P. J. Kortbeek

Acoustic and Thermodynamic Properties of Ethanol from 273.15 to 333.1 5 K and up to 280 MPa

Abstract The velocity of sound in ethanol has been measured in the temperature range between 273.15 and 333.15 K and at pressures up to 280 MPa using the phase comparison pulse-echo method with two reflectors, which has been described previously. The density, isothermal compressibility, isobaric thermal expansion and the specific heat at constant pressure of ethanol have been evaluated from the measured sound velocity, using an improved method of computation.

Acoustic and Thermodynamic Properties of Benzene and Cyclohexane as a Function of Pressure and Temperature

Abstract The phase comparison pulse echo method with two reflectors has been used to determine the velocity of sound in benzene and cyclohexane in the temperature range from 283–323 K and up to the freezing pressures of the liquids, the maximum pressures being 170 and 80 MPa respectively. The density, the isothermal compressibility, the isobaric thermal expansion and the specific heat at constant pressure of both liquids have been evaluated from the measured sound velocity, using a computational method similar to that of Davis and Gordon. The calculated densities for both liquids agree well with those found in the literature.

Compressibility and sound velocity measurements on N2 up to 1 GPa

A gas expansion technique has been used to determine the pVT properties of N2 up to 1 GPa at 298.15 K, with an accuracy of 0.08% in density, 1 mK in temperature, and 0.05%+0.2 MPa in pressure. The sound velocity has been measured by a phase-comparison pulse-echo technique between 123 and 298 K at intervals of 25 K and at pressures up to 1 GPa, with an accuracy of better than 0.02% in sound velocity, 10 mK in temperature, and 0.05%+0.2 MPa in pressure. An equation of state is presented that correlates the density data over the wide pressure range of 36–1000 MPa with maximum deviations between the calculated and the experimental densities of less than 0.05%.

Experimental Equations of State for Some Organic Liquids Between 273 and 333 K and Up to 280 MPa

Abstract Five non-linear and three polynomial isothermal equations of state for liquids have been tested for their performance in describing the data of the density and the isothermal compressibility of benzene and cyclohexane from 288 to 323 K up to the melting pressures, and of methanol and ethanol between 273 and 333 K up to 280 MPa. It is found that the best representation is given by an expansion in temperature and density and the second best by the Usual Tait equation. The coefficients of these two equations for the four organic liquids are obtained by fitting the experimental data by a least squares analysis.

Calculation of thermodynamic properties of dense fluid neon using statistical-mechanical perturbation theory

The theory and potentials described in the preceding paper are used for the calculation of thermodynamic properties of fluid neon between 73 and 348 K and up to the melting line. A polynomial equation of state for correlating the densities between 73 and 323 K and between 30 MPa and 1 GPa is presented. The calculations have been extended up to 6 GPa and the performance of the EXP-6 effective pair potential and the HFD-C2, HFD-B and XC3 pure pair potentials is compared. The effect of the Axilrod-Teller many-body correction term on the pure pair potentials is studied. In the ranges 98-348 K and 0·6-6 GPa the density data are correlated by a MBWR equation of state, and a polynomial expression is given for the sound velocity in these ranges. The pressure and temperature dependences of the specific heat at constant volume are shown. A comparison is made between the experimental pVT and soundvelocity data of Kimura et al. at 295 K and up to 3·5 GPa and our calculations.

Measurements of the compressibility and sound velocity in methane up to 1 GPa, revisited

New density measurements of methane (CH4) at 298.15 K up to 1 GPa are reported. The precision of the measurements is 0.03%, while the estimated accuracy is between 0.05 and 0.1%. Velocities of sound have been remeasured between 148.15 and 298.15 K at intervals of 25 K and at pressures up to 1 GPa, with an estimated accuracy of 0.12% at 100 M Pa, 0.10% at 150 MPa, and 0.08% above 150 MPa. Comparisons with experimental results and equations of state of other workers are presented. The isothermal and the adiabatic compressibility and the ratio of specific heats have been calculated at 298.15 K.

Apparatus for the measurement of compressibility isotherms of gases up to 10 kbar: Experimental data for argon at 298.15 K

An apparatus for the measurement of compressibility isotherms of gases up to pressures of 10 kbar and at temperatures between 273 and 350 K is described. It is based on a gas expansion method in which the pressure distortion of the experimental volume is evaluated by calibration with the measuring gas at lower pressures. The apparatus can easily be adapted for isochoric measurements over a wide temperature range. Measurements on argon at 298.15 K show that the method is capable of giving a precision of 0.02%–0.06% for the density, 0.1% for the pressure, and 2 mK for the temperature.

Measurement of the Compressibility and Sound Velocity of Helium up to 1 GPa

By using a gas expansion technique, the density of helium has been determined at 298.15 K as a function of pressure from 100 MPa to 1 GPa. The precision of the measurements is 0.02%, while the estimated absolute accuracy is about 0.08%. The sound velocity has been measured by a phase-comparison pulseecho technique between 98 and 298 K with intervals of 25 K and at pressures up to 1 GPa, with an accuracy generally better than 0.04%. By combining pVT with velocity-of-sound data at 298 K, the adiabatic compressibility and the ratio of the specific heats are calculated. The experimental sound velocities are compared with the values, predicted from an equation of state as proposed by Hansen.

pVT and sound velocity measurements for CH4 up to 10 kbar

Abstract pVT properties of CH 4 at 298.15 K have been measured up to 10 kbar with an accuracy better than 0.02% in density, 1 mK in temperature and 0.1% in pressure, by a gas expansion technique. The sound velocity has also been measured at temperatures between 148.15 and 298.15 K, with intervals of 25 K and pressures up to 10 kbar, by a phase comparison pulse-echo technique, with an accuracy better than 0.02% in the velocity, 10 mK in temperature and 0.1% in pressure. The experimental data at 298.15 K have been used to calculate the isothermal and adiabatic compressibilities and the ratio of the specific heats at this temperature. The melting line of CH 4 has also been determined with an accuracy which is higher than reported previously.

A high-pressure NMR study of solid carbon tetrafluoride

The fluorine spin-lattice relaxation times T1 and T1p and the NMR lineshape second moments M2 have been measured for solid CF4 as a function of temperature and pressure. The phase diagram is established up to 10 kbar. Evidence is presented for the existence of small cluster of CF4 molecules, reorienting at a much higher rate than the rest of the molecules.