LABORATORY EXERCISES 



251 



Whenever liming alone increases general crop production, 

 fertilizer needs become more urgent, since the increases make a 

 heavier draft on the soil reserve of the plant-food elements. 



Though there are many crops that can tolerate acidity, yet 

 most of them will respond to liming because of the favorable con- 

 ditions created within the soil by the added lime. It is, indeed, a 

 deplorable fact, that in some sections farming without the use of 

 agricultural lime represents much waste of time, money and effort. 



Illustration Material for Lessons. Show 3 forms of agricultural lime 

 burnt lime, hydrated lime and air-slaked lime (carbonate of lime). 



Show 2 or 3 other lime carbonates. 



Show a good grade of pulverized limestone, or other forms of agricul- 

 tural * lime. 



Demonstrations. Material Needed. -Several strips of blue litmus paper; 

 a little vinegar; an orange; an apple; a little ammonia water; a pint each of 

 strongly acid upland soil and undrained acid peat; a Truog soil-acidity testing 

 outfit; a small baking-powder can; a bottle of muriatic acid; several materials 

 containing lime carbonate; 12 tumblers; a 20-mesh screen; a 100-mesh screen; 

 2 tablespoonfuls of coarsely crushed limestone; and a teaspoonful of very finely 

 pulverized limestone. 



To Demonstrate the Reaction of Acid Substances, Including an Acid 

 Soil, on Blue Litmus Paper. Procedure. With blue litmus paper test the 

 reaction of vinegar, of water, ammonia water, apple juice, orange juice, and 

 of strongly acid soil. 



Question. When is a soil said to be acid or sour? 



To Demonstrate the Truog Acidity Test. Procedure. Follow directions 

 accompanying testing outfit. 



A. Demonstrate the reaction of a strongly acid soil. 



B. Test the same soil, only use hard water instead of distilled water. Ex- 

 plain results. 



To Demonstrate the Nature of Soil Acidity. Procedure. A. Fill a small 

 baking-powder can with an acid sandy soil. (Perforate the bottom and place 

 a piece of cheese cloth over the bottom.) Allow about 4 quarts of hot soft 

 water to percolate through the sand. Dry a sample and retest for acidity. 

 Compare the results with first test. 



Question. Why is it not possible to wash out the "acidity" in the 

 sandy soil? 



B. Repeat the experiment and use 'an undrained acid peat soil. Ex- 

 plain results. 



To Show How to Test for a Carbonate. Procedure. Put a teaspoonful of 

 lump lime into a tumbler and pour on it about a tablespoonful of dilute muri- 

 atic acid. Repeat test and use air-slaked lime, limestone, shells, coral, etc. 



To Demonstrate that the Fine Material in Pulverized Limestone is the 

 Quick-acting Material. Procedure. A. Obtain about 2 teaspoonfuls of 

 crushed limestone (from a sample of pulverized limestone) that will not pass 

 through a 20-mesh screen. Wash this coarse material thoroughly several 

 times with acidulated water to remove all adhering fine particles. Obtain a 

 teaspoonful of fine material that will pass through a 100- or 200-mesh screen. 

 Fill a tumbler half full of water and add a few drops of muriatic acid to make 

 distinctly acid to blue litmus paper. Mix thoroughly. Pour one-half of the 

 acid solution into a second tumbler. Into one put the two teaspoonfuls of 

 coarse particles of limestone, stir, and let stand 30 or 45 minutes, then test 



