All reliable sources of data for the static dielectric constant or relative pennittivity of water and steam, many of them unpublished or inaccessible, have been collected, evaluated, corrected when required, and converted to the ITS-90 temperature scale.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.

No abstract

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 p.m in wavelength,-10 to +500 °C in temperature and 0 to 1045 kg m-3 in density. The Lorentz-Lorenz 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 r 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 deficiencies of the equation of state, prevent further improvement of a formulation based on data over as wide a range as considered here. It is shown that the best refractive index data can be used to discriminate between the various formulations of the equation of state of water and steam. It is demonstrated that several recent formulations of optical properties of liquid water over large ranges of wavelength need improvement in the range covered here. The new formulation is used to generate tables of the refractive index of water and steam at six wavelengths in the visible, near-infrared and near-ultraviolet, from o to 500 °C and up to 100 MPa in pressure.

Schiebener et al. published a formulation for the refractive index of water and steam in 1990 ͓J. Phys. Chem. Ref. Data 19, 677 ͑1990͔͒. It covered the ranges 0.2 to 2.5 m in wavelength, Ϫ12 to 500°C in temperature, and 0 to 1045 kg m Ϫ3 in density. The formulation was adopted by the International Association for the Properties of Water and Steam ͑IAPWS͒ 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 formulation was defective. Special attention has been paid to the behavior of the refractive index in the near infrared, where strongly oscillating data were reported after the correlation of Schiebener et al. had appeared, leading to subsequent curtailing of the range of validity of the formulation. Newer results do not show these oscillations. They are compared with the revised formulation.

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.