20 



one gram of potassium nitrite. These flasks were incubated 

 at 33C for seven days, the contents then transferred to the 

 Kjeldahl apparatus and the ammonia determined as in the pre- 

 vious work. 



TABLE VI 



The figures in the above table represent the percentage of 

 nitrogen evolved as ammonia. The conclusion is inevitable 

 that considerable quantities of nitrates or nitrites cannot exist 

 in the soil together with a high percentage of protein nitrogen. 

 The ammonification equilibrium is likewise disturbed by an 

 excess of nitrates or nitrites. 



The figures in the above table seem to indicate that the 

 hydrogen together with a large proportion of the nitrogen, 

 perhaps partly because of the violence of the reaction, on being 

 set free escapes as free hydrogen and nitrogen. We have in 

 each column of the table a consistently decreasing percentage 

 of ammonification. The relation between the peptone and pep- 

 tone-nitrate being uniformly greater than the relation between 

 the peptone-nitrate and peptone-nitrite. This uniformity is 

 pronounced. 



STUDIES ON THE REDUCTION OF NITRATES 



IMPURE CULTURES: One hundred cubic centimeters of 

 Ashby's medium without the carbohydrate, was measured 

 into Erlenmeyer flasks of 250 cc capacity. To each flask was 

 added varying amounts of mannite, dextrose and potassium 

 salts as indicated in the table. These flasks were inoculated 

 with different soils and kept at 28C. 



