HEYDEN-NAHRSTOFF AGAR 93 



4. When completely dissolved adjust the reaction to 



5. Clear with egg-albumen and filter as directed under 

 the preparation of gelatin. 



6. Tube, and sterilize in the autoclave for fifteen minutes. 

 The amount of agar to place in tubes will depend on the 

 purpose for which the agar is to be used. For slants, 

 about 5 c.c. is enough; for plates, about 10 c.c. 



Note. For making especially clear agar, adjust the reaction to (+1.5) 

 with N/i HC1 before adding the agg-albumen. Heat in the steamer until 

 the albumen is coagulated and settled to the bottom of the dish. If it will 

 not settle, stir the agar vigorously and continue heating. It may be three 

 or four hours before it is ready to be filtered. Filtering then consists only 

 in decanting the cleared agar through either a cotton filter or filter-paper. 

 Do not pour the dirt and albumen on to the filter. Titrate and adjust the 

 reaction to (+i). 



Medium 4 

 Heyden-Nahrstoff Agar 



Agar ........................................ 1 2.0 gin. 



Heyden-Nahrstoff ............................. 7.5 gm. 



Distilled water ........... .................... 1000.0 c.c. 



1. To 500 c.c. of cold distilled water in a flask add 7.5 

 grams of Heyden-Nahrstoff. Shake until a good suspension 

 is obtained and allow the mixture to stand for thirty minutes 

 or more. 



2. Heat in steamer or double boiler for one hour, or 

 until the upper portion of the solution is clear. 



3. While hot filter through paper. 



4. Dissolve 1 2 grams of agar in 500 c.c. of water. Filter 

 and mix the Heyden-Nahrstoff and agar solutions. 



5. It is not necessary to adjust the reaction of this medium. 



Heyden-Nahrstoff, The Heyden Chemical Works, 135 Williams St., 

 New York City, N. Y t 



