[boswell] catalysis OF HYDROGENATION BY NICKEL 



17 



separate experiments are shown in the following table, calculated to 

 nitrogen free gases: 



These results in conjunction with the previous experiments show 

 that in the hydrogénation of ethylene reaction (1) occurs at the 

 outset by the loosening of the bonds between the positive and negative 

 hydrogens of neutral hydrogen molecules. This is accomplished by 

 the attraction of negative hydroxyls on the nickel complex for positive 

 hydrogens of hydrogen molecules, without actually combining to 

 form water. Had the hydroxyls been removed in experiment 8, 

 then hydrogen would have been adsorbed according to reaction (4) 

 and hence hydrogen would have disappeared in excess of ethylene 

 hydrogenated. Thus the oscillation of a positive hydrogen atom 

 between a negative hydroxyl group of the nickel complex and a 

 negative hydrogen, is the initial cause of the catalysis of hydrogén- 

 ation. In experiments (5) and (6), which were carried out more 

 slowly, reactions (2), (3) and (4) took part to a greater extent, thus 

 resulting in the disappearance of an excess of hydrogen over that 

 required to hydrogenate the ethylene which disappeared. 



Experiment 9. 



That hydrogen is slowly adsorbed at room temperatures by a 

 nickel catalj^st was shown by filling the apparatus after experiment 

 8 with hydrogen and allowing to stand for four days at room tempera- 

 ture, readings of volume being taken at intervals. 



Time elapsed Burette reading 



325 c.c. 



3 hours 315 



19| " 310 



3 " 310 



22 " 300 



18 " 290 



On now passing nitrogen, water was obtained equivalent to 



27 c.c. of hydrogen. Since at the commencement of this experiment 



the nickel catalyst was prepared by a long treatment with hydrogen 



the surface had probably reached an equilibrium condition, where the 



2— c 



