Rayleigh scattering from a methane–ethane mixture

The Rayleigh linewidth of a methane (71.07%)–ethane mixture was measured by dynamic light scattering near the plait point. Results are reported for the concentration diffusivity and (preliminary only) for the thermal diffusivity. It was found that a large background contribution is present in the concentration diffusivity, in agreement with theoretical predictions. The thermal diffusivity is compared to a one-fluid model introduced previously. A critical temperature of 236.36±0.03 K and a critical pressure of 6.66±0.02 MPa was determined for the mixture.