1919] 



ALLEN — AZOTOBACTER CHROOCOCCUM 



31 



present. The variation in the growths in different flasks 

 shows the undesirability of making a sugar determination on 

 one flask and a nitrogen determination on its duplicate. The 

 sugar determinations above are comparatively inaccurate, 

 owing to the fact that only % of the solution was taken for 

 analysis, hence computations of nitrogen fixed per gram of 

 dextrose consumed have not been made. 



RESTORATION OF SOLID PHASE 



An experiment was next conducted on adding the solid sub- 

 stances, CaC03 and CA 3 (1*04)2, alone and in combination, to 

 filtered (i. e., filtered subsequent to heating to boiling in the 

 presence of CaCO?,) Ashby's tap water solution. The culture 

 medium was therefore directly comparable to that used in ob- 

 taining the data reported ir. tables vn and viii. Twenty-five-cc. 

 portions of this perfectly cl^ar solution were pipetted into 700- 

 cc. flasks and a drop of 0.5 ferric chloride added to each. Cal- 

 cium carbonate and calcium phosphate were added to certain 

 of the flasks according to the plan shown in table ix, which con- 

 tains also the results of the experiment. The flasks were inocu- 

 lated at the same time and from the same suspension as used 

 in the previous experiment. All flasks were incubated on the 

 rotating machine for 10 days. 



TABLE IX 



No. 



45 

 46 



47 

 48 



49 

 50 



51 



52 



53 



54 



Material added to 

 culture medium 



None 

 None 



CaCO, 

 CaCO, 



Ca, (PO«)t 

 Ca. (PO,). 



CaCO,, Ca,(PO.)* 

 CaCO,, Ca,(PO,). 



CaCO,, Ca,(PO<)* 

 CaCO,, Ca,(P04)* 



Treatment 



Inoc. 

 Inoc. 



Inoc. 

 Inoc. 



Inoc. 

 Inoc. 



Inoc. 

 Inoc. 



Sterile 

 Sterile 



Residual 



glucose 



(mgs.) 



294.1 

 215.4 



181.7 

 448.8 



409.0 

 562.0* 



00.0 

 00.0 



448.0 

 450.5 



Nitrogen 

 (mgs.) 



♦ # • 



t t 



* ft 



0.45 

 0.44 



2.16 

 2.14 



0.19 

 0.16 



* Probably an analytical error. 



