SUPPLEMENTARY CHAPTER 



'Pure Cellulose,' Standards of Purity, Normal 

 Cellulose. Cotton cellulose maintains its position as the 

 prototype of the group. When considered as a chemical indi- 

 vidual the structural characteristics of this or any other cellulose 

 are generally ignored ; they are, however, by no means negligible, 

 since variations of form and of physical properties are deter- 

 mined by reaction, and in dealing with the fibrous celluloses 

 these variations, which are definite and in some directions 

 measurable, are a criterion of constitution. While it is true 

 that the main reactions of cellulose are quantitatively invariable 

 over a wide range of varied forms, including the amorphous or 

 structureless, it is now known that this invariability is only 

 apparent, and that the substance itself is so extremely sensitive 

 and labile that it is modified by any and every treatment, even 

 by contact with water. [Cross and Bevan, J. Soc. Dyers and 

 Col. 32, 1916.] 



In evidence of the changes determined by boiling with 

 water, the following results may be cited from recent investi- 

 gations of the authors. 



A specially selected ' sliver ' of Sea Island cotton freed, by 

 the mechanical processes of carding and drawing, from impuri- 

 ties (seed residues), which are present and visible in the raw 

 cotton, and farther treated with neutral solvents to remove 

 such ' impurities-' as oil, wax, and resin, was divided into two 

 portions, (a) and (). The latter was boiled with distilled water 

 for two hours, washed, squeezed, and air-dried ; (a) and (b) were 



