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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:
Oct 13 - Nov 10, 2015
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 104 (Vapour Pressure Curve)
Qualifier:
according to
Guideline:
EU Method A.4 (Vapour Pressure)
GLP compliance:
yes (incl. certificate)
Remarks:
Rheinland-Pfalz, Landesamt für Umwelt, Wasserwirtschaft und Gewerbeaufsicht, Mainz, Germany
Type of method:
effusion method: by loss of weight or by trapping vaporisate
Temp.:
20 °C
Vapour pressure:
0.001 Pa
Remarks on result:
other: calculated value
Temp.:
25 °C
Vapour pressure:
0.001 Pa
Remarks on result:
other: calculated value

RESULTS

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

%

45.0

318.2

1.13E-02

6.77E-04

6.0%

60.0

333.2

5.87E-02

3.87E-03

6.6%

75.0

348.2

2.40E-01

1.23E-02

5.1%

90.0

363.2

9.55E-01

1.96E-02

2.1%

In this table, E-0X represents multiplication with 10-X. Stand. Dev. = Standard Deviation; RSD = Relative Standard Deviation

For the test item SP-173, the following vapour pressures at 20 °C and at 25 °C were calcu-lated from the regression equation:

Vapour pressure at 20°C: 5.40 * 10-04 Pa

Vapour pressure at 25°C: 1.03 * 10-03 Pa

The linear regression of log P vs. 1/T gave a correlation coefficient r of - 0.9999, showing good repeatability and precision. Therefore, the determination is considered as valid.

DISCUSSION

The vapour pressure of the test item SP-173 was determined at five different temperatures (30, 45, 60, 75 and 90 °C) following EU A.4 using the effusion method (weight loss). Experiment 1 (nominal temperature 30 °C) showed only a poor reproducible weight loss, which was considered to be caused by evaporating impurities/humidity. To avoid bias, these measurements were not used for calculations. Four 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 7 % and very good correlation. Therefore, the result of the test can be considered valid.

Description of key information

0.00054 Pa at 20 °C
0.00103 Pa at 25 °C

Key value for chemical safety assessment

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

Additional information

The vapour pressure of the substance trihexyl phosphate (CAS No. 2528-39-4) was measured according to OECD 104 / A.4 by effusion method (weight loss). The results at 20°C and 25 °C were estimated by calculation.