412 



STATE BOARD OF AGRICULTURE 



// 



to 



3: 



8 



c.c. 07 /V ^^^/V. 



Fig. 10. Curves showing pH readings of Ca (OH) 2 solutions without soil. 



ACID TITRATION CURVES NOS. 4 AND 5 



The first group of acid titration curves were obtained by using 

 ALCls and the second group by HCl. 5 gms. of the clay loam soil 

 was used in the acid titrations because this soil had a high neutraliz- 

 ing value for acids as compared to the other soils. No. 4 curves were 

 initial titration curves, and No. 5 curves were drawn on readings taken 

 after one day's standing. The ALClg curves have the same general trend 

 as the HCl curves, but the ALClg one and two day curves lie closer to- 

 gether than those obtained with HCl. Another point of difference in these 

 two groups of curves is that the pH runs lower in case of the HCl titra- 

 tions, which is probably due to the greater dissociation of HCl at the 

 concentrations used. It is not clear, at present, why these curves should 

 have this form. Several reactions were undoubtedly taking place; 

 neutral salts of calcium and magnesium and in smaller quantities of 

 potassium and sodium were formed, acid salts of iron and aluminum 

 were added or formed, weak acids were split off from soil salts, and 

 in case of the HCl titrations, hydrogen ions were added. In addition 

 to the foregoing, other reactions might have taken place. Perhaps the 

 only statement that may be reasonably made in this connection is that. 



