RESEARCH METHODS IX STUDY OF FOREST ENVIRONMENT. 201 



indicator. Place the beaker under the burette, against a white background, and 

 titrate with NaOH to the appearance of the faintest pink color. 



The amount of the titration being determined by readings of the burette, 

 the amount of acid present in the solution is expressed by the amount of lime 

 which would be required to neutralize it. Each 0.01 cubic centimeter of the 

 sodium hydroxide used in titration is equivalent to 0.04 mg. of calcium car- 

 bonate in the 125 cubic centimeter solution used, and while this stands for 

 one-half of the 100 grams of soil treated, it really stands for only two-fifths of 

 the acid in that soil, because the first solution does not completely dissolve the 

 acids. Therefore, each 0.01 cubic centimeter of titration indicates 0.1 mg. of 

 lime necessary to neutralize the 100 grams of soil, or the amount required to 

 neutralize is 0.0001 per cent of soil weight. 



In practice, the amount of lime required to neutralize the first foot of soil 

 is expressed in tons per acre, being computed, of course, on a standard or spe- 

 cific weigbt of soil per acre-foot. 



Space is provided on " Summary of Physical and Chemical Properties of 

 Soil " form for tabulating the computed results of alkalinity and acidity tests 

 in terms of percentages of the weight of soil, which are as serviceable for scien- 

 tific comparisons as any other expression. 



