SYNTHETIC ORGANIC PRODUCTS 483 



ance as before, but are crisper to the touch. The guncotton is 

 washed thoroughly with water to remove the acids, which would 

 cause slow decomposition and perhaps accidental explosion. 



Dried guncotton burns briskly (deflagrates) when set on fire. 

 While wet, it can be moulded and cut without danger. It 

 explodes only when " set off " by a small amount of another 

 explosive. Fulminate of mercury Hg(ONC)2, used in percussion 

 caps, is commonly employed. By such means the explosion is 

 brought about in wet guncotton as easily as in dry. 



In pure form guncotton is used only in torpedoes and submarine 

 mines. It explodes too rapidly to be used in fire-arms or for 

 blasting. 



Smokeless Powder and Dynamite. The violence of gun- 

 cotton is reduced by compressing it, and still more by dissolving 

 it and allowing the solvent to evaporate. Thus, cordite is made 

 by dissolving guncotton (65 parts), nitroglycerine (30 parts) and 

 vaseline (5 parts) in acetone. The resulting paste is rolled and 

 cut into pieces of different dimensions, according to the rate of 

 explosion desired. When the acetone evaporates, the horny 

 cordite remains. These explosives are smokeless because they 

 differ from gunpowder (p. 372) in yielding no solids when they 

 decompose. 



Blasting gelatine, giant powder, and other forms of dynamite 

 are made by dissolving guncotton in nitroglycerine. Substances 

 like nitrate of sodium or of ammonium and sawdust or flour are 

 added to adjust the rate of explosion so that, for example, coal 

 may be split up, but not shattered. 



High Explosives. These are substances which develop their 

 explosive affect at an extremely rapid rate, and are used therefore 

 when a shattering effect of great violence is required, for example 

 in bursting shells or in anti-submarine mines. Trinitro-toluene 

 (TNT) is made by nitrating toluene (p. 353), picric acid (trinitro- 



