.Maci/kod. — Ji<it< (if Oxuhii i(n) of ArcidUlrhnde to Acctir Arid. 41 



All the other experiments quoted were made in semi-darkness ; but 

 the last one quoted was made in absolute darkness. No alteration is, how- 

 ever, noticeable in the reaction. 



In the next two experiments the oxygen was dried with concentrated 

 sulphuric acid instead of calcium-chloride. In the first the efi'ect seems 

 to be to show a retardation, but the value of K' rises again in the second. 

 The extreme sensitiveness of the action to determining agents makes it 

 very difficult to have the conditions exactly the same. In any case there 

 can be no doubt that an action has been going on. 



Partial pressure of nitrogen = 36 mm. 



Partial pressure of nitrogen = 46 mm. 



In the next experiment the oxygen was again dried over calcium- 

 chloride :■ — 



Partial pressure of nitrogen = 24 mm. 



The number of these experiments, in every case the action going on 

 regularly puts it beyond doubt that the action is able to go on at pres- 

 .sures of oxygen above 530 mm., at least under some conditions. In one 



