EXPERIMENT STATION BULLETINS. 393 



while the compounds separated by this reagent in the case of protein 

 consist of mono- and di-amino acids, it does not follow that snch is 

 true in the case of soils. Phospho-tungstic acid precipitates diamino 

 acids from acid solution, leaving the monoamine acids dissolved. While 

 it would undoubtedly act the same whether these acids were derived 

 from animal protein or peat, still, in the latter case, other nitrogenous 

 compounds might be present which would also be precipitated, thus 

 increasing the amount of nitrogen classed as diamino nitrogen. Neither 

 would all of the nitrogenous compounds remaining in solution be nec- 

 essarily mono-amino acids. Jodidi also determined the quantities of 

 amido and ammoniacal nitrogen. He concluded from his work that, 

 in the peat which he used, the ammoniacal nitrogen amounted to but 

 a few thousandths of one per cent. He says : "The bulk of the organic 

 nitrogen, namely two-thirds to three-fourths, calculated upon the nitro- 

 gen in solution by boiling with acids, is present in the form of mono- 

 amino acids, about one-fourth in the form of amides and the rest of the 

 nitrogen represented diamino acids." 



The actual isolation of an individual organic nitrogenous chemical 

 compound from soil was first accomplished by vShorey.^ He extracted 

 the soil with cold alkali, acidified the extract, filtered and neutralized 

 the filtrate with sodium hydrate, filtered and concentrated. From this 

 concentrated solution a pure white crystalline compound separated 

 which had the percentage composition, melting point and other char- 

 acteristics of piccoline carboxylic acid, a true chemical compound whose 

 properties and structural composition w^ere w^ell known. From his 

 method of obtaining this substance, Shorey decided that it was present 

 in the soil as such and was not a decomposition product formed in 

 the laboratoiy during the process of extraction. He shoAved that it did 

 not aid in the growth of plants and was, in fact, harmful to them. 

 While the soil with which he worked w^as not a peat, nor even a muck 

 soil, still the compound which he obtained was no doubt formed from 

 decomposed organic matter of much the same sort from which peat is 

 produced. 



The following year Suzuki^ published researches which gave the first 

 definite knowledge of the individual amino compounds formed in the de- 

 composition of soil organic matter. He worked with three samples of 

 humic acid, one obtained from Merck, one prepared from a soil and 

 one from a compost. He found only small quantities of amino acids 

 present as such, but on boiling with concentrated acid and separating 

 by the Fisher esterification method he obtained from five hundred grams 

 of dry humic acid, 2.39 g. alanin, 2.16 g. leucin, 0.11 g. alanin +amino 

 valeric acid, 0.57 g, of amino valeric acid, 0.67 g, of copper salt of active 

 prolin, 0.06 g. of aspariginic acid, 1.9 g. of ammonia and 30.3 g. of the 

 copper salts of unidentified acids. Glutaminic acid was also found to 

 gether with traces of histidin and tyrosin. As these compounds are 

 typical decomposition products of protein, he concluded that the nitro- 

 gen of humic acid is in the form of a complex protein body. 



The latest work at hand on this subject is by Schreiner and Shorey.^ 

 They have succeeded in isolating from soils, Mstidin and arginin, two 



JRept. of Hawaii Ag. Exp. Sta. 1906, p. 37. 



2Bul. Coll. of Agric, Tokyo, 7, 51.3. Abs. in Chem. Cent. 1907, Vol. 2,'p. 1050. 



sBiill. 74, p. 31, Bureau'of Soils.'U. S. Dept. of Agric. (1910) 



