Diffusion coefficients of two anionic dyes in dilute aqueous electrolyte solution

Diaphragm cells were used to determine diffusion coefficients of two anionic dyes in dilute aqueous electrolyte solution. Allowance was made for disaggregation occurring as dye aggregates traverse the concentration gradient in the diaphragm, and an attempt was made to account for such effects semi-quantitatively. Diffusion coefficients of one of the dyes were measured polarographically, and the results compared with those obtained using diaphragm cells. Steps in the curves of diffusion coefficient against dye concentration suggest that at low concentrations both dyes form dimers; as the concentration is increased the dimers aggregate to form tetramers.