10 MANUAL OF GENERAL AGRICULTURE. 



5. CAPILLARITY. 



Materials: Glass tubes having internal diameters 

 ranging from one-sixteenth to one inch, 4 pans, evaporat- 

 ing dish, alcohol or kerosene. Soil and subsoil collected 

 in Exercise 2. For (d), 4 glass tubes at least 4 ft. long 

 and of any diameter up to one inch, the larger the 

 better, pan, sand, sandy soil, loam, clay, small cloth and 

 string. 



(a) Place the ends of the tubes side by side in a 

 pan of water. Describe what takes. place in the tubes. 

 1. Does the water rise on the inside of each tube or does 

 it rise on both the inside and outside? 2. If two tubes 

 are placed side by side and as close together as possible, 

 what effect has this on the rise of water between them? 



(b) Into a small wide mouth bottle or evaporating 

 dish, pour alcohol or kerosene until it stands about ^in. 

 deep. Fill the bottle with dry sand or finely divided 

 air-dry soil and press down firmly. Let stand for about 

 15 minutes, then apply a lighted match. Result? What 

 does this show? This experiment represents accurately 

 the capillary rise of water in soils to replace that used by 

 the plant or that lost by evaporation. 



(c) Number and weigh four pans, and place in each 

 of two 50 grams of soil, and in each of the remaining 

 two 50 grams of subsoil. With a pestle or glass rod 

 break up all lumps, at the same time spreading the soil 

 evenly on the bottom of the pans. Set aside and leave 

 undisturbed until the next laboratory period. Weigh 

 again and continue to weigh at each successive period 

 until the weights become constant. Compute the per- 

 centage of capillary moisture on the basis of water free 

 soil as found in Exercise 4. The. difference between the 

 total moisture and the amount of capillary moisture 

 represents the hygroscopic moisture of soil. Calculate 

 the per cent hygroscopic moisture in the samples under 

 consideration. 



(d) Close one end of each tube using a piece of 

 cloth and tying with a string. Fill the tubes with finely 



