134 THEJCARBOHYDRATES 



CHARACTERS AND PROPERTIES OF COMPOUND CELLULOSES. 



As already stated, the main characteristic of the group of 

 compound celluloses is that they are composed of one or other 

 form of cellulose combined with some other substances of a 

 non-cellulose nature. 



The nature of the cellulose constituent varies according to 

 the source from which it is obtained, one of the chief char- 

 acteristic differences between such different forms of cellulose 

 being their behaviour on boiling with hydrochloric acid ; thus 

 whereas cotton cellulose yields only about o*i-0'4 per cent of 

 furfurol, jute cellulose under similar conditions yields 3-0-6-0 

 per cent, and straw cellulose yields from I2"0-I5"0 per cent; 

 for this reason the cellulose constituent is regarded as being 

 of the nature of oxycellulose. 



The Non-cellulose Constituent of compound celluloses may 

 vary very considerably in chemical nature, and on this fact 

 depends their classification into — 



{a) Lignocelluloses. 



ib) Pectocelluloses. 



{c) Adipo- or Cuto-celluloses. 

 {a) Lignocelluloses. — In the young cell the walls consist 

 of almost pure cellulose, but, as the cell grows older, the walls 

 may become permeated with what are known as encrusting 

 substances, the process being known as lignification. This 

 change takes place at the expense of the cellulose, and a new 

 substance known as lignocellulose is produced. The extreme 

 limit of this change is the production of wood, which contains 

 only about 50-60 per cent of cellulose, while lignocelluloses 

 still contain about 70-80 per cent. 



These lignocelluloses are considered by most authors to 

 consist of cellulose combined with at least two other non- 

 cellulose constituents ; one of these, A, appears to contain an 

 aromatic nucleus, and the other, B, contains a furfurol-yielding 

 complex, and is probably a pentosane. The two constituents, 

 A and B, are sometimes grouped together as a single sub- 

 stance under the name of lignin or lignone. The constitution 

 of this substance is still unknown. According to Klason * 

 lignin would appear to be related to coniferyl alcohol (p. 186). 



* Klason : " Arkiv. Kern. Min. Geol.," 1908, 3, No. 5, i. 



