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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:
2018-11-20 to 2019-01-17
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
Test no.:
#1
Temp.:
20 °C
Vapour pressure:
0.67 Pa
Key result
Test no.:
#2
Temp.:
25 °C
Vapour pressure:
1.06 Pa
Test no.:
#3
Temp.:
50 °C
Vapour pressure:
8.72 Pa

Effusion method: Knudsen cell

The vapour pressure was measured in the temperature range of 10 to 35 °C. The measured vapour pressure values together with the measured temperatures are listed in the table below:

 

Results of the Effusion method

No.

Temperature / °C

Vapour pressure / Pa

1

10.1

0.25

2

15.2

0.42

3

20.3

0.70

4

25.4

1.14

5

30.4

1.79

6

35.5

2.53

 

The measured vapour pressure of entries no. 4 - 6 in Table 3 is slightly outside the measuring range (10E-3 to 1 Pa) of the Knudsen cell. Nevertheless, as the vapour pressure value above 1 Pa could be detected properly by the Knudsen cell, this value can be used for the evaluation.

 

From the measured data points of the vapour pressure curve the constants A and B of the Antoine equation can be derived by regression of the data points to

A = 11.8394

B = -3522.02

C = 273.15.

 

The vapour pressure of the test item calculated by interpolation and extrapolation of the measured vapour pressure curve for the temperatures 20, 25 and 50 °C:

 

Calculated vapour pressure values for 20, 25 and 50 °C

Temperature /°C

Vapour pressure / Pa

20

0.67

25

1.06

50

8.72

 

 

Conclusions:
The vapour pressure of the test item was calculated by extrapolation of the measured vapour pressure curve for the temperatures 20, 25 and 50 °C to be 0.67 Pa, 1.06 Pa and 8.72 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 was measured in the temperature range of 10.1 to 35.5 °C using the effusion method (Knudsen cell). All measured values showed good reproducibility, giving relative standard deviations of less than 25 %, and good correlation. Therefore, the result of the test according to the guideline criteria was considered to be valid. The vapour pressure was calculated using the linear regression equation of the Log P versus 1/T function. The vapour pressure of the test item was calculated by extrapolation of the measured vapour pressure curve for the temperatures 20, 25 and 50 °C to be 0.67 Pa, 1.06 Pa and 8.72 Pa, respectively.

Description of key information

The vapour pressure of the test item was calculated by extrapolation of the measured vapour pressure curve for the temperatures 20, 25 and 50 °C to be 0.67 Pa, 1.06 Pa and 8.72 Pa, respectively (reference 4.6 -1).

Key value for chemical safety assessment

Vapour pressure:
1.06 Pa
at the temperature of:
25 °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 was measured in the temperature range of 10.1 to 35.5 °C using the effusion method (Knudsen cell). All measured values showed good reproducibility, giving relative standard deviations of less than 25 %, and good correlation. Therefore, the result of the test according to the guideline criteria was considered to be valid. The vapour pressure was calculated using the linear regression equation of the Log P versus 1/T function. The vapour pressure of the test item was calculated by extrapolation of the measured vapour pressure curve for the temperatures 20, 25 and 50 °C to be 0.67 Pa, 1.06 Pa and 8.72 Pa, respectively.