THE STRUCTURAL FEATURES OF CELLULOSE 81 



"End Group Method" clearly yields a number of average molecular 

 weight as in the case of the osmotic method. 



The molecular weight of cellulose and modifications of the origmal 

 Micellar Hypothesis 



Inspection of Table III brings out immediately the striking fact that 

 over a period of only ten or eleven years the estimate of the molecular 

 weight of cellulose has increased some fifty times. Historically the figure 

 proposed by Haworth (100-200 residues in a chain) following so soon 

 after the estimate of 600 A. (= approximately 120 glucose residues), 

 offered apparent confirmation of the original structure envisaged in 

 terms of discrete micelles; and it was possibly this striking agreement 

 which led at the time to the tacit assumption in some quarters that the 

 X-ray determination gave a figure of 600 A., whereas of course this was 

 given as the minimum possible figure. This misconception, curiously 

 enough, still lingers here and there in the literature. 



The succeeding estimates of Staudinger, even though in error by a 

 considerable margin, were so very much greater than either of these that 

 it became clear that, again assuming a micelle length of 600 A. the 

 molecular chains of cellulose must partake in the construction of more 

 than one micelle, and the "fringe micelle" hypothesis was born (Fig. 

 25(a)). Remembering, however, that the X-ray determination implies 

 only that the chains are arranged parallel to each other in a lattice over 

 lengths of at least 600 A., then the structure proposed by Meyer (Fig. 

 25(b)) is equally in harmony with the facts; indeed, on the evidence 

 before us now, it is only in so far as the original estimate of Haworth 

 and Machemer suggests points of weakness spaced some 100-200 units 

 along the chains, that the fringed micelle hypothesis is any longer 

 tenable.* 



The lateral dimensions of the micelle are in somewhat the same 

 position. The value of 50 A. given by X-ray methods can mean that the 

 chains of cellulose he parallel to each other, and spaced exactly the 

 same distance from each other, only over regions of this size. The space 

 in between could be filled with chains of cellulose lying in more random 

 fashion, and even strictly parallel to each other so long as they are not 

 arranged regularly the same distance apart. There is no evidence here, 

 therefore, for discrete particles, and the conceptions of structure as 

 pictured in Fig. 25 are so much more in harmony with the tensile and 



* Recent observations by Svedberg and his colleagues (74) have shown that cellulose 

 (cotton) can, however, be hydrolyzed by 2-5 A'^ H2SO4 to give particles some 600 A. 

 long and 50-100 A. wide, (see p. 90). 



6 



