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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:
March 27, 2018 - March 28, 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
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:
< 0.001 Pa

The vapour pressure was measured in the temperature range of 50 °C to 100 °C. The measured vapour pressures at the corresponding temperatures are listed in Table 1.After the measurement a mass loss of approximately 1 % (w/w) was determined.

Table1: Measured vapour pressures and corresponding temperatures

Temperature / °C

Vapour pressure / hPa

50

2.7 × 10-5

60

4.0 × 10-5

70

5.6 × 10-5

80

5.3 × 10-5

90

3.7 × 10-5

100

3.0 × 10-5

The data points measured from 50 °C to 70 showed a typical behaivior possibly caused by the impurities. The test item showed an unusual vapor pressure behaviour, therefore the vapor pressure values for 20 and 25 °C 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 data point of the measured at 50 °C was used as the starting point for the calculation. The measured vapour pressure at 50 °C was 2.65× 10-5hPa.

Based on this assumption, the constant Aof the Antoine equation was calculated. Subsequently, the vapour pressure at 20 and 25 °C can be calculated with the Antoine equation as follows:

Table3: Calculated vapour pressure at 20, 25 and measured vapor pressure at 50 °C

T / °C

p / hPa

p / Pa

20

< 6.9×10-7

< 6.9×10-5

25

< 1.3×10-6

< 1.3×10-4

50

2.7× 10-5

2.7× 10-3

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.

Table4: Final upper limit values for the vapour pressure at 20 and 25 °C

T / °C

p / hPa

p / Pa

20

< 1×10-6

< 1×10 -4

25

< 1×10 -5

< 1×10 -3

Executive summary:

Based on the measured vapour pressure at 50 °C (vapour pressure balance), the following upper limit vapour pressure values for the test item at 20 and 25 °C were calculated:

T / °C

p / hPa

p / Pa

20

< 1×10-6

< 1×10 -4

25

< 1×10 -5

< 1×10 -3

50

2.7× 10-5

2.7× 10-3

Description of key information

Based on the measured vapour pressure at 50 °C (vapour pressure balance), the following upper limit vapour pressure values for the test item at 20 and 25 °C were calculated:

T / °C

p / hPa

p / Pa

20

< 1×10-6

< 1×10 -4

25

< 1×10 -5

< 1×10 -3

50

2.7× 10-5

2.7× 10-3

Key value for chemical safety assessment

Additional information