MORPHOLOGY 225 



There are, however, two serious objections to these conclusions: 



(1) It is not evident that these initial changes noted by Mulford 

 were due to the nitrifying organisms, as a mixed culture was used; 



(2) Boullanger and Massol found that while the nitrous organism 

 accommodates itself to all ordinary carbonates, it does not attack 

 hydroxylamin hydrochloric!. 



The majority of workers have reported a loss of nitrogen in the 

 nitrification process, there never being the theoretical yield of 100 

 per cent, of the ammonia transformed into nitrous acid, but this 

 may be due to side reactions Lafar considers that the loss may 

 be due to the reaction of the nitrous acid on the undecomposed 

 ammonia in accordance with the equation: 



N 2 3 + 2NH 3 3H,0 + 2N 2 



The whole subject of the metabolism of nitrifiers is indefinite 

 and in need of careful investigation using the latest refined methods. 

 The only fact that does seem to be well established is that the 

 process of nitrification goes in two stages from ammonia to nitrous 

 acid and from nitrous acid to nitric acid. That these two steps 

 are due to two classes of organisms is the claim of most investi- 

 gators. However, Kaserer considers that there is an organism, 



B. nitrator, which can oxidize ammonia direct to nitric acid, the 

 reactions being as follows: 



NH 3 + H 2 CO 3 + O 2 = HNO 3 + H 2 O + CH 2 O 41 Cal. 



CH 2 O + O 2 = H 2 CO 3 + 132 Cal. 



It is interesting to note that the reaction catalyzed by the nitri- 

 fying ferments are similar to reactions catalyzed by ultraviolet 

 rays. Gaudechon exposed solutions at temperatures of 35 to 50 



C. for from three to nine hours at a distance of 3 to (5 cm. from a 

 lamp of 110 watts. Under these conditions the ultraviolet rays 

 oxidized solutions of ammonia in the presence of oxygen to nitrites. 

 Nitrates were in no case formed. Ammonium salts were also 

 oxidized to nitrites, the reaction being slower in the case of the 

 sulphates and chlorids than the carbonates. Urea was first con- 

 verted into ammonia and then into nitrites. Other organic nitro- 

 gen compounds, for example, ethyl- and methylamin, guanidin, 

 hydroxylamin, acetamid, and acetonitril behaved similarly. 



Morphology. Winogradsky described two varieties of the organ- 

 isms capable of changing ammonia to nitrites. One of these in 

 several species was found in all the soils of the Old World (Asia, 

 Africa and luirope) and is known as nitrosomonas. The second 

 is peculiar to the soil of the New World and has received the name 

 of nitrosococcus. 



He described a single species of the nitrosomonas from European 

 soils, namely, Nitrosomonas europcea. This organism is provided 

 15 



