Measurements of Vapor Pressure, Heat Capacity, and Density along the Saturation Line for ε-Caprolactam, Pyrazine, 1,2-Propanediol, Triethylene Glycol, Phenyl Acetylene, and Diphenyl Acetylene

Abstract

This paper reports measurements made for DIPPR Research Project 821 in the 1996 Project Year. Vapor pressures were measured to a pressure limit of 270 kPa (unless decomposition occurred) for all six compounds using a twin ebulliometric apparatus. Additionally, for -caprolactam, measurements at low pressures (0.043 kPa to 3.08 kPa) were performed using an inclined-piston apparatus. Liquid-phase densities along the saturation line were measured for each compound over a range of temperatures (ambient to a maximum of 548 K). A differential scanning calorimeter was used to measure two-phase (liquid + vapor) heat capacities for each compound in the temperature region ambient to the critical temperature or lower decomposition point. A critical temperature and the corresponding critical density were determined experimentally for pyrazine. The results of all the measurements were combined to derive a series of thermophysical properties including critical temperature, critical density, critical pressure, acentric factor, enthalpies of vaporization (within the temperature range ((50 K) of the vapor pressures), enthalpies of fusion if solid at ambient temperature, solubility parameter, and heat capacities along the saturation line. Wagner-type vapor-pressure equations were derived for each compound. In addition, the liquid-phase densities were compared with values derived using a four-term power series in [(1 -T r ) n/3 ]. For -caprolactam, the results of the present measurements were combined with literature values to derive a "Third Law" estimate of sublimation pressures in the region of ambient temperature. All measured and derived values were compared with those obtained in a search of the literature.

An examination of the vaporization enthalpies and vapor pressures of pyrazine, pyrimidine, pyridazine, and 1,3,5-triazine

“…What is presently not known is whether this correlation also applies to pyrimidines and pyridazines. Comparison of the values in column 8 of Table 7 to the literature values reported in the last column of this table for pyrimidine and pyridazine suggests that the correlation may not be [18,19] a Includes a phase transition of 0.9 kJ mol -1 at T = 300.5 [8] applicable to these compounds. Since to our knowledge there are no other vaporization enthalpies reported for pyrimidines and pyridazines in the literature for comparison, it was decided to attempt to predict the vapor pressures of these compounds in an effort to verify the applicability of the slopes and intercepts reported in Table 6 for measuring vaporization enthalpies.…”

“…The vaporization enthalpies for pyrazine, 2-methyl and 2,4-dimethylpyrazine and 2,4,6-trimethylpyridine obtained from reference [7] were calculated from the vapor pressure data provided in that article. The vaporization enthalpy used for pyrazine was an average of the value obtained from references [8,7]. The value for 2,4,6-trimethylpyridine obtained from reference [9] was calculated from the Antoine constants reported for the global fit using Eq.…”

“…These values are included for reference only. Table 1 The vaporization enthalpies (kJ mol -1 ) used as standards or for reference Vapor pressure data used for pyrazine [8], pyridine [12], 3-picoline [13], and 2,6-lutidine [14] have been calculated from the parameters reported for the Wagner equation (Eq. 7).…”

A reference data set for validating vapor pressure measurement techniques: homologous series of polyethylene glycols

“…These data seem to significantly overestimate the vapor pressure and were discarded for the following evaluations. In addition, Grenier et al (1981) have measured gas saturation in an inert carrier gas, and Steele et al (2002), using an ebulliometric technique, have measured the saturation vapor pressure at much higher temperatures from about 400 up to 500 K.…”

1,2-Propanediol. Comprehensive experimental and theoretical study

“…The vapor pressures of (±)-1,2-propanediol (see table 1) were studied earlier [19][20][21][22][23][24][25][26], but no enthalpies of vaporization were derived from those literature data in the original works with the exception of Steele et al [24]. Equations (4) and (5) were applied in this work to each available experimental data set in order to obtain enthalpy of vaporization values and to provide a consistent comparison between literature results and the present work (table 1).…”