La diffusion de la lumière par les mélanges binaires

Light Scattering

“…At ordinary pressures the Rayleigh scattering formula is confirmed, while at high pressures observable departure from this formula is predicted and the depolarization of scattering is found. In several papers the density and compositionfluctuation treatment of scattering from pure liquids (67) and liquid mixtures (66,281,288) was recast in forms suitable for experimental evaluation. Zwanzig (338) investigated the molecular basis of the Einstein-Smoluchowski fluctuation theory of scattering.…”

Light Scattering

“…The third term, t*, which is usually sufficiently small to be neglected (49), is a result of the interaction between the fluctuations in the density of the solution and the concentration fluctuations of the solute. and, recalling Equation 25, Hc/te = Kffi/Re = 1/Af* + 2 Be (83) Each of the quantities on the left-hand side can be determined experimentally.…”

Thermodynamics of binary liquid mixtures by Rayleigh light scattering

“…For a real solution, µ2/5 2 = RT/Xz + bpz/bXz, where µ26 is the excess chemical potential of component 2 due to the nonideality of the solution, and can be calculated from the function [1 -(Rid/Ro)] = -x*(cw/ax2)/Rr = XiX2(d2gVdXidX2)/RT (5) where ge is the molar excess Gibbs free energy. Using the Gibbs-Duhem equation, 4µ + ^µ2 = 0, and activity coefficients, /¡, defined as µ/ = RT In ftl one -Xi d ln/i/dXi -X2 d ln/2/dX2 (6) from which the activity coefficients can be obtained by numerical integration of ln/i = f*^[l -(Rid/Rc)]dX2 The determination of the activity coefficients and the excess Gibbs free energy of mixing of a binary solution by the light scattering technique involves the following steps. The total Rayleigh scattering and depolarization of the two pure liquids and of five to eight solutions is measured.…”