1 1 8 Cellulose 



in part on acidifying the solution, and the gelatinous precipitate 

 gives the characteristic reactions of the original fibre. The 

 fibre is further but slightly affected in structure and physical 

 properties by the treatment. 



At temperatures considerably above the boiling point the 

 action of dilute solutions of the alkaline hydroxide (1-3 p.ct. 

 Na 2 O) takes a different course ; the non-cellulose is attacked 

 and converted into soluble derivatives, and the fibre-bundles 

 are more or less disintegrated. Such processes are, in fact, used 

 on the large scale for the preparation of paper-making pulp 

 (cellulose) from the lignocelluloses. 



(b) On digesting the fibre with dilute solutions of the mineral 

 acids at 60-80, the lignocellulose is again progressively 

 dissolved, the loss of weight sustained by the fibre being 

 proportional to the hydrolysing activity of the acid, and to the 

 conditions of the digestion. In this case also the lignocellulose 

 is attacked as a whole, the insoluble fibrous residue preserv- 

 ing the essential characteristics of the original fibre. The dis- 

 solved portion may be isolated when sulphuric acid (5-7 p.ct. 

 H 2 SO 4 ) is used as the hydrolysing acid by neutralising the solu- 

 tion with barium carbonate, filtering, and evaporating to dryness. 

 The soluble modification of the fibre-substance is obtained as 

 an amorphous, brown, gummy solid, having the same empirical 

 composition as the original fibre. 



On prolonged digestion with the dilute acids (5-7 p.ct. 

 H 2 SO 4 ) the loss of weight sustained by the fibre approximates to 

 a limit at about 30 p.ct. As a result of the treatment, the fibre 

 is disintegrated, the residue being obtained as a mass of brittle 

 fragments. It is to be noted that the disintegration is not a 

 progressive dissection of the ultimate fibres such as results 

 from the alkaline digestions above described but is the result 

 of a change in the physical properties of the fibre- substance 



