Dissociation of hydroxyl groups of cellulose at low ionic strengths

According to Donnan equilibrium theory, the dissociation of the hydroxyl gr oups of cellulose (mercerized cotton) or alkaline adsorption can be treated as a function of the pH and ionic strengths of the external solution, and of the amount of fixed anionic groups in cellulose, by using 1:1- and 1:2-e lectrolytes as a neutral salt to adjust the ionic strength. The acid dissoc iation constant of the hydroxyl group for cellulose was estimated by Neale at 25 degrees C, and this treatment therefore only holds for this temperatu re. The ratios of hydroxide ion concentrations in the inner solution and th ose in the external one, [OH-](i)/[OH-](s), as well as [Cell-O-](i)/[OH-](i )[Cell-O-](i): cellulosate ion concentration in the inner solution) decreas e with a increase in the concentration of hydroxide ions in the external so lution and the fixed anions in cellulose, and with a decrease in the ionic strengths in the external solution, but with little decrease of [Cell-O-](i )/[OH-](i). (C) 1998 Elsevier Science Ltd. All rights reserved.