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Vapour pressure

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Reference
Endpoint:
vapour pressure
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Reason / purpose:
reference to same study
Guideline:
other: vapour-liquid equilibrium method similar to the static method
Deviations:
yes
Remarks:
Measured values corrected using the residual pressure recorded at absolute zero. However, in theory the pressure would increase with temperature. This deviation is not anticipated to have a significant effect on reported value.
Principles of method if other than guideline:
The principle behind the vapor-liquid equilibrium (VLE) apparatus is that evacuating the sample chamber at cryogenic temperatures causes a negligible amount of sample to vaporize but allows the chamber to be emptied of air. When the chamber is brought to temperature, the pressure reading reflects only vaporized sample.
GLP compliance:
no
Type of method:
static method
Remarks:
vapour-liquid equilibrium method
Specific details on test material used for the study:
Lot # 901019573
Test no.:
#1
Temp.:
25.5 °C
Vapour pressure:
0.18 PSI
Key result
Test no.:
#1
Temp.:
25.5 °C
Vapour pressure:
1 241 Pa
Remarks on result:
other: Value calculated from reported PSI value.
Temp.:
180.5 °C
Vapour pressure:
14.7 PSI

It appears as though the chamber was not perfectly evacuated or that there were dissolved non-condensable gases (e.g. N2) in the frozen sample since the system was returned to cryogenic temperatures and the pressure registered a value of 0.18 psia. This value was stable over 45 minutes and was treated as an offset that was subtracted from the other readings in order to determine the “Corrected Vapor Pressure”.

Conclusions:
The vapour pressure of OFPMA was determined following a non-guideline vapour-liquid equilibrium method similar to the static method. The authors assumed the 0.18 psia recorded from the frozen sample once it was returned to the cryogenic temperature was due to the chamber not being perfectly evacuated or that there were dissolved non-condensable gases in the frozen sample. The measured values were corrected using this value; however, in theory the pressure would increase with temperature. This deviation is not anticipated to have a significant effect on the reported measured value; therefore, the vapour pressure of OFPMA is approximately 1241 Pa (0.18 PSI) at 25.5°C.

Description of key information

The vapour pressure of OFPMA was determined following a non-guideline vapour-liquid equilibrium method similar to the static method. The authors assumed the 0.18 psia recorded from the frozen sample once it was returned to the cryogenic temperature was due to the chamber not being perfectly evacuated or that there were dissolved non-condensable gases in the frozen sample. The measured values were corrected using this value; however, in theory the pressure would increase with temperature. This deviation is not anticipated to have a significant effect on the reported measured value; therefore, the vapour pressure of OFPMA is approximately 1241 Pa (0.18 PSI) at 25.5°C.

Key value for chemical safety assessment

Vapour pressure:
1 241 Pa
at the temperature of:
25.5 °C

Additional information