192 Cellulose 



hydrates at 200-300, The quantity obtained in this way is 

 from 30-40 p.ct. of the weight of the wood, together with a 

 considerable quantity of oxalic acid. 



(4) Destructive distillation of the woods (see p. 204) also 

 determines the formation of acetic acid. The following estima- 

 tions of comparative yields are given by W. Rudnew (Dingl. J. 

 264, 88 and 128), the woods being 'distilled' in glass vessels 

 at 150-300. 



Linden . 10*24 

 Birch . . .9*5 

 Aspen . . 8'o6 



Oak . . .7*9 

 Pine . . .5-6 

 Fir . 5-2 



Wood celluloses (birch and pine), isolated by the Schulze 

 process, gave under similar conditions the following yields : 



Birch cellulose . . , .6-2 

 Pine .... 5'0 



From these results it is evident that the CO.CH 2 grouping is 

 a characteristic constitutional feature of the lignocelluloses. It 

 also occurs in derivative forms amongst the products of decom- 

 position of the lignocelluloses by 'natural processes. Thus, e.g., 

 in hippuric acid, benzoyl-amido-acetic acid (p. 151), and in 

 phloroglucol, regarded as 3CO.CH 2 , which occurs in the plant 

 world in a number of derivative forms, and is obtained from 

 several of the natural tannins as a product of fusion with 

 alkaline hydrates. We are not yet in a position, however, to 

 localise the CO.CH 2 groups in the complex lignocellulose 

 molecule, and we cannot go beyond a summing-up of the 

 evidence in general terms. 



(i) Acetic acid is a product of simple hydrolysis, both acid 

 and alkaline, of the lignocelluloses, the proportion being from 

 3-6 p.ct. of the parent substance. 



The formation of an acetic residue is thus a characteristic 

 feature of lignification. If derived from a hexose group (cellu- 



