J. M. H. Levelt Sengers

Refractive index of water and steam as function of wavelength, temperature and density

Based on a comprehensive collection of data previously obtained by Thormahlen et al. on the experimental refractive index of water and steam from the 1870s to the present, a new formulation is presented for the range of 0.2 to 2.5 μm in wave‐length, −10 to +500 °C in temperature and 0 to 1045 kg m−3 in density. The Lorentz‐Lorentz function or molar refraction, a strong function of wavelength but only weakly dependent on density and temperature, is fitted to a selected set of accurate refractive index data. The NBS/NRC equation of state for water and steam, the new international standard, is used to convert the experimental pressures to density.The deviations of all experimental data from the formulation are shown. A detailed assessment of the accuracy of the formulation is presented. Although the formulation does not represent to within their accuracy the data from the best sets in the visible range for liquid water below the boiling point, we show that inconsistencies between data sets, and minor deficie...

Thermophysical Properties of Fluid D2O

The present publication contains data on the thermophysical properties of deuterium oxide (heavy water). It is a companion to the paper on the thermophysical properties of fluid H2O published earlier in this journal by the same authors. The properties are represented by equations which can be readily programed on a computer and incorporated in data banks. All data have been carefully and critically analyzed. The compendium represents the best available data for fluid D2O.

A Formulation for the Static Permittivity of Water and Steam at Temperatures from 238 K to 873 K at Pressures up to 1200 MPa, Including Derivatives and Debye–Hückel Coefficients

A new formulation is presented of the static relative permittivity or dielectric constant of water and steam, including supercooled and supercritical states. The range is from 238 K to 873 K, at pressures up to 1200 MPa. The formulation is based on the ITS-90 temperature scale. It correlates a selected set of data from a recently published collection of all experimental data. The set includes new data in the liquid water and the steam regions that have not been part of earlier correlations. The physical basis for the formulation is the so-called g-factor in the form proposed by Harris and Alder. An empirical 12-parameter form for the g-factor as a function of the independent variables temperature and density is used. For the conversion of experimental pressures to densities, the newest formulation of the equation of state of water on the ITS-90, prepared by Wagner and Pruss, has been used. All experimental data are compared with the formulation. The reliability of the new formulation is assessed in all su...

Revised Formulation for the Refractive Index of Water and Steam as a Function of Wavelength, Temperature, and Density

Schiebener et al. published a formulation for the refractive index of water and steam in 1990 [J. Phys. Chem. Ref. Data 19, 677 (1990)]. It covered the ranges 0.2 to 2.5 μm in wavelength, −12 to 500 °C in temperature, and 0 to 1045 kg m−3 in density. The formulation was adopted by the International Association for the Properties of Water and Steam (IAPWS) in 1991. In the present article, the data, after conversion to ITS-90, have been refitted to the same functional form, but based on an improved equation of state for water adopted by IAPWS in 1995. The revised coefficients are reported, and some tabular material is provided. The revised refractive-index formulation was adopted by IAPWS in 1997 and is available as part of a National Institute of Standards and Technology Standard Reference Database. For most conditions, the revised formulation does not differ significantly from the previous one. A substantial improvement has been obtained in supercooled water at ambient pressure, where the previous formula...

A Database for the Static Dielectric Constant of Water and Steam

All reliable sources of data for the static dielectric constant or relative permittivity of water and steam, many of them unpublished or inaccessible, have been collected, evaluated, corrected when required, and converted to the ITS‐90 temperature scale. The data extend over a temperature range from 238 to 873 K and over a pressure range from 0.1 MPa up to 1189 MPa. The evaluative part of this work includes a review of the different types of measurement techniques, and the corrections for frequency dependence due to the impedance of circuit components, and to electrode polarization. It also includes a detailed assessment of the uncertainty of each particular data source, as compared to other sources in the same range of pressure and temperature. Both the raw and the corrected data have been tabulated, and are also available on diskette. A comprehensive list of references to the literature is included.

