Application of a three-laser optical digital interferometry in a thermogravitational analysis for binary and ternary mixtures

We discuss the application of the three-laser optical digital interferometry method for the determination of transport properties such as the thermodiffusion, the molecular diffusion and the Soret coefficients by the thermogravitational column technique. The primary objective of this study is to illustrate the capabilities and limitations of the method for quantifying these properties in both binary and ternary liquid mixtures from an optical viewpoint. It is concluded that the system is highly robust for the analysis of binary mixtures, with the combination of the results obtained by the three wavelengths increasing the accuracy of the measurement. The study of ternary mixtures, on the contrary, is limited to certain types of conditions. While the accuracy of a three-laser interferometer can be improved, the method may be compromised if the optical contrast factor matrices are poorly conditioned.