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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:
1995-02-15 to 1995-02-20
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
The study was conducted according to an internationally recognised method, and under GLP. However, the testing conditions were not the most suitable for the range considered. Purity and isomers composition are available from the notifier. Therefore validation applies with restrictions.
Qualifier:
according to
Guideline:
EU Method A.4 (Vapour Pressure)
GLP compliance:
yes (incl. certificate)
Remarks:
UK GLP compliance programme (inspected on 31 January 1994 / signed on 16 March 1994)
Type of method:
isoteniscope
Specific details on test material used for the study:
Storage conditions: metal bottle at room temperature.
Key result
Temp.:
20 °C
Vapour pressure:
17.2 Pa
Remarks on result:
other: mean of three runs (extrapolated)
Temp.:
25 °C
Vapour pressure:
23.3 Pa
Remarks on result:
other: mean of three runs (extrapolated)

Run 1:

A fresh sample of test material was boiled for approximately 41 minutes. Temperature and pressure readings (21 pairs) were taken between 236 and 175°C.

The measurements gave the regression for run 1:

Log10VP (Pa) = -2263.675 / T (K) + 9.049

Standard deviation in slope is 14.0177 (0.62%) and SD in intercept is 0.029 (0.32%).

Coefficient of determination was calculated from the data: R2= 0.9993

The above yields a calculated vapour pressure at 298.15 K of 28.597 Pa.

Run 2:

A fresh sample of test material was boiled for approximately 19 minutes. Temperature and pressure readings (28 pairs) were taken between 253 and 197°C.

The measurements gave the regression for run 2:

Log10VP (Pa) = -2354.323 / T (K) + 9.208

Standard deviation in slope is 12.429 (0.53%) and SD in intercept is 0.025 (0.27%).

Coefficient of determination was calculated from the data: R2= 0.9993

The above yields a calculated vapour pressure at 298.15 K of 20.509 Pa.

Run 3:

A fresh sample of test material was boiled for approximately 11 minutes. Temperature and pressure readings (22 pairs) were taken between 254 and 170°C.

The measurements gave the regression for run 3:

Log10VP (Pa) = -2366.434 / T (K) + 9.255

Standard deviation in slope is 13.514 (0.57%) and SD in intercept is 0.028 (0.30%).

Coefficient of determination was calculated from the data: R2= 0.9993

The above yields a calculated vapour pressure at 298.15 K of 20.803 Pa.

The test material did not change in appearance under the conditions used during the determination.

Conclusions:
Low volatility (based on volatility bands criteria for occupational exposure (Chesar / ECETOC TRA), << 500 Pa).
Executive summary:

The vapour pressure of the test substance was measured under GLP according to EU A4 guideline, isoteniscope method.

Three runs were performed, with respectively 21 measurements recorded between 236 and 175°C, 28 measurements recorded between 253 and 197°C, and 22 measurements recorded between 254 and 170°C. The slope and intercept of the linear relashionship between log VP and 1/T were calculated for each run. Vapour pressure of test substance was derived from the mean log VP extrapolated from these equations.

The vapour pressure of the test substance is ca 23.3 Pa at 25°C, and 17.2 Pa at 20°C (extrapolated).

Description of key information

Low volatility.

Key value for chemical safety assessment

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

Additional information

A reliable experimental study, conducted according to a recognized EC method and under GLP, is available. Despite restrictions due to applicability domain of the method, it is considered as a key study. Measurements were performed between 170 and 254°C, and the extrapolated result at 20°C is retained as key value for purpose of CSA.

It should be noted that, due to the multi-isomers nature of the substance, this result may refer to the most volatile one, as confirmed by a corresponding normal boiling point of 286°C, while the measured range is 282 - 303°C. However, as structures are close and b.p. range limited, vapour pressure is not anticipated to vary significantly between components.