20 



PRACTICE 9 



Determination of the Volume Weight and Apparent Specific 

 Gravity of Soils. 



The volume weight of a soil is the weight of a certain unit of 

 volume and the cubic centimeter is taken as this unit. In determin- 

 ing the apparent specific gravity, the pore space is not taken into ac- 

 count. This gives a result much less, numerically, than the real spe- 

 cific gravity. 



Find the volume weight and apparent specific gravity of sand, loam, 

 silt, clay and peat. 



Weigh an empty and thoroughly cleaned soil tube.* Fill the 

 tube with one of the soils to be tested by simply pouring the soil in 

 loosely till it reaches the crease near the top, being careful not to com- 

 pact the soil by jarring or jolting. Weigh, empty and then fill again 

 with the same soil in the same way, using the average of the two 

 weights of soil from which to determine the volume weight and ap- 

 parent specific gravity. Treat each soil in the same way. Determine 

 the amount of water-free soil in each case by using the percent of hy- 

 groscopic moisture found in Practice 6. Find volume of soil tube by 

 filling with water to the crease and weighing. The weight in grams 

 will give the volume in cubic centimeters since one cc. of water 

 weighs approximately one gram. The weight of the soil divided by 

 the volume of the tube will give the weight of one cubic centimeter 

 of soil or the volume weight of soil. Numerically, this is the appar- 

 ent specific gravity. 



Volume weight of soil ~ ._ _, . ~ ., 



— Apparent Specific Gravity of Soil- 



Repeat the above process with each soil but use the compacting 

 machine in filling the tubes, allowing the weight to fall three times 

 from the 12-inch mark upon each measure of soil. 



The volume weight and apparent specific gravity of soils varies 

 with the amount of compaction. A freshly plowed field is much 

 lighter per cubic foot than one compacted by rains, tramping or by 

 means of the roller. 



Why is the apparent specific gravity of sand higher than that of 

 loam? 



Why is the apparent specific gravity of peat so low? 



Sand has less pore space than clay. 



How will this affect the apparent specific gravity? 



What would be the weight of a cubic foot of each kind of soil both 

 compact and loose? 



A galvanized iron tube two inches inside diameter and 12 inches long, closed at one 

 A crease one inch from the top indicates the height to which ii may lie tilled- 



