174 



Conductivities and Viscosities in Pure and in Mixed Solvents. 



SERIES 3. 



For series 3, Durham sandy loam, pulverized four days in a ball mill, 

 was used. The manipulation was the same as for series 2, except that 

 the fractional percolates were 100 c.c. instead of 50 as in the previous 



TABLE 100. Absorption of potassium solution by a finely pulverized sandy loam from a solution 

 of potassium chloride containing 78 parts per million of potassium. 



TABLE 101. Removal of ab- 

 sorbed potassium by leaching 

 with distilled water. 



series, making the total volume of the solution twice as great. An 

 inspection of table 100 brings out the surprising fact that the amount 

 of potassium in the solution has been increased instead of decreased by 

 its contact with the soil. 



A part of this increase in concentration is undoubtedly due to the 

 fact that the pulverized soil has given up some of its potassium to the 



percolating solution. However, this is not 

 sufficient to account for all of the increase in 

 potassium content. In column 3 of table 100 

 is given the potassium in the fractional per- 

 colates, after they have been corrected for the 

 water-soluble potassium of the soil. This cor- 

 rection is based upon the assumption that 

 pure water in contact with the soil will dis- 

 solve potassium at the same rate, and in the 

 same amounts as the very dilute solution of 

 potassium chloride used in these experiments. 

 Proceeding upon this assumption, pure water 



was percolated through the sample of pulverized soil, and the amount 

 removed by the water was applied as a correction to the correspond- 

 ing fractional percolates of the salt solution. 



The results given in table 100 are shown graphically by the curves in 

 figure 21. The dotted line forming the upper arm of the curve repre- 

 sents the original concentration of the successive fractions, while the 

 solid line represents the strength of the solutions after the correction 

 has been applied. It will be seen that, even after the correction has 

 been made, the solution still maintains a concentration higher than the 

 original salt solution. This appears to be a case of selective absorption, 

 in which the solvent (water) is absorbed more rapidly than the dissolved 



