Investigation of the Application of a Two-Wavelength Mach-Zehnder Interferometer to Measure Soret Coefficients

We developed a measurement method of Soret coefficient ST using a two-wavelength Mach-Zehnder interferometer. Temperature gradient was applied to pure molten salol or the salol - 6 mol% tert-butyl alcohol solution in a quartz cell. The direction of the temperature gradient was opposite to the gravity vector so as to suppress the convection. The movement of the interference fringes in solution side was evaluated by the number of the dark lines crossing a measuring point from right to left. The changes of temperature and concentration were measured using the number of the dark lines. Wavy noise found in measured number of the dark lines could be removed by subtracting one in the cell wall. The temperature change agreed with one measured using thermocouples. The results show that the measurement method in this study enables the contactless ST measurement.