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Physical & Chemical properties

Vapour pressure

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Reference
Endpoint:
vapour pressure
Type of information:
experimental study
Adequacy of study:
key study
Study period:
23. Jan. 2018 to 27. Feb. 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 104 (Vapour Pressure Curve)
Version / remarks:
OECD Guidelines for the Testing of Chemicals, Method No. 104, adopted 23. Mar. 2006: “Vapour Pressure“
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method A.4 (Vapour Pressure)
Version / remarks:
Commission Regulation (EC) No 761/2009 of 23. July 2009, published on 24. Aug. 2009 Method A.4: “Vapour Pressure”
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of method:
effusion method: Knudsen cell
Specific details on test material used for the study:
No further details specified in the study report.
Key result
Temp.:
20 °C
Vapour pressure:
0 Pa
Key result
Temp.:
25 °C
Vapour pressure:
0 Pa

FINDINGS

 

Sample Weights

The mass of sample in the respective cell is presented in the following table:

Sample Weights

Parameter

Cell empty

Cell + test item

Cell + test item + cap

Test item

Unit

g

g

g

g

Knudsen-cell 1

2.57338

3.85744

4.06851

1.28406

Knudsen-cell 2

2.56881

3.89945

4.11356

1.33064

Knudsen-cell 3

2.53824

3.83578

4.04864

1.29754

Knudsen-cell 4

2.55390

3.86293

4.07445

1.30903

 

Measurement Data

The data of the evaluated experiments is presented in the following tables:

Measurement Data Experiment 1

Experiment

1

 

 

 

Nom. Temperature

30

°C

 

 

Date and time START

 

23.01.2018 14:35

24.01.2018 12:25

25.01.2018 12:28

Date and time END

 

24.01.2018 11:25

25.01.2018 11:20

26.01.2018 11:30*

Parameter

Weight m

Weight m

Weight m

Weight m

Unit

g

g

g

g

Knudsen-cell 1

4.06851

4.06839

4.06869

4.06853

Knudsen-cell 2

4.11356

4.11349

4.11380

4.11368

Knudsen-cell 3

4.04864

4.04863

4.04896

4.04892

Knudsen-cell 4

4.07445

4.07440

4.07473

4.07460

*The samples were stored in an exsiccator after the weighings until start of the next measurement series due to organisational reasons.

 

Measurement Data Experiment 2

Experiment

2

 

 

 

Nom. Temperature

45

°C

 

 

Date and time START

 

29.01.2018 11:44

30.01.2018 12:10

31.01.2018 12:23

Date and time END

 

30.01.2018 11:10

31.01.2018 11:30

01.02.2018 11:15

Parameter

Weight m

Weight m

Weight m

Weight m

Unit

g

g

g

g

Knudsen-cell 1

4.06853

4.06821

4.06792

4.06793

Knudsen-cell 2

4.11368

4.11338

4.11325

4.11322

Knudsen-cell 3

4.04892

4.04853

4.04833

4.04832

Knudsen-cell 4

4.07460

4.07419

4.07396

4.07397

 

Measurement Data Experiment 3

Experiment

3

 

 

 

Nom. Temperature

60

°C

 

 

Date and time START

 

01.02.2018 12:10

05.02.2018 11:10

06.02.2018 12:40

Date and time END

 

02.02.2018 10:00*

06.02.2018 11:45

07.02.2018 11:45*

Parameter

Weight m

Weight m

Weight m

Weight m

Unit

g

g

g

g

Knudsen-cell 1

4.06793

4.06762

4.06709

4.06664

Knudsen-cell 2

4.11322

4.11296

4.11226

4.11212

Knudsen-cell 3

4.04832

4.04800

4.04750

4.04689

Knudsen-cell 4

4.07397

4.07364

4.07305

4.07240

*The samples were stored in an exsiccator after the weighings until start of the next measurement series due to organisational reasons.

