ON NITRIFICATION 



485 



with the omission of the furnace. The manometer of the previous 

 experiment was also replaced by a paraffin-oil manometer guarded 

 from the external carbon dioxide by a soda lime tube. A barium 

 hydroxide bulb was placed between the culture flask and the 

 suction pump to allow the detection of even small traces of 

 CO2. Aeration was carried out for two hours during which time 

 the flasks were often shaken. After aeration, the bulb of 

 Ba(0H)2 was inserted and aeration continued for one half hour 

 more during which time the hydroxide showed no turbidity. 

 The results of these experiments are given in table 4 in which is 

 also given the activity of the cultures in the period of preparation. 



It appears therefore that nitrification takes place normally at 

 the expense of the carbon dioxide formed by the reactions in the 

 culture medium and that therefore it must be assumed that the 

 suggestion of Duclaux was based upon facts which could not well 

 be utilized in the formulation of the hypothesis. 



As may be seen, the cultures here used were in full and inten- 

 sive nitrosofermentation and the carbon sources varied. Yet 

 owing to the specific arrangement of the experiments, there 

 should be a possibiUty of separating the supplies at their point 

 of formation. In fact, if a very small inoculum were used in 

 place of the very great ones used in the previous experiments, 

 it should be possible to diminish appreciably if not to stop com- 

 pletely the formation of the supplies due to equation II. This 

 was done in experiment 227-a. 



