224 NITRIFICATION 



It is quite likely that all organic compounds are first trans- 

 formed into ammonia by other organisms before they are nitrified. 

 Demoussy found this to be true of monomethylamin, trimethylamin, 

 anilin, pyridin, and quinolin, and, according to Lohnis, calcium 

 cyanamid. This is also true for carbamid, thiocarbamid, uric 

 acid, acetamid, anilin sulphate, methylamin sulphate, ammonium 

 oxalate, asparagin and ammonium sulphate, which, with the excep- 

 tion of .thiocarbamid and anilin sulphate, are readily transformed, 

 according to 'Busier, into ammonia by other bacteria and then 

 nitrified. Hence, the early conclusion reached by Winogradsky- 

 that pure cultures of nitrifying bacteria are incapable of nitrifying 

 organic nitrogen has been borne out by other investigators. 

 Where contrary results have been reported it has been due to 

 the presence of other organisms by which the nitrogen has been 

 converted into ammonia and then nitrified. The process is cata- 

 lyzed by oxidizing enzymes which must be specific in their action, 

 for Omelianski found the nitrifying organisms unable to oxidize 

 mineral compounds such as sodium sulphite and phosphite. 



Oxidation in this case cannot be regarded as being of a violent 

 nature and it scarcely seems conceivable that the nitrosomonas 

 should be able to oxidize ammonia direct to nitrous acid without 

 passing through intermediate stages of oxidation. Most workers 

 consider it probable that in the oxidation of the ammonium radical 

 there are formed certain intermediate substances which must be 

 regarded as more or less hydroxylated ammonium radicals. 



Mulford, in a study of the bacterial oxidation of aqueous solu- 

 tions of ammonium salts on experimental filters inoculated from 

 actively nitrifying sew'age filters found that the oxidation proceeded 

 in a series of stages compatible with the hypothesis that the hydro- 

 gen atoms are successively hydroxylated with the subsequent elimi- 

 nation of water. Hydroxylamin salts and salts of hyponitrous 

 acid and nitrous acids were found as intermediate compounds. 



o 



// 

 /N 



H H 



/ / 



N H -> N H 



\ \ 



H OH 



OH nitrous 



ammonia Jjydroxylaiiiin acid 



\N-OH 



\ 

 dihydroxylamin OH 



trihydroxyl- 

 amin acid 



