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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:
10 December 2003 to 17 December 2003
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
Qualifier:
according to guideline
Guideline:
EPA OPPTS 830.7950 (Vapor Pressure)
Deviations:
no
GLP compliance:
yes
Type of method:
gas saturation method
Temp.:
25 °C
Vapour pressure:
0 Pa
Temp.:
20 °C
Vapour pressure:
0 Pa

Table 1: Results for the test material (experiments in the solid phase)

Temperature (ºC)

Saturation Gas Flow Rate (N2) (ln/h)

Volume (ln)

Duration of experiment (h)

Amount of transported substance (µg)

Vapour pressure (Pa)

50.34

12.00

1433.295

119.45

3.4

2.17 x 10-5

79.90

12.09

261.663

21.65

37.5

1.31 x 10-3

100.58

3.06

46.209

15.11

76.9

1.52 x 10-2

100.57

6.01

35.313

5.88

62.5

1.62 x 10-2

100.55

11.97

40.684

3.40

72.9

1.64 x 10-2

26.86

12.08

2697.570

223.30

<1

<3.39 x 10-8

 

Equation for the calculation of the vapour pressure of the test material at a given temperature:

P = (G*R*273.15)/(Mg*Vo*1000)

where:

P = Pressure in Pascal

G = amount of transported substance in µg

R = gas constant = 8.31451 J/mole*K

Mg = Molecular weight = 248.3

Vo = Gas volume in ln, litre normal (0 °C, 1 bar)

Remarks:

- The volume of nitrogen is given in litres at normal conditions (0 ºC and 1 atmosphere).

- In all experiments the condensation temperature was at least 30 ºC lower as the oven temperature .

- The gas flow rate was ranged from 3 L/h until 12 L/h. A saturation control was performed at 100.6 °C. The scattering of the vapour pressure measured at 100.6 °C for 3.1 L/h, 6.0 L/h and 12.0 L/h was in the normal error limit for the gas saturation method. The measured values were 1.52 x 10-2 Pa, 1.62 x 10-2 Pa and 1.6 x 10 -2 Pa.

The measurements in the solid state were fitted with a linear regression. For the measurement at 26.9 °C only a lower limit for the collected amount of substance was determined, this was omitted from the fit. Examination of the coefficients determined that the measurement at 26.9 °C was in accordance with the correct vapour pressure determined with the other points in the fit.

 

The coefficients of the equation:

Ln P = -A/T + B

where:

A = 15885.2062

B = 38.364589

Correlation with the regression line = 0.999 with P in Pascal and T in Kelvin

Heat of sublimation = 132.1 kJ/mole

 

Melting point (DSC) : 195.1 °C

Heat of fusion (DSC) : 29.2 kJ/mol

Vapour pressure at 20 °C: 1.3 x 10-7 Pa

Vapour pressure at 25 °C: 3.3 x 10-7 Pa

 

Heat of vaporisation = heat of sublimation - heat of fusion = 102.9 kJ/mol

  

The equation of the extrapolated curve to the liquid state:

 Ln P = -A/T + B

where:

A = 12373.2735

B = 30.864486

Heat of evaporation: 102.9 kJ/mol.

 

The system was checked for suitability using hexachlorobenzene. The experimental data obtained were in good agreement with the reference values provided in the guideline.

Conclusions:
Under the conditions of the test, the vapour pressure of the test material was determined to be 1.3 x 10^-7 at 20 °C and 3.3 x 10^-7 at 25 °C with a heat of sublimation of 132.1 kJ/mole. The study is considered to be reliable, relevant and adequate for risk assessment purposes.
Executive summary:

The vapour pressure of the test material was determined in accordance with the standardised guidelines OECD 104, EU Method A.4 and EPA OPPTS 830.7950 using the gas saturation method. The suitability of the test system was checked against the literature values provided by the OECD guideline for hexachlorobenzene, which were found to be in agreement with experimentally obtained values. Under the conditions of the test, the vapour pressure of the test material was determined to be 1.3 x 10-7 at 20 °C and 3.3 x 10-7 at 25 °C with a heat of sublimation of 132.1 kJ/mole.

Description of key information

1.3 x 10^-7 Pa at 20 °C

3.3 x 10^-7Pa at 25 °C

Heat of sublimation of 132.1 kJ/mole, OECD TG 104, Geoffroy 2003

Key value for chemical safety assessment

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

Additional information

The vapour pressure of the test material was determined in accordance with the standardised guidelines OECD 104, EU Method A.4 and EPA OPPTS 830.7950 using the gas saturation method. The suitability of the test system was checked against the literature values provided by the OECD guideline for hexachlorobenzene, which were found to be in agreement with experimentally obtained values. Under the conditions of the test, the vapour pressure of the test material was determined to be 1.3 x 10-7 Pa at 20 °C and 3.3 x 10-7 Pa at 25 °C with a heat of sublimation of 132.1 kJ/mole. The study was performed in line with GLP and accepted standardised guidelines with a high standard of reporting. The study was assigned a reliability score of Klimisch 1 and considered suitable for assessment as an accurate reflection of the test substance.

The available data are considered to be complete and the result determined, 1.3 x 10-7 Pa at 20 °C, was taken forward for risk assessment.