 

Measurement Data Experiment 4

Experiment

4

 

 

 

Nom. Temperature

75

°C

 

 

Date and time START

 

12.02.2018 10:00

13.02.2018 12:35

14.02.2018 12:35

Date and time END

 

13.02.2018 11:25

14.02.2018 11:50

15.02.2018 13:30

Parameter

Weight m

Weight m

Weight m

Weight m

Unit

g

g

g

g

Knudsen-cell 1

4.06664

4.06374

4.06296

4.06119

Knudsen-cell 2

4.11212

4.10882

4.10710

4.10479

Knudsen-cell 3

4.04689

4.04335

4.04098

4.03873

Knudsen-cell 4

4.07240

4.06801

4.06502

4.06179

 

Measurement Data Experiment 5

Experiment

5

 

 

 

Nom. Temperature

90

°C

 

 

Date and time START

 

15.02.2018 14:20

19.02.2018 07:45

20.02.2018 07:50

Date and time END

 

16.02.2018 11:20*

20.02.2018 06:48

21.02.2018 07:10

Parameter

Weight m

Weight m

Weight m

Weight m

Unit

g

g

g

g

Knudsen-cell 1

4.06119

4.05388

4.03785

4.02314

Knudsen-cell 2

4.10479

4.09380

4.07511

4.05576

Knudsen-cell 3

4.03873

4.02750

4.01000

3.99259

Knudsen-cell 4

4.06179

4.04822

4.02693

4.00977

*The samples were stored in an exsiccator after the weighings until start of the next measurement series due to organisational reasons.

 

Measurement Data Experiment 6

Experiment

6

 

 

 

Nom. Temperature

105

°C

 

 

Date and time START

 

21.02.2018 08:30

22.02.2018 08:10

26.02.2018 11:30

Date and time END

 

22.02.2018 06:55

23.02.2018 07:00*

27.02.2018 11:45

Parameter

Weight m

Weight m

Weight m

Weight m

Unit

g

g

g

g

Knudsen-cell 1

4.02314

3.99294

3.97475

3.96142

Knudsen-cell 2

4.05576

4.01903

4.00541

3.99599

Knudsen-cell 3

3.99259

3.95871

3.94358

3.93324

Knudsen-cell 4

4.00977

3.97750

3.96299

3.95172

*The samples were stored in an exsiccator after the weighings until start of the next measurement series due to organisational reasons.

 

CALCULATION OF RESULTS

 

Equation

The vapour pressure was calculated using the following equation:

p = (m/KAt)√(2ᴨRT/M)

 

with

Equation Parameters

Parameter

Explanation

Source/Value

p

Vapour pressure in Pa

To be calculated

m

Weight loss in kg

Value given in tables (calculation results) is divided by 1000

t

Time in s

As given in tables (calculation results)

A

Area of aperture in m2

7.854 * 10-7/m2

K

Correction factor

0.909

R

Universal gas constant in J/Mol*K

8.314472

T

Temperature in K

As given int able (calculation results)

M

Molecular weight in kg/Mol

0.3042

 

The correction constant is dependent upon the relation length/radius of the aperture of the Knudsen cell and is stated in the literature as follows:

Correction factor K

Relation

0.2

K

0.909

With the chosen length of the aperture 0.1 mm and the chosen radius 0.5 mm, a relation of 0.2 was calculated, and a correction factor of 0.909 was used.

 

Calculation Results

The calculation results of experiment 3 – 5 (nominal temperature 60 -90 °C) are given in the tables below.

In all table, E-0X represents multiplication with 10-X. Experiment 1-2 and 6 (nominal temperature 30 – 45 and 105 °C) showed no reproducible weight loss. Therefore, they were not used for calculation.

