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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:
2018-07-11 to 2018-08-29
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 104 (Vapour Pressure Curve)
GLP compliance:
no
Type of method:
effusion method: isothermal thermogravimetry
Temp.:
20 °C
Vapour pressure:
10.2 Pa
Key result
Temp.:
25 °C
Vapour pressure:
13.5 Pa

Results

For each isothermal temperature, the evaporation rate was determined. Weight losses were detected at all temperature steps from 30 °C to 300 °C. However, it was not feasible to calculate one overall mean vapour pressure due to the non-linear graph of log(pT) vs. 1/T. A reason for this behaviour can be traced back to the sample itself which is a mixture of different compounds. Therefore, three different vapour pressures were calculated using individual data sets limited to 30 °C to 80 °C (data set 1), 140 °C to 180 °C (data set 2), and 230 °C to 260 °C (data set 3), respectively. The Table 1 below lists the resulting data observed from the linear regression as well as the calculated vapour pressures for each data set.

Table 1: Resulting data from linear regression of the Clausius-Clapeyron graph of the test item

 

data set 1 (30 °C – 80 °C)

data set 2 (140 °C – 180 °C)

data set 3 (230 °C – 260 °C)

slope

-2113.17

-1068.25

-559.19

intercept

8.22

4.75

3.27

0.9986

0.9910

0.9473

pT (20 °C) [Pa]

10.2

12.8

23.2

pT (25 °C) [Pa]

13.5

14.8

24.9

Conclusions:
Due to the test item's nature of being a mixture of different components, a distinct vapour pressure could not be calculated. Referring to the determined evaporation rates at the lowest temperature range examined for calculation, the vapour pressure was found to be 10.2 Pa at 20 °C and 13.5 Pa at 25 °C.
Executive summary:

The vapour pressure of the test item was determined according to OECD 104. Thereby, a distinct vapour pressure could not be calculated due to the sample's nature of being a mixture of different components. Referring to the determined evaporation rates at the lowest temperature range examined for calculation, the vapour pressure was found to be 10.2 Pa at 20 °C and 13.5 Pa at 25 °C.

Description of key information

The vapour pressure of the test item was determined according to OECD 104. Thereby, a distinct vapour pressure could not be calculated due to the sample's nature of being a mixture of different components. Referring to the determined evaporation rates at the lowest temperature range examined for calculation, the vapour pressure was found to be 10.2 Pa at 20 °C and 13.5 Pa at 25 °C.

Key value for chemical safety assessment

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

Additional information