Improvements in the Acid-Hydrolysis Method of Determining the Crystallinity of Cellulose

Abstract

In a study of the acid-hydrolysis method [5] for the determination of the degree of crystal linity of cellulose fibers, a technique has been developed for the solvent removal from the hydrolysis residues of all but traces of the humic substances which are formed from the soluble hydrolysis products and which interfere with the crystallinity determination. Although ammonium hydroxide and pyridine were effective solvents, hot 50-percent aqueous monoethanolamine was found to be the most practicable means of removing these humic sub stances. Its effectiveness was demonstrated ( a) by showing that the weights of the extracted residues were the same as the weights of residues corrected by computations based on data from experiments with glucose; ( b) by varying the liquid-solid ratio during hydrolysis and showing the uniformity of the weights of the resulting ethanolamine-extracted residues; and (c) by obtaining equal extrapolated values for degree of crystallinity from parallel extracted and un extracted but mathematically corrected hydrolysis series. Data are presented to show that preliminary extraction with either 1-percent sodium hydroxide or ethanolamine to remove the noncellulosic constituents does not change the crys tallinity values of samples of cotton and cotton linters. A revised crystallinity procedure is described which incorporates the improvements de scribed above.