Densities and Viscosities of Oleic Acid at Atmospheric Pressure

The densities of oleic acid were measured over the temperature range from (293 to 459) K at atmospheric pressure using a densimeter based on the modified hydrostatic weighing method. The dynamic viscosities of the same oleic acid sample were measured using a capillary viscometer (VPZ-2 m) in the range from (293 to 363) K at atmospheric pressure. The combined expanded uncertainty of the density, atmospheric pressure, viscosity, and temperature measurements at the 95% confidence level with a coverage factor of k = 2 is estimated to be 0.15%, 1.0%, 3.5%, and 15 mK, respectively. The values of uncertainty for density and viscosity include the effects of purity and calibration (total expanded uncertainty). These experimental data were used to develop wide-range correlations for the density and viscosity based on theoretically confirmed Arrhenius–Andrade and Vogel-Tamman-Fulcher (VTF) models. The value of the glass temperature ( T _g= 179.78 K.) for the oleic acid was estimated using the VTF parameters derived from the present viscosity measurements. To additionally validate the reliability of the measured density data, the same oleic acid samples were measured using the pycnometric method. The present study showed that the densities measured using the modified hydrostatic weighing densimeter (HWD) agree with the values obtained using the pycnometric method within 0.09% for Sample 1 and 0.25% for Sample 2.     

Surface tension coefficient of the n-pentane+n-heptane system near the “liquid-gas” critical point

The surface tension coefficient of the n-pentane + n-heptane binary system near the liquid-gas critical point is experimentally measured for five concentrations of n-heptane. Measurements are made by the capillary rise method at temperatures in the range of 293 K to T_c for each concentration. Analysis is based on predictions of different theoretical models.Institute of Physics, Daghestan Division, Russian Academy of Sciences, Makhachkala. Translated from Inzhenerno-fizicheskii Zhurnal, Vol. 63, No. 6, pp. 684–690, December, 1992.     

Method of equivalent equations and the parameters of model intermolecular potentials

Using the method of equivalent equations we obtain improved (true) values for the parameters of the spherical shell potential for n-pentane.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 51, No. 4, pp. 529–633, October, 1986.     

Experimental and theoretical studies of the crossover behavior of the specific heat Cv,x of ethane,propane, and their mixture at critical isochores

The specific heat at constant volume, C_v, of propane, and mixture with a concentration ofx=0.0081 cool fraction of propane was measured along the critical isochores at temperatures between 290 and 400 K. The measurements were performed with a high-temperature constant-volume adiabatic calorimeter. The uncertainty of most of the measurements is estimated to be less than 1.5%. Measurements have been carried out in both the one- and two-phase regions. The results for the pure components are compared with earlier measurements. Crossover equations forC, obtained on the basis of the renormalization-group method and -expansion are applied to represent our experimental specific heat data for ethane, propane. and its mixture along the critical isochores.     

Thermodynamic Properties of Methanol in the Critical and Supercritical Regions

The isochoric heat capacity of pure methanol in the temperature range from 482 to 533 K, at near-critical densities between 274.87 and 331.59 kg· m⁻³, has been measured by using a high-temperature and high-pressure nearly constant volume adiabatic calorimeter. The measurements were performed in the single- and two-phase regions including along the coexistence curve. Uncertainties of the isochoric heat capacity measurements are estimated to be within 2%. The single- and two-phase isochoric heat capacities, temperatures, and densities at saturation were extracted from experimental data for each measured isochore. The critical temperature (T_c = 512.78±0.02K) and the critical density (ρ_c = 277.49±2 kg · m⁻³) for pure methanol were derived from the isochoric heat-capacity measurements by using the well-established method of quasi-static thermograms. The results of the C_VVT measurements together with recent new experimental PVT data for pure methanol were used to develop a thermodynamically self-consistent Helmholtz free-energy parametric crossover model, CREOS97-04. The accuracy of the crossover model was confirmed by a comprehensive comparison with available experimental data for pure methanol and values calculated with various multiparameter equations of state and correlations. In the critical and supercritical regions at 0.98T_c≤ T ≤ 1.5T_c and in the density range 0.35ρ_c ≤ ρ leq 1.65 ρ_c, CREOS97-04 represents all available experimental thermodynamic data for pure methanol to within their experimental uncertainties.     

