GASEOUS COMBUSTION AT HIGH PRESSURES. 287 



a thorough mixing process, after which a sample of the mixture was withdrawn 

 through the bottom valve for subsequent analysis. In cases where the mixture under 

 investigation was one of three constituents, the first two (one of which was always 

 the oxygen) were first of all mixed in the bomb in their proper proportions, and this 

 first mixture was always checked by analysis before the third constituent was added. 

 Moreover, in all such cases, the special mixing device was brought into play after the 

 addition of each constituent so as to ensure perfect homogeneity and accuracy in 

 composition of the final mixture exploded. 



Immediately before firing the mixture, the connections between the admission valve 

 of the bomb and the standard gauge were filled up with oxygen to a pressure just 

 below that of the mixture in the bomb ; on momentarily opening the admission valve 

 a little of the mixture in the bomb would pass outwards into the connections, and the 

 gauge would within two or three seconds record the exact pressure (i.e., to within O'l 

 atmosphere) of the mixture remaining in the bomb. On again closing the admission 

 valve a moment later the pressure indicated by the gauge plus one atmosphere (since 

 the gauge readings were pressures ftborc the atmospheric pressure) would be the 

 " observed initial firing pressure." 



After firing the mixture, the excess pressure in the connections between the 

 admission valve of the bomb and the gauge was blown off, and then, after opening the 

 valve of the bomb, the gauge reading was once more recorded. This reading was 

 subsequently multiplied by a factor (the numerical value of which had been previously 

 accurately determined by actual trial) representing the ratio of the whole volume of 

 the bomb plus outside system, up to and including the tube of the gauge (now 

 occupied by the products of explosion), to that of the bomb ; the reading so multiplied 

 plus 1'0 atmosphere would thus accurately represent the actual pressure of the cold 

 gaseous products in the bomb after the explosion. 



In cases where the mixture fired in the bomb contained constituents which would 

 deviate from BOYLE'S law at high pressures more than the diatomic gases hydrogen, 

 oxygen, and carbon monoxide (which for all practical purposes may be considered as 

 deviating equally within the limits of pressure covered by the experiments included in 

 this memoir) the " observed initial firing pressures " were subject to a certain 

 correction on this account. In the cases of methane and ethylene, the values for PV 

 as determined by POUILLET for pressures between 1 and 40 atmospheres were used 

 in calculating the " correction " to be applied in any particular case. In the case of 

 ethane, however, for which no authentic data could be found in scientific literature, a 

 set of values were determined by direct comparison of the actual volumes (l) of 

 hydrogen and (2) of ethane, respectively, measured at 15 C. and 760 mm., required 

 to fill up bomb, A, to certain definite pressures, e.g., 5, 10, 15, 20 and 25 

 atmospheres, respectively. The various pressures tabulated in the subsequent part of 

 this paper represent the experimental pressures after due " correction " for deviations 

 from BOYLE'S law in each particular case. 



