THE ORGANIC MATTER OF THE SOIL 107 



but quantitative determinations are uncertain. These com- 

 pounds produce ammonia readily, the rate depending on their 

 chemical structure. 



The present knowledge of the chemical constitution of the 

 soil organic matter is due largely to investigations prosecuted 

 by the United States Bureau of Soils. 1 As a result of several 

 years work a large number of compounds were isolated. Some 

 are original constituents of the plant tissue but the bulk has 

 arisen through the process of organic decomposition. 



The compounds isolated were classified from the chemical 

 standpoint under four heads, those containing: (1) carbon 

 and hydrogen; (2) carbon, hydrogen, and oxygen; (3) car- 

 bon, hydrogen, and nitrogen, or carbon, hydrogen, oxygen, 

 and nitrogen; (4) sulfur in combination with any or all of 

 the elements listed above. With the possible presence in 

 soils of compounds containing so many elements, it is little 

 wonder that the subject is a complicated one. It is evident, 

 moreover, that any list now available will be only partial, and 

 that many other compounds of even more intricate composi- 

 tion will be isolated later. 



A list of some of the compounds isolated from soil organic 

 matter by the Bureau of Soils follows: 



thus becomes acet-amide (CH a C0NH 2 ). Amino-acids are produced by 

 replacing one of the alkyl/hydrogens with NH 2 . Acetic acid thereby 

 becomes amino-acetic acid or glycocoll (CH 2 (NH 2 )COOH). Protein/hy- 

 drolysis is probably as follows: 



^Acid amides 

 Proteins — > Proteoses — > Peptones — » Peptides S~ 



^Amino-acids 



1 Sehreiner, O. and Shorey, E. C, The Isolation of Harmful Substances 

 from Soils; U. S. Dept. Agr., Bur. Soils, Bui. 53, 1909; also Buls. 47, 70, 

 74, 77, 80, 83, 87, 88, and 90. See also, Sullivan, M. X., Origin of 

 Vanillin in Soil; Jour. Ind. & Eng. Chem., Vol. 6, No. 11, pp. 919-921, 

 1914. Kelley, W. P., The Organic Nitrogen of Hawaiian Soils; Jour. 

 Amer. Chem. Soc, Vol. XXXVI, No. 2, pp. 429-444, Feb., 1914. Walters, 

 E. H., Proteoses and Peptones in Soils; Jour. Ind. & Eng. Chem., Vol. 

 7, No. 10, pp. 860-863, 1915. Lathrop, E. C, Protein Decomposition 

 in Soils; Soil Sci., Vol. I, No. 6, pp. 509-532, June, 1916. 



