1919] 



ALLEN — AZOTOBACTER CHROOCOCCUjNI 



35 



TABLE XI 



AZOTOBACTER DEVELOPMENT IN "HE PRESENCE OF GLYCEROLPHOSPHATE 





No. 



Treatment 



Shelf 



67 

 68 

 69 

 70 



Check 

 Check 

 Inoc. 

 Inoc. 



Shaker 



71 



72 



Inoc. 

 Inoc. 



Shelf 



73* 

 74* 

 75 

 76 



Check 

 Check 

 Inoc. 

 Inoc. 



Shaker 



77 

 78 



Inoc. 

 Inoc. 



Cont. of culture at end 



Base 

 added 



' 



Sugar 

 (mgs.) 







 

 

 





 



910. 

 914. 

 913. 

 912. 



908. 

 908. 



Nitrogen 

 (mgs.) 



0.16 

 0.16 

 0.10 

 0.13 



0.08 

 0.10 



CaCO, 

 CaCO, 

 CaCO , 

 CaCO, 



901. 

 904. 

 848. 

 820. 



0.09 

 0.22 

 0.67 

 0.99 



CaCO, 

 CaCO, 



275. 

 268. 



1.88 

 2.05 



500-cc. flasks. 



ACTION OF PROTECTIVE COLLOIDS 



If now one of the effects of mechanical agitation is to hasten 

 the solubility of phosphates, it ought to be possible to replace 

 this action in part by the use of protective colloids ; that is, the 

 colloid, by preventing the ccmplete flocking out of these com- 

 pounds, would cause a greater surface to be exposed to the ac- 

 tion of the solvent. Agar naturally suggested itself as a pos- 

 sible protective colloid, and its function as such was studied in 

 two ways: (a) in solid media, and (b) in filtered and non-fil- 

 tered liquid media. 



Solid 



Two asrars were prepared from 



chemicals obtainable and redistilled water, and the 



pared with the regul 



In the case of 



agar the phosphates were allowed to precipitate before the 

 agar was added. In the cag e of the second medium one half 

 the agar was added to a solution containing the calcium and 

 magnesium salts, the other half to a solution containing the 

 phosphate. The exact procedures were as follows : 



Agar I (phosphates allowed to precipitate before the addi- 

 tion of aerar). 



