8G2 STATE BOARD OF AGRICULTUIIE. 



TABLE 13. FREEZING POIN T DEI'RIOSSION OF SOILS WHICH WKHK TillOATED WITH 

 SALT SOLUTIONS AND TITRATED WITH Ca(OH):. 



Reafjents. Depression. 



2 gni. soil plus 2 c.c. N/10 NaNOs plus 10 c.c. water 070°C 



plus 4 c.c. Ca(OH)2 052 



plus 4 c.c. Ca(OH)2 046 



plus 4 c.c. Ca(OH)2 041 



plus 4 c.c. Ca(OH)2 051 



2 gm. soil plus 2 c.c. ii/lO CaNOs plus 10 c.c. water OSB^C 



plus 4 c.c. Ca(OH)2 050 



plus 4 c.c. Ca(OH): 041 



plus 4 c.c. Ca(OH)2 037 



plus 3 c.c. Ca(0H)2 047 



2 gm. soil plus 2 c.c. ii/lO K2S04 plus 10 c.c. water 041°C 



plus 4 c.c. Ca(OII)2 039 



plus 4 c.c. Ca(OH)2 032 



plus 4 c.c. Ca(OH)2 031 



plus 3 c.c. Ca(0H)2 039 



2 gm. soil plus 2 c.c. n/10 CaHP04 plus 10 c.c. water 020°C 



plus 4 c.c. Ca(OH)2 Oil 



plus 4 c.c. Ca(OH)2 010 



plus 4 c.c. Ca(0H)2 019 



It is at once seen that the general type of numerical data and curve 

 yielded by the soils which were treated with soluble salts is almost ex- 

 actly the same as that obtained when a pure acid or acid salt or a soil 

 treated with an acid or acid salt is titrated with Ca(OH)o. The ir- 

 resistable and logical conclusion immediately appears to be, therefore, 

 that the substance produced in the soils when they are treated with dif- 

 ferent soluble salts, consists either of a soluble free acid or an acid salt. 

 This conclusion appears to be supported by what is already known con- 

 cerning the reaction betv/een a salt solution and the soil. According to 

 the adsorption and chemical theories, when a soil reacts with a salt, the 

 base of the salt is taken up by the soil and leaves in solution a free acid, 

 or the base taken up releases a weaker base such as aluminum, which 

 combines with the acid radical of the salt to form an acid salt. 



Hence, the ansAver to the above question, what is the nature of the 

 substance produced in the soil by the application of soluble salts, which 

 increases the lime requirement, appears to he that it consists either of 

 a free acid or an acid salt^ but most likely the latter. 



At this point it should be stated that the above explanation as to the 

 cause of the acid curve, applies only to the neutral salts and not to the 

 acid phosphate salts, CaH^ (POJo and K.HPO^. These phosphate salts 

 are acid salts and will produce the acid curve even before they are 

 applied to the soil. The acid curve produced after they are applied to 

 the soil is doubtless due to the same compounds and not necessarily to 

 some other acid or acid salt formed. 



It should also be recorded that the acid curve will be obtained upon 

 the application of soluble salts only when the soil shows a lime require- 

 ment, by the freezing point method. If the soil shows no lim.e require- 

 ment, such as the quartz sand, the acid curve will not be obtained, ex- 

 cept in the case of the phosphate salts. The same is true when a soil is 

 alkaline or already saturated with a base. If a soil, however, takes up 

 only a very small amount of lime, the acid curve wall be very unpro- 

 nounced. 



Not all neutral salts give in the soil an acid curve of the same degree 

 of pronouncement. That is to say the amount of decrease in the de- 

 pression is not the same for all neutral salts. Thus Ca(NOJ._,, NaNOs, 



