829 



The author believes the loss of nitrogen may be attributed to the pro- 

 cess of nitrification. In no case was N2O found, although nitric acid 

 occurred in considerable quantities. The author thiidis it is tlierefore 

 safe to conclude that in the oxidation of ammonia to nitric acid in the 

 soil under natural conditions loss of nitrogen through the formation of 

 N2O does not take place, provided, of course, that after the formation 

 of nitric acid no reduction takes place by which all of the lower oxida- 

 tion products of nitrogen might be formed. 



In the next series of experiments the loss of nitrogen through the 

 decomposition of organic nitrogenous material was determined indirectly 

 by means of the difference method. These experiments embraced three 

 series, in all of which the material was ventilated witli air which had 

 been thoroughly washed to free it of ammonia and nitrogen acids. The 

 apparatus was made all in one piece to exclude the possibility of any 

 nitrogen compounds entering at the joints. The total nitrogen was 

 determined in the material taken at the beginning and close of each 

 experiment, and provision was made for collecting all nitrogen com- 

 pounds generated in the meantime. No addition of nitrogenous com- 

 pounds was made to the soils used, although a small amount of calcium 

 carbonate was added. The soils were partly from the experimental fields 

 of Poppelsdorf and partly from the Schultz-Lupitz lupine soil. Alto- 

 gether six such experiments were made, two of which were with steril- 

 ized soil. They lasted about 340 days. In no case was there an increase 

 of combined nitrogen, but on the contrary there was a loss in every 

 experiment e.ccept the two with sterilized soil, in which case the amount 

 remained practically unchanged. This is a further indication that by 

 the simple chemical action of the oxygen of the air without the activity 

 of bacteria, which in these experiments lasted nearly a year,, there is 

 scarcely any danger of a loss of nitrogen from the oxidation of the 

 nitrogenous substances. In the next series of experiments ammonium 

 sulphate and ground bone were each mixed with soils, and ground 

 bone and ground blood were both used without soils, receiving addi- 

 tions of calcium carbonate in some cases and in others none. Where 

 soils were used a very slight loss of nitrogen accompanied nitrification. 

 In the other experiments no nitric or nitrous acids were formed and no 

 nitrification was detected, but considerable ammonia was given off. 

 There was a gain in nitrogen in the latter cases, indicating that here 

 materials comparatively rich in nitrogen and in which decomposition 

 Avas far advanced had fixed nitrogen from the air. Berthelot ascribes 

 this fixation only to soils jioor in nitrogen, but these as well as earlier 

 experiments by Tacke seem to show that it may also be effected by 

 materials rich in nitrogen. 



The object of the fourth series of experiments was to study the reten- 

 tion of nitrogen by certain materials. Ground horn was mixed in sepa- 

 rate cases with its weight of double superphosphate containing 33.7 per 

 cent soluble phosphoric acid, of superphosphate containing 8.6 per cent 

 soluble phosphoric acid, and of superphosphate gypsum, respectively, 



