618 



Prof. W. M. Thornton 



on the 



Table III. 

 Tungsten Wires. 



n Per cent. Calorific 

 ^ as - in Air. Value. 

 Hydrogen 30 581.C 



b. 

 307* 



Carbon Monoxide 33 63 



Methane 10 212 



340 

 340 



Coal Gas 15 c. 120 



330 



* With molybdenum -wires b was 345. 



4. Methane. 

 There is very great difficulty in igniting methane by any; 

 wire whose melting-point is below about 1800° C. It is 

 practically impossible to do so with platinum except in a 

 stream of gas. This confirms the observations of Wullner 

 and Lehmann and Couriot and Meunier. When a vessel is 

 used of so large a volume that fresh gas is swept over the 

 wire continuously by convective movement ignition can in 

 certain cases occur, but in a vessel of the volume and shape 

 used here it was not found possible to ignite methane, in any 

 proportion of mixture, by platinum wires. This might well 

 have been the result of complete burning out of the com- 

 bustible gas or the formation of an inert residue. In order 

 to test this a sparking plug was fitted in one of the cross 

 arms of the explosion vessel. After the platinum wires had 

 become white-hot, melted and fused in the mixture without 

 igniting it, a spark was passed at the plug. In every case 

 explosion followed. 



2-0 A_ 



18 



1-6 

 1-4 



1-2 

 1-0 

 0-8 





\ 



CH 4 





















\ 























\ 











FIG 



.3 











\ 



V 



iH 6 















B* 



































""OS 



Ht ^ 

























P£TF 



Sot?*- 



© 8 JO ix 



Q\ PT. WIRES 



14- 16 



18 "2.0 



2,-Z 



An estimate of the current which would ignite methane 

 by 0*1 millimetre platinum wire, if this did not melt, can 

 be made from results with ethane, pentane, and petrol given 



