urade. 

 Date. . 



EXERCISE 6 



Volume-weight or Apparent Specific Gravity 



(23) 



Purpose. — To compare the weight of a tube of soil with the weight of a 

 tube of water filled to exactly the same height. This result will give 

 the apparent specific gravity of the soil or the weight of soil compared 

 with an equal volume of water. If desired the sample may he taken 

 with a tube shown in Fig. 5. 



1. Take one of the special tubes which has the opening at the bottom plu^ 



with a cork stopper and from which the brass strainer has been removed; 

 or use a tube with solid bottom as 

 in Fig. 6. (Schools not equipped 

 with soil tubes may use tin cans.) 



2. Be sure that the tube is dry. Then 



weigh it carefully on the balances. 



3. Fill the tul)e with sand to within one 



inch of the top, pouring it in loosely. 

 Weigh carefully on the balances. 



4. Empty the soil back into the right 



bin and fill the tube again, but this 

 time compact the soil in the com- 

 pacting machine. If no compacting 

 machine is available, pack the soil 

 by dropping the tube from the 

 height of five inches five times upon 

 a book. 



5. Repeat this operation for all of the 



Fig. 5. — Soil sam- 

 pling tube for taking a 

 sample of surface soil 

 in an undi.sturbed con- 

 dition — useful in deter- 

 mining the volume 



eight of soi 

 field condition. 



Fig. 0. — Twelve-inch 

 tube with solid bottom, 

 for use in determining 

 volume-weight and 

 pore space. 



the tabic 



6. Finally fill the tube with water to exactly one inch from the top and weigh 



carefully. 



7. If the real specific gravity of these soils is known secure them from the 



instructor and then compute the porosity of each. See (3) below. 



8. The following formulas may be followed in working out the calculations: 



Volume-weight = Weight of a tube full of soil (1) 



Weig ht of Soil 

 Weight of Water 



Apparent Specific Gravity 



^^O-lAS^^n^H 



(2) 

 (3) 



