UREA GELATIN 99 



1. Heat in the steamer or over a free flame until the 

 precipitate settles. 



2. Filter and sterilize. 



3. In order to diminish the loss of ammonia from urea 

 the culture-media should be sterilized in the steamer 

 twenty minutes on three successive days. 



Medium 20 

 Urea Solution 



Certain forms of urea fermenters prefer a medium richer 

 in urea. This may be prepared by adding 10 per cent, of 

 urea to the bouillon. 



Medium 21 

 Urea Solution 



Urea (CO(NH2)2) 30.0 gm. 



Dibasic potassium phosphate (K2HPO4) 0.5 gm. 



Calcium citrate (Ca3(C6H507)2 4- 4H2O) lo.o gm. 



Tap-water looo.o c.c. 



Sohngen, N. L., Centbl. Bakt. (etc.), Abt. 5, Bd. 23, p. 94, 1909. 



Medium 22 

 Urea Solution 



Urea (CO(NH2)2) 5o-ogni- 



Dibasic potassium phosphate (K2HPO4) 0.5 gm. 



Soil extract loo.o c.c. 



Tap-water 9<^-<^ c.c. 



Lahnis, F., Centbl. Bakt. (etc.), Abt. 2, Bd. 14, p. 7Hi iQ^S- 



Medium 23 

 Urea Gelatin 



Gelatin 120 to 150 gm. 



Urea (CO(NH2)2) 20 c.c. 



Bouillon ( — i.o) 1000 c.c. 



