454 



Prof W. M. Thornton on tlte Ignition of 



It retards ignition either by arcs or hot wires. But if the 

 readier ignition of the higher paraffins is to be regarded 

 as caused by the hydrogen atoms their influence must 

 follow a higher power than the first, or that of the carbon 

 must remain constant. For the curve, fig. 5, may be taken 

 as a straight line through the origin combined with an 

 hyperbola. Writing (i — i Q ) = an c l{nB.) 2 , where n G is the 

 number of carbon atoms and nn that of the hydrogen atoms 

 in a molecule, and noting that ns_ = 2n c + 2 } then 



1 



(t-to)=a/4l« +2+ -J 



When the value of the coefficient a, derived from the 

 currents in fig. 5, is constant, it is evidence that the igniting 

 current is proportional to the ratio «c/(«h) 2 « From the 

 figure z = -06, or is negligibly small. For ethane a = 2008, 

 propane 18'55, pentane 19*0. It is therefore probable that 

 the relative influence of carbon and hydrogen atoms on the 

 ignition of the higher paraffins is defined by{i — io) = an c /(i>ii) 2 . 

 where a is constant. 



1-4 



1? 





c ^ 

















I-o 



/ 



s 





^€ 













•8 











n^% 











g 



/ 















CgHjj 





•4 





















.? 



K 



/ 



F 



IG.5 







































i 



2 



.0 2 



>0 A 



O 5 



6 



7 



b a 







5. The Form of the Curve of Inflammability. 

 There is a close resemblance between fio-. 1 and the 

 curve of change of state. The shape of the ignition 

 curve can be varied by the rate of break or by the "use of 

 alternating current. Change of frequency has an extra- 

 ordinary influence on the current required for io-nition*. 



* " The Electrical Ignition of Gaseous Mixtures " Proc Kov Soc A 

 vol. xc. 1914, fig. 9. J ' 



