394 STATE BOARD OP AGRICULTURE. 



of the hexone bases, as well as three other compounds of more complex 

 structures, namely, cytosine, xanthine and hypoxan thine. The three 

 last differ considerably from any of the substances previously discovered 

 in soils and account for some of the non-protein nitrogenous compounds 

 of hitherto unknown constitution. 



Owing to the fact that some investigators have worked with humic 

 acids while others have used the peat or soil itself, it is impossible to 

 assemble the results of these various investigators in such a way as to 

 compare accurately the actual amounts of the different kinds of nitro- 

 gen found by each. In a general way, though, the results agree. Thus 

 the ammoniacal nitrogen seems to represent only a very small part of 

 the total. The amount in the amido form is somewhat greater, while 

 that present as primary amines is the largest of the three. From 

 Schreiner's and Shorey's work some of the remainder consist of 

 pyridine, pyrimidine and purine compounds. Most of the nitrogen in 

 soil organic matter seems, however, to exist in combinations concern- 

 ing which we know nothing. 



Amino Nitrogen in Peat.^ 



It may be seen from this review of the work done on soil organic 

 matter, but little reliable data has been obtained on the amount of 

 amino nitrogen in soils and no general method is in vogue for its de- 

 tennination. As amino nitrogen can usually be easily converted by 

 micro-organisms into a form available for plant use, such a method 

 might be of considerable importance, not only from a scientific stand- 

 point, with a view of determining the constitution of humus compounds, 

 but also from a practical standpoint as an aid in determining the 

 amount of nitrogen available for plant food. While some of the nitrogen 

 of amino acids, and possibly of other amino compounds, may be split 

 off on heating with strong bases, nothing like a complete decomposition 

 could be conveniently obtained, and this method of procedure would 

 also give, as is well known, all of the nitrogen present in the form of 

 ammonia and acid amides. Neither can precipitants of such a general 

 nature as phospho-timgstic acid be depended upon in a mixture of com- 

 pounds such as one gets in the extract of a soil rich in organic matter. 

 The method originated by Sachsse and Kormann^ which, as later modi- 

 fied by Boehmer,^ was used by Dojarenko as previously cited, isi free 

 from these objections. Moreover, it has recently been so perfected by 

 Van Slyke* that it can be ixjrformed with great speed and accuracy. 

 In principle it depends upon the action of nitrous acid on primary 

 amines. In this reaction the nitrogen is set free in the elemental state 

 according to the equation, 



RNH^ -f HNO2 > ROH -1- Nj -f H2O. 



and can be measured as such. The NO gas formed by the secondary 

 decomposition of the nitrous acid 



2 HNO3 > NO +N02 ^- H,,0. 



'This part of the work was carried on with the assistance of Mr. O. B. Winter. 



2Vers. Stat. 17, 88; 17, .'^21 (1874). 



8Vers. Stat. 28, 247 (1882). 



^Proc. 60C. Exp. Biol, and Med. 7, 46 (I9IO); Beritche d. Deutsh. Chem. Gesel. 43, 3170. (1910.) 



