VEGETABLE FIBRE AND CELLULOSE 359 



and subsequently washed free from the acid and dried produces 

 parchment paper, a tough translucent material extensively used 

 for a great variety of purposes. 



So far only those agents have been considered which, while 

 affecting the structure of the fibre by removing impurities or by 

 adding to the cellulose the elements of water, do not destroy the 

 integrity of the molecule which may be practically represented 

 by the symbols C 12 H 20 10 , though the molecule is probably 

 much more complex. But acids when concentrated or allowed 

 to act for a long time are capable of breaking up this association 

 of carbon hydrogen and oxygen, by causing the assumption of 

 the elements of water and a subsequent disruption of the molecule. 

 The product is glucose, identical with the substance called grape 

 sugar which is widely distributed in the vegetable kingdom. 

 It is especially found in fruits and other sweet parts, where it is 

 usually accompanied by another compound called fruit sugar 

 having the same composition, and common cane sugar. 

 Glucose is manufactured from starch by boiling it with dilute 

 sulphuric acid, and when the change is complete, neutralising the 

 liquid with chalk, filtering from the gypsum formed, and then 

 evaporating the purified and decolourised syrup in vacuum pans. 

 Woody fibre treated in the same way also yields glucose. 



The chemist has been very busy in this kind of work and 

 especially also in the development of processes which lead up to 

 the production of paper. We may consider in outline the 

 preparation of cellulose fibre from the various coniferous woods 

 growing most abundantly in the northern countries of Europe, 

 Sweden, Norway, and the shores of the Baltic. The processes 

 involved are divisible into two classes in which the details vary, 

 but they are both applicable to other raw materials, such as 

 esparto grass and straw. In the one case caustic soda is the 

 agent employed, in the other a bisulphite of lime or magnesia. 



According to the former method of procedure, the raw material, 

 pine or fir wood deprived of bark, is heated with a rather 

 strong solution of caustic soda in a boiler which bears steam 

 pressure, and of which the contents can therefore be heated 

 considerably above the ordinary boiling-point of water. The 

 chemical changes which take place are very complex, but the 

 result is that the greater part of the cellulose remains unaltered 

 or only hydrated, while the encrusting ligno-cellulose, etc., is 

 dissolved out. About one-third of the weight of white pine wood 



