42 Transact ion ^. 



experiment, to confirm that acetic acid was formed, at the end of the 

 experiment, instead of letting in the hydrate, the reaction-vessel was taken 

 out of the bath, and acetic acid was found in the bottom of the pipette. 

 On breaking the end and letting the liquid out on blue litmus-paper the 

 paper was turned red and the smell of acetic acid was very noticeable. 



The results of these experiments are opposed to those of Dr. Ewan, for 

 although the value of K' shows a decrease with rise of pressure of oxygen 

 there is nothing to show that the action does not go on at least up to very 

 much higher pressures than were found by him. It does not, on the face 

 of it, seem probable that an action which went on readily when the pressure 

 of oxygen was 450 mm. should cease when the pressure was raised only 

 another 100 mm. If there are any oxygen atoms present with the pressure 

 at 450 mm., there seems to be no theoretical reason why they should not 

 exist in at least almost as large numbers Avith the pressure at 550 mm., 

 allowing that the external conditions are the same. It seems to me ex- 

 tremely probable that some retarding influence was present of which Dr. 

 Ewan was unconscicms. As has been pointed out, in the earlier experi- 

 ments little or no action went on, on account undoubtedly of the pre- 

 sence of the paraldehyde, especially when the oxygen-pressure was at all 



Thus, comparing the last experiment quoted with one with similar pres- 

 sures, only using a different sample of aldehyde, the difference is at once 

 seen : — 



It is just possible that the sample used by Dr. Ewan was not free from 

 paraldehyde. It must be noted also that the average value of his constant 

 at 21° C, worked out by the same method as mine, is only 1-2, whereas- 

 mine is 2-2. 



As will be shown in the next section, many other substances affect the 

 speed of the action, showing how easy it would be for the conditions to 

 be different when apparently the same. 



Some Catalytic Agents affecting the Reaction. 



1. The effect of impure aldehyde has already been shown by comparing 

 the results obtained with two different samples. Nothing more need be 

 said at this stage. 



2. lmj)urities in the Oxygen. — The oxygen was kept in liell jars over 

 water. To this water considerable quantities of sodium-hydrate were 

 added, to dissolve out any traces of chlorine, or oxides of chlorine, 

 which are evolved when manganese-dioxide and potassium-chlorate are 

 heated. On one occasion pure water was used in the jars, and the 

 oxygen used immediately it had been collected, before the traces of 

 impurities had dissolved. The effect of this trace of chlorine was almost 

 to stop the reaction. The conditions of the experiment were otherwise 

 the same as they had been. 



