364 Sir Robert Robertson [May 6, 



Pressures Developed by Ammonium Nitrate, Amatols, and T.N.T. 



It will be seen that the addition of 40 per cent, of ammonium 

 nitrate to T.N.T. does not markedly reduce its heat value, rate of 

 detonation, or pressure developed, and that 80/20 has a high content 

 of heat energy, but a rate of detonation and pressure lower than 

 T.X.T. itself. It is, however, still sufficiently violent to fragment 

 shell satisfactorily, and the somewhat slower development of the 

 pressure, together with the high calorific value of the explosive, may 

 be of advantage in enabling the fragments to acquire a higher velocity. 

 It will also be observed that ammonium nitrate itself under a powerful 

 initial impulse gives rise to a notable pressure, so that that ingredient 

 is not to be looked on as a diluent of the T.N.T., but as an explosive 

 substance, as well as a purveyor of the oxygen in which T.N.T. is 

 deficient. 



Smoke. — For the purpose of correct ranging and locating the 

 position of burst, an explosive developing smoke is desirable. Amatol 

 80/20, when used alone, had the disadvantage that it gave no smoke, 

 as the products of the detonation are colourless gases, thus : — 



2C 7 H 3 N 3 6 + 2lNH 4 N03 = 24N 2 +47H 2 + 14C0 2 ; 



whereas, when picric acid or trinitrotoluene detonates, a large quantity 

 of unconsumed carbon is set free, affording a black cloud useful for 

 the purpose of observation. 



Mixtures capable of producing a white smoke, useful for aerial 

 observation, were then added, and as a result of investigations as to 

 the best method of securing its dissociaton, ammonium chloride in 

 conjunction with the ingredients of amatol was localised at the base 

 of the filling. 



Needless to say, there were many other developments in explosives 

 practice during the war, but the example of the train of detonation 

 leading up to the complete detonation of a high explosive shell was 

 chosen to exemplify the subject of this discourse, since it included 

 many features and new problems which had an intimate connection 

 with the technical development of the subject. 



To secure the high percentage of detonations that our artillerists 

 •obtained with the freedom from prematures which they always 



