126 ORGANIC AGRICULTURAL CHEMISTRY 



hoi. This production of alcohol from cellulose is in the experi- 

 mental stage, as the process has not yet been perfected so as to 

 be generally profitable on the commercial scale. Starch is still 

 the chief source for the manufacture of alcohol. When unsized 

 paper (filter paper) is treated with concentrated sulphuric acid 

 for a short time and the acid then removed by washing with 

 water, the paper is changed into a tough membrane-like form, 

 which is known as parchment paper. 



Cellulose is insoluble in dilute acids or alkalies, and the 

 fibrous part of plant food not dissolved by such treatment is 

 largely cellulose and is termed in analysis of foodstuffs crude 

 fiber. Such crude fiber or cellulose is largely indigestible, pos- 

 sessing a coefficient of digestibility in domestic animals of only 

 about 30 to 60 per cent. The purest form of cellulose readily 

 obtainable is made from cotton fiber or filter paper by washing 

 in alcohol, ether and dilute acids and alkalies. A reagent which 

 dissolves cellulose is the so-called Schweitzer's reagent, which 

 consists of copper hydroxide dissolved in ammonia. 



Paper. — Paper in its various forms or grades consists of more 

 or less pure cellulose. The source of the cellulose for the manu- 

 facture of paper may be the straw of cereals or grasses, cotton 

 fiber either as such or as worn-out cotton cloth, the fiber of such 

 soft woods as spruce or pine, and linen, which is the cellulose 

 fiber of flax. Such material is first shredded and then treated 

 with solvents such as alcohol, ether and dilute alkalies and 

 acids, in order to remove all oils, gums and other soluble constit- 

 uents. The fibrous pulp thus obtained is then passed through 

 rolls and dried in the form of thin sheets. The material is 

 bleached to remove all coloring matter, and is sized with rosin, 

 to give it a smooth surface. The purity of the product and the 

 fineness of its texture depend upon the thoroughness of the 

 treatment. The strength and durability depend upon the 

 physical character of the fiber used. Linen papers are stronger 

 and are more durable than those made from cotton or wood. 

 The fine filter paper used in chemical laboratories is practically 

 pure cellulose. 



