Turbidity Data of Weightless SF6 Near its Liquid–Gas Critical Point

Abstract

Light transmission measurements performed in SF6 close to its liquid–gas critical point are used to obtain turbidity data in the reduced temperature range \({\frac{T-T_{\rm c}}{T_{\rm c}}=[1.6\times10^{-7}{-}1.6\times10^{-3}]}\) (T is temperature, Tc is the critical temperature). Automatic experiments (ALICE 2 facility) were made at a near critical density, i.e., \({\frac{\left\langle \rho\right\rangle -\rho_{\rm c}}{\rho_{\rm c}}=0.8\,\%}\), in the one-phase homogeneous region, under the microgravity environment of the Mir Space Station (\({\left\langle \rho\right\rangle}\) is the average density, ρc is the critical density). The turbidity data analysis verifies the theoretical crossover formulations for the isothermal compressibility \({\kappa_{T}}\) and the correlation length ξ. These latter formulations are also used to analyze very near Tc thermal diffusivity data obtained under microgravity conditions by Wilkinson et al. (Phys. Rev. E 57 436, 1998).