THE NITROGEN CYCLE 215 



This circumstance is of considerable importance in connection 

 with the purification of sewage. If the fermentation is allowed 

 to proceed till approximate completion, and a drop of the 

 solution is examined under the high-power microscope 

 (-5^- inch oil immersion), the micrococcus can be plainly 

 seen. 



Similar results are obtained if, instead of urine, an 

 artificial solution is made up in the following proportions 

 and similarly fermented : 



Water 1500 grams 



Urea 33 



Sodium chloride . . . . . . 18 



Potassium hydrogen phosphate . . 5 



Magnesium sulphate . . . . 0'5 gram 



The reaction which takes place in both these cases consists 

 in a simple hydrolytic change resulting in the formation of 

 ammonium carbonate, thus : 



CO(NH 2 ) 2 + H 2 = (NHJjCOj 



It has been found that the same organisms which bring 

 about the conversion of urea into ammonia will also decompose 

 uric acid, with production eventually of ammonia ; and 

 hippuric acid, with formation of benzoic acid and glycin 

 (glycocoll or ammo-acetic acid), according to the following 

 equation : 



C 6 H 5 CONHCH 2 COOH + H 



= C 6 H 5 COOH + CH 2 NH 2 COOH 



Hippuric acid or benzoyl-glycin Aminc-acetic acid or glycin 



Like all other fermentations, the ammoniacal fermentation 

 ceases when a certain concentration is reached. In this case 

 fermentation proceeds until the ammonium carbonate formed 

 reaches a concentration of 13 per cent. 



