Mar. u, 1918 Nitrifying Bacteria and Tricalcium Phosphate 679 



The application of calcium carbonate notably stimulated the nitrifi- 

 cation of dried blood, and after 56 days the yield was approximately the 

 same as from ammonium sulphate. On the other hand, tricalcium 

 phosphate produced no stimulation in the nitrification of dried blood at 

 any period, but the application of both calcium carbonate and tricalcium 

 phosphate promoted active nitrite formation, which during the last 

 period of the experiment resulted in the oxidation of approximately as 

 much nitrogen as in any other case in the experiment. The final oxida- 

 tion to nitrate in this case, however, was very feeble throughout the 

 entire experimental period. 



It is evident from the above results, therefore, that, while tricalcium 

 phosphate may promote nitrification in the absence of carbonate, more 

 favorable conditions for nitrification were produced by calcium carbonate 

 than by tricalcium phosphate. 



Large amounts of calcium carbonate were made soluble by the nitrifi- 

 cation of ammonium sulphate in the sand series, but since enfeebled 

 nitrification of ammonium sulphate took place when tricalcium phos- 

 phate only was added, relatively small increases in soluble calcium were 

 produced. At the final period of the experiment, however, the increase 

 in soluble calcium resulting from tricalcium phosphate and the small 

 amounts of nitrogen that had been oxidized agree closely with theo- 

 retical calculation. 



Again, considerably less calcium was dissolved in the nitrification of 

 dried blood than in that of ammonium sulphate, a result which is in 

 harmony with generally accepted vievv's regarding the nature of the 

 oxidation products formed in the two cases. With the latter sulphuric 

 acid is formed in addition to nitrous acid, while with the former carbonic 

 acid is probably one of the end products. 



The limited nitrification of dried blood, found where tricalcium phos- 

 phate had been added, was associated with a lower soluble-calcium 

 content than occurred where tricalcium was added alone. But in view 

 of the fact that not more than 30 per cent of the nitrogen was oxidized, 

 it is probable that the medium remained alkaline as a result of the 

 ammonification of the dried blood, and, consequently, the lower yields 

 of soluble calcium may have been due to slight precipitarion of calcium 

 as calcium carbonate. 



It is especially interesting that smaller amounts of calcium were 

 dissolved by the nitrification of ammonium sulphate and dried blood 

 in the presence of both calcium carbonate and tricalcium phosphate 

 than with calcium carbonate alone. 



Considering the phosphoric-acid determinations, it is at once apparent 

 that nitrification did not produce an increase in the solubility of tri- 

 calcium phosphate when carbonate was present. In the absence of 

 carbonate, however, an increase in solubility resulted from the nitrifica- 

 tion of ammonium sulphate. In this case, although nitrification was 



