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Physical & Chemical properties

Vapour pressure

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Reference
Endpoint:
vapour pressure
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2012
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
EU Method A.4 (Vapour Pressure)
Deviations:
no
Qualifier:
according to
Guideline:
OECD Guideline 104 (Vapour Pressure Curve)
Version / remarks:
(2006)
Deviations:
no
Qualifier:
according to
Guideline:
other: OECD 113 (1981) Screening test for thermal stability and stability in air
Deviations:
no
Principles of method if other than guideline:
Procedure
Thermal Stability:
As a preliminary measurement the thermal stability was determined by differential scanning calorimetry (DSC). The test item and the standard material (aluminium oxide) were heated up from ambient temperature to the final temperature (400 °C) at a constant heating rate (3 K/min) in a defined atmosphere (nitrogen). Closed glass crucibles were used as containers for the test item and the standard material. The quantity of heat absorbed or released was measured and recorded. About 8 mg of the test item was used.

Vapour Pressure Balance (Effusion Method):
The test item was degassed under vacuum at approximately 0.00001 hPa at 80 +/- 5 °C for approx. 9.5 hours before the measurement.
The apparatus consists of a high vacuum chamber. The test item is filled into a furnace in the chamber from which the sample evaporates. The temperature of the cell with the test item is controlled by a surrounding heater. The vapour forms a molecular jet of defined geometry limited by an orifice. The molecular jet can be interrupted by a shutter between the orifice of the cell and the plate of the balance. The vapour jet is condensed on a plate cooled down below - 100 °C by a surrounding copper baffle which is in contact with liquid nitrogen. The plate forms one end of an ultra micro balance. Using the shutter between the orifice and the balance, the increase of mass during an elapsed time period is recorded.
The vacuum in the chamber is maintained by a turbo-molecular pump in combination with a rotary pump down to a pressure of < 0.00001 hPa. The residual pressure is low enough to avoid condensation of gaseous impurities on the plate of the balance. ln addition the cooled copper baffle condenses all molecules with low vapour pressure.
The vapour pressure of the test item is calculated from the increase of mass Δm during an elapsed time period Δt. The vapour pressure was calculated according to the following equation:

P1 = k1 x √(T/M) x Δm/Δt

P1 = Vapour pressure in hPa
k1 = 0.00161 hPa x√(g/mol/K) x (s/µg)
The constant k1 combines the constant and known values (physico-chemical and geometric) and adapts the formula to the used dimension.
T = Temperature in K
M = Molecular mass in g/mol
Δm = Weight increase in µg on the ultra micro balance
Δt = Opening time of the orifice in s

The recommended range of the vapour pressure for this method is 0.00001 to 0.01 hPa and for the temperature between approximately 0 and 150 °C.
GLP compliance:
yes (incl. certificate)
Type of method:
effusion method: vapour pressure balance
Temp.:
20 °C
Vapour pressure:
0 Pa
Remarks on result:
other: extrapolated value
Temp.:
25 °C
Vapour pressure:
0 Pa
Remarks on result:
other: extrapolated value
Temp.:
50 °C
Vapour pressure:
0 Pa
Remarks on result:
other: extrapolated value

lndividual Results

Thermal Stability:

The DSC-measurement in a closed glass crucible with the test item showed no endothermic effect, but an exothermal effect in the temperature range 310 - 360 °C with an energy of 54 J/g.

Vapour Pressure Balance (Effusion Method):

The vapour pressure was measured in the temperature range of 29 °C to 110 °C. Above approximately 83 °C a vapour pressure could be measured. The measured vapour pressures at the corresponding temperatures are listed in the following table: For a conservative evaluation of the vapour pressure curve a molecular mass of 600 g/mol was used.

 Temperature / °C  Vapour pressure / hPa
 82.8 3.7 x 10 -5 
 90.6  9.1 x 10 -5
 97.1  1.5 x 10 -4
 104.1  2.5 x 10 -4
 110.1  3.5 x 10 -4
Conclusions:
Extrapolated vapour pressure values of the substance are 0.000005 Pa at 20 °C, 0.0000095 Pa at 25 °C and 0.00017 Pa at 50 °C.
Executive summary:

The purpose of this study was the determination of the vapour pressure of the test item according to the EU A.4 (Vapour pressure balance) and OECD test guidelines, OECD 104 (Vapour pressure; 2006) and OECD 113 (Screening test for thermal stability and stability in air; 1981). The extrapolated vapour pressure was 0.000005 Pa at 20 °C, 0.0000095 Pa at 25 °C and 0.00017 Pa at 50 °C.

Description of key information

Extrapolated vapour pressure values of the substance are 0.000005 Pa at 20 °C, 0.0000095 Pa at 25 °C and 0.00017 Pa at 50 °C.

Key value for chemical safety assessment

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

Additional information

The purpose of this study was the determination of the vapour pressure of the test item according to the EU A.4 (Vapour pressure balance) and OECD test guidelines, OECD 104 (Vapour pressure; 2006) and OECD 113 (Screening test for thermal stability and stability in air; 1981).