EXPERIMENT STATION BULLETINS. 



723 



the solubilitA' of a soil becomes constant at the various water contents 

 before the same extent of solubility is attained ami tliat there is no 

 tendency of this equality being attained, no matter how long the soil 

 anrt water remain in contact. Tlius, the solubility of soils in a water 

 content of 1 of soil to o of water becomes constant when it is only half 

 as great as that in the same soil at a water content of 1 of soil to .7 of 

 water, and that no matter how long the soil is left in contact with the 

 water, this eciuality is not reached. 



From these findings the practical conclusion naturally follows that 

 in the humid regions the soil solution never becomes saturated. 



Rate and Extent of Solubilitv of Subsoils Which Were Previously 

 Washed, and the Ratio of Soil to Water Was About 1 to .7 and the 

 Mixture Maintained at Room Temperature. 



All the soils employed in the foregoing series of studies were surface 

 soils. From various standpoints it appeared very desirable to employ 

 also subsoilfj in the general studv on the rate and extent of solubility 

 of soils. Accordingly, samples of subsoils at the depth of one and 

 one-half feet were taken, washed while fresh, placed in the freezing 

 point tubes, added water to them to bring them up to the water content 

 of 1 of soil to .7 of water, and then the freezing point depression deter- 

 mined as usual. The data procured are epitomized in table 28. 



TABLE 2S. — RATE AND EXTENT OF SOLUBILITY OF SUBSOILS. RATIO OF SOIL TO 

 WATER WAS ABOUT 1 TO .70 AND MIXTURE MAINTAINED AT ROOM TEMPER- 

 ATURE. FIGURES REPRESENT FREEZING POINT DEPRESSION. 



Apparently the rate of solubility of these subsoils is somewhat faster 

 than that of the surface soils already considered. On the other hand, 

 their extent of solubility is very small, amounting only to about 550 

 parts per million in the clays and clay loams and about 150 parts per 

 million in the sands, at the end of 78 days. 



The apparent greater rate of solubility of these subsoils over the sur- 

 face soils may be partly due to the insuiTicient washing of the former. 

 These subsoils were employed in the fresh condition and many of them, 

 and especially the clays, clay loams and silt loams, were so sticky that 

 it was impossible to wash them by the leaching process. Hence, the 

 salts, probably were not all washed away and went into solution rather 



