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Vapour pressure

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Description of key information

Vapour Pressure 28 Pa at 20 °C, EU Method A.4, Younis (2015)

Key value for chemical safety assessment

Vapour pressure:
28 Pa

Additional information

The vapour pressure of the test material was investigated in accordance with the standardised guideline EU Method A.4 under GLP conditions via the static method using a U-tube manometer.

The static method involved placing a sample in a bulb maintained at constant temperature and connected to a pressure monitor and a vacuum pump.

A sufficient quantity of sample was added to the static method glassware. The glassware was attached to the vacuum system and both the system and the filled glassware were evacuated to a pressure of 13.3 Pa (0.1 torr). The vacuum was broken with nitrogen and the system was evacuated again. This procedure was repeated a further two times to remove any residual oxygen.

After the sample had been degassed, the vacuum line valve was closed along with the relevant static method glassware valves. The filled static method glassware was positioned in the constant temperature bath at the desired starting temperature. As the static apparatus approached temperature equilibrium in the bath, nitrogen was added to the gas-sampling system until its pressure equals that of the sample.

Periodically the pressure of the nitrogen in the gas-handling system was adjusted to equal that of the sample. When the static apparatus reaches temperature equilibrium, final adjustments of the nitrogen pressure were made to equal the vapour indicated by the manometer section of the apparatus. When the liquid levels in the manometer arms were equal in height, balance was indicated. The nitrogen pressure in the system was recorded at the balance point. In the case of solids, depending on the pressure and temperature ranges, manometer liquids such as silicon fluids or phthalates were used.

The temperature of the constant-temperature bath was increased by an appropriate amount. As the temperature rose, the pressure balance in the system was maintained. When temperature equilibrium was reached, final adjustments of pressure were made to establish balance. The system pressure was then recorded. This process was repeated at regular intervals until an adequate range of pressures had been obtained.

Results are subject to only slight errors for samples containing non-volatile impurities. The recommended range is 10^-2 to 10^5 Pa.

Under the conditions of the study the test material was determined to have a vapour pressure of 28 Pa at 20 °C (mean of two runs).