ON NITEIFICATTON 491 



The results obtained in this, the second, period of incubation 

 are striking. Ammonium sulphate will be nitrified, although 

 slowly, in the presence of a non-carbonated base, the difference 

 in the results of experiments 234 and 240 being due to the time 

 factor. The lag in nitrite formation in cultures 51, 6 and 61 

 may be explained in either of two ways: (a) distillation of the 

 ammonium carbonate, and (b) retarding effect of this compound 

 with subsequent volatilization of considerable quantities of 

 ammonia. In fact in the cultures 6 and 61 a concentration of 

 ammonium carbonate was used such as to give 28 mgm. of 

 nitrogen in 25 cc. of solution, a quantity twice as great as that 

 of the ordinary Omeliansky solution. 



The results relating to the nitrification in the presence of a 

 non-carbonated base are then in accord with the findings of 

 Ashby and of Hopkins and "Whiting and it is possible that the 

 atmospheric carbon dioxide, here, played an important role in 

 the process of nitrification. That ammonium carbonate is 

 nitrifiable as such should be assumed from the work of Warington, 

 but additional proof is furnished by experiments here to be 

 related. 



Experiment 2Jf.l 



Fifty cubic centimeters of Omehansky solution from which 

 the ammonia source was omitted, were sterilized in 750 cc. 

 Erlenmeyer flasks. After cooling they received sterile magne- 

 sium carbonate suspension or magnesium oxide and either 1 

 cc. of a sterile 10 per cent ammonium sulphate solution or 0.5 

 cc. of a 17.2 per cent anmionium carbonate^ solution pasteurized 

 at 60°C. 



The arrangement of the experiments^ and the results obtained 

 are given in table 8. 



1 The carbonate used in all these experiments was a mixture of the normal 

 carbonate and the carbamate of the following empirical formula: (NH4)2C03. 

 NH4CO2NH2. 



" The term capped in this and other experiments refers to the mercury or 

 paraffin oil seals used in order to avoid the escape of volatile substances from the 

 nitrifying systems. Their efficiency may be noticed by a comparison of the 

 results obtained in nos. 3 and 4 of table 8. 



