CONSTITUENTS OF PLANTS, ETC. 315 



unsized paper or old linen with a warm solution of po- 

 tassium hydrate, then with cold dilute hydrochloric acid, 

 then with ammonia water and alcohol, repeating the process 

 several times. Thus purified it is white, translucent, and 

 unalterable in the air; it is insoluble in water, alcohol, 

 ether, and oils, but is decomposed by strong acids. Nitric 

 acid converts it into gun-cotton, as explained in 433 ; sul- 

 phuric acid diluted with about one half its volume of water 

 acts upon cellulose in a peculiar manner, converting it with- 

 out change of composition into a tough substance resem- 

 bling animal parchment and applicable to the same pur- 

 poses. This so-called "vegetable parchment" is manu- 

 factured on a large scale. 



431. Linen and Cotton. These are composed of fibres of 

 wood, long and pliant. Hemp is also another form of a 

 similar kind. Linen is the inner bark of the flax plant. It 

 is separated from the outer bark by rotting and breaking. 

 In rotting there is long exposure to moisture and air, which 

 rots the outer bark, and in the breaking this is beaten and 

 rubbed off. Then follows the hatcheling, by which the fine 

 fibres are separated from each other but left parallel, and 

 the tangled ones are taken out, making what is called the 

 tow. The flax thus obtained has a gray color, which is re- 

 moved by bleaching and boiling with lye. Cotton is in the 

 form of fine hollow hairs, which are beautifully arranged in 

 the cotton-plant around the seeds. All cotton, except the 

 Nankin cotton, which is yellow, is so white that it would 

 need no bleaching were it not that in spinning and weaving 

 it oil and dirt are necessarily gathered upon it. 



432. Uses of "Wood. We put woody fibre to a great va- 

 riety of uses. We build houses with it, and fill them with 

 wooden furniture. Out of this fibre we make thread, twine, 

 cordage, and fabrics of every variety. We clothe ourselves 

 with it ; we write and print upon it ; we even eat it as a 



