25 



TABLE IX 



Soils number 37, 49, and 61 in dextrose gave on the 

 eleventh day very appreciable reaction for nitrite; not until 

 the fifteenth day did this totally disappear. An inspection of 

 this table conveys the idea at once that the nitrite disappears 

 from the mannite-containing medium more rapidly than from 

 the dextrose. 



THE REDUCTION OF NITRITES IN PEPTONE 

 SOLUTION 



IMPURE CULTURES: Fifty cubic centimeters of a medium 

 containing ten grams of peptone, together with one gram of 

 potassium nitrite per liter of distilled water, were measured 

 into 150 cc Erlenmeyer flasks and sterilized. These flasks 

 were each inoculated with one gram of soil and incubated at 

 33C. After periods of time as indicated in the table number 

 X, the solutions were tested for the presence of nitrites. On 

 sterilizing peptone-nitrite solution in the Arnold, the liquid 

 assumes a more decided yellow color than the peptone-nitrate 

 solution. A quantitative determination shows that a portion 

 of the nitrite has combined with the peptone, therefore the 

 results are invariably low. All of the soils contained organisms 

 which rapidly reduced nitrites to free nitrogen. The rapidity 



