172 



Conductivities and Viscosities in Pure and in Mixed Solvents. 



and the potassium was determined calorimetrically. Immediately 

 following the percolation with the solution of potassium chloride, pure 

 distilled water was forced through the sample at the same rate in order 

 to study the removal of the absorbed potassium. As a check upon the 

 calorimetric determinations, the specific conductivity of the fractional 

 filtrates was determined by measuring the conductivity of the solutions 

 in a standardized Arrhenius cell, according to the method described by 

 Jones. 1 



TABLE 98. Absorption of potassium by a sandy loam soil, from a solution of potassium chloride 



containing 62 parts per million of potassium. 



TABLE 99. The removal of the absorbed potassium by leaching with distilled water. 



It will be seen from table 98 that the first 10-minute contact of the 

 solution with the soil reduced its concentration from 62 parts per million 

 to 40 parts per million. At the end of the second 10 minute period 

 the strength of the solution is further reduced to 36 parts per million, 

 but from this point the concentration of the solution rises until the 

 fifth and last fraction is reached, when the concentration is within 3 

 parts per 1,000,000 of the concentration of the original solution. The 

 third column shows that the amount of potassium retained by the soil 

 rises gradually to 233 parts per million of the dry soil, when 250 c.c. 

 of solution has passed through. 



Figures 18 and 19 represent graphically the results given in tables 

 98 and 99. In figure 18 are shown the results based upon the concen- 

 tration of the successive fractional filtrates ; the large curve representing 

 the concentration in parts per million of potassium, and the small curve 

 the specific conductivities. The curve for the potassium shows that 

 the first three fractions of the filtrate are reduced approximately to 

 two-thirds of the strength of the original solution. With the increase 



Clements of Physical Chemistry, 4th edition, pp. 377 to 383. 



