Direct determination of temperature dependence of refractive index of liquids

Abstract

A new, direct method for determination of the temperature dependence of refractive index has been developed. It consists of an interferometric examination of a liquid in which a temperature gradient is established and maintained. The experiments reported were performed with a Bryngdahl wavefront shearing interferometer [J. Opt. Soc. Am. 53, 571 (1963)] and a He–Ne laser light source. Results for ${\mathrm{(\partial \; n/\partial \; T)}}_p{\text{/10}}^{\text{−4}}\mathrm{\hspace{0.17em}°}{\mathrm{K}}^{\text{−1}}$ at 1 atm, 298.15°K, and 632.8 nm are: H₂O, −0.989; CCl₄, −5.70; C₆H₁₂, −5.38; and C₆H₆, −6.21; with an overall experimental standard deviation of about 1%. Effective molecular radii and polarizabilities of these liquids are calculated from the Böttcher equation.