EXPERIMENT STATION BULLETINS. 829 



TABLE 2. THE FREEZING POINT DEPRESSION OF SOILS TO WHICH WERE ADDED 

 HCl AND Al2(N03)3 AND TITRATED WITH Ca(0H)2. 

 Reagents. Depression. 



Soil plus HCl 050°C 



plus 10 c. c. Ca(OH)2 038 



plus 2 c. c. Ca(OH)2 036 



plus 2 c. c. Ca(OH)2 039 



plus 2 c. c. Ca(OH)2 041 



Soil plus Al2(N03)6 049''C 



plus 6 c. c. Ca(OH)2 039 



plus 4 c. c. Ca(0H)2 03.5 



plus 1 c. c. Ca(OH)2 036 



plus 5 c. c. Ca(OH)2 040 



It Will at once be seen that when a soil is treated with an acid or acid 

 salt and then titrated Avith Ca(0H)2 almost exactly the same general 

 results are obtained as when the acid and acid salt are titrated alone. 

 The main difference being that the lower part of the cmwes of the soils is 

 not so sharply pointed as that of the solution. Occasionally the lower 

 part of the curves of the soils may be slightly flattened. 



The above type of curve is designated for convenience, and will be 

 referred to throughout this paper as an acid curve. 



The second principle, that if a soil does not contain a free acid or acid 

 salt but possesses an absorptive power for Ca(0'H)2 the freezing point 

 depression will remain the same as more and more of Ca(0H)2 is added 

 to the soil, until the absorptive power is satisfied and then it will com- 

 mence to rise with further addition of Ca(0H)2 was established in 

 natural soils. The procedure consisted of adding 10 c. c. of water to 2 

 grams of soil and then titrating with Ca(0H)2 in the same manner as 

 above. Table 3, with its accompanying figures 3a and 3b contain the 

 general type of results obtained. 



TABLE 3. THE FREEZING POINT DEPRESSION OF SOILS TO WHICH WERE ADDED 



DIFFERENT AMOUNTS OF Ca(0H)2. 

 Reagents. Depression. 



2 gm. Soil No. 1 plus 10 c. c. water 010°C 



plus 5 cc. Ca(OH)2 010 



plus 3 cc. Ca(OH)2 010 



plus 1 cc. Ca(OH)2 010 



plus 1 cc. Ca(OH)2 012 



plus 3 cc. Ca(0H)2 •. 020 



2 gm. Soil No. 2 plus 10 c. c. water 01 1°C 



plus 5 cc. Ca(OH)2 : Oil 



plus 1 cc. Ca(OH)2 012 



plus 2 cc. Ca(0H)2 021 



It becomes immediately evident that the second principle, namely that 

 when a soil does not contain a free acid or acid salt but possesses an 

 absorptive power for Ca(0II)2 the depression remains constant as more 

 and more of the Ca(0H)2 is added until the absorptive power is satis- 

 fied, and then it begins to increase with further addition of Ca(OH)n, 

 is fully confirmed by the above data. 



The curve typifjdng the second principle is designated for convenience, 

 and will be referred to throughout this paper as an adsorption curve. 



If a soil possesses both an acid and an absorptive power, the curve 

 obtained Avill be similar to that shown in Figure 2 which is an acid curve. 



There still remains the third principle to illustrate, namely, that when 

 a soil is alkaline or already saturated with bases, the freezing point de- 

 pression will commence to rise almost immediately upon adding a small 

 amount of Ca(0H)2. A typical example of this principle is afforded in 



