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Physical & Chemical properties

Vapour pressure

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Administrative data

Link to relevant study record(s)

Reference
Endpoint:
vapour pressure
Type of information:
experimental study
Adequacy of study:
key study
Study period:
from 2017-04-24 to 2017-07-04
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 104 (Vapour Pressure Curve)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method A.4 (Vapour Pressure)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of method:
effusion method: Knudsen cell
Key result
Temp.:
20 °C
Vapour pressure:
0 Pa
Temp.:
25 °C
Vapour pressure:
0 Pa

Calculation of results

All calculation results are given in the tables below. In all tables, E-0X represents multiplication with 10-X. Experiment 1-4, 8, 9 showed no relevant or reproducible weight loss. Therefore, these experiments were not used for calculation.

Table 1: Calculation Results Experiment 5

Experiment

5

 

 

 

 

 

 

 

 

Real Temperature in K

363.2

 

 

 

 

 

 

 

 

Real Temperature in °C

90.0

 

 

 

 

 

 

 

 

Date of Measurement

02.06.2017 12:30

07.06.2017 10:10

08.06.2017 12:10

Elapsed Time in s

85800

81000

89400

Parameter

Weight
loss

to be
used

Vapour
pressure

Weight
loss

to be
used

Vapour
pressure

Weight
loss

to be
used

Vapour
pressure

Unit

g

yes/no

Pa

g

yes/no

Pa

g

yes/no

Pa

Knudsen-cell 1

0.00124

yes

5.44E-03

0.00049

yes

2.28E-03

0.00036

yes

1.51E-03

Knudsen-cell 2

0.00089

yes

3.90E-03

0.00063

yes

2.93E-03

0.00033

yes

1.39E-03

Knudsen-cell 3

0.00111

yes

4.87E-03

0.00040

yes

1.86E-03

0.00027

yes

1.14E-03

Knudsen-cell 4

0.00130

yes

5.70E-03

0.00030

yes

1.39E-03

0.00049

yes

2.06E-03

Mean

 

no

 

 

yes

2.11E-03

 

yes

1.53E-03

Standard deviation:

 

 

 

 

 

6.51E-04

 

 

3.91E-04

Mean of measured values:

 

1.819E-03

 

 

 

 

 

 

Standard deviation:

 

4.156E-04

RSD:

22.8%

 

 

 

 

If “no” is stated in the respective column: measurement was not considered for the calculation of the mean.

Table 2: Calculation Results Experiment 6

Experiment

6

 

 

 

 

 

 

 

 

Real Temperature in K

378.2

 

 

 

 

 

 

 

 

Real Temperature in °C

105.0

 

 

 

 

 

 

 

 

Date of Measurement

09.06.2017 11:25

13.06.2017 11:55

14.06.2017 11:50

Elapsed Time in s

81600

92700

83700

Parameter

Weight
loss

to be
used

Vapour
pressure

Weight
loss

to be
used

Vapour
pressure

Weight
loss

To be
used

Vapour
pressure

Unit

g

yes/no

Pa

g

yes/no

Pa

g

yes/no

Pa

Knudsen-cell 1

0.00231

yes

1.09E-02

0.00292

yes

1.21E-02

0.00291

yes

1.33E-02

Knudsen-cell 2

0.00224

yes

1.05E-02

0.00295

yes

1.22E-02

0.00264

yes

1.21E-02

Knudsen-cell 3

0.00234

yes

1.10E-02

0.00274

yes

1.13E-02

0.00288

yes

1.32E-02

Knudsen-cell 4

0.00241

yes

1.13E-02

0.00294

yes

1.22E-02

0.00307

yes

1.41E-02

Mean

 

yes

1.09E-02

 

yes

1.20E-02

 

yes

1.32E-02

Standard deviation:

 

 

3.32E-04

 

 

4.10E-04

 

 

8.14E-04

Mean of measured values:

 

1.203E-02

 

 

 

 

 

 

Standard deviation:

 

1.126E-03

RSD:

9.4%

 

 

 

 

Table 3: Calculation Results Experiment 7

Experiment

7

 

 

 

 

 

 

 

 

Real Temperature in K

393.2

 

 

 

 

 

 

 

 

Real Temperature In °C

120.0

 

 

 

 

 

 

 

 

Date of Measurement

20.06.2017 11:55

21.06.2017 12:00

22.06.2017 12:00

Elapsed Time in s

88500

83400

83400

Parameter

Weight
loss

to be
used

Vapour
pressure

Weight
loss

to be
used

Vapour
pressure

Weight
loss

to be
used

Vapour
pressure

Unit

g

yes/no

Pa

g

yes/no

Pa

g

yes/no

Pa

Knudsen-cell 1

0.11283

yes

4.99E-01

0.02090

yes

9.81 E-02

0.01739

yes

8.16E-02

Knudsen-cell 2

0.06804

yes

3.01E-01

0.03774

no

 

