Inflammability of Gaseous Mixtures. 191 



gas are whole numbers *. It will be shown that the pro- 

 portions of oxygen in the limiting mixtures are in regular 

 systems. 



Burgess and Wheeler have shown f that in the case of 

 the paraffins the lower limit of inflammability is inversely 

 proportional to the calorific value of the gas, but this is also 

 the case when the number of oxygen atoms in the limit 

 mixture bears the same proportion in each gas to those 

 required for perfect combustion. It seemed therefore worth 

 while to examine whether in general the proportion of 

 oxygen in the limiting mixtures has any definite relation to 

 that for perfect combustion. 



The following are values of the limits recently observed : 

 n is the number of oxygen atoms required for the normal 

 combustion of one molecule m of the gas. A mixture m + n 

 gives this condition. 



Table I. 



TT T . ., Nearest whole 



Gas. Upper Limit. n nU> number ^ 



obs. composition. 



Hydrogen 60 1 60 4m+n 622 



Methane 14-8 4 59-2 2m+?* + ] 141 



Ethane 107 7 74"9 2m+n 10'5 



Propane 7*35 10 73-5 2m+n 76 



Butane 57 13 74'1 2m+n 5-9 



Pentane 4*5 16 72'0 2m+n 4"9 



Methyl alcohol 2P0 3 63'0 2m+n 216 



Ethyl alcohol 9'5 6 57'0 3m+2n 9'35 



Hydrogen sulphide . 19-0 3 57*0 2m+n 21 '6 



Carbon monoxide... 700 1 70*0 6m+n 71*2 



Benzene 8'0 9 72-0 2m+n 8'4 



Acetylene 46'0 3/2 69 3m +n 45'0 



Ethylene 17"5 4 70 2m+n 171 



Cyanogen 38'0 2 76 3m+n 38-2 



Carbon disulphide. . 45'0 3/2 67*5 3m+n 45*0 



The products nU are fairly constant in one of two groups, 

 as shown in the figure. On the upper curve, that of the 

 heavier paraffins, the product is between 69 and 75 ; in the 

 lower, that of methane, between 57 and 65, 



* " The Ignition of Gases by Condenser Discharge Sparks," Proc. 

 Roy. Soc. A. vol. xci. p. 17 (1914). "The Ignition of Gases by Im- 

 pulsive Electrical Discharge," Proc. Roy. Soc. A. vol. xcii. p. 381 (1916). 



t " The Lower Limit of Inflammation of Mixtures of the Paraffin 

 Hydrocarbons and Air," by M. J. Burgess and R. V. Wheeler, Chem. 

 Soc. Journ. vol. xcix. p. 2013 (1911). 



