52 T raiiHitctions. 



General Conclusions. 



The general conclusions arrived at are : — 



1. That acetaldehyde is oxidized directly to acetic acid, the action 

 taking place between the aldehyde molecules and the free oxygen atoms 

 present. 



2. That, with certain modifications, the action can be said to proceed 

 with a velocity proportional to the pressure of aldehyde and to the square 

 root of the pressure of oxygen. 



3. The two chief modifications to be remembered are : {a.) That at no 

 time during the reaction has equilibrium been established between the 

 oxygen atoms formed and the oxygen molecules re-formed, the result being 

 that more oxygen atoms are available for combination than would be cal- 

 culated from a state of equilibrium, and the extent of this excess depends 

 on the percentage pressure of aldehyde, (b.) That it is possible that the 

 collision between an oxygen molecule and an aldehyde molecule may result 

 in the breaking-up of the oxygen molecule. 



4. That the existence of a maximum pressure of oxygen above which 

 the action does not proceed is doubtful. Any such maximum is certainly 

 much higher than that indicated by Dr. Ewan. There was no cessation 

 of action with a pressure of 850 mm. of oxygen. 



5. That the action is greatly influenced by catalytic agents of every kind. 



6. The effect of rise of temperature is to increase greatly the speed of 

 the reaction, the value of the constant at 50° C. being four times as great as 

 at 25° C. 



Preliminary Note on the White Substance formed bt the Interaction of 

 Mercury, Aldehyde, and Oxygen. 



Mention is made by Dr. Ewan of the fact that a mixture of aldehyde and oxygen 

 attacks mercury, forming a white substance, and giving off an inflammable gas which 

 is not absorbed by alkaline pyro-solution. There can be no doubt that the white sub- 

 stance is formed, and experiments were made to establish its nature and manner of 

 formation. 



No action was observed between the pure acetaldehyde and mercury. 



On allowing oxygen to pass into the reaction - vessel, which had contained the 

 mercurv and aldehyde for three hours, the formation of the white substance was soon 

 noted. In fifteen minutes an incrustation had formed on the surface of the mercury. 

 After fifteen hours a considerable quantity of white substance was obtained. 



If any inflammable gas unabsorbed by alkaline pyro-solution is formed, it is 

 extremely small in quantity, and not at all as much as would be expected from the quan- 

 tity of white substance formed. 



In appearance and properties the white substance distinctly resembles mercurous 

 acetate, and a considerable amount of evidence has been gained in support of the view 

 that, as formed, it is mercurous acetate, an oxide of mercury being first formed bj- the 

 action of the oxygen on the mercury, and this then attacked bj- the acetic acid. 



The white substance carries small particles of mercury, which can be separated 

 with verv great difticultv. 



