U Professor W. A. Bone [Feb. 27, 



surface comhustion, as a means of greatly increasing the general 

 efficiency of heating operations wherever it can be conveniently 

 applied. 



There are critics who, whilst admitting the accelerating inflnence 

 of an incandescent surface npon gaseous combustion, are sceptical 

 about the process being really flameless. The force of such objec- 

 tions largely disappear when we get into close quarters with the 

 phenomenon, and realize how extremely slow a transaction flame 

 combustion really is when considered in terms of molecular time. 

 Take, for example, the case of such a quick-burning mixture as 

 electrolytic gas (2H2 + O2). When this is ignited at atmospheric 

 pressure, the flame is initially propagated by conduction with a 

 uniform slow velocity of 20 metres per second, and during this initial 

 period of " injiammation," the total duration of chemical change in 

 each successive layer is something like the order of ^^ second, an 

 interval of at least one hundred million times as Ions; as the averao'e 

 interval between successive molecular collisions in the gas. Even 

 after " detonation " has been set up in the mixture, when the com- 

 bustion is propagated from layer to layer as a wave of adiabatic 

 compression, at a velocity of 2820 metres per second, the total dura- 

 tion of chemical change is still of the order of 5-0V0 o^' rirwo^ second, 

 or about a million times as long as the interval between successive 

 molecular collisions. 



To illustrate how a flame may be extinguished by the introduction 

 of an active catalysing surface, I will perform an experiment which 

 was first exhibited here a year ago by my colleague Professor the 

 Hon. E,. J. Strutt, who has very kindly lent me his apparatus. 

 Most of you will be familiar with his discovery of the active modifi- 

 cation of nitrogen produced by a powerful electric discharge. This 

 bulb (capacity 300 c.c.) is full of rarefied nitrogen, at a pressure of 

 about iV nim. ; and in the side tube lies an oxidized copper wire, 

 which fits it as closely as is consistent with easy sliding. 



If the nitrogen in the bulb be subjected to a powerful elec- 

 trodeless discharge, it is transformed into an active condition ; the 

 gas continues to glow brilliantly, owning to the fact that the 

 "active" modification is reverting to the ordinary kind producing 

 a luminosity which may be regarded as a condition analogous with 

 flame. The glow will last for a minute or more during the progress 

 of the chemical reversion, and finally dies out when the latter is 

 completed 



But if, on repeating the experiment, the bulb be tilted so that 

 the oxidized copper wire drops into the glowing gas, the luminosity is 

 instantly extinguished. This shows that the reversion process is so 

 enormously accelerated by the surface that practically the whole of 

 the chemical action is concentrated at the surface, and instantaneously 

 completed there, thus extinguishing the glow. 



I think we have, in Professor Strutt's experiment, a close analogy 



