124 Phenomenon of Absorption in its Relation to Soils 



G. C. Schmidt^ has found that adsorption is slowest if the adsorbent is 

 placed directly into the solution. If the equiUbrium is first established 

 and the solution is then diluted the new equilibrium is attained almost 

 immediately. Air films in the adsorbent are suggested as a cause for 

 the slower rate with the fresh material. 



Table I. Absorption of oxalic acid by soil. 

 Oxalic acid 



•4 -5 -6 



C gms. per litre 

 Fig. 1. Absorption of oxalic acid by soil in presence of excess nitric acid. 



1-0 



The simultaneous adsorption of two substances from solution is 

 of much interest to the soil chemist. As already stated Van Bemmelen 

 had shown that one adsorbed substance can be replaced by another 



1 Zeits. phys. Chem. 1910, 74, 689. 



