378 CHEMICAL DISCOVERY AND INVENTION 



substance is called cellulose, it has the composition expressed by 

 the formula (C 6 H 10 5 )w, and it forms the fundamental material 

 of vegetable tissues in general. Clean cotton consists of almost 

 pure cellulose, and when ignited it burns away leaving only a 

 minute quantity of mineral matter in the form of ash. 



When cotton is immersed in strong nitric acid an interchange 

 takes place which may be expressed by the following equation : 



(C 6 H 10 5 ) 2 +3HN0 3 =[C 6 H,0 2 (N0 3 ) 3 ] 2 +3H 2 



in which it is obvious that the product is a nitrate, and its 

 formation is comparable with the production of a nitrate when 

 caustic potash is mixed with nitric acid. Water is in both cases 

 formed simultaneously : 



KHO+HN0 3 -KN0 3 +H 2 0. 



In the case of cellulose three stages of nitration are possible, 

 the products being represented by formulse, thus : 



[C 6 H 9 4 (N0 3 )] 2 [C 6 H 8 3 (N0 3 ) 2 ] 2 [C 6 H,0 2 (N0 3 ) 3 ] 2 . 



It has long been known that when starch, paper, cotton fibre, 

 or other vegetable material is soaked in very strong nitric 

 acid and is subsequently washed in water and dried, the 

 cotton or other material is scarcely changed in appearance, but 

 it is found to have increased in weight, 1 part of cotton giving, 

 according to the theory explained above, 1-8 parts of nitrated 

 cotton. This material is extremely inflammable, and on contact 

 with a flame disappears instantaneously with a bright flash. 

 The Swiss chemist Schonbein, so long ago as 1845, proposed to 

 use this product as a substitute for gunpowder. It was, how- 

 ever, many years before the manufacture of gun-cotton could be 

 carried on without danger of explosion, and before the product 

 could be obtained in a condition in which it could be stored and 

 used for any purpose with reasonable safety. A long series of 

 experiments, conducted first by the Austrian General von Lenk, 

 and later by Sir Frederick Abel in this country, led to the 

 discovery of the conditions necessary for this object, the first 

 essential being the removal of the last traces of acid from the 

 nitrated cotton. 



At the present day gun-cotton as well as nitroglycerine, to be 

 described later, is manufactured in large quantity in many 

 countries in which the regulations controlling the operations 



