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Many of the methods used to study the fine structure of cellulose are tedious and not suitable for routine use. In the present work, an equilibrium moisture regain method which can be carried out on a large scale with a high degree of accuracy has been developed. The method is illustrated by a wide variety of cellulose materials covering a wide range of moisture sorption capacity. The terms "accessibility" and "crystallinity" are discussed and possible errors arising from assumed equivalence of these terms are pointed out. A preliminary attempt to evaluate both accessibility and crystallinity of cellulose from moisture regain data has been made. This evaluation results in a proposed revision of the scale of reported crystallinities of various types of cellulose. The hydrolysis method for studying cellulose accessibility has been compared with moisture regain and x-ray diffraction methods. It is proposed that recrystallization of cellulose during hydrolysis is a determining factor in this method and, therefore, that published data obtained from hydrolytic studies should be reconsidered.

A study has been made of the effect of fine structure on the decrystallization process which results from the ball‐milling of cellulose. The rate of decrystallization is sensitive to the type of fine structure and is accelerated by the presence of moisture. The extent of chain degradation was greater in air atmosphere than in carbon dioxide, suggesting that mechanically induced free radical degradation occurs along with other chain‐breaking processes. A study of the density and moisture regain of the samples after various times of milling showed that a linear relation between regain and density held over the entire range studied. The relation was the same for native and regenerated cellulose. The process of recrystallization of the ball‐milled samples was studied under various conditions and compared to the hydrolytically induced recrystallization of rayons. The type of lattice which develops on recrystallization was found to depend on the original lattice, the extent of ball‐milling and the conditions of recrystallization. A highly ball‐milled sample could be made to recrystallize as cellulose I, II, or IV depending on the conditions.

The lack of agreement among various crystallinity and accessibility methods for cellu losic materials is explained in terms of the lateral-order distribution concept. A new definition of the order function is proposed which is more in keeping with recent infrared evidence showing that celluloses differ in distribution of hydrogen bond strengths rather than in actual number of hydrogen bonds. Some of the physical and chemical methods which can give empirical-order distribu tion information for native and regenerated samples are reviewed critically and some data are compared with results based on conventional crystalline-amorphous delineation.

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