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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:
January 12, 2015 - January 28, 2015
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
EU Method A.4 (Vapour Pressure)
Deviations:
no
Qualifier:
according to guideline
Guideline:
OECD Guideline 104 (Vapour Pressure Curve)
Deviations:
no
Principles of method if other than guideline:
Due to the unusual behaviour of the test item (possibly caused by the evaporation of volatile impurities and/or decomposition of the test item) the vapour pressure was estimated from the highest measured vapour pressure.

GLP compliance:
yes (incl. QA statement)
Type of method:
effusion method: vapour pressure balance
Temp.:
20 °C
Vapour pressure:
0 Pa
Temp.:
25 °C
Vapour pressure:
0 Pa
Temp.:
50 °C
Vapour pressure:
0 Pa

Results: 

The vapour pressure was measured in the temperature range of 100 °C to 120 °C in intervals of 5 K. The measured vapour pressures at the corresponding temperatures are listed in Table 1.

Table 1: Measured vapour pressures and corresponding temperatures

Temperature / °C

Vapour pressure / hPa

100*

4.99 × 10-5

105*

1.51 × 10-5

110*

2.22 × 10-5

115*

1.75 × 10-5

120*

1.40 × 10-5

100**

4.41 × 10-5

105**

4.16 × 10-5

110**

2.92 × 10-5

115**

2.53 × 10-5

120**

1.52 × 10-5

*first run

**second run

The first run showed a decreasing vapour pressure at increasing temperatures. In order to exclude an influence of volatile impurities the measurement was repeated. In this second run the test item was held at 80 °C for 5 h to vaporize volatile impurities of the test item. However the second run showed the same decreasing tendency as the first run. This behaviour could have been caused by any remaining volatile impurities or by a decomposition of the test item releasing smaller fragments of it with a higher vapour pressure. Due to the unusual behaviour no further evaluation of the measurement was performed.

Since the test yielded an unusual behaviour of the vapour pressure the values for 20, 25 and 50 °C were estimated according to the Antoine equation. For an extrapolation a conservative assumption of the Antoine constant C is 273.15. This results in a linear dependency of log(p) of the inverse Temperature 1/T (in K). Values for the resulting slope of the Antoine equation (constant B) for substances of high molecular weight, which can be derived from literature values (e.g. Handbook of Chemistry and Physics) are lower than -5000. Thus, for a conservative estimation of the vapour pressure of the test item at 20, 25 and 50 °C, a value of -5000 for constant B and a value of 273.15 for constant C, respectively, were used. The data point of the measurement with the highest vapour pressure at 100 °C was used as the starting point for the calculation. The measured vapour pressure at 100 °C was 4.99× 10-5 hPa. Due the unusual behaviour of the vapour pressure this value was rounded up to 1.00× 10-4hPa. Based on this assumption, the constant A of the Antoine equation was calculated and subsequently, the vapour pressure at 20, 25 and 50 °C can be calculated with the Antoine equation as follows:

Table 2: Calculated vapour pressure at 20, 25 and 50 °C

T / °C

p / hPa

p / Pa

20

< 2.2×10-8

< 2.2×10-6

25

< 4.3×10-8

< 4.3×10-6

50

< 8.5× 10-7

< 8.5× 10-5

 

This is a conservative estimation of the vapour pressure of the test item for the listed temperatures. In order to further ensure a conservative approach the vapour pressures were rounded up to the next order of magnitude in order to obtain final upper limit values for the vapour pressure.

Table 3: Final upper limit values for the vapour pressure at 20, 25 and 50 °C

T / °C

p / hPa

p / Pa

20

< 1×10-7

< 1×10-5

25

< 1×10-7

< 1×10-5

50

< 1× 10-6

< 1× 10-4

 

Executive summary:

Due to the unusual behaviour of the test item (possibly caused by the evaporation of volatile impurities and/or decomposition of the test item) the vapour pressure was estimated from the highest measured vapour pressure. The following vapour pressure values for the test item were extrapolated from this estimation:

T / °C

p / hPa

p / Pa

20

< 1×10-7

< 1×10-5

25

< 1×10-7

< 1×10-5

50

< 1× 10-6

< 1× 10-4

Description of key information

The vapour pressure of the test item was determined according to the European Commission Regulation (EC) No. 440/2008, Method, A.4. Vapour pressure: Vapour pressure balance and according to the OECD test guideline, OECD 104 Vapour pressure.

Key value for chemical safety assessment

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

Additional information

Due to the unusual behaviour of the test item (possibly caused by the evaporation of volatile impurities and/or decomposition of the test item) the vapour pressure was estimated from the highest measured vapour pressure. The following vapour pressure values for the test item were extrapolated from this estimation:

T / °C

p / hPa

p / Pa

20

< 1×10-7

< 1×10-5

25

< 1×10-7

< 1×10-5

50

< 1× 10-6

< 1× 10-4