ON NITRIFICATION 



493 



Experiment 244 



A solution prepared as follows: sodium chloride 1 gram; dipo- 

 tassium phosphate 0.5 gram; hydrated magnesium sulphate 

 0.51 gram; hydrated ferrous sulphate 0.364 gram; distilled water 

 500 cc. Fifty cubic centimeter portions pipetted into six large 

 flat-bottomed Fernbach flasks fitted with paraffin oil seals. 



After sterihzation flasks 1, 2 and 3 received sterile MgCOs. 

 Mg (OH) 2 and 1 cc. of a sterile 10 per cent (NH4)2S04 solution, 

 while nos. 4, 5 and 6 received only 1.5 cc. of a 6.75 per cent 

 pasteurized solution of ammonium carbonate. Subsequently all 

 were inoculated. Flasks 2 and 5 received a small container of 

 concentrated KOH in the neck while flasks 3 and 6 were washed 

 free of all carbon dioxide by aeration for one hour, the air issuing 

 from the flasks at the end of this time causing no turbidity in 

 Ba(0H)2 when passed through it. Inoculation was made with 

 an active culture of Nitrosococcus, and incubation was at 25°C. 

 for fifteen days. Analysis of the cultures after this period gave 

 the results presented in table 9. 



TABLE 9 



Experiment 246 



Erlenmeyer flasks of 750 cc. capacity were used with mercury 

 seals, and 50 cc. of the solution used in the previous experiment. 

 After sterilization, 1 cc. of the pasteurized solution of ammonium 



