EXPERIMENT STATION BULLETINS. 715 



mucks and i>eats allowetl only a very small amount of material to go into 

 solution. 



Georgia Cecil clay iNo. It. Memphis silt loam (Xo. 19 », and <.lhio silt 

 loam (Xo. 22 1 need special attention. All these soils show an exceed- 

 ingly slow rate and a very small extent of solubility. In these respects 

 they resemble very much the pure sandy soils or quartz sand. The Cecil 

 clay refused to yield more material to solution even when its temperature 

 was raised to .53 = C and kept there for 30 days. 



Eate and Extent of Solubility of Natural or Untreated Soils. Mois- 

 ture Maintained at Optimum Content and Soils Kept Mostly Outdoors. 



In The preceding study the rate and extent of solubility of the natural 

 or untreated soils were measured at the water content of supersaturation. 

 In the present study it was decided to measure these factors at the 

 optimum moisture content and thus under more or less practical or 

 field conditions. In order to afford a true and reliable basis of coni- 

 parison in the results between the two sets of moisture content the same 

 kind of soils were used in both cases. The procedure employed in a 

 preArious study was also used here. It consisted of placing a certain 

 amount of soil on a filter paper in a ftmnel and 'gashing until all its free 

 soluble salts were eliminated. Then a small sample of the washed soil 

 was taken air-dried, and its freezing point depression determined by 

 using 1-5 grams of soil and 10 c.c. of water. The rest of the soil was 

 allowed to remain in the funnel undisturbed and to lose water tmtil its 

 moisture content was reduced to about the optimum point. Then the 

 soil was placed in a glass tumbler, thoroughly stirred and weighed. Water 

 was added to it. thereafter, as often as it was deemed necessary in order 

 to keep it at the optimum moisture content. Meanwhile, the soil was 

 kept outdoors, under as natural conditions as x>ossible. most of the time. 

 At the end of 10, 30. and 60 days a small composite sample was taken, 

 air dried, and its freezing point depression determined as originally. 



The results procured in this study are presented in table 23. The 

 number of each soil corre.<!ponds to the ntimber in table 22 where the high 

 moisture content was employed. 



TABLE 23. — KATE AXP EXTENT OF SOIXBILITT OF XATUKAL SOILS. AT OPTIMUM 

 MOISTFKE COXTEXT. KEPT M<^<TT Y OUTDOORS. FIGURES REPRESENT FREEZ- 

 ING POEXT DEPRESSION. 



