Soret, thermodiffusion, and mean diffusion coefficients of the ternary mixture n-dodecane plus isobutylbenzene+1,2,3,4-tetrahydronaphthalene

We have investigated thermodiffusion in ternary mixtures of dodecane (nC12), isobutylbenzene (IBB), and 1,2,3,4-tetrahydronaphthalene (THN) by means of two-color optical beam deflection over the entire ternary composition space. The Soret and the thermodiffusion coefficients S-T,S-i'(c(1),c(2)) and D-T,D-i'(c(1),c(2)), respectively, have been determined for all three components i and fitted by smooth approximating polynomials in the independent concentrations c(1) (nC12) and c(2) (THN). Both the Soret and the thermodiffusion coefficient are negative for nC12 and positive for THN over all compositions. In case of IBB, they change sign, being negative for THN-rich and positive for nC12-rich mixtures. Both the positive and negative signs and the sign change are in agreement with qualitative predictions based on the recently introduced thermophobicity concept [S. Hartmann et al., Phys. Rev. Lett. 109, 065901 (2012); J. Chem. Phys. 141, 134503 (2014)]. For isothermal diffusion, a mean diffusion coefficient (D) over bar but neither the diffusion matrix nor its eigenvalues could be determined. (C) 2015 AIP Publishing LLC.