RESEARCH METHODS IX STUDY OF FOREST ENVIRONMENT. 199 

 APPENDIX C. 



STANDARD TITRATION METHODS FOR SOIL ACIDITY AND FOR CARBONATES 



("BLACK ALKALI"). 



The following procedure in titration for the alkalinity and acidity tests is 

 practically that followed by the Bureau of Soils, and a number of soil depart- 

 ments in the agricultural experiment stations : 



The equipment required * is two 50-cubic centimeter burette titration ap- 

 paratuses, one 50-cubic centimeter graduate, one 250-cubic centimeter gradu- 

 ate, two 50-cubic centimeter Nesslar tubes, 1-liter flask, four 100-cubic centi- 

 meter beakers, two 50-cubic centimeters Royal Berlin porcelain evaporating 

 dishes, one 50-cubic centimeter pipette, two ordinary pipettes or droppers, 

 bottles and jars for reagents, analytical balance, numerous quart jars with 

 screw caps or stoppers, and reagents as indicated by the procedure. The 

 necessary reagents are prepared as follows: 



(1.) Standard Potassium hydrogen sulphate solution: 



The average single test will not require over 5 cubic centimeters of this 

 solution. Dissolve 5.58 grams of pure KHS0 4 in 1 liter of water, and 

 dilute 100 cubic centimeters of this solution to 1 liter. Place the dilute 

 solution in burette jar No. 1. for alkalinity titrations. 

 (2.) Phenolphthalein indicator: 



A drop or two for each alkalinity and acidity test is required. Dissolve 

 1 gram of phenolphehalein in 100 cubic centimeters of 50 per cent alcohol. 

 Neutralize by adding a few drops of centinormal alkali, until faintly red, 

 then add a drop of centinormal acid, which should remove the color. 

 (3.) Methyl orange indicator: 



A drop or two for each alkalinity test is required. Dissolve 1 gram 

 of methyl orange (indicator) in 1 liter distilled water. 

 (4.) Normal alkali is prepared by dissolving 39.96 grams of NaOH in 1 liter 

 of water. Since only a few drops of the centinormal solution are needed 

 in preparing the phenolphthalein indicator, and the exact strength is un- 

 important, use in about the proportion of 0.04 gram per 100 cubic centi- 

 meter of water. 

 (5.) Centinormal acid CHCI) : 



Exact strength unimportant. About 2 drops in 100 cubic centimeters of 

 water give approximately correct strength. 

 (6.) Standard sodium hydroxide solution: 



Compute quantity required at rate of one-half to 1 cubic centimeter per 

 acidity test made. The solution is not normal, but is computed so that 

 I cubic centimeter will have the equivalent value of 4 mg. of calcium. 

 Dissolve 6. 1 grams of pure NaOH in 1 liter of freshly boiled distilled 

 w;ner. Place this in burette jar No. '2. for acidity titrations. Exclude air 

 from the Jar as far ;is possible and make-up fresh solution frequently. 

 ■7 1 Normal potassium nitrate solution: 



Use 250 cubic centimeters for each son examined for acidity. Dissolve 

 LO0.93 grama of pure K.vo ; in 1 liter of distilled water. 



Alkalinity Tkst. 



Place hxi grama of air-dried soil of the sample to be examined In a quart 

 Jar; add 200 cubic centimeters of distilled water; shake occasionally during 



• n,. special eqnipmi hi required t<> conducl the work at experiment stations should cost 

 approximately $20 to %'-'<■ 



