GUMS, PECTINS, AND CELLULOSES 73 



Cellulose is acted upon by caustic alkalies in a variety of 

 ways. When fused with a mixture of dry sodium and potassium 

 hydroxides, it is decomposed into oxalic and acetic acids. When 

 heated with a 10 to 15 per cent solution of caustic soda, cellulose 

 fibers thicken and become translucent, thus resembling silk fibers. 

 This process, known as " Mercerizing," is largely used for the 

 production of commercial fabrics. 



Acids also act on cellulose in a variety of ways. When heated 

 with nitric acid (sp. gr. 1.25), it is converted into oxy cellulose; 

 while dilute sulfuric acid, under similar conditions, yields hydro- 

 cellulose, a substance having the formula Ci2H22On, which 

 retains the fibrous structure of the original cellulose but which, 

 when dry, may be rubbed up into a fine powder. Concentrated 

 nitric acid, or better, a mixture of concentrated nitric and sulfuric 

 acids, acts upon cellulose, converting it into various nitro-deriva- 

 tives, several of which have great industrial value. The number 

 of NOs groups which unite with the cellulose molecule under these 

 conditions depends upon the temperature, pressure, etc., employed 

 during the nitration process; di-, tri-, tetra-, penta-, and hexani- 

 trates are all known. Pyroxylin, or collodion, is a mixture of the 

 tetra- and penta-nitrates, which is soluble in alcohol and is used 

 in surgery, in photography, and in the manufacture of celluloid, 

 which is a mixture of collodion and camphor. The hexanitrate, 

 Ci2Hi4(NO3)eO4, is the violent explosive known as gun-cotton. 



Gentler oxidizing agents, such as " bleaching powder," etc., 

 have no effect upon cellulose, and hence are extensively used in 

 the treatment of cotton and other vegetable fibers, in preparation 

 for their use in the manufacture of textiles, paper, etc. 



Cellulose is indigestible in the alimentary tract of animals, but 

 the putrefactive bacteria which are generally present there ferment 

 it, with the production of acids of the " fatty acid " series, carbon 

 dioxide, methane, and hydrogen. Excessive fermentations of 

 this kind are responsible for the distressing phenomenon known as 

 " bloat." 



The compound celluloses comprise the larger proportion of the 

 material of the woody stems of plants. They consist of a base 

 of true cellulose, which is either encrusted with or chemically com- 

 bined with some non-cellulose constituent. Depending upon the 

 nature of the non-cellulose component, the compound /celluloses 

 are divided into three main groups, known respectively as (1) 



