THE COMPOSITION OF THE SOIL 



103 



approximately equal to 2. Other soils of volcanic origin from 

 Java gave up larger amounts of base relative to the silica, but 

 in no case were the ratios constant whole numbers ; the 

 alkaline bases showed the same lack of constancy in the ratios 

 to A1 2 O 3 . 



TABLE XXX. RATIO 



MOLECULES OF SiO 2 

 MOLECULES OF ALO, 



EXTRACTED FROM VARIOUS 



SOILS. VAN BEMMELEN (22). 



Alkaline bases extracted from a heavy clay, Surinam. 



Different soils gave up different proportions of alkaline 

 bases, but again without showing definite simple ratios one to 

 another. Detailed studies of clay revealed the presence of 

 chemically unchanged crystals of the original silicates and 

 also of easily soluble substances including a fusible group with 



molecules of SiO 2 



ratio \ 1 f A1 ^ varying from 3 to 6, and a silicate 



molecules of A1 2 O 3 J 



resembling kaolin with ratios varying between 2 and 3. The* 

 easily soluble material represents the products of weathering 

 since it does not occur in rocks. If it were a definite chemical 

 compound the ratio of its constituents should be constant 

 whole numbers, but this is not the case. It behaves, however, 