 

Calculation Results Experiment 3

Experiment

3

 

 

 

 

 

 

 

 

Real Temperature in K

333.2

 

 

 

 

 

 

 

 

Real Temperature in °C

60.0

 

 

 

 

 

 

 

 

Date of Measurement

02.02.2018 10:00

06.02.2018 11:45

07.02.2018 11:45

Elapsed Time in s

78600

88500

83100

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

0.00031

yes

1.32E-03

0.00053

yes

2.01E-03

0.00045

yes

1.81E-03

Knudsen-cell 2

0.00026

yes

1.11E-03

0.00070

yes

2.65E-03

0.00014

yes

5.64E-04

Knudsen-cell 3

0.00032

yes

1.36E-03

0.00050

yes

1.89E-03

0.00061

yes

1.64E-03

Knudsen-cell 4

0.00033

yes

1.41E-03

0.00059

yes

2.23E-03

0.00065

yes

2.62E-03

Mean

 

yes

1.30E-03

 

yes

2.20E-03

 

yes

1.86E-03

Standard deviation:

 

 

1.33E-04

 

 

3.34E-04

 

 

9.34E-04

Mean of measured values:

 

1.787E-03

 

 

 

 

 

 

Standard deviation:

 

4.529E-04

RSD:

25.3%

 

 

 

 

 

Calculation Results Experiment 4

Experiment

4

 

 

 

 

 

 

 

 

Real Temperature in K

347.2

 

 

 

 

 

 

 

 

Real Temperature in °C

75.0

 

 

 

 

 

 

 

 

Date of Measurement

13.02.2018 11:25

14.02.2018 11:50

15.02.2018 13:20

Elapsed Time in s

91500

83700

89100

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

0.00290

yes

1.09E-02

0.00078

yes

3.19E-03

0.00177

yes

6.80E-03

Knudsen-cell 2

0.00330

yes

1.24E-02

0.00172

yes

7.04E-03

0.00231

yes

8.88E-03

Knudsen-cell 3

0.00354

yes

1.33E-02

0.00237

yes

9.70E-03

0.00225

yes

8.65E-03

Knudsen-cell 4

0.00439

yes

1.64E-02

0.00299

yes

1.22E-02

0.00323

yes

1.24E-02

Mean

 

yes

1.32E-02

 

yes

8.04E-03

 

yes

9.19E-03

Standard deviation:

 

 

2.36E-03

 

 

3.87E-03

 

 

2.34E-03

Mean of measured values:

 

1.015E-02

 

 

 

 

 

 

Standard deviation:

 

2.722E-03

RSD:

26.8%

 

 

 

 

 

Calculation Results Experiment 5

Experiment

5

 

 

 

 

 

 

 

 

Real Temperature in K

363.2

 

 

 

 

 

 

 

 

Real Temperature in °C

90.0

 

 

 

 

 

 

 

 

Date of Measurement

16.02.2018 11:20

20.02.2018 06:48

21.02.2018 07:10

Elapsed Time in s

75600

82980

84000

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

0.00731

yes

3.38E-02

0.01603

yes

6.76E-02

0.01471

yes

6.13E-02

Knudsen-cell 2

0.01099

yes

5.09E-02

0.01869

yes

7.88E-02

0.01935

yes

8.06E-02

Knudsen-cell 3

0.01123

yes

5.20E-02

0.01750

yes

7.38E-02

0.01741

yes

7.25E-02

Knudsen-cell 4

0.01357

yes

6.28E-02

0.02129

yes

8.98E-02

0.01716

yes

7.15E-02

Mean

 

yes

4.99E-02

 

yes

7.75E-02

 

yes

7.15E-02

Standard deviation:

 

 

1.20E-02

 

 

9.38E-03

 

 

7.92E-03

Mean of measured values:

 

6.626E-02

 

 

 

 

 

 

Standard deviation:

 

1.452E-02

RSD:

21.9%

 

 

 

 

 

Evaluation

The measured values for temperature and vapour pressure were evaluated as follows:

Evaluation of Calculated Values

Parameter

T

Mean p

1/T

Log p

Unit

K

Pa

1/K

Log Pa

Values

333.2

1.79E-03

3.0012E-03

-2.7479

348.2

1.02E-02

2.8719E-03

-1.9935

363.2

6.63E-02

2.7533E-03

-1.1787

In this table, E-0X represents multiplication with 10-X.

 

RESULTS

 

Test item

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

Experimentally Determined Vapour Pressures

T

T

p

Stand. Dev. p

RSD p

°C

K

Pa

Pa

%

60.0

333.2

1.79E-03

4.53E-04

25.3%

75.0

348.2

1.02E-02

2.72E-03

26.8%

90.0

363.2

6.63E-02

1.45E-02

21.9%

In this table, E-0X represents multiplication with 10-X.

