BEYRINCK'S SOLUTION 197 



3. Boil for five minutes, allow to stand, and decant off clear 

 fluid from sediment. 



4. Tube and sterilise as for nutrient bouillon. 



Media for the Study of Earth Bacteria, Nitrogen Fixers. 



Earthy Salts Agar (Lipman and Brown). (For the enumeration 

 of soil organisms.) 



1. Measure out 



Agar 20 grammes. 



Emulsify in 200 c.c. distilled water. 



2. Wash the agar emulsion into a tared 2-litre flask with 400 c.c. 

 distilled water. 



3. Weigh out 



Peptone 0.5 gramme. 



Emulsify in 50 c.c. distilled water and add to the contents 

 of the flask. 



4. Bubble live steam through the mixture for twenty minutes 

 to dissolve the agar. 



5. Weigh out and mix 



Dextrose. 10.0 grammes. 



Potassium phosphate .... 0.5 gramme. 



Magnesium sulphate 0.2 gramme. 



Potassium nitrate 0.06 gramme. 



and add to the contents of the flask. 



6. Adjust the weight of the medium mass to the calculated fig- 

 ure for one litre (1025 grammes) by the addition of distilled water 

 at 100 C. 



7. Titrate the medium mass and adjust the reaction to +5. 



8. Cool to 60 C. Clarify with egg and filter. 



9. Tube in quantities of 10 c.c. and sterilise as for nutrient agar. 



Beyrinck's Solution. I. (For the cultivation of nitrogen fixing 

 organisms.) 



1. Weigh out and mix i gramme potassium hydrogen phos- 

 phate, 0.2 gramme magnesium sulphate, and 0.02 gramme sodium 

 chloride. 



2. Dissolve in water 1000 c.c., in a 2-litre flask. 



3. Add i c.c. of a one per thousand aqueous solution of ferrous 

 sulphate. 



4. Add i c.c. of a one per thousand solution manganese 

 sulphate. 



5. Weigh out 20 grammes dextrose and add to the contents of 

 the flask (dextrose up to 40 grammes may be used for the different 

 organisms) . 



6. Steam for twenty minutes, filter. 



7. Tube, and sterilise as for nutrient bouillon. 



