NONEQUILIBRIUM FLUCTUATIONS IN LIQUIDS AND LIQUID-MIXTURES SUBJECTED TO A STATIONARY TEMPERATURE-GRADIENT

We have investigated non-equilibrium fluctuations in liquids subjected to a stationary temperature gradient by performing small-angle Raylei gh scattering experiments. Experimental results have been obtained for liquid toluene, liquid n-hexane and for three mixtures of these liqui ds. The experiments confirm that the strength of the non-equilibrium f luctuations is proportional to the square of the temperature gradient and inversely proportional to the fourth power of the wave number of t he fluctuations. In the case of the pure liquids excellent agreement i s obtained with theoretical predictions based on the linearized equati ons of fluctuating hydrodynamics. In the case of the mixtures some que stions remain about the magnitude of the Soret effect.