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



of platinum on electrolytic gas is inexact. Platinum 

 ignites electrolytic gas because the combustion of the 

 small proportion of the gas necessary to raise the tem- 

 perature of the platinum to the "ignition point " leaves 

 a mixture which is still highly explosive in spite of its 

 admixture with the steam formed. But in the case of 

 the fire-damp mixture the proportion of methane is 

 initially so low that it will not inflame in contact with a 

 flame. The explanation therefore involves the supposition 

 that a catalyst can cause a gas to lose part of its chemical 

 energy as heat but at the same time makes it more chemi- 

 cally ' active ' in propagating a flame. If magnesia dust 

 can effect this, a fortiori platinum might be expected to 

 effect it. 



Two series of experiments were undertaken. 



1. The direct combustion of weak mixtures of coal- 

 gas and air with and without non-combustible dust, on a 

 small scale, in order to see whether any difference in the 

 propagation of the flame could be noticed. 



2. The heating of a length of platinum wire in weak 

 mixtures by an electric current to show that by this 

 means a non-explosive mixture could not be made to 

 explode, but rather that an explosive mixture thus treated 

 would become non-explosive owing to the combustion on 

 the platinum wire. 



I . Direct experiments zvith calcined magnesia dust. 



The apparatus consisted of a thick vertical glass tube, 

 37cm. long by 4cm. wide, closed at the bottom end, and 

 fitted at the top with a cork. The cork carried a leading 

 tube through which a previously made mixture of air and 

 gas could be introduced from a gas holder. The leading 

 tube went to the bottom of the wide tube, and was drawn 



