Wild and Anderson. — Absorption of Lime by Soils. 471 



The first explanation is put out of court by the consideration that if 

 we were concerned only with a mass action, then the amount of lime with- 

 drawn from solution by a given weight of the same soil would always be 

 the same, provided always that sufficient time were allowed for the com- 

 pletion of the action. Variations in the concentration of the solution would 

 not affect the result, provided that the solution has enough lime to satisfy 

 the soil. Now, we have determined by preliminary experiments (see 

 Journ. Ag. Sci., vol. 8 ; also this article, p. 475) the time necessary for 

 the completion of the action ; but, even allowing this time, we have found 

 a variable absorption of the kind already described. Within fairly wide 

 limits, the greater the initial concentration of the solution the greater is 

 the absorption. 



We turn, therefore, to the second suggestion. The literature of 

 " adsorption " by soils has been summarized by Patten and Waggaman* 

 and more recently by Prescott.f The following is from Russell's Soil 

 Conditions and Plant Growth, p. 58 (new ed., 1915): — 



" Van Bemmelen has demonstrated a close parallelism between the various 

 interchanges and absorptions shown by the soil and those shown by 

 colloids ; and there is considerable evidence in other directions that some 

 of the soil constituents, especially the clay, possess all the properties of 

 colloids. Now, the adsorption by colloids can generally be represented by 

 the equation- — 



y i 2 



— = kc n 

 m . 



where y = amount absorbed by quantity m of adsorbent ; c = equi- 

 librium concentration of dissolved substance ; k and n are constants de- 

 pending on the nature of the solution and the adsorbent. Wiegner has 

 shown that the interaction between ammonium salts and soil accords 

 entirely with this reaction, and Prescott finds the same holds true with 

 adsorption of phosphates from their solution by soil." 



In this paper an attempt is made to test the applicability of this 

 formula to the absorption of lime by soil. Table V shows some results 

 obtained with the soil* from field 21 (Lincoln College)— 



Table V. — Absorption of Lime by. Soil No. L21 from Calcium-bicarbonate 

 Solutions of varying Concentrations. 



0-0155X 

 0-120 



These results are plotted in fig. 1. It is evident that the part of the 

 curve that embraces the results with higher concentrations is of the 

 parabolic type, and would presumably approach that form more nearly 

 if determinations had been made with solutions of greater strength. 



In order, therefore, to experiment with a solution richer in lime a satu- 

 rated solution of lime-water was employed ; and as with caustic lime a 



* H. E. Patten and W. H. Waggaman, Absorption by Soils, U.S. Dept. of Agric, 

 Bureau of Soils, Bull. No. 52, 1908. 



t J. A. Prescott, The Phenomenon of Absorption in its Relation to Soils, Journ. 

 Ag. Sci., vol. 8, 1916, p. 111. 



