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Vapour pressure

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Description of key information

Considering all available data (experimental and modelised), the vapour pressure ranges from 0.23 to 4.42 Pa at 25 °C. The consistency of data found from different methodologies reveals the representativity of the values reported here. 
Besides, the key value for the vapour pressure of 4-chlorobenzotrichloride has been chosen based on the most conservative and reliable data, i.e 4 Pa at 20 °C.

Key value for chemical safety assessment

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

Additional information

In company investigation conducted by Schwiersch (1975), the vapor pressure of 4-chloro-benzotrichloride was measured for seven temperatures between 100 and 220°C in order to establish the Antoine equation. The Antoine equation is a logaritmic linear relation between the vapor pressure of a substance and its temperature.

With this linear relation the vapor pressure can be determined for other temperatures.

The Antoine equation was found to be equal to:

  • log P = 2.844398 + (-29977.626 / (273.15+T)) for P in mBar and T in °C
  • log P = 8.719495 + (-29977.626 / (273.15+T)) for P in Torr and T in °C

Hence, In this study, the vapor pressure of 4-chloro-benzotrichloride was extrapolated at 20°C and is equal to 0.031 Torr or 4.2 Pa. However, this private investigation is poorly documented and thus should be considered as not assignable.

The value reported for vapour pressure by Hommel (2002) in "Hommel interaktiv - Handbuch der gefährlichen Güter", 0.04 mBar at 20°C, is very close to the extrapolated value given by Schwiersch (1975). Besides, this handbook is considered as reliable with restrictions according to the ECHA guidance on specific endpoint guidance, chapter R7.a.

The remaining data are the results of QSARs approaches.

In a first estimation, the vapour pressure of 4 -chlorobenzotrichloride (CAS n° 5216 -25 -1) has been estimated with the modified grain method with the software MPBPVP (v 1.43) of the EPI suite (v 4.00).

In this modelisation, the software MPBPVP (v 1.43) of the EPI suite (v 4.00) returned a vapour pressure of 3.32 Pa at 25 °C for the the 4-chlorobenzotrichloride.

According to the ECHA guidance on specific endpoint guidance, chapter R7.a, the vapour pressure can be estimated with the modified grain method, a QSAR approach, with the help of the software MPBPVP (v 1.43) of the EPI suite (v 4.00). Hence, this method is an accepted calculation method and this result should be considered as reliable with restrictions.

In a second estimation, the vapour pressure of 4 -chlorobenzotrichloride (CAS n° 5216 -25 -1) has been estimated with the software SPARC (w4.5.1529 -s4.5.1529).

In this modelisation, after encoding of the smile formula and setting the melting point at 5.82 °C, the software returned a vapour pressure of 0.23 Pa at 25 °C for the the 4 -chlorobenzotrichloride. Without setting the melting point, the software returned a vapour pressure of 2.83 Pa at 20 °C.

According to the ECHA guidance on specific endpoint guidance, chapter R7.a, the vapour pressure can be estimated with the the QSAR approach of the software SPARC (w4.5.1529-s4.5.1529). Hence, this method is an accepted calculation method and this result should be considered as reliable with restrictions.

Considering these estimated data and their incertainties, considering the poor quality of the only available experimental data and considering the availability of peer-reviewed data, it has been chosen that the key value for the endpoint of vapour pressure would be the value of the Hommel handbook.