THE ABSORPTIVE PROPEETIES OF SOILS 265 



ical. Warington ^ also believed in the chemical hypothesis. 

 Liebig, however, regarded absorption as largely physical. Van 

 Bammelen^ was the iir4 to direct attention to the importance 

 of both organic and inorganic colloidal matter to absorption 

 phenomena. This type of explanation seems the most plau- 

 sible in light of present knowledge of the colloidal state of cer- 

 tain soil constituents and from the fact that a soil very often 

 does not remove different bases in chemically equivalent 

 amounts.^ The fact that a soil apparently .saturated with one 

 base is able to absorb quantities of another is additional argu- 

 ment against a purely chemical explanation. 



In the soil, especially if it is of a clayey nature, there always 

 exist certain quantities of hydrated aluminum silicates of 

 indefinite chemical constitution. They are generally colloidal 

 in nature.^ Such materials, as well as those of an organic 

 character, possess high absorptive capacities, not only be- 

 cause of their tremendous surface exposures but also because 

 of their tendency to react quickly and easily with substances 

 in the soil solution. According to Van Bemmelen, who made 



^Warington, E., On the Fart Taken hy Oxide of Iron aiid Alumina 

 in Absorptive Action of Soils; Jour. Chem. Soc, (London), Vol. 6, 

 pp. 1-19, 1868. 



2 Van Bemmelen, J. M., Die Ahsorptionsverhindungen wid das Ahsorp- 

 tionsvermogen der Aohererde; Landw. Vers. Stat., Band 35, Seite 75, 

 1888. Also, Die Absorption, Dresden, 1910. 



®Tlie uncertainty regarding the real e3:planation of absorption is 

 shown by the controversy of Weigner, who holds to the colloidal theory, 

 with Gans, who believes the phenomenon is chemical. 



Weigner, G-., The Chemical or Physical Nature of Colloidal Aluminum 

 Silicates Containing Water; Centrbl. f. Min. u. PalaontoL, No. 9, j)p. 

 262-272, 1914. 



Gans, E., Concerning the Chemical or Physical Nature of Colloidal 

 Water-containing Aluminum Silicates; Centrbl. f. Min. u. PalaontoL, 

 No. 22, pp. 699-712; No. 23, pp. 728-741, 1914. 



*The absorptive capacity of the soil is often ascribed to zeolites. 

 The presence of zeolites in the soil, however, is extremely improbable. 

 Water and the absence of oxidizing agents are essential for their for- 

 mation. They are products of hydrometamorphism and not of weather- 

 ing. It seems probable that the processes of weathering are not only 

 opposed to zeolite formation but would destroy those already present. 



Merrill, G. P., Weathering of Micaceous Chieiss; Bui. Geol. Soc. Amer., 

 Vol. 8, pp. 162-166, 1879. 



