i6 



the latter two within about a week's time. In the case of these fertiHzers, 

 the surface of the soil became acid after the lower portions. When di- 

 sodium phosphate was applied, the surface of the soil became alkaline 

 to litmus, the deeper parts becoming alkaline more slowly. Tests on 

 Section 275 (500 P) on February 18, 1915, and on 291 (1000 P) on March 

 22, 19 15, showed that the soil at each successive inch to the bottom of the 

 bench, was alkaline to litmus. In so far as could be determined by this 

 method, applications of potassium sulfate and of sodium chloride did not 

 change the reaction of the soil.* Hence an opportunity was given to study 

 the effect, upon the acidity of the cell sap, of fertilizers producing increased 

 acidity in the soil, alkalinity, and no change in reaction, and upon the re- 

 lation the changes bore to injury from overfeeding with the fertilizer. 



Determinations were made by titrating at about 15° with C02-free 

 KOH, approximately 0.02 N, i cc. portions of sap diluted to 6 cc. with 

 C02-free water, using phenolphthalein as the indicator. Results are cal- 

 culated as cc. of normal acid per cc. sap.** 



* See, however, Maschaupt.'^" 

 ** For memoir on acidity in plants, see Astruc* 

 *** Boiling a solution of CO2 in distilled water under diminished pressure by warm- 

 ing the test tube with the hand was found completely to remove the CO2. Similar treat- 

 ment of sap gave identical values for acidity before and after. Hence, the acidity 

 was not due to dissolved CO2. 



