Nitro-Glyckrixe Explosives. 99 



as the volume of yases is slightly higher, but the temperature, oa 

 the other hand, slightly lower. Nitro-glycerine, it will be remem- 

 bered, contains slightly' more oxygen than is necessary for its com- 

 plete combustion, but' nitro-cellulose. on the other hand, contains 

 a great deal too little. It so happens, however, that the proportions 

 in which these two generally occur in Blasting Gelatine are com- 

 plementary, and the result is a complete combustion into carbonic 

 acid, water and nitrogen, three very innocuous gases. 



The proportions in which they are formed by weight are roughly 

 as follows : — • 



Carixmic Acid 6i'7% 



Water ^o'3% 



Nitrogen ]8"o'','', 



The volume produced from one kilo calculated al the average 

 temperature and depth of mine working, viz.. 25°C. and 200 metre 

 are as follows : — 



J 92 Litres Nitrogen J7"48% vol. 



422 Litres Carboiiic Acid ■j2'^2% vol. 



This is on the assumption, of course, that all the water is condensed. 



As already remarked, the other gelatinous exjjlosives used on 

 the South African l'"ields are on the main only modifications of 

 Blasting Gelatine, but of a lower grade. The l)est known is 

 "Gelignite," which generally consists of 60", of Blasting Gelatine,' 

 and 40"^J of a mixture of nitrates with some organic matter such as 

 wood pulp. The result is a gelatinous explosive of much the same 

 density as Blasting Gelatine, but about 20% weaker. 



I have ])erhai)s now said enough aljout the exiilosives used on 

 these tie]<ls. but I cannot leave the subject altogether without 

 referring to what is perhaps the most interesting and instrticti\e part 

 which nitro-glycerine plays in the world's economy. 



Forty years ago. the idea of being able to tame nilro-gKcerine 

 to such an extent that it could l)e capaijle of being used as an instru- 

 ment tor industrial develo])ment was believed in b\ few. if anv. 

 We have seen. an<l we know now how" all this came about, but even 

 15 years ago, no one would have believed it ])f)ssil)le to further tame 

 it that it could be used as a i)ropellant. Yet this has taken place, 

 and we have in Cordite, perhaps the most powerful propellant ever 

 known, and at the same time the one most easilv tamed and most 

 amenable to the requirements of the artillerist. Nitro-glycerine is. 

 of course, the principal ingredient of Cordite, and we have the 

 strange anomaly of its (N.G.) being at one and the same time the 

 most powerful blasting and propelling agent as also the mildest and 

 best mannered of explosives. 



To Nobel we are again indebted for this idea, and though his 

 original specification has not l)een followed in everv case. mc>st of 

 the great European Powers have adopted a propellant containing 

 greater or less proportions of nitroglycerine. The phenomenon 

 of a powder being, at the same time a blasting and a propelling 

 agent is not, of course, unknown, and for hundreds of vears out- 

 old friend black poAvder had to act in this capacit\. and it is reallv 



