EXPLOSIVES 383 



porating the liquid with a sufficient quantity of a fine silicious 

 earth, called kieselguhr. The product is dynamite, which is 

 familiar enough by name to the public. 



Nitroglycerine is produced very simply by the interaction of a 

 mixture of nitric and sulphuric acid with pure glycerine. 



Glycerine is the secondary product obtained in boiling fat or 

 oil with caustic alkali for the purpose of producing soap. But a 

 large quantity is also produced by distilling fats in super-heated 

 steam, when the fatty acid and glycerine are obtained, and it is 

 only necessary to evaporate the watery part of the distillate to 

 obtain the glycerine. 



Glycerine, or glycerol as it is called in systematic chemical 

 language, is a familiar colourless syrupy liquid, with a sweet 

 taste. It mixes with water in all proportions, and when mixed 

 with nitric acid it is converted into the nitrate, or nitroglycerine, 

 at the same time that water is produced : 



While formerly only small quantities at one time of glycerine 

 were acted on by the acids, a charge of 1400 Ibs. of glycerine may 

 be now used in one operation in the apparatus called a nitrator- 

 separator. In the modern practice a mixture of strong nitric 

 acid with sulphuric acid is used, to which is added a certain 

 amount of anhydrous sulphuric acid in the form of what is called 

 oleum, which combines with a larger proportion of water, with 

 the result that the yield of nitroglycerine is not far short of the 

 theoretically possible amount. From the formulae 100 parts of 

 glycerine should yield 246-7 parts of the nitrate, while in practice 

 upwards of 230 parts are obtained. 



" The nitrator separator is a cylindrical leaden vessel with a 

 coned top ; inside are placed leaden coils, through which cooling 

 water circulates, and pipes through which compressed air is 

 blown to mix the contents. The glycerine is introduced in the 

 form of a fine spray under the acid by means of a special injector 

 worked also by compressed air. Long thermometers passing 

 through the top of the nitrator-separator enable the temperature 

 to be watched, and it is the business of the man in charge of the 

 operation to see that the temperature does not ri^e beyond a 

 certain point, generally 28 C. By reducing the flow of the 

 glycerine and by increasing the agitation with the air any 

 undue tendency to rise can usually be checked. 



