70 



PLANT COMPOUNDS 



a transparent film that is used for photographic purposes. 

 It is also a superior insulating material for electric wires. 



From the above discussion it can be seen that cellulose 

 has both acid and basic properties, since it forms compounds 

 with bases like sodium and copper hydroxides, on the one 

 hand, and with nitric and acetic acids, on the other. On 

 the whole, however, it is exceedingly inert, resisting all 

 ordinary decomposition and decay. It is not fermentable. 

 It finds its chief use on account of this decay-resistant 



Fig. 20. — Cotton fiber. Magnified. Drawing by C. A. Smith. 



property in the manufacture of rope, cotton cloth, linen 

 cloth, paper, and other articles, all of which are made of 

 cellulose from different sources. 



Cotton fiber (Fig. 20) is the purest form of cellulose, 

 but even that must be treated with alkali, acid, alcohol, and 

 ether to remove impurities attached to it, such as proteins 

 and fats. In the case of flax used for linen and hemp used 

 for rope, various processes are employed to free the crude 

 cellulose fibers from their encrusting substances. In making 

 paper from wood, the lignin and other impurities are dis- 

 solved away by a weak caustic soda solution (Soda Process), 

 or an acid sulphite solution (Sulphite Process). The remain- 



