16 THE ROYAL SOCIETY OF CANADA 



of the particles and at the next instant more closely associated with 

 each other in hydrogen molecules. A small portion of the impacts of 

 positive hydrogens of gas molecules and negative hydroxyls on the 

 surface result in the permanent formation of molecules of water 

 which are evolved as such. This view is further confirmed by 

 experiment 8. 



Reaction (2) represents a reaction very slow in comparison with 

 reaction (1) and which is constantly taking place during the hydro- 

 génation. Negative hydroxyls on the surface are constantly and very 

 slowly being removed and hydrogen being adsorbed. 



Reaction (3) represents the reaction of this adsorbed hydrogen 

 with unchanged nickel oxide in the interior of the particles. Here 

 also the water represented is not all evolved in the free state but 

 partly goes to reform hydrogens and hydroxyls on the surface. 



Finally, after long use the oxygen remaining on the catalyser 

 either as negative hydroxyls or unchanged nickel oxide in the interior 

 becomes very small and nothing remains finally but nickel particles 

 with adsorbed hydrogen thus — 



H + 



Ni H- 



H + 



H- 



I 

 I 



As we shall see, nickel in this condition is a very poor catalyst 

 for hydrogénations. The activity of the catalyst is associated with 

 its oxygen content and its activity can be restored by reoxidation 

 and partial reduction. 



Experiment 8. 



If this explanation is correct it should be possible to catalyse 

 the union of ethylene and hydrogen, i.e., bring about reaction 1 which 

 is fast, without causing any appreciable changes by reactions 2 and 

 3, which are relatively much slower reactions, if the mixture of ethylene 

 and hydrogen is left in contact with the catalyst for only a short time. 

 Accordingly the catalyst was again oxidized by oxygen and reduced 

 at 275° by hydrogen for eight hours and the hydrogen displaced by 

 nitrogen. Mixtures of hydrogen and ethylene were successively 

 passed back and forth over the catalyst, each mixture being in contact 

 with the catalyst for only 15 to 20 minutes. The hydrogen used up 

 and the ethane formed were determined. The results of three 



