62 CARBOHYDRATES 



Their strength becomes approximately 20 per cent greater, their affinity 

 for dyes is greatly increased, and a smooth glossy surface is produced. 



Synthetic yarn, also known as rayon or artificial silk, is a cellulose 

 product that has achieved great importance since World War I. In 1949 

 nearly 500,000 tons were produced in America, while world production 

 in 1947 was twice this figure. The rapid progress of this industry in the 

 United States is indicated by the fact that only 63,500 tons of rayon were 

 produced in 1930. Synthetic yarns are made from xanthate, acetate, 

 nitrate, and cuprammonium compounds of cellulose. Of the four, the 

 most important is the type produced by the xanthate or viscose process, 

 which uses sodium hydroxide and carbon disulfide as the chemicals for 

 dissolving the cellulose. Although the term "rayon" was originally 

 applied solely to the product of this process, the Federal Trade Commis- 

 sion has ruled that all manufactured textile fibers of cellulosic origin 

 shall be included in the term. 



The cellulose products, instead of being spun as a thread, may be 

 produced in the form of a sheet or film. Cellophane, a colorless trans- 

 parent material which is extensively used for wrapping purposes, is made 

 by the viscose process, in which the cellulose is regenerated in the form 

 of a sheet of varying thickness. Motion picture films and glass substi- 

 tutes, which allow the ultraviolet rays of the sunlight to pass through, are 

 other examples of sheet cellulose products. ''Safety glass" used in auto- 

 mobiles usually consists of a sheet of glass on each side of a layer of 

 cellulose acetate. Cotton lacquers, such as Duco, which in recent years 

 have come into extensive use for the surfacing of automobiles and furni- 

 ture, contain as one of their essential constituents some ester of cellulose, 

 usually the nitrate or acetate. 



Nitrate esters of cellulose are used for many purposes. Cellulose 

 trinitrate [C6H702(N03)3]a; is the well-known explosive, guncotton. The 

 less completely nitrated cellulose is known as pyroxylin and is extensively 

 used in the manufacture of plastics, such as celluloid. Celluloid is a 

 mixture of two parts pyroxylin and one part camphor. The strongly 

 combustible nature of all celluloid materials is due to the presence of 

 the nitrate groups. Collodion is a solution of pyroxylin in alcohol and 

 ether. AVhen this solution is painted over a wound, the alcohol and 

 ether evaporate leaving a thin membrane, "new skin." When used in 

 manufacture of artificial silk, cellulose nitrate must be denitrated to 

 render it noninflammable. This is accomplished by treatment with an 

 acid sulfide, for example, sodium acid sulfide (NaHS) . 



Cellulose is not acted upon by the enzymes of the digestive tract of 

 vertebrates. However, certain snails and insects secrete an enzyme, 

 cellulase, which is capable of digesting cellulose. Cows, sheep, and 

 horses consume large quantities of cellulosic material, and a large pro- 

 portion of this material (50 to 85 per cent) disappears from the digestive 



