Temperature Dependence of Critical Opalescence in Carbon Dioxide

Abstract

Rayleigh scattering has been studied along the critical isochore and the coexistence curve of carbon dioxide. Measured intensities interpreted according to the theory of Ornstein and Zernike agree with expectation based on classical $\mathrm{PVT}$ measurements. It is suggested that over many decades of temperature distance from $T_c$ the $\mathrm{PVT}$ and optical data are consistent with a reduced compressibility ${\left(\frac{\partial \rho }{\partial \mu }\right)}_T=\Gamma t^{-\gamma }$, and ${\Gamma }^{\prime }{\mathrm{}(-t)\mathrm{}}^{{-\gamma }^{\prime }}$, with $t=\frac{(T-T_c)}{T_c}$, where $\gamma =1.17\mathrm{}\pm 0.02={\gamma }^{\prime }$ and $\Gamma =0.072\mathrm{}\pm 0.006=4.1{\Gamma }_{\mathrm{gas}}^{\prime }\simeq 3.6{\Gamma }_{\mathrm{liq}}^{\prime }$.