RIGHT USE OF LIME IN SOIL IMPROVEMENT 



The method of making this test is simple, 

 and consists in placing a measured quantity 

 of soil in a flask, to which is added a solu- 

 tion composed of 20% calcium chlorid and 

 2% zinc sulfid. The mixture of soil and 

 chemical solution is heated to the boiling 

 point by means of an alcohol lamp, and the 

 boiling continued for a minute for the pur- 

 pose of driving off the carbonic acid gas, 

 which is liberated first. The boiling is con- 

 tinued and a piece of moistened paper, pre- 

 viously impregnated with lead acetate, is 

 placed over the mouth of the flask. If the 

 soil contains acid, a chemical reaction 

 occurs between it and zinc sulfid, and hy- 

 drogen sulfid gas is liberated. The quan- 

 tity of acidity in the soil determines the 

 quantity of gas which comes in contact with 

 the lead acetate paper, and this determines 

 the depth of color produced on the paper. 

 A slight brownish color indicates the 

 presence of very little acidity, while an in- 

 tense black signifies the presence of injuri- 

 ous amounts of acidity. There are various 

 degrees of coloration between these two ex- 

 tremes, and each gives an accurate indica- 

 tion as to the quantity of lime required to 

 correct the acidity. 



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