THE ABSORPTIVE PROPERTIES OF SOILS 357 



periments by numerous investigators have been rather 

 widely accepted as indicating that the zeolites are at 

 least partly responsible for the absorptive properties of 

 soils. It has been shown further that the absorptive 

 power of a soil is more or less proportional to the quantities 

 of acid-soluble silicates it contains. The zeolites being 

 rather easily soluble in strong mineral acids, it is held 

 that the bases so combined are more readily available 

 to plants than in most combinations found in the soil, 

 and yet are not easily leached out of it. 



258. Presence of zeolites questioned. On the other 

 hand, zeolites have never been definitely proved to be 

 present in soils. Merrill l has attempted to show that 

 they cannot be of wide occurrence in soils, but neither 

 their absence nor their presence has been demonstrated. 

 Since the time when Way first published his researches 

 in 1850, the zeolite constituents of the soil have generally 

 been held to be largely responsible for its absorptive 

 power for bases. 



259. Absorption of phosphoric acid. It has already 

 been said that although hydrochloric, sulfuric, and nitric 

 acids are not absorbed by soils, except in small quantities, 

 phosphoric acid is absorbed and retained in an almost 

 insoluble condition so far as extraction with water is 

 concerned. That this absorption cannot be due to 

 zeolites is generally conceded, and has recently been 

 demonstrated, for permutite at least, by Rostworowski 

 and Wiegner, 2 who in a carefully conducted experiment 



1 Merrill, G. P. Rocks, Rock Weathering, and Soils, pp. 

 362-367. New York. 1906. 



2 Rostworowski, S., and Wiegner, G. Die Absorption der 

 Phosphorsaure durch "Zeolithe" Permutite. Jour. f. Landw., 

 Band 60, Seite 223-235. 1912. 



