The Determination of Soret Coefficients in Molten Salts by a New Method Using Fiber‐Optic Spectroscopy

Abstract

Soret coefficients are conventionally determined electrochemically from concentration measurements at two positions in a column of liquid exhibiting a thermal gradient. These concentration differences with temperature have not previously been measured using absorption spectroscopy measurements and Beer's law. Such measurements can be achieved with a fiber‐optic spectrophotometer and an accurately calibrated thermal gradient furnace. Many readings were taken, yielding statistically significant Soret coefficient values for Fe(III), Cr(III), and Ni(II) in molten eutectic and for Ni(II) in molten eutectic. The results are comparable to those obtained in aqueous systems. The necessary precautions are evaluated and described. The high‐temperature systems chosen are probably the most severe test possible for this new technique for determining Soret coefficients.