PRACTICE X (Continued) 



What relat^u exists between size of particles and shrinkage ? 

 What effect has clay and organic matter on shrinkage ? 



References. 



'' Soils/' Lyon and Fippin, pp. 98-99. 



'' Physical Properties of Soil," Warington, pp. 35-36. 



"Soils," Hilgard, pp. 112-114. 



PRACTICE XI 



DETERMINATION OF THE APPARENT SPECIFIC GRAVITY OF SOILS 



In determining apparent specific gravity the pore space is not 

 taken into account. Then apparent specific gravity is much 

 less, numerically, than real specific gravity. Find the apparent 

 specific gravity of sand or sandy loam, gray silt or gray silt 

 loam, brown silt loam, clay or clay loam, and peat. 



Weigh a clean empty soil tube.^ Fill the tube with one of the 

 soils by simply pouring it in loosely until it reaches the crease 

 near the top, being careful not to compact it by jarring or jolt- 

 ing. Weigh, empty, and then fill again with the same soil m the 

 same way, using the average of the two weights to determine the 

 apparent specific gravity. 



Treat each soil in the same way. 



Calculate the weight of water-free soil taken in each case by 

 using the average per cent of hygroscopic moisture found in 

 Practice VI. These average figures will be given to the class 

 by the instructor. 



Find the volume of the soil tube by filling with water and 

 weighing. The. weight in grams will give the volume of the 

 tube in cubic centimeters, since 1 cc. of water weighs approxi- 

 mately 1 g. The weight of the soil divided by the volume 

 of the tube gives the weight of 1 cc. of soil, or the volume 

 weight of the soil. Xumerically this is the apparent specific 

 gravity. 



Repeat the above process with each soil, but compact the soil. 

 Lift the base on which the tube stands to the 6 -inch mark and 

 let it drop. Do this six times. Repeat, refilling each time until 

 tube is full to the crease. 



1 A brass tube 2 inches in diameter and 12 inches long, closed at one end. 



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