EXTENSION COURSE IN SOILS. 67 



provement of the soil for the work of nitrifying bacteria; and (3) an 

 increase in the beneficial results from potassium salts and phosphates. 

 While there may still be some question as to the exact chemical changes 

 in the soil from the use of lime, experimental work at different stations 

 has now quite clearly proved beneficial results to the extent of profit 

 from the use of lime with potassium salts, phosphates, or manures 

 over the use of any of these alone. The extent of these benefits, of 

 course, varies with the type of soil. 



EXERCISES, LESSON IX. 



SOIL ACIDITY AND LIMING. 



Materials required. — Two long pickle bottles; a small quantity of clay soil; soft 

 water; littiewater; a bottle of dilute muriatic acid ; some powdered limestone, marble 

 dust, old wood^ashes, coal ashes, air-slaked lime, baking soda, and quicklime; blue 

 and red litmus paper; some common salt; a few sweet apples; a bar of soap; vinegar 

 and sugar; samples of soil from the community; a few old cups and saucers. 



The flocculating effect of lime on heavy clay (Ref. Nos. 1, p. 243; 4, p. 228; 7, p. 379). — 

 In each of two long, clean pickle bottles put a teaspoonful of fine clay soil. Fill both 

 bottles within 2 inches of the top with soft water. Into one bottle pour about three 

 tab lespoonf Ills of limewater. Shake both thoroughly for two or three minutes and 

 note the formation of floccules in the bottle containing the limewater. Set the bottlea 

 aside and note the comparative rate of clearing by settling. What is meant by soil 

 fiocculation? How does limewater aid in clearing the turbid water? 



Simple chemical test for carbonates. — Effervescence occurs when muriatic acid cornea 

 in contact with carbonates. This is a simple chemical test by which carbonates may 

 be determined. 



(a) Place a quarter of a teaspoonful of powdered limestone in an old cup or saucer, 

 pour on about a tablespoonful of dilute muriatic acid, and note results. What causes 

 the bubbling or effervescence? .' 



Apply this test to the following substances: Marble dust, wood ashes (old), coal 

 ashes, air-slaked lime, baking soda, and fresh quicklime. What kind of gas is chem- 

 ically combined in all carbonates? How does this gas differ from that given off by our 

 lungs? What kinds of carbonates do most limestones contain? Baking soda? 



THE USE OF LITMUS PAPER. 



(Ref. No. 9, pp. 41-57.) 



Litmus paper may be used to determine the reaction of liquids. — (a) Dip a small piece 

 of blue litmus paper into an acid solution. What happens? Try a piece of red litmus 

 paper. . Any reaction? Acid turns blue litmus paper red. 



(b) Dip a piece of blue litmus paper into an alkaline solution. Any reaction? Test 

 with a piece of red litmus paper. What change takes place? 



An alkaline solution turns red litmus paper blue. An alkaline solution is the oppo- 

 site in reaction to an acid solution. 



(c) Determine the reaction that pure water has on blue and red litmus paper. 

 Water is a neutral liquid, neither acid nor alkaline. 



(d) By the use of blue and red litmus paper determine the reaction of the following 

 solutions: A common salt solution, sweet apple juice, soapy water, and vinegar solu- 

 tion sweetened with sugar. 



Litmus-paper test for acid soils. — Since an acid solution will turn blue litmus paper 

 red„we can tell by use of blue litmus paper whether or not a soil is quite acid. 



