16 



THE AVAILABILITY OF VARIOUS COMPOUNDS FOR 

 NITROGEN FIXATION 



TABLE III 



STUDIES ON AMMONIFICATION IN MIXED 

 CULTURE 



The original 70 samples were used in connection with this 

 experiment. The medium consisted of a solution of ten grams 

 of Witte's peptone per liter of distilled water. One hundred 

 cubic centimeters of this solution were measured into flasks 

 of 500 cc capacity, sterilized, and inoculated with one gram of 

 soil. After seven days incubation at 33 C, the contents of 

 these Erlenmeyer flasks were transferred to the Kjeldahl 

 apparatus, ten grams of magnesium oxide added, and the am- 

 monia distilled over into semi-normal hydrochloric acid, and 

 titrated back with semi-normal ammonium hydroxide, using 

 congo red as indicator. In order to ascertain the percentage 

 of nitrogen in the peptone, a composite sample was taken 

 from the thirteen stock bottles, intimately mixed, and run by 



