136 SOIL BACTERIOLOGY 



Test for Ammonia. Add to a drop of Nessler's solution 

 in a test plate a loopful of the solution to be tested. A 

 deep golden-yellow color indicates the presence of ammonia. 



(7) Trommsdorfs Reagent for Nitrites: 



1. Add slowly, with constant stirring, a boiling solution 

 of 20 grams of zinc chlorid in 100 c.c. of distilled water to 

 a mixture of 4 grams of starch in water. Continue heating 

 until the starch is dissolved as much as possible, and the 

 solution is nearly clear. 



2. Then dilute with water and add 2 grams zinc iodid. 



3. Dilute to i liter and filter. 



4. Store in well-stoppered bottles in the dark. 



Test for Nitrites. Place 3 drops of Trommsdorfs reagent 

 in depression on test plate. Add i drop of dilute sulphuric 

 acid (i 13). Remove a loopful of the solution to be tested 

 and touch to surface of reagent. A blue color indicates the 

 presence of nitrites. 



(8) Sulphanilic Reagent for Nitrites: 



(a) Sulphanilic acid 0.5 gm. 



Acetic acid (33 per cent.) 15- c.c. 



(&) Alpha-naphthylamin o.i gm. 



Distilled water 20.0 c.c. 



Acetic acid (33 per cent.) 150.0 c.c. 



Dissolve the alpha-naphthylamin by heating in 20 c.c. of 

 water, filter, then add the acetic acid. Combine solutions 

 (a) and (6), and keep in a tightly stoppered bottle. This 

 solution is sensitive to 2 parts of nitrite in 10,000,000, 

 giving a reddish-pink color. 



Griess, Ber. d. deutsch. chem. Gesell., 12, p. 426, 1870. 



