1907.] on Fifty Years of Explosives. 461 



dependent on the rapidity of combustion ; the loss of heat, and conse- 

 quently of pressure, being due to the conununication to the explosion 

 vessel, that communication being extremely rapid. 



I now turn to this diagram, which shows the difference in the 

 transformation of explosives more readily than if I gave merely the 

 figures. 



The explosives I have selected for comparison are the Italian 

 Ballistite and Norwegian 165. The lines for the fprmer are in red, 

 those for the latter in black, and you will observe how great the 

 differences are. 



Thus, with Italian Ballistite the percentage of CO2 commences at 

 26 per cent., rising to o5 per cent., while the Norwegian commences 

 at 13 per cent., rising, at "5 density, to 3o per cent. AVith the 

 Italian the CO commences at a little above 20 per cent., falling to a 

 httle less than 14 per cent., while the Norwegian commences at 89 

 per cent., falling to 20 per cent. The hydrogen with the Italian 

 varies very httle at about 10 per cent., while the Norwegian falls 

 from 20*5 per cent, to 7 ' 7 per cent. With marsh gas both explosives 

 commence with a trace ; but the Norwegian rapidly increases to over 

 12 per cent., while the Italian only reaches 2 • 7 per cent. 



The Italian has from 29 per cent, to 24 per cent, aqueous vapour, 

 while the Norwegian is practically constant at 14 per cent. 



The wide differences of the transformation under considerable 

 differences of pressure can be seen from the diagram I have just 

 explained, but a better idea of these changes and of the different 

 percentages of the component gases can be arrived at by throwing on 

 the screen for the modern explosives the changes and the proportions 

 of the same gas for the several explosives. 



Here, for example, you see* how widely the percentage of CO" 

 varies with all the modern explosives with the density. Take M.D. 

 With a density of '05 there is only 15 per cent., while at -5 density 

 it is nearly o2 per cent. You will observe also that, although there 

 is a very wide difference, nearly !?> per cent., between Italian Balhstite 

 and Nitrocellulose, as the density increases the difference in all the 

 explosives lessens, so that there is only about 3 per cent, difference in 

 CO2 between the whole of the explosives at a density of '5. The 

 percentage of CO2 in the old gunpowder is also shown. 



^ Taking now CO, the difference between the several explosives is 

 quite as great as in the case of CO2, but here the curves show that, 

 with increase of pressure, the percentages are decreasing rapidly, 

 while, as we would expect, the tendency of the curves to approximate 

 at the higher densities is clearly shown. 



You will note that the Italian Ballistite, which in the last 

 diagram was the highest curve, is now the lowest, and, in fact, as 

 might perhaps be anticipated, the position of the curves is exactly 

 reversed. 



The next element, of which I show the curves, represents the per- 



