106 SOIL BACTERIOLOGY 



up in dishes, and add enough culture-media to half cover 

 blocks. 



5. Inoculate the surface of blocks and incubate at 25 

 to 30 C. 



DENITRIFICATION 



Medium 33 

 Solution for Nitrate Reduction 



(a) Potassium nitrate (KNO 3 ) i gm. 



Asparagin (C^s^Os + H 2 O) i gm. 



Water 250 c.c. 



(&) Citric acid (C 6 H 8 O 7 + H 2 O) 5.0 gm. 



or Neutral sodium citrate 8.5 gm. 



Monobasic potassium phosphate (KH2PO4).. . . i.o gm. 



Magnesium sulphate (MgSO4 + 7H 2 O) i.o gm. 



Calcium chlorid (CaCl 2 + 6 H 2 O) . 0.2 gm. 



Ferric chlorid (FeCl 3 + 6H 2 O) trace 



Distilled water 250.0 c.c. 



Neutralize the citric acid solution with a 10 per cent, 

 solution of sodium or potassium hydroxid, using phenol- 

 phthalein as an indicator. Mix the two solutions, cool to 

 15 C., and add sufficient water to make i liter. If the 

 asparagin and potassium nitrate are dissolved along with 

 the other salts, a decomposition may occur. This is marked 

 by a browning of the liquid due to the presence of nitrous 

 acid. 

 For a solid medium add 15 grams of agar to i liter. 



Medium 34 

 Nitrate Bouillon 



Potassium nitrate (KNO 3 ) 5 gm. 



Bouillon . 1000 c.c. 



