EXPERIMENT STATION BULLETINS. 421 



SUMMARY 



The object of this research was to determine the neutralizing value 

 of mineral soils for acids and alkalis by means of the hydrogen elec- 

 trode and indirect titration. Some of the conclusions drawn are listed 

 below. 



1. The neutralizing value of mineral soils for acids and alkalis" may 

 be quite accurately determined and methods are devised for this pur- 

 pose. 



2. When soils are treated with Ca(0H)2 the reaction proceeds 

 slowly and comes to an equilibrium on pH 7.00 with the quantity of 

 Ca(OH)„ required to raise the pH of soils to this point in at least 24 

 hours but in presence of an excess of Ca(OH)o an equilibrium is not 

 obtained, indicating that this further reaction is continuous over a 

 long period of time. 



3. At least one end point in the soil — Ca(OH)o reaction appears 

 to be slightly above pH 7.00. 



4. Ca(0H)2 forms salts with soil acids. 



5. A soil-acid equilibrium may be obtained in a short period of time 

 in presence of an excess of acid and this equilibrium is quite constant 

 over a period of several days, showing that a rather sharp distinction 

 may be made between reactive and inactive soil bases. 



G. Weak soil acids are split off when soils are treated with strong 

 acids. 



7. When the methods devised for determining active bases and excess 

 acids in soils were applied to a series of soils of varying pH, no direct 

 relationships were discovered between soil class, active bases, excess 

 acids and pH; however, a direct relationship was exposed between the 

 base-acid ratio and pH of the soils. 



8. The pH and base-acid ratio plotted as a curve corresponds to the 

 normal hydrogen ion concentration curve obtained in weak acid-alkali 

 titrations. 



9. The quantities of lime required to neutralize a series of miscel- 

 laneous soils do not correlate with their degree of acidity. 



10. The base-acid ratio in soils is believed to be of great practical 

 importance. 



REFERENCES CITED 



(1) Clark, W. Mansfield. 1921. The determination of hydrogen ions. 



Williams and Wilkins Co., Baltimore. 



(2) Gillespie, L. J. and Hurst, L. A. 1917. Hydrogen -ion concentra- 



tion measurements of soils of two types; Caribou loam and 

 Washburn loam. In Soil Science, V. 4, p. 313. 



(3) Hildeband, Joel H. 1913. Some applications of the hydrogen elec- 



trode in analysis, reasearch and teaching. In Jour. Amer. Chem. 

 Soc. V. 35, No. 7, p. 847. 



(4j Hoagland, U. R. 1917. The effect of hydrogen and hydroxyl ion 



