34 



Expenment No. 4- 



EFFECTS OF LIME ON rLAiSTIf W)1LS. 



Two students will work together as in experiment No. 3. 



1. Weigh out live 50-gram samples of the clay soil. 



2. To sample — 



No. 1 add 0. 5 per cent calcium hydrate. 

 No. 2 add 1 per cent calcium hydrate. ' 

 No. 3 add 5 per cent calcium hydrate. 

 No. 4 add 10 per cent calcium hydrate. 

 No. 5 add no calcium hydrate. 



3. Mix each sample thoroughly in a soil pan, and add just enough water to make 

 plastic. 



4. Fill into molds in the form of sticks, using care to compress all samples to the 

 same degree, and transfer to the oven and l)ake at 110° C for 4 to 5 hours. 



5. Test the strength of each stick of baked clay by supporting u})on blocks and 



suspending weights until the clay is fractured. Note weight required in each case 



and fill in results below: 



Grams. 



0. 5 per cent broke with 



1 per cent broke with 



5 per cent broke with 



10 per cent broke with 



Control broke with 



Explain the loss of plasticity due to the lime: . 



Experiment No. 5. 



DETERMINATION OK THE APPARENT SPECIFK' (IRAVITY OF SOILS. 



Use each of the four soils as in former experiments. 



1. Weigh carefully in empty and thoroughly cleaned soil tube ((t). 



2. Fill it with one of the soils to be tested, which must first be well pulverized if 

 lumpy. In filling use the soil-compacting machine, allowing the weight to fall three 

 times from the 0-inch mark upon each cupful of soil. Fill the tube to the crease 

 near the top. 



3. Weigh the filled tul)e carefully {b). 



A. The area of the bottom of the tube is 20 square centimeters. From this com- 

 pute the number of cubic centimeters of soil which it contains (c). 



5. Determine the amount of hygroscopic moisture in a special sam})le of the soil, 

 according to direction given under Experiment No. 2 [d). 



Calridatioiis — 



b — (n-frf) = weight of the given volume of soil. 



Therefore, v^ + ■' = weight of 1 cc. of soil= volume weight of soil. 



c 



Volume weight of soil , .-5 •- 



^pj—-, r^. ? =apparent specific gravitv. 



V olume weight ot water 



I find the aj>parent specific gravitj' to be as follows: Sand, ; gravel, ; 



loam, ; clay, . 



The volume weight or apparent specific gravity of soils varies with the amount of 

 packing, a freshly plowed field being much lighter per cubic foot than one com- 

 l)acted by rains or tramping. 



Explain the object of using the .soil-compacting machine in this experi- 

 ment. , 



