CARBOHYDRATES 1 27 



Mercerized Cotton and Artificial Silk. — When ordinary 

 cotton is treated with moderately strong alkahes, compounds 

 are formed with the cellulose which decompose again with 

 water, yielding hydrates of cellulose. The cotton so treated 

 maintains its general character, but is more or less transparent, 

 resembling silk in appearance and possesses greater strength 

 than the original cotton. It can also be dyed more readily 

 than the original cotton. Such a product is known as mer- 

 cerized cotton. This is not, however, what is known as artificial 

 silk. The latter is prepared from cellulose by various methods. 

 A solution of cellulose in Schweitzer's reagent or a solution of 

 certain derivatives, e.g. nitrates or acetates, is passed through 

 capillary tubes into a liquid which reprecipitates the cellulose 

 or its derivatives. It is thus obtained in the form of fine threads 

 or fibers consisting of pure cellulose or some derivative of it. 

 As it is thus obtained it possesses many of the characters 

 of silk and is commercially used as artificial silk. It can be 

 readily dyed, possesses considerable silky luster, but though 

 more durable and stronger than cotton or other cellulose fibers 

 is not as strong or as durable as pure silk. 



Explosives and Celluloid. — The chemical derivatives of cel- 

 lulose are chiefly of two classes, viz. nitrates and acetates. 

 These have been referred to as having been used in the prepa- 

 ration of artificial silk. The nitrates of cellulose are, however, 

 a very important class of derivatives in themselves. When 

 treated with nitric acid cellulose forms derivatives containing 

 two to six nitric acid groups. When a mixture of nitric and 

 sulphuric acid is used, six nitric acid groups unite with the 

 cellulose and the compound, cellulose hexanitrate, is formed. 

 This compound is highly explosive and is the chief constituent 

 of gun cotton. Gun cotton explodes violently when struck or 

 when set off by means of a detonator, but will burn quietly when it 

 is ignited. It is used as an explosive by itself or mixed with nitro- 

 glycerin. It is also a constituent of some smokeless powders. 



When cellulose is treated with nitric acid in a less concentrated 

 form or for a shorter time, the nitrates of cellulose containing 