The susceptibility critical exponent for a nonaqueous ionic binary mixture near a consolute point

We report turbidity measurements of a nonaqueous ionic solution of triethyl n‐hexylammonium triethyl n‐hexylboride in diphenyl ether. A classical susceptibility critical exponent γ=1.01±0.01 is obtained over the reduced temperature range 10−4≤ t≤10−1. The best fits of the sample transmission had a standard deviation of 0.39% over this range. Ising and spherical model critical exponents are firmly excluded. The correlation length amplitude ξ0 from fitting is 1.0±0.2 nm which is much larger than values found in neutral fluids and some aqueous binary mixtures.

Thermodynamic Properties of Steam in the Critical Region

An analysis is presented of the experimental data on thermodynamic properties in the critical region of steam. The model used is that of revised and extended scaling, as given by the modern theory of critical phenomena. All thermodynamic properties are given in closed (parametric) form. The model has, in addition to three universal constants that are given by theory, sixteen adjustable parameters that were obtained by least‐squares fit to PVT and speed‐of‐sound data. It is valid in the range 200–420 kg/m3 in density and 644–693 K in temperature. It accurately represents the experimental data for equation of state, vapor pressure, latent heat, specific heats Cp and Cv and speed of sound. Our analysis permits new estimates of the critical parameters of steam, and has led to a number of conclusions regarding the mutual consistency of the experimental data. Tabulated values of the thermodynamic properties of steam are appended to the paper.

Application of the Taylor dispersion method in supercritical fluids

This paper describes some of the experimental and theoretical problems encountered when the Taylor dispersion method is applied to the measurement of diffusion coefficients near gas-liquid critical points. We have used our own measurements of diffusion of benzene and toluene in supercritical carbon dioxide, along with measurements from several other sources, to illustrate some of the experimental challenges. Special attention is given to the peak shape. The intercomparisons are greatly simplified by comparing the experimental data as functions of density, rather than pressure. We find large and unexplained discrepancies between the various experimental sources. We discuss the theoretical predictions for the relationships between the diffusion coefficients and diffusivities obtained from Taylor dispersion and dynamic light scattering in fluids near critical points. We conclude that there is no strong reason to press for Taylor dispersion measurements near the gas-liquid critical point of the carrier gas.

Critical behaviour of ionic fluids

The past 25 years have seen detailed experimental confirmation, in many fluids, of concepts from the theory of critical phenomena. It has been demonstrated that fluids belong to the universality class of the 3D Ising model, with critical exponents as given by renormalization group calculations. Nevertheless, there is an important class of fluid systems, those with ionic components, for which it is not clear that the notions of critical behaviour developed for uncharged systems apply. We will review the available experimental evidence, and assess the state of theoretical knowledge.

Turbidity, light scattering, and coexistence curve data for the ionic binary mixture triethyl n-hexyl ammonium triethyl n-hexyl borate in diphenyl ether

We report turbidity, light scattering, and coexistence curve data for a solution of triethyl n-hexyl ammonium triethyl n-hexyl borate in diphenylether. We recently reported that the present sample shows much higher turbidity than that of K. S. Zhang, M. E. Briggs, R. W. Gammon, and J. M. H. Levelt Sengers [J. Chem. Phys. 109, 4533 (1998)] for an earlier sample. An analysis of the data shows that nonclassical critical behavior is favored in the reduced temperature range from 10−5 to 10−2. At fixed reduced temperature, the correlation length is about twice as large as that of the previous sample. The correlation length amplitude calculated from the fit is 1.4 nm±0.1 nm. A detailed data analysis points out the limitations of turbidity measurements far away from the critical point. The intensity of scattered light was measured at 90°. Multiple scattering is relevant in the wider vicinity of the critical point and was corrected for by a Monte Carlo simulation method. An Ising-type exponent for the correlation ...