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Physical & Chemical properties

Vapour pressure

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Description of key information

Several vapour pressure values were reported at several temperatures. Since very little detail is available with regard to the measured datea, the vapour pressure was also calculated with EPI Suite (vs 4.10) using the modified Grain method and with SPARC (v. 4.6). EpiSuite yielded the most conservative value of 0.207 Pa at 25°C. This value was used in further assessments. 

Key value for chemical safety assessment

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

Additional information

The vapour pressure of 44PD (CAS 101 -96 -2) was calculated with EPI Suite, using a QSAR approach, based on the modified Grain model. The predicted value for the vapour pressure 0.207 Pa (at 25 °C) can be considered reliable as the substance falls within the applicability domain of the model, taking into account the excellent standard deviation and standard deviation error of the predictions against the training dataset, which consists of 3037 compounds, of which some have similar structures to 44PD.

EPI Suite was also used to calculate the vapour pressure at higher temperature to allow for a comparison with the two supporting studies. The vapour pressure that was documented in the toxicological profile was somewhat lower than the estimated value by EPI Suite: Tox. profile 1330 Pa at 170 °C and EPI Suite 2080 Pa at 170 °C. Still, given the uncertainty in the extrapolation with EPI Suite, the lack of experimental detail in the suporting study and the general difficulties in vapour pressure measurementes the results are very much comparable.

Besides EpiSuite, SPARC was also used to calculate the vapour pressure. The outcome was a Vp of 0.04 Pa at 25°C.

The values documented in the Tox. Bewertung are higher than the model result at 20 °C and lower at 196 °C and therefore more difficult to compare. However, the value at 20 °C (160 Pa) appears to be very high compared with the result at 196 °C (4400 Pa). The result at 196 °C in itself is in good agreement with the result in the toxicological profile and the modelling result. Finally, because the result from the NTP Chemical Repository is a clear outlier, it was not further taken into consideration.

Because of reliability and because EpiSuite yielded the most conservative value, a vapour pressure of 0.207 Pa at 25 °C is used as the key value.