SOILS FERTILIZEES. 623 



the nitrogen present in the soil can be extracted and then separated into various 

 groups of definite composition. 



" The amount of total nitrogen extracted from the soil of the various plat? 

 examined, by boiling with hydrochloric acid, vras on the average 75.83 per cent 

 (from 71.12 to 81.2 per cent), the balance (from 28.88 to 18.8 per cent) having 

 remained undissolved. 



" The acid-soluble nitrogen is made up as follows: Ammoniacal nitrogen, from 

 1.22 to 1.07 per cent (from 0.99 to 1.14 per cent of the total soil nitrogen) ; nitric 

 nitrogen, from 0.07 to 1.46 per cent (from 0.05 to 1.14 per cent of the total soil 

 nitrogen) ; nitrogen of acid amids, from 25.23 to 33.03 per cent; nitrogen of 

 diamino acids from 11.61 to 13 per cent ; nitrogen of monamino acids from 22.2 

 to 55.66 per cent. The rest of the organic nitrogen consists of compounds other 

 than acid amids and amino acids. 



" By boiling with water, only a small proportion of nitrogen, namely from 2.92 

 to 9.96 per cent of total soil nitrogen, could be extracted from the various 

 soils investigated. This, taken together with the fact that the bulk of the soil 

 nitrogen is made up of acid amids and amino acids all of which are fairly solu- 

 ble in water, makes it very likely that these compounds are present in the soil 

 not in a free state, but in some kind of combination." 



It was observed in plats which had received the more recent applications of 

 organic manures that, with the exception of from 8 to 12 per cent, the organic 

 nitrogen consisted of acid amids. diamino acids, and monamino acids, but in 

 plats which had not been recently manured a considerable percentage, from 47 

 to 60 per cent, of compounds belonging to other classes than acid amids and 

 amino acids were found. 



" Since we have found that the oi'ganic nitrogenous compounds in Iowa soils 

 as well as in Michigan peat soils are made up chiefly of acid amids and amino 

 acids, despite a considerable variety of the sources of the organic nitrogen, it 

 seems fairly safe to state that the bulk of the organic nitrogen in the majority 

 of soils, if not in all, consists very likely of acid amids and amino acids." 



The chemical nature of the organic nitrogen in the soil, S. L. Jodidi 

 (Jour. Amer. Chem. Soc, 33 (1911), .Yo. 7, pp. 1226-1241; abs. in Chem. Abs., 5 

 {1911), No. 19, p. 3313). — This article presents the more strictly chemical 

 phases of work more fully reported above. 



Organic nitrogenous compounds in peat soils, II, C. S. Robinson (Michigan 

 Sta. Tech. Bui. 7, pp. 22, figs. 2). — This is a continuation of work previously 

 noted (E. S. R., 22, p. 618), reviewing the results of investigations on the com- 

 position of the organic matter of peat soils and dealing pax'ticularly with 2 

 compounds, leucin and isoleucin, which were isolated from such soils in con- 

 siderable quantities. 



" The work reported in this paper and that done by Suzuki proves quite 

 conclusively that a considerable portion of the nitrogen is present in the form 

 of a protein compound or a mixture of such compounds which can be broken 

 down on treatment with acids in the same manner as casein, egg albumin, etc. 

 In the samples of peat studied for this work about 26 per cent of the total 

 nitrogen was combined in this form in such a way that it could be converted 

 by hydrolysis into primary amins, probably with the formation of amino acids. 

 About 10 per cent of the total nitrogen is due to the presence of acid amids. 

 From the work of Schreiner and Shorey purin, pyrimidin and pyridin com- 

 pounds constitute a part of the remainder. The greater part is, however, pres- 

 ent in forms concerning which we know nothing and which may represent the 

 most important factors in aiding or inhibiting plant growth. It seems prob- 

 able, from the work done so far, that the classes of compounds constituting 



