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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:
2002
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study without detailed documentation
Qualifier:
according to guideline
Guideline:
EU Method A.4 (Vapour Pressure)
Deviations:
no
GLP compliance:
no
Type of method:
other: Knudsen effusion method
Temp.:
20 °C
Vapour pressure:
0.17 Pa
Remarks on result:
other: 95 % confidence interval: 0.13¿0.23 Pa
Temp.:
25 °C
Vapour pressure:
0.22 Pa
Remarks on result:
other: 95 % confidence interval: 0.19¿0.25 Pa
Temp.:
30 °C
Vapour pressure:
0.27 Pa
Remarks on result:
other: 95 % confidence interval: 0.25¿0.29 Pa

The evaporation rates were measured at different temperatures (27-34 °C). Using the method of least squares Antoine coefficients of 4.91 and -1661.01 of the regression straight line were calculated (wih 95 % confidence interval). The vapor pressures were obtained from the results of least square calculation.

Conclusions:
The vapor pressure of heptanoic anhydride is 0.22 Pa obtained at 25°C with a 95% confidence intervall of 0.19-0.25 Pa.
Executive summary:

A vapor pressure balance was used for the determination of the vapor pressure. The method corresponds to the Knudsen effusion method as described in the EC Testing Guideline A.4. For measurement, the vapor jet of the test substances leaving a heatable Knudsen cell through an aperture of known size under high vacuum conditions is condensed on the cooled scale pan of a precision microbalance. The evaporation rate is determined from the increase in weight per unit time from which the vapor pressure was calculated with the Hertz-Knudsen- Langmuir equation.

Therefore, the vapor pressure of heptanoic anhydride is 0.22 Pa obtained at 25°C with a 95% confidence intervall of 0.19-0.25 Pa.

Description of key information

The vapor pressure of heptanoic anhydride is 0.22 Pa obtained at 25°C with a 95% confidence intervall of 0.19-0.25 Pa.

Key value for chemical safety assessment

Vapour pressure:
0.22 Pa
at the temperature of:
25 °C

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