Refractive Indices and Dielectric Constants of Liquids and Gases under Pressure

Several interpolation formulas are given which reproduce refractive index and dielectric constant data for liquids and gases at high pressures. These formulas involve functions of the refractive indices and dielectric constants which appear in the formulas of Lorentz-Lorenz, Clausius-Mosotti, Gladstone and Dale, the empirical Eykman formula, etc. One formula shows the reciprocals of these functions to be linear in the specific volumes at various pressures. Another interpolation formula, involving the reciprocals of the same functions, contains a logarithmic term which is similar to that appearing in the Tait equation for compressibilities of liquids. The parameters involved in the Tait equations for compressibilities and in the analogous interpolation formula for refractive indices and dielectric constants are discussed. The article also shows that the Tait equation which has been so successfully adapted to compressibility data of liquids can also be applied to gases.