Isochoric Heat Capacity of Heavy Water at Subcritical and Supercritical Conditions

The heat capacity of heavy water was measured in the temperature range from 294 to 746 K and at densities between 52 and 1105 kg·m^–3 using a high-temperature, high-pressure adiabatic calorimeter. The measurements were performed at 14 liquid and 9 vapor densities between 52 and 1105 kg·m^–3. Uncertainties of the measurements are estimated to be within 3% for vapor isochores and 1.5% for the liquid isochores. In the region of the immediate vicinity of the critical point (0.97T/T _c1.03 and 0.75/_c1.25), the uncertainty is 4.5%. The original C _V data were corrected and converted to the new ITS-90 temperature scale. A parametric crossover equation of state was used to represent the isochoric heat capacity measurements of heavy water in the extended critical region, 0.8T/T _c1.5 and 0.35/_c1.65. The liquid and vapor one- and two-phase isochoric heat capacities, temperatures, and saturation densities were extracted from experimental data for each measured isochore. Most of the experimental data are compared with the Hill equation of state, and the overall statistics of deviations between experimental data and the equation of state are given.     

Isochoric Heat Capacity Measurements for 0.5 H2O+0.5 D2O Mixture in the Critical Region

The isochoric heat capacity C _V of an equimolar H₂O+D₂O mixture was measured in the temperature range from 391 to 655 K, at near-critical liquid and vapor densities between 274.05 and 385.36 kgm^–3. A high-temperature, high-pressure, nearly constant-volume adiabatic calorimeter was used. The measurements were performed in the one- and two-phase regions including the coexistence curve. The uncertainty of the heat-capacity measurement is estimated to be ±2%. The liquid and vapor one- and two-phase isochoric heat capacities, temperatures, and densities at saturation were extracted from the experimental data for each measured isochore. The critical temperature and the critical density for the equimolar H₂O+D₂O mixture were obtained from isochoric heat capacity measurements using the method of quasi-static thermograms. The measurements were compared with a crossover equation of state for H₂O+D₂O mixtures. The near-critical isochoric heat capacity behavior for the 0.5 H₂O+0.5 D₂O mixture was studied using the principle of isomorphism of critical phenomena. The experimental isochoric heat capacity data for the 0.5 H₂O+0.5 D₂O mixture exhibit a weak singularity, like that of both pure components. The reliability of the experimental method was confirmed with measurements on pure light water, for which the isochoric heat capacity was measured on the critical isochore (321.96 kgm^–3) in both the one- and two-phase regions. The result for the phase-transition temperature (the critical temperature, T _{C, this work}=647.104±0.003 K) agreed, within experimental uncertainty, with the critical temperature (T _{C, IAPWS}=647.096 K) adopted by IAPWS.     

Two-Phase Isochoric Heat Capacity Measurements for Nitrogen Tetroxide in the Critical Region and Yang–Yang Relation

The two-phase isochoric heat capacity of nitrogen tetroxide was measured in the temperature range from 261.74 K to the critical temperature (431.072 K) at densities between 201.21 and 1426.5 kg·m^–3 using a high-temperature and high-pressure adiabatic calorimeter. The measurements were performed in the two-phase region for 26 isochores (15 liquid and 11 vapor densities) including the coexistence curve and critical region. Uncertainties of the measurements are estimated to be 2%. The original temperatures and C _V data were converted to the ITS-90. The liquid and vapor two-phase isochoric heat capacities, temperatures, and densities at saturation were extracted from experimental data for each measured isochore. From measured (T _S, _S, C _V2, C _V2) data, the values of second temperature derivatives of vapor-pressure d ² P _S/dT ² and chemical potential d ² /dT ² were derived using the Yang–Yang relation. The results were compared with values calculated from other vapor-pressure equations. The values of saturated densities and critical parameters derived in calorimetric experiments were compared with literature data. The unusual temperature behavior of d ² P _S/dT ² and d ² /dT ² was found at low temperatures around 351 K and near the critical point.     

Calorimetric Cv-V-T measurements and the equation of state for n-Propyl alcohol

Calorimeteric C_v-V-T measurements have given a new equation of state for n-propyl alcohol, which incorporates qualitative features of the critical point and the stability limit for the homogeneous phase (spinodal).Deceased.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 51, No. 2, pp. 275–281, August, 1986.     

Density of rocket propellant (RP-1 fuel) at high temperatures and high pressures

Density of rocket propellant (RP-1 fuel) has been measured with a constant-volume piezometer immersed in a precision liquid thermostat. Measurements were made in the temperature range from 301 to 745 K and at pressures up to 60 MPa. The uncertainty of density, pressure, and temperature measurements were estimated to be 0.1%, 0.05%, and 15 mK, respectively. The measured values of density were compared with the data reported in the literature and with the values calculated from a surrogate mixture model (equation of state). The average absolute deviation (AAD) between the present data and the values reported in the literature was 0.13%.