1904.] The Retardation of Combustion ~by Oxygen. 89 



and water is an endothermic process. In fact, it is to be supposed 

 that water is readily oxidised at temperatures such as prevail in 

 combustions. If, however, the formation of water be regarded as 

 involving the changes 



H OHH HOH HO 



2H 2 2 * -- ^ 2H 2 + 2 



it follows that water and oxygen will mutually hold each other in 

 check : so that when electrolytic gas is exploded there will be a 

 deficiency of oxygen, as it were, owing to its conversion into hydrogen 

 peroxide, which may be regarded as relatively, if not entirely, in- 

 operative as an oxidising agent at high temperatures in presence of 

 oxygen. On the other hand, when excess of oxygen is present, the 

 water which is the effective catalyst will be more or less held back, 

 also in consequence of its oxidation to hydrogen peroxide. The 

 marked influence of hydrogen in promoting the combustion of electro- 

 lytic gas is in full harmony with this conclusion ; indeed, it is difficult 

 to explain it in any other way than by supposing that, when present 

 in excess, the hydrogen serves to promote the dissociation of the 

 peroxide by diminishing the proportion of active oxygen present : in 

 other words, according as hydrogen or oxygen is in excess, equilibrium 

 is disturbed in one direction or the other. The interaction of hydrogen 

 and oxygen may, perhaps, be supposed to be incomplete at high tem- 

 peratures, less because the steam is partially dissociated than on 

 account of the division of the oxygen between the hydrogen and 

 water. 



[Note added June 29. The experiments on the oxidation of ethane 

 at so low a temperature as 300, recently described by Bone and 

 Stockings, have shown that change proceeds with surprising rapidity 

 in the case of mixtures containing ethane and oxygen in the ratio 

 2 : 1 or 1 : 1, the oxygen disappearing within 30 45 minutes; whereas 

 when sufficient oxygen was present to burn the hydrocarbon completely 

 to steam and carbon dioxide (1 : 3 -5), a considerable quantity of 

 oxygen and some ethane remained unchanged even after 2 days. 

 There can be little doubt, therefore, that oxygen has a specific retarding 

 effect even at so low a temperature as 300 ; and there would seem to 

 be no reason to suppose that the changes which occur at low tem- 

 peratures are in any essential respect different from those at high 

 temperatures.] 



