11 



containing 1.5 per cent nitrogen. No ammonia was evolved on 

 making alkaline, but about 23 per cent of the total nitrogen was 

 evolved on treatment with sodium hypobromite. Detmer believed, 

 however, that humic acid did not contain nitrogen, but that the 

 nitrogen found was present in some organic compound occurring as 

 an impurity in his humic acid preparation. By a tedious process 

 he was able to lower the nitrogen content of his humic acid to 

 0.179 per cent. 



Ritthausen (1877) attributed the high nitrogen content of peat 

 to the formation of complex, difficultly decomposable materials by 

 absorption of ammonia and pointed to the low ammonia content as 

 an indication of it, claiming it was not present as such after absorp- 

 tion. In an attempt to disprove Ritthausen's theory, Sivers (1880) 

 found that he could expel only very small amounts of ammonia by 

 heating with potassium hydroxide. He concluded that all the am- 

 monia taken in remained as such, and did not go to form complex 

 compounds. He maintained that most of the nitrogen was in the 

 form of protein but presented no conclusive evidence. Grouven 

 (1883) tried to show that the nitrogen of humus was due to the 

 absorption of ammonia by humic acids, but found frojn various 

 samples that only one-fiftieth of the total nitrogen was liberated 

 on heating with milk of lime, and only one-twentieth when heated 

 for two hours with potassium hydroxide. 



It was found by Loges (1886) that the hydrochloric acid ex- 

 tract of the soil gave a precipitate with phosphotungstic acid, which 

 is recognized as being a precipitating agent for certain nitrogenous 

 compounds. Baumann (1887) found that certain black Russian 

 soils rich in humus, containing but small traces of ammonia in the 

 soil, gave a considerable amount of it on boiling the soil with dilute 

 hydrochloric acid. From this he suggested the presence of amino 

 and amide compounds in the soil. About the same time this sub- 

 ject was more thoroughly investigated by Berthelot and Andre 

 (1886). They found that the nitrogenous matter was split up pro- 

 ducing ammonia and soluble nitrogenous compounds, and that the 

 hydrolysis goes further the greater the strength of the acid, the 

 longer it is in contact with the soil and the higher the temperature. 

 A soil containing 0.174 per cent of nitrogen was heated on a water 

 bath for two hours with 7 per cent hydrochloric acid and 31.9 per 

 cent of its nitrogen was dissolved. Of this soluble nitrogen 17.8 

 per cent was ammonia. Similar experiments were conducted using 

 3.4 per cent hydrochloric acid, and 0.7 per cent hydrochloric acid 

 and distilled water. 



Warington (1887) working with a sample of Rothamsted soil, 

 which had been heavily manured, showed the presence of a small 

 amount of amide nitrogen by using both hypobromite and nitrous 

 acid. It seems highly probable from these experiments that at 

 least a part of the nitrogen in the soil is present as amino com- 

 pounds. Eggertz (1888) found that the nitrogen content of thir- 

 teen samples of humus varied from 2.59 to 6.43 per cent and states 

 that the nitrogen was present in organic form and not as an am- 

 monium salt. Sestini (1899) also showed the presence of amino 



