CULTURE MEDIA 37 



without allowing the plate to become dry. The dishes are kept 

 until needed for use. 



Medium 87 



Ammonium Sulphate Cellulose Agar^ 



(a) Agar 10 . gm. 



Ammonium sulphate ((NH4)2S04) 2.0 gm. 



Dipotassium phosphate (K2HPO4) 1.0 gm. 



Magnesium sulphate (MgS04-7H20) 1.0 gm. 



Sodium chloride (NaCl) 1.0 gm. 



Calcium carbonate (CaCOs) 2.0 gm. 



Tap water 500.0 cc. 



(6) Cellulose solution 500. cc. 



1 McBeth, I. G., Soil Sci., 1: 438, 1916. 



1. Pour 1,000 cubic centimeters of ammonium hydroxide, 

 specific gravity 0.90, into a glass-stoppered bottle; add 250 cubic 

 centimeters of distilled water and 75 grams of pure copper 

 carbonate; shake the solution vigorously until all the copper is 

 dissolved (about 10 to 15 minutes are ordinarily required). 



2. To the copper-ammonium solution add 15 grams of high- 

 grade sheet filter paper; shake vigorously at intervals of 10 

 minutes for 3-^ hour. Examine the solution carefully to see that 

 the paper is completely dissolved. If any particles of paper 

 remain in the solution, the shaking must be continued until the 

 solution is perfectly clear. Dilute 250 cubic centimeters of the 

 ammonium-copper-cellulose solution to 10 liters with tap water; 

 add slowly, with frequent shaking, a weak hydrochloric acid 

 solution prepared by adding 500 cubic centimeters of concentrated 

 acid to 10 liters of tap water. Continue the addition of the 

 acid until the blue color disappears; add a slight excess of acid, 

 shake thoroughly, and allow to stand a few minutes. The finely 

 precipitated cellulose will rise to the top, due to the large quantity 

 of free hydrogen liberated in the precipitation process. Shake 

 the solution vigorously at intervals of a few minutes to dislodge 

 the hydrogen. As soon as the free hydrogen has escaped, the 

 cellulose will settle rapidly. 



3. Wash through repeated changes of water until free from 

 copper and chlorine. After the washing is complete, bring the 



