Profile Refractometry for Measuring the Soret Effect

Profile refractometry is a laser-based technique for measuring the index of refraction of a fluid as a function of time and position in a fluid. The technique was developed for use in quantifying the Soret effect in a binary fluid subject to an applied thermal gradient. (The Soret effect is the mass diffusion of chemical species due to an imposed thermal gradient.) More precisely, profile refractometry enables measurement of both dynamic and steady-state local gradients in the index of refraction of the fluid. These gradients are related in a known way to gradients in the composition of the fluid and thus to the Soret coefficient.