Vapor pressure of 1-octanol below 5 kPa using DSC

• ASTM E 1782 (vapor pressure by DSC) is useful above 5 kPa using pinholes <75 μm.
• Below 5 kPa, boiling endotherms are unacceptably broad with the recommended pinholes.
• Use of larger pinholes (up to 350 μm) at low pressures improves endotherm shape.
• 1-Octanol results show good agreement with literature using larger pinholes at low pressures.

American Society for Testing and Materials (ASTM) Method E 1782-08, Standard Test Method for Determining Vapor Pressure by Thermal Analysis recommends use of hermetic-type sealable sample pans with a single 50–75 μm pinhole in the lid for pressures between 5 kPa and 2 MPa. At pressures below 5 kPa using the recommended pinhole range, boiling endotherms become increasingly broad. Earlier studies demonstrated qualitative improvement in endotherm sharpness with use of larger pinholes (up to 350 μm) at pressures below 5 kPa. In the current work, the vapor pressure of 1-octanol was determined in accordance with ASTM E 1782-08 using pinholes ranging from 75 to 350 μm from atmospheric pressure down to 0.197 kPa. These results clearly indicate that vapor pressure data in good agreement with the literature can be produced for 1-octanol at pressures as low as 0.2 kPa if pinhole sizes up to 350 μm are used; the results are comparable to those generated using the current ASTM-recommended pressure and pinhole parameters.