HOW SOILS TAKE UP THE RAIN 87 



a. Soluble Matter in Soil. Get a filter paper and a funnel 

 ready for use (see 84, text). Nearly fill the filter paper with 

 black loam, packing the soil in as tightly as you can. Pour 

 through the soil 100 cu. cm. of boiling water, about 5 cu. cm. 

 (a teaspoonful) at a time. Catch the filtrate, and evaporate it 

 in a clean porcelain or tin dish over a can of boiling water. 

 Describe the material that remains after evaporation. 



b. Organic Matter in Soil. Put into your iron dish the soil 

 that is left in the funnel, and heat the dish. Heat gently at 

 first, so as to dry the soil; finally heat it as hot as you can. 

 Note how the color of the soil is changed by the heating. What 

 caused the dark color? Why does it disappear? 



c. Put a teaspoonful of fresh loam into a beaker or flask, 

 shake or stir it up with about 50 cu. cm. of water, and pour 

 off the turbid liquid. Do this twice more. To the soil that 

 remains add a test tube full of dilute hydrochloric acid. Boil 

 the mixture gently for about 10 minutes. 



What is the appearance of the substance that is left? What 

 is the advantage of having this substance in soil? Can you 

 suggest what materials may have been taken out of the soil by 

 means of the hydrochloric acid? See 217, text. 



d. Soil Absorbs Heat. Fill one saucer with dark, black loam 

 and 'another with white sand. Make sure that the two have 

 the same temperature; then expose them both to bright sun- 

 light. After 10 minutes take the temperature of each. Is one 

 warmer than the other? Which one? Why? 



EXERCISE 84 

 HOW SOILS TAKE UP THE RAIN 



Apparatus and Materials. Vinegar or ketchup bottle with bottom 

 removed, fruit jar, measuring cup, Bunsen burner, piece of muslin, 

 string, gravel, sand, loam, and clay; watch or clock. 



