MOISTURE IN TEXTILES 



235 



caustic soda can a differentiation be detected in the cross-sectional 

 structure of the fiber to indicate this growth-ring character. Thus 

 the fibrils are considered as being separated by air spaces on all sides, 

 the whole cotton hair is spongy, and the surfaces of cellulose bounding 

 these air spaces are internal surfaces of the fiber. 



Slip spirals are visible in the hair surface at high magnification. 

 Though decidedly irregular, they appear to cross the pits at approxi- 

 mately right angles, suggesting that there are additional internal 

 surfaces at these points. 



Cellulose from all sources appears to consist of definitely arranged 

 crystallites or micellae.* Haworth ^ suggested that cellulose is com- 

 posed of an elementary group consisting of two CeHioOs units, called 

 cellobiose (Fig. 5- A). Figure 5-B indicates how these cellobiose units 

 are joined together end to end to provide the fibrous structure of 

 native cellulose. 



/i CELLOBIOSE ^ 



B 

 one end of cellulose chain 



Fig. 5 — Molecular structure of cellulose. 



Diffraction and chemical evidence indicate that the cellobiose units 

 are arranged parallel to the &-axis of the unit cell, with one cellobiose 

 group at each common edge of adjacent cells and one through the 

 center of each cell. These form long primary valence chains arranged 

 parallel to the fiber axis and are held together laterally by cohesive 

 forces. Figure 6 shows this conception of the unit cell as given by 

 Meyer ar d Mark.^ 



* Sponsler and Dore,^ Meyer and Mark,^ Freudenberg,^ Herzog,' Polanyi.* 



