106 NATURE AND PROPERTIES OF SOILS 



dant results, but these were explained for the time being by 

 assuming that the discrepancies occurred because of added 

 molecules of water. 



Later investigators, while progressing rather slowly toward 

 definite results, did accomplish one thing of importance. They 

 threw considerable doubt on the old ideas of the Mulder 

 school of chemists. 



One of the men, whose work established beyond a doubt the 

 fact that organic matter was a mixture of very complicated 

 compounds, was Van Bemmelen. 1 His investigations still 

 further showed that the soil organic matter was largely in a 

 colloidal condition, and, therefore, exhibited properties quite 

 distinct from those shown by true solutions or matter in a 

 coarse state of division. 



In recent years, Baumann 2 by his researches has shown 

 freshly precipitated organic matter to possess properties which 

 are largely colloidal in nature. Among these characteristics 

 are high water capacity, great absorptive power for certain 

 salts, ready mixture with other colloids, power to decompose 

 salts, great shrinkage on drying, and coagulation in the pres- 

 ence of electrolytes. Jodidi 3 has studied the composition of 

 the acid-soluble organic nitrogen in peat and mineral soils. 

 The nitrogenous compounds thus obtained can be divided into 

 the following groups: (1) ammoniacal nitrogen, (2) nitric 

 nitrogen, (3) acids amides, (4) mon- and diamino-acids. The 

 two latter groups 4 carry the bulk of the organic nitrogen, 



1 Van Bemmelen, J. M., Die Absorptions Verbindungen und das Ab- 

 sorptionsvermogen der Ackererde; Landw. Versuch. Stat., Band 35, 

 Seite 67-136, 1888. 



2 Baumann, A., Untersuchungen tfber die Hummussauren ; Mitt. d. K. 

 bayr. Moorkulturanstalt, Heft 3, Seite 53-123, 1909. 



"Jodidi, S. L., Organic Nitrogenous Compounds in Peat Soils I; Mich. 

 Agr. Exp. Sta., Tech. Bui. 4, Nov., 1909. Also, The Chemical Nature of 

 the Organic Nitrogen in Soil; la. Agr. Exp. Sta., Ees. Bui. I, June 1911. 



4 Amides or acid amides are formed from organic acids by replacing 

 the hydroxyl of the carboxyl group with NH 2 . Acetic acid (CH 3 COOH) 



