[No public or meaningful name is available]

Vapour pressure

Link to relevant study record(s)

Reference

Endpoint:

vapour pressure

Type of information:

experimental study

Adequacy of study:

key study

Study period:

23 January 2018 to 27 February 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:

2006

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method A.4 (Vapour Pressure)

Version / remarks:

2009

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

effusion method: Knudsen cell

Key result

Test no.:

#1

Temp.:

20 °C

Vapour pressure:

0.003 Pa

Key result

Test no.:

#1

Temp.:

25 °C

Vapour pressure:

0.004 Pa

Sample Weights

Knudsen-cell 1: 0.64935 g test material

Knudsen-cell 2: 0.69900 g test material

Knudsen-cell 3: 0.67754 g test material

Knudsen-cell 4: 0.65529 g test material

 

Observations

30 °C: At the first measurement of experiment 1, all cells were slightly contaminated. Therefore, the cells were meticulously cleaned and weighed. This weight was used as initial weight for the subsequent measurements. To avoid bias, this measurement was not used for calculations.

60 °C: At the second measurement of experiment 3, all cells were slightly contaminated. Therefore, the cells were meticulously cleaned and weighed. This weight was used as initial weight for the subsequent measurements. To avoid bias, this measurement was not used for calculations.

60 °C: At the third measurement of experiment 3, cell 1 and 4 were slightly contaminated. Therefore, the cells were meticulously cleaned and weighed. This weight was used as initial weight for the subsequent measurements. To avoid bias, this measurement was not used for calculations.

 

Calculation Results

Experiment 1:

Temperature: 303.2 K; 30.0 °C

Mean of measured values: 4.223E-03

Standard deviation: 2.825E-06; RSD: 0.1 %

 

Experiment 2:

Temperature: 318.2 K; 45.0 °C

Mean of measured values: 6.321E-03

Standard deviation: 1.802E-03; RSD: 28.5 %

 

Experiment 3:

Temperature: 333.2 K; 60.0 °C

Mean of measured values: 8.612E-03

Standard deviation: 2.495E-03; RSD: 29.0 %

Evaluation

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

Table 1: Evaluation of Calculated Values

Temperature (K)	Mean p (Pa)	1/T (1/K)	log p (log Pa)
303.2	4.22E-03	3.2982E-03	-2.3744
318.2	6.32E-03	3.1427E-03	-2.1992
333.2	8.61E-03	3.0012E-03	-2.0649

 

- A graph with log p vs. 1/T was plotted. Since the values were correlated by a linear relation, the data could be fitted by linear regression.

Slope: -1043.6

Intercept: 1.0719

Correlation Coefficient (r): -0.9988

Coefficient of Determination (r^2): 0.9976

 

Test Material

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

Table 1: Experimentally Determined Vapour Pressures

Temperature (°C)	Temperature (K)	Vapour Pressure (Pa)	Standard Deviation (Pa)	RSD p (%)
30.0	303.2	0.00422	0.00000283	0.1 %
45.0	318.2	0.00632	0.00180	28.5 %
60.6	333.2	0.00861	0.00249	29.0 %

RSD = Relative standard deviation.

- The following vapour pressures at 20 and 25 °C were calculated from the regression equation:

Vapour pressure at 20 °C: 3.25 x10^-03 Pa

Vapour pressure at 25 °C: 3.73 x10^-03 Pa

 

- The linear regression of log p vs. 1/T gave a correlation coefficient r of - 0.9988, 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:

Vapour pressure (positive control) at 30 °C: 1.60x10^-1 Pa

Criterion for the vapour pressure of the positive control at 30 °C: 0.44x10^-1 - 2.44x10^-1 Pa

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

 

Discussion

- The vapour pressure of the test material 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 4 - 6 (nominal temperature 75 - 105 °C) showed no reproducible weight loss. When visible contaminations, caused by explosive evaporation of the test material, 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 30 % (limit value from the guideline 30 %) and good correlation. Therefore, the result of the test can be considered valid.

Conclusions:

Under the conditions of this study, the vapour pressure of the test material at 20 °C was 3.25 x10^-03 Pa and at 25 °C was 3.73 x10^-03 Pa.

Executive summary:

The vapour pressure of the test material was investigated in accordance with the standardised guidelines OECD 104 and EU Method A.4, under GLP conditions.

The vapour pressure was determined 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).

The graph 1/T vs. log (p) showed a straight line with a correlation coefficient of -0.9988. For the test material the vapour pressures at 20 °C and at 25 °C were calculated from the regression equation.

Under the conditions of this study, the vapour pressure of the test material at 20 °C was 3.25 x10^-03 Pa and at 25 °C was 3.73 x10^-03 Pa.

Description of key information

Under the conditions of this study, the vapour pressure of the test material at 20 °C was 3.25 x10^-03 Pa and at 25 °C was 3.73 x10^-03 Pa.

Key value for chemical safety assessment

Vapour pressure:

0.003 Pa

at the temperature of:

20 °C

Additional information

The vapour pressure of the test material was investigated in accordance with the standardised guidelines OECD 104 and EU Method A.4, under GLP conditions. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

The vapour pressure was determined 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).

The graph 1/T vs. log (p) showed a straight line with a correlation coefficient of -0.9988. For the test material the vapour pressures at 20 °C and at 25 °C were calculated from the regression equation.

Under the conditions of this study, the vapour pressure of the test material at 20 °C was 3.25 x10^-03 Pa and at 25 °C was 3.73 x10^-03 Pa.