Diffusion and self-diffusion in ideal associated solutions

Abstract

For isothermal isobaric diffusion in ideal associated solutions it is shown that the diffusional fluxes of the various solute components i, J_i, are given by J_i=–grad D^*_iC_i where C_i is the concentration of component i in moles per unit volume and D^*_i is its self-diffusion coefficient. This result follows if (a) aggregate monomer equilibrium is maintained when diffusion takes place, and (b) the diffusional fluxes of the various aggregate species, r, are given by J_r=–D_r grad C_r, in accordance with Fick's first law or (c)J_r=–grad D_rC_r where D_r is the self-diffusion coefficient of species r.