M.U'm;oi). — lidte of ().vi<l(i1 ion of AcciohUhydc to Arefic Acid. 47 



and any agent which tended to lessen the number would have a very- 

 marked effect on the speed of the action. Water-vapour is an example 

 of an agent which favours the formation of atoms, and it is possible that 

 paraldehyde-vapour has the opposite tendency. 



In any case, the extreme sensitiveness of the action would lend support 

 to the assumption that it is an indirect one, taking place between the oxygen 

 atoms and the aldehvde molecules. 



The Effect of Different Percentage Pressures of Aldehyde on 



THE Value of K'. 



It can be seen from a glance at the experiments quoted that the value of 

 K' is smaller when the oxygen-pressure is high, the aldehyde remaining 

 constant. It was found, however, that on raising the aldehyde-pressure 

 to something more nearly equal to that of the oxygen-pressure the value 

 of K' again rose, even when the oxygen-pressure was high. This is further 

 illustrated by experiments made at 25° C. and 30° C. : — 



Partial pressure of nitrogen = 37 mm. 

 Partial pressure of acetic acid = 12 mm. 



In this experiment, though the oxygen-pressure was 602 mm. at the 

 commencement, the action went on rapidly, the value of K' being practi- 

 cally the same as in the first experiment. 



Partial pressure of nitrogen =17 mm. 

 Partial pressure of acetic acid = 15 mm. 



