The vapor pressures of TATP over the temperature range 269 85-306 95 K and DADP over the temperature range 265 85 294 85 K were determined using a modified Knudsen effusion apparatus The Clausius Clapeyron plot of log(10)(p(Pa)) with 1/T provided a straight line for each material This expression for TATP is log(10)(p(Pa))=-(4497 +/- 80)/T(K)+(15 86 +/- 0 28) (error limits are 95% confidence limits) and for DADP it is log(10)(p(Pa))= (4417 137)/T(K)+ (16 31 0 48) These expressions yield values of the vapor pressure at 298 15 K of 6 Pa for TATP and 17 Pa for DADP, and heats of sublimation of 86 2 1 5 kJ mol(-1) for TATP and 84 6 +/- 2 6 kJ mol(-1) for DADP At tempts were made to determine the vapor pressure of HMTD but it appears to have a vapor pressure too low for our system to reliably determine A two month experiment did provide an upper limit estimate for the vapor pressure of HMTD of approximately 0 04 Pa at room temperature Melting point and melting point range were used as verification of the identity and purity of the TATP and DADP used in these experiments but this was not possible with HMTD since it detonates prior to melting