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

Abstract

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.

Concentration dependent refractive index of a binary mixture at high pressure

“…In order to validate the high pressure cell and the measurement technique, we measured the refractive index of three different pure fluids (toluene, hexane, and water, which refractive indices as a function of pressure are given in literature [29][30][31] ) as a function of pressure in the range from atmospheric pressure up to 50 MPa. In Fig.…”

Schlieren Visualization of Water Natural Convection in a Vertical Ribbed Channel

“…For liquids, dn/dT has to be experimentally determined. In the case of water, Harvey et al [6] reported the refractive index at different wavelength in the visible spectrum, versus pressure and temperature. A fitting of data, at the atmospheric pressure and averaged over the visible wavelength range, gave n 0 = 1.335 (at 20°C) and the following relationship of dn/dT with T in the 15-40°C range…”

Response to “Comment on ‘Mixture model description of the T-, P dependence of the refractive index of water’ ” [J. Chem. Phys. 115, 7795 (2001)]

“…1͑a͒. The most important insights from this analysis lie not in the quality of the fit ͑which is high, 2 ϭ0.24ϫ10 Ϫ10 ͒ nor in a detailed comparison with the fitting function of Harvey et al 9 which was required to address a much broader range of temperature, pressure, and wavelength conditions. Rather, the value of the mixture model approach is revealed in Figs.…”

“…10 We focus on the Saubade data because it covers the particularly interesting temperature range where the refractive index has a local maximum making the physical consequences of the mixture model most apparent. To compare with the refractive index fitting function of Harvey et al 9 the IPTS-68 temperatures were converted to their ITS-90 equivalents 12 and the results are plotted in Fig. 1͑a͒.…”

“…We further agree with Harvey 4 that for very precise comparisons, care must be taken to compensate for the very small temperature shifts resulting from revisions in the accepted standard for the International Temperature Scale over the years. However, although Harvey 4 specifically refrains from commenting on the validity of the mixture model description of liquid water, focusing on whether the uncertainty in the Tilton and Taylor 3 data is best represented by the authors' stated value, 3 1ϫ10 Ϫ6 , or by the average standard deviation of their smoothing equation, 3 1.2ϫ10 Ϫ6 , or by a ''reasonable estimate'' of the result of a modern uncertainty analysis, 4 2 ϫ10 Ϫ6 , suggests that the mixture model analysis can be thought of as another empirical fitting function comparable to others 3,[5][6][7][8][9] in the literature. Such a conclusion loses sight of the physical motivation underlying the mixture model analysis which leads to physically meaningful fitting parameters not found in other treatments.…”