27 



method of Schiff (1900, 1901, 1902) as modified by Sorensen (1908), 

 Henriques (1909), and Henriques and Sorensen (1910). 



In a comparison of the amount of di-amino* acid nitrogen, 

 calculated as if histidine, arginine, and lysine were present in about 

 equal amounts, he finds that in plot E, 101.8 per cent; plot Q, 84.8 

 per cent; and plot U, 93.9 per cent of the nitrogen in the phos- 

 photungstate fraction was actually present as di-amino acids. 



However, he obtains widely divergent results for mon-amino 

 acid nitrogen; in plot E, 91.64 per cent; plot Q, 52.63 per cent; 

 plot U, 40.12 per cent; plot H, 88.31 per cent; and plot J, 92.11 

 per cent of the total nitrogen in the "filtrate from the bases" was 

 actually present as mon-amino acid nitrogen whereas all should 

 have been present in this form if dealing with pure proteins only. 

 He, therefore, concludes that the di-amino and mon-amino acids, 

 or in other words, the bases and filtrate from the bases by hydro- 

 lyzing soils, contain other products- than are formed by hydrolysis 

 of pure proteins. 



In a series of fertilized soils studied by Lathrop an.d Brown 

 (1911) they find that almost 98 per cent of the nitrogen in the soil 

 is of organic nature. The ammonia and nitrate nitrogen constitute 

 the remainder. Employing the same method to the distribution of 

 the soil organic nitrogen as Shorey (1905), they boiled 100 grams of 

 soil with 500 cc. of hydrochloric acid (sp. gr. 1.115) for three hours, 

 and used the filtrate after making to definite volume for the 

 analyses. The figures given for ammonia nitrogen represent the 

 actual amount of nitrogen as ammonia obtained by hydrolysis and 

 does not include the ammonia nitrogen already present in the 

 soil. They find that the plots which have received organic fer- 

 tilizers give the largest amount of ammonia on hydrolysis, the 

 amount being highest in the plot which has received manure alone 

 and lowest in the check plot. 



Of the five soils studied, four contained over 25 per cent of 

 the "humin" nitrogen soluble in acid, while the other only showed 

 about half as much. Since the nitrogen of the soil not soluble in 

 acid may be considered "humin" nitrogen, the total amount in this 

 form in the above four soils was over 53 per cent, while in the 

 other soil, which received dried blood, it amounted to only 43 per 

 cent. 



However, the fractions which they determined have actually 

 very little significance in a discussion of protein hydrolysis products, 

 inasmuch as a three-hour hydrolysis is far too short a time to com- 

 pletely decompose the protein molecule. This explains their high 

 figures for humin nitrogen and low ones for mon-amino acid 

 nitrogen. The di-amino and mon-amino acid nitrogen differ rather 

 widely but there seems to be no agreement between the form of 

 nitrogen and the plot treatment. 



*The exact interpretation of his data is difficult to understand. 



