464 Sir Andrew NohU [Jan. 18, 



explosives, identical temperatures somewhere between the densities of 

 •3 and "35, and above these densities agree as well as we have any 

 right to expect, but below these temperatures there are wide differ- 

 ences, and the question is, how are these differences to be explained ? 



Before attempting an explanation, I throw on the screen two 

 pairs of curves, showing the temperatures derived from the two 

 formulte. 



The red lines show the temperatures derived from the first 

 formula, the black from the second, and you will note how wide is 

 the difference between the two curves at the lowest density, the 

 differences being approximately 2000° C. and 1500° C. You will 

 observe also, that the equations give identical temperatures for the 

 two explosives at the density of '35, and above that density the 

 accordance is as close as we have any right to expect from observa- 

 tions of this nature. 



At the densities with which artillerists are concerned, say a mean 

 density of • 2, you will observe that in the case of the Cordite the 

 difference of 2000° C. is reduced to 800° C, and with the Norwegian 

 the difference of 1500° C. is reduced to 600° C, and, as you see, at a 

 density of * 35 there is, for both explosives, no difference at all. 



Now the question is, how are we to account for this remarkable 

 difference ? And the answer I have ventured to give is as follows : — 



At atmospheric pressure CO2 commences to be dissociated at 

 about 1300° C, and this dissociation will give rise to a fall in 

 temperature. 



At high densities, as I have said, the two equations give accordant 

 results. I therefore think it reasonable to suppose that the results 

 recorded are due to dissociation at the feeble pressures at low 

 densities, which dissociation is prevented by the high pressures 

 existing at densities above -3. 



It is worth while examining whether there is any corroboration to 

 be obtained for this view with the explosives I am referring to. The 

 difference given by the two formula varies from 2200° C, in the case 

 of the explosive that gave the highest heat, to 050° C. in that which 

 gave the lowest. Now if my view be correct, the difference between the 

 two formulas ought to depend chiefly upon the amount of COo to be 

 dissociated, and on the amount of heat to cause that dissociation — 

 the higher heat, of course, dissociating a larger proportion of CO2, 

 while if there be a larger quantity of CO2 there is more for the 

 higher heat to operate on. 



My view is, that these facts are sufficient to account for the 

 difference between the formulas in the case of the explosives of 

 which I am speaking. 



Now what are the facts ? With Itahan BalUstite, which gives 

 the highest difference, the resultant CO2 amounts to 37 per cent, of 

 the permanent gases, while Nitrocellulose gives only 18 per cent. 

 Again, Italian Ballistite gives 1228 units of heat, while Nitrocellulose 



