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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:
31 Aug - 01 Sep 2015
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 104 (Vapour Pressure Curve)
Qualifier:
according to guideline
Guideline:
EU Method A.4 (Vapour Pressure)
GLP compliance:
no
Type of method:
effusion method: Knudsen cell
Specific details on test material used for the study:
Storage conditions: ambient temperature (10 – 30 °C)
Temp.:
ca. 50 °C
Vapour pressure:
ca. 0 hPa
Temp.:
ca. 25 °C
Vapour pressure:
ca. 0 hPa
Temp.:
ca. 20 °C
Vapour pressure:
ca. 0 hPa

Results
The vapour pressure was measured in the range of 71 to 120 °C.

Table 1 – Measured vapour pressures and corresponding temperatures

Temperature [°C]

Vapour pressure [hPa]

71

4.2E-05

80

1.0E-05

90

4.9E-06

100

5.8E-06

110

5.1E-06

120

1.1E-05

 

Discussion: Data points measured at 71 and 80 °C were excluded in the evaluation because the showed a typical deviation caused by volatile impurities at the beginning of a measurement. As the test did not yield vapour pressure sufficiently high to extrapolate to 20, 25, and 50 °C, these values were estimated using the Antoine equation (Eq. 1).

For constant C, a value of 273.15 was assumed and for constant B a value of -5000 was assumed. The vapour pressure at the highest measurement point (120 °C) was used for the calculation since all others were below the detection limit (1.0E-05 hPa). Constant A in the Antoine equation (Eq.1) was calculated:

A = log (1.0E-05) – [-5000/(273.15 + 120)] = 7.72

The vapour pressure at 20, 25 and 50 °C can then be calculated: log p = 7.72 + [-5000/(273.15 + T)]

Table 2 – Calculated vapour pressures from experimental data

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

This is a conservative estimation of the vapour pressure of the test item for the listed temperatures.

Final Results

Table 3– Extrapolated vapour pressure values from experimental data

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

The following vapour pressure values for the test item were extrapolated from the experimental data: 0.000000046 p/Pa at 20°C; 0.000000089 p/Pa at 25°C; 0.0000018 p/Pa at 50°C.