Measurement and correlation of the (p, ρ,T) relation of ethylene II. Saturated-liquid and saturated-vapour densities and vapour pressures along the entire coexistence curve

Abstract

Comprehensive and accurate measurements of the saturated-liquid and saturated-vapour densities together with the vapour pressure of pure ethylene were carried out from T = 104 K (triple-point temperature Tt = 103.989 K) to 0.025 K below the critical temperature. The critical constants (Tc = 282.350 K, rc = 214.24 kg·m −3 , pc = 5.0418 MPa) and the isothermal compressibilities in the critical region close to the phase boundary have also been determined from these measurements. Comparisons with experimental results of previous workers are presented. Based on the new values from this work, new correlation equations for the vapour pressure, the saturated-liquid density, and the saturated-vapour density have been established.

The vapour pressure of cyclohexane over the whole fluid range determined using comparative ebulliometry

“…Although Wagner equations with (5 + 1) terms have been used only rarely, (18) particularly in the case of hydrocarbons, (20) we believe it is justified for the results reported here because the least significant term in equation (7) has an F statistic of 2757 and σ (ln p) has been reduced by factors of 10 and 2, respectively, compared with the Xiang equation and the best (4 + 1)-term equation. Equation (7) predicts a critical pressure of 4080.3 kPa which is higher than Hugill and McGlashan's direct static measurement of (4075 ± 2) kPa.…”

Measurement and correlation of the (p,ρ,T) relation of nitrogen. I. The homogeneous gas and liquid regions in the temperature range from 66 K to 340 K at pressures up to 12 MPa

“…This densimeter was developed in order to obtain accurate (p, r, T ) measurements of pure fluids in the homogeneous gas and liquid phase including the critical region and, in particular, the entire (vapour + liquid) coexistence curve. Up to now, comprehensive measurements on methane, (3)(4)(5)(6) carbon dioxide, (7)(8)(9) argon, (10,11) and ethylene (12,13) have been carried out successfully; nitrogen, (14) sulphur hexafluoride, (15) and the refrigerants R12 and R22 (16) have been measured in parts of the fluid region. The design of the densimeter was described in detail in previous papers; (3,6) therefore only the measuring principle is briefly explained here.…”

Measurement and correlation of the (p,ρ,T) relation of nitrogen. II. Saturated-liquid and saturated-vapour densities and vapour pressures along the entire coexistence curve

“…As well as the saturation densities of methane, (3,4) carbon dioxide, (5) argon, (6) and ethylene, (7) the saturated-vapour densities of nitrogen along the largest part of the coexistence curve were determined in the following way. In the lid of the measuring cell (see the schematic drawing in reference 3), an especially designed small reference cell was included which was filled with nitrogen in such a way that the fluid was in the phase equilibrium (vapour + liquid).…”

“…Figure 5 shows an enlarged section of figure 4 for the temperature range (T c − 3.7 K) E T E T c . Taking into account the reproducibilities of the measured saturation densities, the probable course of r d in the critical region is plotted; the course of r d turns down significantly for temperatures above 125.7 K. Taking into account our experiences based on the investigations of the critical region of methane, (4) carbon dioxide, (5) argon, (6) and ethylene, (7) the illustrated course of r d is the probable one. But it should be noted that either a straight course or a stronger curvature of r d might also be possible.…”