EXAMINATION OF SOIL 1 71 



EXERCISE 2. THE FORMATION OF AMMONIA 



Experiment i. — Formation of ammonia from pep- 

 ton — 



1. Test the remainder of the solution in Exercise i 

 for ammonia. 



2. Make a quantitative determination of ammonia 

 by distillation and nesslerization. 



Experiment 2. — Formation of ammonia from urea — 



1. Prepare a solution as follows: 



Urea i gram 



Pepton 0.2 gram 



Distilled water 100 c.c. 



This solution must not be sterilized, as heat breaks 

 up urea into ammonia and carbon dioxid. 



2. Inoculate with some garden earth. 



3. Incubate at room temperature for one week. 



4. From time to time moisten a piece of filter paper 

 with Nessler's solution and pour a few drops from the 

 flask on the paper. A yellow or brown color indicates 

 the formation of ammonia. 



SECTION 4 



THE FORMATION OF NITRITES FROM AMMONIA 

 AND ISOLATION OF NITRITE BACTERIA 



EXERCISE I. THE FORMATION OF NITRITES 



1. Prepare five flasks and place 50 c.c. of the solu- 

 tion on p. 38 in each. Number these flasks con- 

 secutively. 



2. Inoculate flask i with soil, and incubate at room 

 temperature. 



