synopsisThe diffusion of sodium chloride in dilute solutions of carboxymethylceilulose (CMC) was studied using the porous frit technique. It was found that at relatively low CMC concentrations the diffusivity of sodium chloride (D) i s higher than that in water (Do); with increasing CMC concentration, the diffusivity decreases gradually and reaches a value lower than that in water. The relation between the diffusivity (D) and CMC concentration (C,) was represented by the equation D = a -bC,. The effect of temperature on the diffusivity of sodium chloride in CMC solutions was found to obey the Arrhenius equation with an activation energy of 2230 cal/mol.