Abstract
The generally accepted model for diffusion of ionic dyes into cellulosic substrate is based on a heterogeneous system in which dye anions diffuse through the liquid in the pore of the substrate and are simultaneously adsorbed on the pore walls. By use of this model investigations were carried out to study the diffusion of Orange II through cellophanes containing carboxyl groups in the presence of various electrolytes (NaCl, Na2SO4, CH3COONa, C2H5COONa, C6H5COONa, CH3C (CH3) CH2SO3Na and C6H5SO3Na) at 50°C.
A linear relationship was found between the square root of the obtained diffusion coefficient through the liquid in the pore and the reciprocal of the square root of the ionic strength of each electrolyte. These results could be explained by means of the equation by Warwicker and other investigators.
However, the diffusion coefficients didn't depend only on the ionic strength, but also on the kind of electrolyte; i.e. the electrolytes having SO-3 group increased the diffusion coefficient more markedly than those having COO- group. The same effect was observed also in the diffusion coefficient in the bulk liquid, which was measured by the capillary method.
Such variation of diffusion coefficient with the kind of electrolyte was explained by the generally accepted suggestion that water structure around SO3- group is broken and that around COO- group is enhanced.
