Soret Effect in a Nonionic Surfactant System

摘要

We studied the thermal diffusion behavior of C_(10)E_8 (decyl octaethylene glycol ether) in water by means of thermal diffusion forced Rayleigh scattering (TDFRS). We determined the two diffusion coefficients D_T, D and the Soret coefficient S_T in a concentration range from w = 5 wt % to 25 wt % in a temperature range from T = 20°C to 40°C. The obtained Soret coefficients S_T were positive for all temperatures and concentrations. Additionally, we also performed dynamic light scattering experiments in the same temperature range in order to compare the measured diffusion constants and characterize the system. Special attention was paid to the tiny amount of inert dye which needs to be added for absorption and thermalization of the light energy. The influence of an organic dye and an organic coloured salt on the experimentally determined transport properties has been studied. The results show that all coefficients are independent of the choice of the dye for this particular surfactant system.