WOODY FIBRE. 141 



readily be separated from the other matters with 

 which it is associated, bj bruising and long-continued 

 boiling in water and spirit; by these means the softer 

 or more soluble substances may be separated, and 

 pure lignin is left. In the process for preparing flax, 

 the stems of the flax plant are allowed to remain in 

 water for some time; the green soft parts decay, 

 and at last nothing but the lignin or woody fibre is 

 left. 



320. Pure lignin is a white, tough, fibrous substance, 

 composed of an infinite number of very fine threads 

 or fibres, perfectly insoluble in water, and not at all 

 altered by keeping in dry air. When heated in the 

 air it soon turns brown, being partly decomposed: if 

 it be still further heated, it takes fire and burns with 

 a bright flame, the results of its combustion being 

 water and carbonic acid gas. Its composition is — 



Carbon 4980 



Oxygen 4462 



Hydrogen . . , . , . 558 



10,000 



321. The woody fibre of plants is not pure b'gnin. 

 It consists of cells and tubes more or less incrusted 

 and filled up with resinous and other matter, which 

 renders them stifi" and hard. The fibre of fine linen 

 or cotton may be taken as an example of tolerably 

 pure lignin ; because the foreign matters originally 

 associated with it have been almost entirely removed, 



