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Vapour pressure

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Description of key information

Vapour pressure < 0.0009804 Pa at 25 °C, OECD 104, EU Method A.4, Tremain (2013b).

Key value for chemical safety assessment

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

Additional information

In the key study (Tremain, 2013b) the vapour pressure of the test material was investigated in a GLP study which was conducted in accordance with the standardised guidelines OECD 104 and EU Method A.4 using a vapour pressure balance.

A sequence of runs was started after a sample of test material had been under vacuum for approximately 46¼ hours. Temperature and pressure readings were taken between 60 and 70 °C with a one hour dwell at 60 °C between runs.

A sequence of 10 runs was completed. No statistical analyses were performed because the balance readings were too low and variable for a line of best fit to have any meaning. Instead it was considered more appropriate to impose a regression slope on a chosen data point to provide an estimate of the maximum value for the vapour pressure at 25 °C.

Run 10 was chosen because the sample had been under vacuum for the longest period prior to the run and so degassing would have been the most complete. The reading at 61 °C (334.15 K) was chosen because his is the data point which gives the highest estimated vapour pressure at any given temperature when a slope of -1500 K is imposed upon it.

The value of -1500 K is an in-house value and is the shallowest slope observed whilst determining the vapor pressure on a wide range of samples using the vapour pressure balance method. Extrapolation to 25 °C gave a vapour pressure of 9.804 x 10-4Pa which has been taken as a maximum for this test material.

Although the vapour pressure of the substance was not precisely determined due to its extremely low value, in order to allow the Chesar software to run correctly a surrogate value of 0.0009804 has been entered as the key value for safety assessment.