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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:
November 14, 2016
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 104 (Vapour Pressure Curve)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method A.4 (Vapour Pressure)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of method:
effusion method: isothermal thermogravimetry
Key result
Test no.:
#1
Temp.:
20 °C
Vapour pressure:
0 Pa

The evaporation rate of the test substance (VT) was calculated from the weight loss of the test substance at defined temperatures in a constant stream of nitrogen over periods of time. Linear regression analysis of log VT versus 1/T (1000/T) was performed for the test substance and for each reference substance. The evaporation rates at 20 °C (VT, 20) were determined from these relationships. The relationship between the values of VT, 20 of the reference substances and their known vapor pressures was established as a regression equation. The relationship between evaporation rate and vapor pressure, derived for 20 °C, includes the characteristics of the experimental setup, which are subsequently employed in the calculation of vapor pressure values at other temperatures.

Equation for the regression line of log PT as a function of log VT used for calibration:

log PT = 4.8560+1.1723 x log VT

The coefficient of correlation (R2) was 0.9977.

Equation for the temperature dependence of the vapor pressure of the test substance:

log PT=C+D x (a / T+b)=C+(D x b)+(D x a) / T

Conclusions:
Under the study conditions, the vapor pressure of the test substance was calculated (mean of three determinations) to be 2.23-E06 Pa at 20 °C.
Executive summary:

A study was conducted to determine the vapour pressure according to OECD 104 resp. EU A.4 Method, in compliance with GLP. The vapor pressure of the test substance at 20 °C (PT, 20) was evaluated using the isothermal thermogravimetric effusion method. According to the guideline this method was validated in the range 10+E10 to 1 Pa using a set of reference substances with known vapor pressures. Based on the results from the pre-test the main test with three replicates was done between 130 °C and 180 °C. The test substance was added to the glass plate. The plate was placed in the TGA instrument. The weight loss of the test item was measured continuously as a function of time at different temperatures at constant nitrogen flow. Measurement program was: start at minimum temperature of 130 °C following with temperature increase: 10 °C with a ramp of 10 °C/min, Isothermal interval of 5 min and end temperature: 180 °C. A value of the vapour pressure of the test substance was determined using weight loss data obtained between 140 °C and 170 °C. Under the study conditions, the vapor pressure of the test substance was calculated (mean of three determinations) to be 2.23-E06 Pa at 20 °C (Wagner Rivas, 2017).

Description of key information

Determination of the vapour pressure according to OECD Guideline 104 and EU Method A.4 (Wagner Rivas, 2017).

Key value for chemical safety assessment

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

Additional information