[boswell] catalysis OF HYDROGENATION BY NICKEL 



21 



Volume at end 145 



c.c. 



Reduction in volume 200 c.c. 



Oxygen in residual gas 140 c.c. 



Hydrogen in residual gas 5 c.c. 



Water evolved 0956 g. 



.". 40 c.c. oxygen and 160 c.c. hydrogen disappeared. 



Now 40 c.c. of oxygen require 80 c.c. hydrogen for combination, 

 giving .060 g. water. Therefore, 80 c.c. hydrogen disappeared in 

 excess of the hydrogen required to combine with the oxygen which 

 disappeared. 



The interpretation of these results by means of the mechanism 

 here advanced is not strained and seems convincing: 



a 



N'l 



\0H~ /y-^l- 



\0H' 



hA- 



H 



•a» 



9/^ 



H' 

 H'*'-i-4HiO 



I 

 i 



According to this, 4 volumes of hydrogen are represented as disappear- 

 ing for every one volume of oxygen. Actually 160 c.c. hydrogen and 

 40 c.c. oxygen disappeared in the experiment. The amount of water 

 required by the above equation for a disappearance of 160 c.c. 

 hydrogen at 22°C. and 760 mm. is .1190 g., whereas only .0956 g. 

 were evolved. That is, .0234 g. water was held on the catalyser 

 probably mechanically. 



That there was now little oxygen in the form of hydroxyl on the 

 surface of the particles was shown by the fact that upon now passing 

 a mixture of ethylene and hydrogen at 150° over the catalyst for one 

 hour no hydrogénation of ethylene occurred. Upon raising the 

 temperature to 275 water was evolved and hydrogénation of ethylene 

 occurred. That is, before combination of hydrogen and ethylene could 

 be catalysed it was necessary for the hydrogen on the suiface of the 

 particles to difïuse into the interior of the particles and there reduce 

 more unchanged nickel oxide. 



The use of the conception of dissociated hydrogen into positive 

 and negative hydrogens is not new. It has been employed by physical 

 investigators for some time. Its first use by chemists has been more 

 recent. Lewis (12) has expressed the opinion that the mechanism of 

 hydrogénation by nickel involves the dissociation of hydrogen followed 

 by collisions of the substance to be hydrogenated with the metal 



