ON GASEOUS COMBUSTTON. 



483 



Bomb 



Capacity in cm." . 

 Surface in cm.' 2 . 

 Surface per unit volume 



Diameter in cm. .... 

 Length of firing piece in cm. 

 Travel of flame before reaching 

 the piston in cm 



<D T3 





2H. 2 +0. 2 

 200+0, 



CH,+20, 



C. 2 N. 2 +0 2 

 C,N,+20., 



Time required for flame to travel from 

 the firing piece to piston of indicator. 

 Mivturp [ 2 H. 2 + 0. 2 .... 

 Mlxture (2CO+0. 2 .... 



300 

 216 

 0-72 



6-0 

 0-3 



0-1 



Atms. 

 7-41 

 9-29 



13-94 



0-00104 sec. 

 0-01286 sec. 



B 



1,500 

 648 

 0-43 



14-2 

 5-3 



16-3 



Atms. 



9-69 



9-93 



14-81 



Perhaps the most notable feature about these results is the smallness 

 of the difference between the pressures observed with bombs A and C 

 in any particular case. These differences might at first sight be attri- 

 buted to the (supposed) much smaller cooling influence of the walls 

 of the bomb C as compared with bomb A, but if this were the true 

 explanation the difference should be greater with the slow-burning 



mixture than with the fast-burning 



200+0^ 



opposite was the case. Moreover 



mixture 2H 2 + 2 with twice its own volume of 



obliterated the difference between the pressures observed 



2H 2 + 2 , whereas the 

 the fact that dilution of the 



almost 

 the 



nitrogen 



in 



pG 



cases of bombs A and C (the ratio r for the diluted being 0.95, as 



against 0'76 for the undiluted mixture) is all against the cooling theory. 

 The more probable explanation is to be found in the fact that, owing to 

 the much longer travel of the flame before it reached the piston of the 

 indicator in bomb as compared with A, the explosion would be in a 

 more advanced phase of its development, and this would be most marked 

 in the case of the fastest burning mixtures. Berthelot and Vieille assumed 

 that in the above experiments completion of the combustion syn- 

 chronised with the attainment of maximum pressure, and attributed 

 the marked disparity between the observed pressures (bomb C) and those 

 calculated from the heats of combustion (on the assumption of adiabatic 

 conditions) to a rapid increase in the specific heats of steam and carbon 

 dioxide at high temperatures. They considered it improbable that dis- 

 sociation phenomena play any conspicuous part in limiting the pressures 

 attained. 



Mallard and Le Chatelier, 1 who used a Bourdon gauge for measuring 

 pressures and applied a ' cooling correction ' to their results, arrived at 

 practically the sump conclusion ns "Berthelot and Vieille 2 respecting both 

 1 hoc. ctt. - Ann. Chita. Phys. [vi.], 4, 13. 



