GOG STATE BOARD OF AGRICULTURE. 



logical activities of any kind were at niinininm, especially the lirst ten 

 days. 



With the above explanation in mind the qnestions now may be 

 answered. From the data it would appear that equilibrium is attained 

 at the end of about (>0 days, as at this period solubility becomes station- 

 ary or negligible. And if equilibrium is attained then the solution must 

 also be saturated, at least with some of the soil constituents. 



AVhile the results show an apparent e(|uilibrium there are many evi- 

 dences which seem to make doubtful if it is the real equilibrium. In 

 the first place, if the soil which shows a constancy in solubility at the 

 high water content is allowed to lose moisture so that its water content 

 is reduced to about the optimum point, the freezing point depression or 

 the amount of material in solution is far greater than at the high 

 moisture content where equilibrium is shown to have been reached. 

 Now according to the laws of solubility, if the solution were at equili- 

 brium and saturated at the high moisture content the solution should 

 become super-saturated at the lower moisture content and the solutes 

 should separate out so that the solution would again be at equilibrium 

 and saturated as required by the new conditions. In that event then 

 the freezing point depression at the low moisture content should be the 

 same as that at the high. Instead of that, the depression, as has already 

 been stated is much greater at the low moisture content. 



In the second place, since the soil is a complex and heterogeneons mass, 

 composed of minerals, colloids, organic matter, etc., it does not seem 

 possible that it forms definite chemical compounds with the salts. And 

 if it does not form definite chemical compounds it probably does not 

 have a definite solubility, in the physical-chemical sense. 



In the third place, since the soil contains organic matter it does not 

 seem reasonable to believe that definite equilibrium, in the physical- 

 chemical sense, is attained. 



The conclusion appears inevitable, therefore, that the equilibrium in- 

 dicated by the experimental data is not a true and definite equilibviuiii 

 in the physical-chemical sense, but only an apparent equilibrium. The 

 true equilibrium is probably never attained because many salts formed 

 in the soil, such as NaNOo, KCl, NaoCOg, CaSO^, etc., have a very high 

 solubility constant and a tremendous amount of them is required to 

 form a saturated solution. Furthermore, if the soil is considered as it 

 actually is and not speaking from tlieoretical principles, it is probably 

 not proper to speak of true equilibrium, in a chemical-pliysical sense. 

 This logically follows from the fact that the soil is a heterogeneous mix- 

 ture composed of mineral solids, organic matter, gas, and a liquid, and 

 contains organisms, and in the process of solution, hydrolysis, biolog- 

 ical decomposition, etc., many substances are formed, which once formed 

 do not depend in their solubility upon the substance from which they 

 were formed, and consequently there cannot be a true solubility as is 

 chemically understood. 



The solubility of the soils under consideration would probably con- 

 tinue for many months, if not almost indefinitely, if it were not for some 

 factors which create a limitation in the amount of material going into 

 solution, and after a certain time cause even a reverse action. Just 

 what these factors are is not known, but some may be suggested. It has 



