Acid behavior of carboxylic derivatives of cellulose. Part II. Oxycellulose

Abstract

AbstractThe acid behavior of nitrogen dioxide, periodate—chlorite, and alkaline hypobromite oxycelluloses in presence of potassium chloride solutions of different concentrations has been studied. Experimental results indicate that the carboxylic groups in oxycelluloses are not free from mutual electrostatic interactions. In agreement with the behavior of carboxymethylcellulose and other soluble polyelectrolytes, the pK values increase with increasing degree of dissociation and decrease with increasing concentration of potassium chloride in the system. The titration results can be described by the modified from of the Henderson equation pH = pKm + n log α/(1 – α), the value of n being always greater than unity. Experimental results have also been treated in an entirely new way, that of splitting the system into two equipotential phases: (1) the internal phase consisting of both the oxycellulose and its imbibed solution and (2) the external fluid phase. The Donnan theory of membrane equilibrium has been applied in calculating the internal pH values. It has been found that although the measured external pH values decrease considerably with increasing salt concentration, the calculated internal pH values are independent of salt concentration.