Measurement of non-isothermal transport coefficients in a near-eutectic succinonitrile/(d)camphor mixture

We have determined nonisothermal diffusive transport coefficients of a succinonitrile-(d)camphor mixture with a composition of c = 0.239 wt.-frac. (d)camphor at a temperature of 318.2 K, which is close to the eutectic point. The employed experimental techniques are optical beam deflection in a Soret cell and photon correlation spectroscopy. The diffusion coefficient is D = (1.43 ± 0.04) × 10^-10 m² s^-1, the thermodiffusion coefficient is D_T = (2.00 ± 0.06) × 10^-12 m² s^-1 K^-1, and the Soret coefficient is S_T = (1.40 ± 0.02) × 10^-2 K^-1. Camphor migrates toward the lower and succinonitrile migrates toward the higher temperatures. While the diffusion coefficient is in good agreement with the literature, the Soret coefficient has been determined for the first time. Our analysis shows that a significant concentration shift can be established in the liquid mixture in the presence of a temperature gradient. The mixture has a negative separation ratio, which leads to convective instabilities if heated from above.