The vapor pressures of four lower alkyl phosphonate compounds, dimethyl phosphonate (DMHP, CAS 868-85-9), dimethyl methylphosphonate (DMMP, CAS 756-79-6), diethyl methylphosphonate (DEMP, CAS 683-08-9), and diisopropyl methylphosphonate (DIMP, CAS 1445-75-6), have been measured by complementary methods that allow data collection at ambient and high temperatures by use of gas saturation and differential scanning calorimetry, respectively. Kosolapoff (J. Chem. Soc.195529642965) reported vapor pressure data above 200 Pa for several of these compounds measured by use of isoteniscope, although the lowest data points were deemed to be “not trustworthy” by the author. Our report extends the low end of the measured data range by 2 to 3 orders of magnitude in pressure. Antoine correlations, normal boiling temperatures, temperature-dependent enthalpies of vaporization, and volatility have been derived based on the measured data reported herein. The advantages of using complementary methodology and measuring, as opposed to extrapolating, data have been demonstrated in this work.

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No abstract

The vapor pressures of low-volatility chemical warfare (CW) agents, their byproducts and degradants, and simulants are important physical data that are needed for accurate vapor generation, for filter modeling and testing, and for assessing the environmental fate of the materials. This report documents the measurement of the vapor pressure of 1,4-dithiane (DTH), a byproduct associated with vesicant chemical warfare agent bis-2-chloroethyl sulfide (HD), in the range of (296.65 to 376.95) K. By combining our measurements with a study of the thermodynamic properties of the compound in the subambient range, we were able to calculate Antoine parameters that can be used to extend estimates of the vapor pressure from T ) (256.95 to 376.95) K. We have calculated a value of 10.6 Pa for the vapor pressure of the compound at 298.15 K. This contrasts with the accepted value of 107 Pa.

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