0.02351

yes

1.10E-01

Knudsen-cell 3

0.07572

yes

3.35E-01

0.03518

yes

1.65E-01

0.02067

yes

9.70E-02

Knudsen-cell 4

0.10393

yes

4.60E-01

0.02184

yes

1.02E-01

0.01093

yes

5.13E-02

Mean

 

no

 

 

yes

1.22E-01

 

yes

8.51E-02

Standard deviation:

 

 

 

 

 

3.75E-02

 

 

2.54E-02

Mean of measured values:

 

1.035E-01

 

 

 

 

 

 

Standard deviation:

 

2.604E-02

RSD:

25.2%

 

 

 

 

If “no” is stated in the respective column: measurement was not considered for the calculation of the mean.

Experiment 1-4 and 8-9 (nominal temperature 30 to 75 °C and 135 to 150 °C) showed only a poor reproducible weight loss. When visible contaminations, caused by explosive evaporation of the test item, were observed, the cells were meticulously cleaned and weighed. This weight was used as initial weight for the subsequent measurements. To avoid bias, these measurements were not used for calculations.

At temperature of about 145 °C a dehydratation in the melting point study was observed (refer to IUCLID Section 4.2 "Melting point / freezing point"), therefore, no reprodusible vapour pressure can be determined.

Table 4: Evaluation of calculated values

Parameter

T

Mean P

1/T

Log P

Unit

K

Pa

1/K

log Pa

Values

363.2

1.82E-03

2.7533E-03

-2.7402

 378.2

1.20E-02

2.6441E-03

-1.9199

393.2 

1.03E-01

2.5432E-03

-0.9852

Table 5: Parameters of Linear Regression

Parameter

Value

Slope

-8342.7

Intercept

20.2003

Correlation Coefficient r

-0.9982

Coefficient of Determination r²

0.9963

Final results

The following vapour pressures were determined experimentally and considered as valid (mean and standard deviation given):

Table 6: Experimentally Determined Vapour Pressures

T

T

P

Stand. Dev. P

RSD P

°C

K

Pa

Pa

%

90.0

363.2

1.82 x 10-3

4.16 x 10-4

22.8%

105.0

378.2

1.20 x 10-2

1.13 x 10-3

9.4%

120.0

393.2

1.03 x 10-1

2.60 x 10-2

25.2%

Stand. Dev. = Standard Deviation; RSD = Relative Standard Deviation

For the test item the vapour pressures at 20 °C and at 25 °C were calculated from the regression equation.

The linear regression of log P vs. 1/T gave a correlation coefficient r of -0.9982, showing good repeatability and precision. Therefore, the determination is considered as valid.

Conclusions:
For the test item the following vapour pressures at 20 °C and at 25 °C were calculated from the regression equation:
- at 20 °C: 5.52E-9 Pa
- at 25 °C: 1.66E-8 Pa
Executive summary:

In a study the vapour pressure of the test item was determined at nine different temperatures (30, 45, 60, 75, 90, 105, 120, 135 and 150 °C) according to OECD TG 104 and EU method A.4 by using the effusion method (weight loss). Experiment 1-4 and 8-9 (nominal temperature 30 to 75 °C and 135 to 150 °C) showed only a poor reproducible weight loss. When visible contaminations, caused by explosive evaporation of the test item, were observed, the cells were meticulously cleaned and weighed. This weight was used as initial weight for the subsequent measurements. To avoid bias, these measurements were not used for calculations. Three experiments could be evaluated as they showed relevant and reproducible weight loss. The experiments used for calculation showed good reproducibility, giving relative standard deviations of less than 26 % and good correlation. Therefore, the result of the test could be considered valid. For the test item the following vapour pressures were calculated from the regression equation: 5.52 x 10-9 Pa for 20 °C and 1.66 x 10-8 Pa for 25 °C.

Description of key information

For the test item the following vapour pressures at 20 °C and at 25 °C were calculated from the regression equation:

- at 20 °C: 5.52E-9 Pa

- at 25 °C: 1.66E-8 Pa

Key value for chemical safety assessment

Vapour pressure:
0 Pa
at the temperature of:
20 °C

Additional information

In a study the vapour pressure of the test item was determined at nine different temperatures (30, 45, 60, 75, 90, 105, 120, 135 and 150 °C) according to OECD TG 104 and EU method A.4 by using the effusion method (weight loss). Three experiments could be evaluated as they showed relevant and reproducible weight loss. All evaluated experiments showed good reproducibility, giving relative standard deviations of less than 26 % and good correlation. Therefore, the result of the test can be considered valid. For the test item the following vapour pressures were calculated from the regression equation: 5.52 x 10-9 Pa for 20 °C and 1.66 x 10-8 Pa for 25 °C (reference 4.6-1).