22 



In an extensive examination of the nitrogen compounds of 

 processed fertilizers, Lathrop (1914) has reported the presence of 

 certain protein-like substances similar to those described above. 



In his studies on the chemical nature of the organic nitrogen 

 in the soil, Jodidi (1911) thought water would be preferable to 

 either acids or alkalies for the purpose of extraction, since it would 

 not be so liable to alter the organic nitrogenous materials. He 

 found that the direct extraction of a soil by boiling with water for 

 ten hours removed only 2.92 per cent, and for twenty-four hours 

 the highest amount removed from any soil was 9.96 per cent of the 

 total soil nitrogen. Shmook (1914), however, reports 19.10 per 

 cent of the total nitrogen of a Laterite soil of Russia to be water 

 soluble. 



The literature has been very thoroughly summarized by Potter 

 and Snyder (1914) in regard to the determination of ammonia in 

 soils. Both their work and that of Jodidi ( 1909) indicates that the 

 amount of ammonia is small. Kelley and Thompson (1914) in a 

 study of some Hawaiian soils reached the conclusion that ammonia 

 and nitrate nitrogen constitute but a small percentage of the total 

 nitrogen, and that the nitrogen is very largely in organic combina- 

 tion. 



It is known that only a small part of the soil nitrogen is dis- 

 solved by dilute acids, yet it has been shown by Kelley and Thomp- 

 son (1914) that 1 per cent hydrochloric acid dissolves some organ- 

 ic nitrogen, for in every instance the soils contained only about 

 half as much ammonia nitrogen as was extracted by the acid. 



In the soil studies of Potter and Snyder (1915 a) they find that 

 the nitrogen extracted by 1 per cent hydrochloric acid varied from 

 about -1.2 to 2.3 per cent of the total nitrogen, except in the case of 

 the peat it was only 0.67 per cent. This is contrary to the findings 

 of Gortncr (1916 a). Working with eight mineral soils he finds a 

 maximum of 4.18 per cent of the total nitrogen soluble in 1 per 

 cent hydrochloric acid with an average of 3.17 per cent. In three 

 peats he finds a maximum of 7.50 per cent with an average of 3.78 

 per cent, and in five samples of unchanged vegetable materials (oat 

 straw, alfalfa hay, oak leaves, sweet fern leaves, and grass from a 

 peat bog) he finds a maximum of 34.58 per cent with an average of 

 20.10 per cent. These findings would seem to indicate that in the 

 transformation of vegetable materials into the true organic mat- 

 ter of the soil there is a fall in the proportion of the total nitrogen 

 soluble in very dilute acids. 



Shorey (1905) published results of his investigations which 

 gave the first definite knowledge of the individual amino acids 

 formed in the decomposition of soil organic matter. He worked on 

 a Hawaiian soil with a view to classifying the decomposition prod- 

 ucts of the nitrogenous substances in the soil. The method applied 

 was that proposed by Osborne and Harris (1903) for classifying the 

 decomposition products of proteins resulting from acid hydrolysis. 

 The method is a modification of that proposed by Hausmann (1899) 

 and is in short as follows : After hydrolysis the excess of the 



