VAPOR-PRESSURE, HEAT-CAPACITY, AND DENSITY ALONG THE SATURATION LINE,MEASUREMENTS FOR DIMETHYL ISOPHTHALATE, DIMETHYL CARBONATE, 1,3,5-TRIETHYLBENZENE, PENTAFLUOROPHENOL, 4-TERT-BUTYLCATECHOL, ALPHA-METHYLSTYRENE, AND N,N'-BIS(2-HYDROXYETHYL)ETHYLENEDIAMINE

This paper reports measurements made for DIPPR Research Project 821 in the 1993 Project Year. Vapor pressures were measured to a pressure li mit of 270 kPa or lower decomposition point for all seven compounds us ing a twin ebulliometric system and, for dimethyl isophthalate and N,N '-bis(2-hydroxyethyl)-ethylenediamine, additionally an inclined-piston apparatus. Liquid-phase densities along the saturation line were meas ured for each compound over a range of temperature (ambient to a maxim um of 548 K). A differential scanning calorimeter (DSC) was used to me asure two-phase !liquid + vapor) heat capacities for each compound in the temperature region ambient to the critical temperature or lower de composition point. Where possible, the critical temperature and critic al density for each compound were determined experimentally. The resul ts of the measurements were combined to derive a series of thermophysi cal properties including critical temperature, critical density, criti cal pressure, acentric factor, enthalpies of vaporization (restricted to within +/-50 K of the temperature region of the experimentally dete rmined vapor pressures), enthalpies of fusion if solid at ambient temp erature, solubility parameter, and heat capacities along the saturatio n line. Wagner-type vapor-pressure equations were derived for each com pound. In addition, the liquid-phase densities were compared with valu es derived using a three-term [(1 -T-r)(1/3)] power series. All measur ed and derived values were compared with those obtained in a search of the literature. Recommended critical parameters are listed for each o f the compounds studied. A ''Rule-Of-Thumb'' derived in the 1992 Proje ct Year is used to estimate thermal decomposition temperatures by radi cal scission from a knowledge of the bond dissociation energy or vice versa.