss of approx.14 % (w/w) was determined.

Table1: Measured vapour pressures and corresponding temperatures

Temperature / °C

Vapour pressure / hPa

70

8.7 × 10-6

80

5.5 × 10-6

90

4.9 × 10-6

100

9.2 × 10-6

110

7.2 × 10-6

120

2.2 × 10-5

 

Only the data point measured at 120 °C was above the detection limit (1 × 10-5hPa). Since the test did not yield vapour pressures sufficiently high to extrapolate to 20, 25 and 50 °C these values were estimated. According to the Antoine equation, the vapour pressure can be calculated.

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 item at 20, 25 and 50 °C, a value of -5000 for constant B and a value of 273.15 for constant C, respectively, were used. The last data point of the measurement at 120 °C was used as the starting point for the calculation. The measured vapour pressure at 120 °C was 2.19× 10-5hPa. Based on this assumption, the constant A of the Antoine equation was calculated. Subsequently, the vapour pressure at 20, 25 and 50 °C can be calculated with the Antoine equation.

Table2: Calculated vapour pressure at 20, 25 and 50 °C

T / °C

p / hPa

p / Pa

20

< 1.0×10-9

< 1.0×10-7

25

< 1.9×10-9

< 1.9×10-7

50

< 3.9×10-8

< 3.9×10-6

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.

Table3: Final upper limit values for the vapour pressure at 20, 25 and 50 °C

T / °C

p / hPa

p / Pa

20

< 1×10-8

< 1×10-6

25

< 1×10-8

< 1×10-6

50

< 1×10-7

< 1×10-5

 

Executive summary:

Based on the measured vapour pressure at 120 °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

< 1×10-8

< 1×10-6

25

< 1×10-8

< 1×10-6

50

< 1× 10-7

< 1× 10-5

 

Description of key information

Based on the measured vapour pressure at 120 °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

< 1×10-8

< 1×10-6

25

< 1×10-8

< 1×10-6

50

< 1×10 -7

< 1×10-5

 

Key value for chemical safety assessment

Additional information