188 § 105. ANALYSIS OF SOILS AXD ROCKS. 



ABSORPTIVE PROPERTIES OF THE SOIL. 



105. To determine the coefficients of absorj^tion of the 

 soil for the more important elements of plant-food, treat 

 125 grms. of the air-dried soil with 500 c.c. of a '1^^, 

 atomic solution, that is, a solution containing in 1 litre ^ (.^ 

 of an equivalent expressed in grammes, of ammonic chlo- 

 rid-e ; shake the mixture frequently during a cold digestion 

 of 24 hours, decant and filter as large a j)ortion of the 

 liquid as possible, and determine the loss of the salt in a 

 measured aliquot part of the filtrate. In some cases it is 

 desirable also to make a complete analysis of this filtrate 

 in order to learn what elements have taken the place of 

 the ammonium in the solution. 



Make similar experiments with potassic chloride, mag- 

 nesic chloride, calcic chloride, hydric disodic phosphate, 

 sodic chloride, and sodic silicate. 



Or, according to Knop's method, dissolve together po- 

 tassic and calcic nitrate, common potassic phosphate, and 

 magnesic sulphate, in a litre of water, in such a propor- 

 tion that the solution shall contain 1.5 grms. of each com- 

 pound, estimated as anhydrous salt. Treat 125 grms. of 

 soil with 500 c.c. of this solution, shake the mixture fre- 

 quently during 24 hours, filter off 300 or 400 c.c, and 

 make a complete analysis of the solution, according to 

 Scheme T., a and ^, and determine chlorine in the usual 

 manner in another portion of the same solution (§ 63). 



STATEMENT OF THE RESULTS OF THE ANALYSIS. 



106. The following Scheme is intended to assist the 

 analyst in putting together the results of a soil analysis ; 

 it is conformed mainly with the directions given by 

 Wolff, and the percentages, though hypothetical, do not 

 differ much from the average results of the later analyses 

 of soils that have been made ; as the i:>lan is given merely 