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

 

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

Results Test Item

Vapour pressure at 20 °C:

4.36 * 10-06Pa

Vapour pressure at 25 °C:

1.00 * 10-05Pa

 

The linear regression of log p vs. 1/T gave a correlation coefficient r of -0.9989, showing good repeatability and precision. Therefore, the determination is considered as valid.

 

Positive Control

For Diethylphthalate the following vapour pressure was determined and compared with recommended value:

Results Positive Control

Vapour pressure (positive control) at 30 °C:

1.60 * 10-1Pa

Criterion for the vapour pressure of the positive control at 30 °C:

0.44 * 10-1– 2.44 * 10-1Pa

 

The vapour pressure met the validity criteria. Therefore, the study can be considered as valid.

 

Discussion

The vapour pressure of the test item Trixene AS was determined at six different temperatures (30, 45, 60, 75, 90 and 105 °C) according to OECD 104 resp. EU A.4 using the effusion method (weight loss). Experiment 1-2 and 6 (nominal temperature 30 – 45 and 105 °C) showed no 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. All evaluated experiments showed good reproducibility, giving relative standard deviations of less than 27% (limit value from the guideline 30%) and good correlation.

Therefore, the results of the test can be considered valid.

Conclusions:
For the test item Trixene AS, the following vapour pressures at 20°C and at 25°C were calculated from the regression equation:
Vapour pressure at 20°C: 4.36E-6 Pa
Vapour pressure at 25°C: 1.00E-5 Pa
The linear regression of log p vs. 1/T gave a correlation coefficient r of - 0.9989, showing good repeatability and precision. Therefore, the determination is considered as valid.
Executive summary:

Determination of the Vapour Pressure of Trixene AS ac-cording to OECD 104 resp. EU A.4 using the effusion method: Knudsen Cell.

 

Findings and Results:

The vapour pressure of Trixene AS was determined according to OECD 104 resp. EU A.4 using the effusion method (weight loss).

 

Vapour pressure was examined at six different temperatures. Three temperatures could be evaluated as they showed reproducible weight loss. For these temperatures, 1/T was plotted against log (p).

 

Vapour Pressures (Effusion Method)

Experiment

T

Mean p

Stand. Dev. p

RSD p

No.

K

Pa

Pa

%

3

333.2

1.79E-03

4.53E-04

25.3%

4

348.2

102E-02

2.72E-03

26.8%

5

363.2

6.63E-02

1.45E-02

21.9%

In this table, E-0X represents multiplication with 10-x.

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

 

The graph 1/T vs. log (p) shows a straight line with a correlation coefficient of - 0.9989.

 

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

Vapour pressure at 20 °C: 4.36 * 10-06Pa

Vapour pressure at 25 °C: 1.00 * 10-05Pa

Description of key information

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

Vapour pressure at 20 °C: 4.36 x 10-06Pa

Vapour pressure at 25 °C: 1.00 x 10-05Pa

Key value for chemical safety assessment

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

Additional information

The vapour pressure of Trixene AS was determined according to OECD 104 resp. EU A.4 using the effusion method (weight loss).

 

Vapour pressure was examined at six different temperatures. Three temperatures could be evaluated as they showed reproducible weight loss. For these temperatures, 1/T was plotted against log (p).

 

Vapour Pressures (Effusion Method)

Experiment

T

Mean p

Stand. Dev. p

RSD p

No.

K

Pa

Pa

%

3

333.2

1.79E-03

4.53E-04

25.3%

4

348.2

102E-02

2.72E-03

26.8%

5

363.2

6.63E-02

1.45E-02

21.9%

In this table, E-0X represents multiplication with 10-x.

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

 

The graph 1/T vs. log (p) shows a straight line with a correlation coefficient of - 0.9989.

 

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

Vapour pressure at 20 °C: 4.36 * 10-06Pa

Vapour pressure at 25 °C: 1.00 * 10-05Pa