202 CELLULOSE. 



of the soft, pulpy mass of juicy fruits and roots, and, 

 on the other hand, of the tough tissue-fibres of cotton, 

 flax, and hemp. These differences are produced chiefly 

 by the deposit of woody substance (incrusting sub- 

 stance, xylon, lignin) on the cell-walls, which forms 

 the principal mass of wood and the woody portions of 

 fruit kernels, but which appears to be nothing but 

 cellulose in a very compact state of aggregation, 

 thoroughly penetrated by or combined with other sub- 

 stances, simultaneously secreted. 



Purification. From the tender parts of plants, 

 crushed as thoroughly as possible, pure cellulose is 

 obtained by successive digestions with dilute potassa, 

 dilute sulphuric acid, water, alcohol, and ether. It can 

 be also obtained from fine white paper, already almost 

 pure cellulose, which, during the process of prepara- 

 tion, has been thoroughly disorganized. 



Properties. Pure cellulose is an amorphous, white 

 body, insoluble in water, alcohol, ether, dilute alka- 

 lies, and acids. It is soluble in a solution of copper 

 hydroxide in ammonia, and is precipitated from these 

 solutions in an amorphous condition by acids, alka- 

 line salts, solutions of gum and sugar. 



Transformations. "When heated with potassium hy- 

 droxide and a little water to 200, without access of 

 air, it forms hydrogen, methyl alcohol, potassium oxa- 

 late, acetate, propionate, and carbonate, without sepa- 

 ration of carbon. 



Cellulose, or broken-up wood, straw, linen, paper, 

 cotton, etc., when gradually ground together with con- 

 centrated sulphuric acid, so that no elevation of tem- 

 perature or discoloration takes place, are transformed 

 into an homogeneous, pasty mass. If water is then 

 quickly added, a white amorphous body, amyloid, is 

 separated, which, with iodine, gives a blue color. 

 When paper is dipped for a few moments into mode- 

 rately concentrated sulphuric acid, and then washed 

 with water and ammonia, it is changed superficially into 

 amyloid, and forms a substance similar to parchment 

 (vegetable parchment), which is translucent, of great 



