SIR ANDREW NOBLE: RESEARCHES ON EXPLOSIVES. 225 



developed does not vary greatly ; at higher pressures the heat increases considerably, 

 thus compensating for the loss of potential energy due to the decrement in the volume 

 of gas generated. 



Plates 7, 8 and 9 show graphically the great changes that take place in the 

 decomposition of the gases in passing from densities of 0'05 to 0*45. 



In all, carbon monoxide and dioxide change places, the two gases having equal 

 volumes in the case of cordite 24'2 per cent, at a density of 0'19, in the case of M.D. 

 25 '5 per cent, at a density of 0'32, and with nitrocellulose 26 per cent, at a density 

 of 0-36. 



The changes with hydrogen and methane are equally striking, the hydrogen in 

 cordite falling from a maximum of nearly 16 per cent, in volumes to about 9 '5, while 

 the methane increases from about 0'2 per cent, to about 5 '5 per cent. In M.D. the 

 volumes of hydrogen fall from about 19 per cent, to about 10 '4 per cent., while the 

 volume of methane increases from about 0'3 per cent, to nearly 9 per cent., and in 

 nitrocellulose the volume of hydrogen falls from 207 per cent, to about 11 per cent., 

 the methane increasing from 0'5 per cent, to a little over 9 per cent. 



In the tables I have submitted it will be observed that the specific heats and the 

 temperatures of explosion have been given, but in regard to temperatures so far 

 above those in regard to which accurate observations have been made the figures I 

 give can only be taken as provisional. The specific heats of the various gases have 

 been taken at the values usually assigned to them. Of course, it cannot be assumed 

 that these specific heats remain unchanged over the wide range of temperature 

 necessary, although I believe it has been found that the specific heats of some 

 permanent gases such as nitrogen and oxygen are but slightly altered up to 800 C. 



The temperatures of explosion which, as I have said, can only be taken as 

 provisional, have been obtained by dividing the units of heat (water gaseous) by the 

 specific heats, and, although provisional, can safely be used in comparing the 

 temperatures of explosion of the three explosives. The temperatures of explosion, for 

 example, of cordite and nitrocellulose at the density of 0'20 may tolerably safely be 

 taken to be in the ratio of 51 to 36. 



I am, from other considerations, inclined to believe that the temperatures I have 

 obtained and given in the tables are not very far removed from the truth. I tried with 

 cordite to confirm the results by using the equation of dilatability of gases. At the 

 high pressures the results were satisfactory, but quite the reverse at the lower 

 densities. 



The comparative approximate potential energies are obtained by multiplying the 

 volume of gas produced by the temperature of explosion. The means for the three 

 explosives are respectively: cordite, 0'9762 ; M.D., 0'8387 ; nitrocellulose, 07464. 

 The highest potential energy (taken as unity), it will be noted, was obtained from 

 cordite at a density of 0'5. 



I submit that the wide differences in the transformation of the three explosives 



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