Inflammability of Gaseous Mixtures. 193 



formula, ethane may be chosen. In this case the upper limit 



is at 2C 2 H 6 + 7 , giving 



4x100 



= 10*53 per cent, of gas 



4 + 7x4-85 



in air. The agreement between the calculated and observed 

 values shows that in the upper limit mixtures of the paraffins 

 there is twice the volume of inflammable gas as in the mixture 

 for perfect combustion. In certain endothermic compounds, 

 acetylene, cyanogen, and carbon disulphide, there is three 

 times this volume, in hydrogen four, and in carbon monoxide 

 six times. The upper limits of inflammability of any gas in 

 a homologous series of which the first terms are known can 

 then be calculated from the equation typical of the compound. 

 3. While the upper limit mixtures of the paraffins contain 

 twice as much combustible gas as those for perfect com- 

 bustion, ignition fails at the lower limit when there is twice 

 as much oxygen, being first possible when there is one atom 

 of oxygen less than this. The mixture m + 2n is uninflam- 

 mable, ?n + (2n — 1) is the lower limit for the paraffins. In 

 the case of ethane it is at C 2 H 6 + Oi 3 , which gives a percentage 



,2x100 . 



° f 2 + 13x4-85 =308mair - 



Gas. 11. 



Hydrogen 1 



Methane 4 



Ethane 7 



Propane 10 



Butane 13 



Pentane 16 



Benzene 15 



Methyl alcohol 3 



Ethyl alcohol 6 



Acetylene 5 



Cyanogen 4 



Carbon disulphide . . 6 



Hydrogen sulphide. . 3 



Carbon monoxide ... 1 



Ethylene 6 



The paraffins form one group in which benzene falls, as 

 it did at the upper limit, acetylene, cyanogen, and carbon 

 disulphide, with the alcohols, another. Cyanogen falls into 



Phil. Mag. S. 6. Vol: 33. No. 194. Feb. 1917. O 



Table II. 







L Ob8. 



Nearest mixture 



L cal. 



L?i L . 



rn+n^. 



41 



m+9n 



4-4 



369 



56 



m+(2n-l) 



5-5 



39-2 



31 



m+(2n-l) 



3-08 



40-2 



2-17 



m + (2n-l) 



2-12 



41-2 



1-55 



m + (2n-l) 



1-62 



38-8 



1-35 



m + (2n-l) 



1-31 



41-8 



1-5 



m+(2w-l) 



1-4 



43-5 



5-5 



m+(3w-2) 



5-5 



38-5 



2-8 



w+(3w-2) 



2-5 



44-8 



30 



m+(3w-2) 



3-0 



390 



76 



m+(3n-2) 



7-6 



760 



2-5 



m+(3?i-2) 



2-5 



400 



4-5 



m+3n 



4*47 



40-5 



126 



m+3n 



12-1 



37-8 



57 



m+{n+\) 



5-57 



399 





Mean 



. 40-1 



