Accessibility of Cellulose by the Thallous Ethylate Method—Application to the Measurement of Cellulose Liquid Interactions1

Abstract

The extent of thallation of cellulose by reaction with thallous ethylate in benzene is advanced as a method for measuring the accessibility of cellulose. The method is demon strated by its application to a series of samples of fibers that have been swollen to varying degrees by immersion in different solvents and transferred by solvent exchange to ben zene. The extent of reaction is related to the swelling power of the immersion liquid and to the assumed microfibrillar structure of the fiber wall. About 14% of the hydroxyl groups are found to be accessible in water swollen cotton fibers while 0.9% are accessible in the same fibers dried from water. The measurement of accessibility of cellulose to a reagent of moderate molecular size and under conditions which do not affect the sample accessibility offers advantages over alternative methods.