368 



ME. J. E. PETAVEL ON THE PRESSURE OF EXPLOSIONS. 



C is closed and the pressure and composition of the mixture adjusted by means of the 

 apparatus described below. 



After each explosion the sphere is washed out first with a solution of caustic 

 potash, then with distilled water. 



Cylindrical Enclosure. 



The cylindrical enclosure, shown in fig. 6, is also made of mild steel. 



The dimensions are: external diameter 12 '2 centims. ; internal diameter 3 "17 

 centims. ; length of bore 69'64 centims. It has, therefore, a capacity of 550 cub. 

 centims. and an internal surface of 709 sq. centims. roughly speaking, the same 



D 



33" - 



Fig. 6. Cylindrical enclosure. 



The recording gauge screws in at A, the firing plug at B, and two valves at C and D respectively. The 

 volume of this enclosure is nearly the same as that of the sphere, its surface 2 '17 times as great. 



volume as the sphere, but rather more than twice its surface. The various apertures 

 are identical to those of the spherical enclosure and the gauges and other fittings can, 

 therefore, serve for either apparatus. This cylinder has been used up to 2000 

 atmospheres and would doubtless be safe at a considerably higher pressure. 



Firing Plug. 

 The design of the firing plug is clearly shown in fig. 7. 



Standard Gauges. 



A vast number of measurements of statical pressure had to be made during the 

 course of the work, more especially for the part dealing with gases. For this purpose 

 the connections were arranged so that the gauges could be easily interchanged, each 

 one being used for the range over which it was most sensitive. To determine the 

 initial pressure and composition of the gaseous mixtures, two independent sets of 

 observations were always taken. The pressure was first roughly adjusted to the 

 desired amount by means of direct-reading Bourdon gauges, then accurately 

 measured by a standard gauge. A series of mercury columns were used for the lower 

 pressures and manometers of the Cailletet type for the higher pressures. The various 



