24 



I a-Naphthylamine 1.00 gram 



Distilled water 100.00 grams 



II Sulphanilic acid 50 gram 



Dilute acetic acid 150.00 cc 



These solutions were kept in separate glass stoppered 

 bottles. 



In the performance of the operation 5 cc of the culture 

 medium were transferred to a Nesslerizing tube by means of a 

 pipette, about 25 cc of distilled water added, and 1 cc of each 

 of the above solutions introduced. The solution was brought 

 up to the 50 or 100 cc mark with distilled water. The quan- 

 titative estimation of the nitrite was determined by the col- 

 orimic method. Every sample of soil without exception con- 

 tained bacteria which reduced nitrates to nitrites. The odors 

 emanating from these cultures and from the ammonfication 

 experiments were exceedingly offensive. To determine the 

 possibility of reduction of nitrates in soil infusion, 100 cc of 

 distilled water was measured into each of nine 250 cc Erlen- 

 meyer flasks; to each flask was added 100 mg of potassium ni- 

 trate free from nitrite. These flasks were inoculated with 

 soils 5, 47, 49, 51, 54, 55, 57, 60 and 61 respectively. They 

 were incubated at 33C for seven days. Tests were then made 

 for nitrites and all without exception were found to be negative. 

 No reduction is therefore probable except in the presence of 

 considerable available nitrogen. 



STUDIES ON THE REDUCTION OF NITRITES 



IMPURE CULTURES: One hundred cubic centimeters of 

 Ashby's medium without the carbohydrate, were measured 

 into 250 cc Erlenmeyer flasks. To each flask was added vary- 

 ing amounts of mannite, dextrose and potassium salts as in- 

 dicated. These flasks were inoculated with one gram of the 

 different soils and incubated at 28C for the length of time and 

 with the results recorded below in table No. IX. 



