SILICATE JELLY FOR THE NITRIFYING BACTERIA 103 



insufficient quantity of hydrochloric acid was added. 

 Repeat, using more acid. 



5. Prepare a solution containing the nutrient salts 

 suitable for the growth of the desired organism. This 

 solution should contain the salts in from 2.5 to 5 times the 

 desired strength. 



6. Tube and sterilize the nutrient solution. If 5 times 

 normal strength is taken, use about 3 c.c. per tube, or 5 c.c. 

 if 2.5 times normal strength. 



7. Pour the silicic acid mixture into a sterile Petri dish. 

 Inoculate the sterile nutrient solution and add a sufficient 

 amount of a sodium carbonate solution to neutralize the 

 excess silicic acid in the mixture and a few drops, in excess. 

 Now pour this into the dish with the silicic acid, rotate, 

 and allow the plate to harden on an even surface. After 

 a few moments this mixture should harden. The plates 

 may be handled similar to agar plates. The concentration 

 of silicic acid mixtures determines the strength of the 

 nutrient solution to use. 



A modification of the Stevens and Temple method, Centbl. Bakt. (etc.), 

 Abt. 2, Bd. 21, pp. 84-87, 1908. 



B. Undialyzed 



1. Dissolve 8.40 grams of sodium silicate (Na 2 SiO 3 ) and 

 24 grams of potassium silicate (K 2 Si0 3 ) in 500 c.c. of 

 distilled water. A mixture of sodium and potassium 

 silicate decreases the sodium salt in the final medium. 



2. Prepare dilute hydrochloric acid in such a way that it 

 requires slightly more than i c.c. of the sodium potassium 

 silicate solution to neutralize i c.c. of the HC1. 



3. Add to the hydrochloric acid solution the nutrient 

 salts suitable for the growth of the nitrifying bacteria. 



4. With methyl-orange as an indicator, standardize the 



