CELLULOSE 



207 



Associated with this classification was the conception that 

 there existed in the plant several distinct varieties of cellulose. 

 Thus Cross and Bevan found that the cellulose obtained after 

 delignification of the straw of cereal grasses and of esparto 

 when distilled with hydrochloric acid gave considerable 

 quantities of furfural, from which they concluded such 

 cellulose to be possessed of furfural-producing groups which 

 they termed furfuroids. It has, however, been shown by 

 Irvine and Hirst * that esparto cellulose consists of a mixture 

 of ordinary cellulose with a pentosan, xylan, in the proportion 

 of, approximately, 80 to 20, and that by repeated treatment 

 with alkali the xylan could be dissolved out. The same state 

 of affairs has been shown to hold for straw cellulose by Heuser 

 and Haag,t and in view of the proved existence of pentosans 

 in such cases Heuser and others consider the identity of cellu- 

 loses from different sources to be established, and regard Cross 

 and Bevan's assumption of the existence of furfuroids to be 

 unnecessary. 



One of the richest sources of cellulose in nature is the 

 cotton plant. The following table, taken from Bowman, | re- 

 presents approximately the composition of cotton fibre from 

 various sources : — 



Although the raw cotton wool is amongst the purest of 

 mature structures with respect to its cellulose, it requires 

 treatment before it can be regarded as approximating to a 



* Irvine and Hirst : " J. Chem. Soc," 1924, 135, 15. 



•j- Heuser and Haag : " Zeit. angew. Chem.," 1918, 31, 99, 103, 166, 

 172 ; also Heuser and Aiyar : id., 1924, 37, 27. 



t Bowman : "The Structure of the Cotton Fibre," London, 1908, 

 p. 147. 



