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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:
15 Dec 2016 - 11 Jan 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reference:
Composition 0
Qualifier:
according to
Guideline:
OECD Guideline 104 (Vapour Pressure Curve)
Version / remarks:
adopted in 1995
Deviations:
no
Qualifier:
according to
Guideline:
EU Method A.4 (Vapour Pressure)
Version / remarks:
adopted in 2008
Deviations:
no
GLP compliance:
no
Type of method:
effusion method: Knudsen cell
Test material information:
Composition 1
Specific details on test material used for the study:
Storage conditions: ambient temperature (10 to 30 °C)
Temp.:
20 °C
Vapour pressure:
< 0 hPa
Temp.:
25 °C
Vapour pressure:
< 0 hPa
Temp.:
50 °C
Vapour pressure:
< 0 hPa

Results
The test item was degassed at 50 °C for 8 h before the measurement. The vapour pressure was measured in a range of 70 to 120 °C.

Table 1 – Meaured vapour pressure and corresponding temperatures

Temperature [°C]

Vapour pressure [hPa]

70

1.2E-05

80

3.5E-06

90

3.7E-06

100

5.2E-06

110

3.5E-06

120

2.1E-06

 

The data point measured at 70 °C was taken into account for further evaluations because it shows a typical deviation caused by volatile impurities at the beginning of a measurement. This behavior could be caused by water of crystallization. Data points measured between 80 and 120 °C were below the detection limit of 1.0E-05 hPa.

Vapour pressures obtained were not sufficiently high to extrapolate to 20, 25 and 50 °C. Therefore, these values were estimated using the Antoine equation (Eq. 2).

Constant C was assumed to be equal to 273.15 and constant B was -5000. The detection limit (1.0E-05 hPa) at the highest measuring point (120 °C) was used for the calculation as all measured vapour pressures were below the detection limit.

A = 1.0 log10-5– [-5000/(273.15 + 120)] = 7.72

The vapour pressure at 20, 25 and 50 °C can then be calculated with the Antoine equation. Based on the detection limit and the highest measurement point at 120 °C, the following upper limit vapour pressures for the test item were calculated.

T [°C]

p [hPa]

p [Pa]

20

< 4.6E-10

< 4.6E-08

25

< 8.9E-10

< 8.9E-08

50

< 1.8E-08

< 1.8E-06

Description of key information

< 4.6E-10 hPa at 20 °C
< 8.9E-10 hPa at 25 °C
< 1.8E-08 hPa at 50 °C

(OECD 104, estimated using Antoine equation)

Key value for chemical safety assessment

Additional information

Vapour pressures obtained were not sufficiently high to extrapolate to 20, 25 and 50 °C. Therefore, these values were estimated using the Antoine equation.