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PRACTICE 15. 

 DETERMINATION OF ACIDITY (OR LIME REQUIREMENT) OF SOILS. 



Each group of students will work upon one of a group of soils selected 

 by the instructor using surface, sub-surface, and subsoil samples. 



Place 100 gm. of soil in a 400 cc. (or 12 oz.) wide-mouthed bottle, add 

 250 cc. normal potassium nitrate solution, stopper, and shake continuously 

 for three hours in a shaking-machine, or every five minutes by hand. Let 

 stand over night. Draw off 125 cc. of the clear supernatant liquid, boil 

 10 minutes to expel carbon dioxid, cool, and titrate with the standard 

 sodium hydroxid, using phenolphthalein as indicator. 



Surface. Subsurface. Subsoil. 



Titrations (i) cc. NaOH 



(2) cc. NaOH 



Average cc. NaOH 



Are carbonates present in the soil? Explain the test for carbonates. 



Calculate the results obtained and with these record the results obtained 

 by three members of each group as indicated on the following page. Con- 

 sider 7 acre-inches to weigh 2,000,000 ft). 



What kind of crops, and in what way, does ground limestone mainly 

 benefit? 



