EXPEEIMENTS ON SOLID AND GASEOUS EXPLOSIVES. 



377 



curve is perfectly normal, showing clearly the three distinct stages of combustion 

 referred to on p. 373. 



The law of combustion by parallel surfaces as expounded by VIEILLE* applies well 

 to the case of cordite, t 



0.005 



0.010 



0.015 



0.005 



0.010 



Time in seconds. 



0.015 



Fig. 14. Showing the rate of rise of pressure for cordite of the smallest diameter. 

 Diameter 0'035 inch (0'89 millim.). 



A, spherical enclosure ; charge uniformly distributed ; gravimetric density 074. B, cylindrical enclosure ; 

 charge uniformly distributed ; gravimetric density 0'075. C, cylindrical enclosure; charge concen- 

 trated in one quarter of cylinder, nearest the recorder; gravimetric density 0'075. 



The speed at which the flame travels inwards towards the centre of each cord is 

 uniform and relatively slow. When unconfined, cordite burns at a rate of about 

 0'5 centim. per second. In a closed vessel the average speed increases to 5 centims. 

 per second for an explosion developing 500 atmospheres, 8 centims. for a maximum of 

 1000 atmospheres, and 11 centims. per second for 2000 atmospheres.^ 



The shape of the curve representing the rise of pressure depends essentially on two 



* 'Comptes Eendus,' vol. 118, pp. 346, 458, 912; 1894. 



t The peculiarly regular combustion of cordite was first noticed by NOBLE, who in 1892 ('Proc. Roy. 

 Soc.,' vol. 52, p. 129) remarks that the pieces of cordite blown from the muzzle of the experimental gun he 

 was using were so uniformly decreased in diameter that they might readily have been mistaken for newly 

 manufactured cordite of smaller diameter. 



| The time required for the full pressure to develop is, therefore, proportional to the diameter of the 

 cord. The formula L == r/c (where L is the time in seconds and the radius in centimetres) gives a fair 

 approximation, though, as we shall see, the actual time varies somewhat, according to the conditions of the 

 experiment. The constant c is characteristic of the explosive and, of course, equal to the above rates of 

 combustion. 



VOL. CCV. A. 3 C 



