1919] 



ALLEN AZOTOBACTER CHROOCOCCUM 



39 



TABLE XIV 



MODIFIED ASHBY'S SOLUTION WITHOUT AGAR 





No. 1 





Shelf 



109* 

 110* 

 HI 

 112 



Shaker 



113 

 114 



Treatment 



Unfiltered 



Nitrogen 

 (mgs.) 



.07 



.03 



1.18 



0.98 



1.23 

 1.31 



Filtered 



Shelf 



Shaker 



* 300-cc. flasks used 



In a similar experiment using Kaserer's medium 2 per cent 

 mannite was used as the energy source instead of the 1 per 

 cent dextrose employed by Kaserer. Furthermore, the po- 

 tassium silicate which we had available was so strongly alka- 

 line that the medium had to be partially neutralized after this 

 material was added. The medium was prepared as follows : 

 One gm. A1 2 (S04) 3 and 0.25 gm. of FeCl 3 were dissolved in 

 approximately 350 cc. of distilled water, the solution heated, 

 and the Fe and Al precipitated with Na 2 HP0 4 solution. The 

 precipitate was thrown down by means of a centrifuge, de- 

 canted, washed once by the same process, and then suspended 

 in 700 cc. water containing 15 cc. of 10 per cent potassium sili- 

 cate solution. The suspension was then strongly alkaline, and 

 the required amount of N/10 acid as determined by titration 

 was added to adjust the reaction to P H 8, the volume then 

 made to 1 liter, distributed in bottles, and shaken on a machine 

 for 4 hours. Complete solution was not effected. There was 

 then added to the 1-liter portion : 



Mannite 20 



gms 



1 gm. 



1 



Calcium sulphate 



Manganese sulphate 



Magnesium sulphate 1 gm 



Sodium chloride 1 gm 



gm 



