8 Dixon & Lowe, Experiments on Abel's theory. 



does not have any such effect as that described by Abel. 

 That it does not alter the lower limit of explosiveness is 

 shown by the 6 % mixture ; and that the character and 

 rate of propagation of the flame is not altered is shown 

 by the experiments with the 8 % and 9% mixtures. 



2. Effect of Electrically Heated Platimim Wire on 

 Weak Mixttires. 



The apparatus used consists of a glass tube 3" diameter 

 10" long, fitted with a rubber stopper bored to fit two 

 glass tubes and four brass wires. The glass tubes are 

 fitted with taps for leading in the gas. The brass wires 

 are connected to the secondary circuit of an induction 

 coil, and a spark can be made to pass between the ends. 

 The wires are coimected through a variable number of 

 lamps to the 200 volt lighting circuit, thus heating a 

 platinum wire. 



A short platinum wire (4*4 cm.) heated by a current 

 which in air brings it to a full red heat, when immersed in 

 a mixture of coal-gas and air containing 8% of coal-gas, 

 glows very brightly, and may even get so hot as to fuse. 

 As soon as the wire reaches a certain temperature (the 

 ignition point of the gas), the gas explodes. 



When the same wire is only gradually heated, by a 

 regulated current, not allowing it to get above a dull 

 redness for about a minute, it may then be heated to 

 whiteness, or an electric spark may be passed without 

 exploding the gas. The reason for this is that so much 

 oxidation of the hydrogen present has taken place that 

 the composition of the mixture has been reduced below 

 the explosive limit (about 6% coal-gas). 



A platinum wire i metre long, heated by a current, 

 which in air brings it to dull redness, when heated in 8% 

 mixture glows brightly but does not explode the gas. 



