Vapor pressures of explosives and drugs

The vapor pressures of many explosive compounds and illicit drugs are extremely low relative to volatile organic compounds. Determining accurate vapor pressure values at ambient temperature can be difficult. Vapor pressure measurements at higher temperatures are often used with vapor pressure equations to extrapolate the vapor pressure to 25 °C. Many researchers have measured and reported vapor pressure values for explosives or drugs, and there can be large variations (orders of magnitude) in reported vapor pressure values. Advances in sensitivity of vapor detection technologies has enabled measurement of the vapor pressure of low-volatility compounds at lower temperatures resulting in updated vapor pressure values in the literature. Knowing accurate vapor pressures of compounds is important to understand the feasibility of detecting substances for a variety of security applications.

This review of experimentally-measured vapor pressures of explosives and drugs is intended to be a companion to the prior review in TrAC by Ewing et al. (2013). Updates are provided on reported vapor pressure values of various explosives since the prior review. The content is expanded to include some vapor pressure values of drugs with the same intent as to provide benchmark levels in estimating vapor concentrations that could be available for detection. Vapor pressure relationships traceable to the original citations, including the temperature ranges for the measurements, are compiled. After critical examination of the available data, the vapor pressure values at 25 °C are tabulated and summarized in a figure, which displays the relationship of vapor pressures between various explosives and drugs.