How to calculate specific gravity of soil

DETERMINATION OF SPECIFIC GRAVITY OF SOIL SOLIDS 
(IS 2720 Part- 3 1980)

Name of the Experiment	Determination of specific gravity of soil solids
Theory
Specific gravity of soil solids is the ratio of weight, in air of a given volume; of dry soil solids to the weight of equal volume of water at 4ºC.Specific gravity of soil grains gives the property of the formation of soil mass and is independent of particle size. Specific gravity of soil grains is used in calculating void ratio, porosity and degree of saturation, by knowing moisture content and density. The value of specific gravity helps in identifying and classifying the soil type
List of Equipment needed
1. Pycnometer                                   4. Oven 2. 450 mm sieve                                5. Glass rod 3. Weighing balance                          6. Distilled water
Procedure
1. Dry the pycnometer and weigh it with its cap. (W1) 2. Take about 200gm of oven dried soil passing through 4.75mm sieve into the pycnometer and weigh again (W2). 3. Add sufficient de-aired water to cover the soil and screw on the cap. 4. Shake the pycnometer well and remove entrapped air if any. 5. After the air has been removed, fill the pycnometer with water completely. 6. Thoroughly dry the pycnometer from outside and weigh it (W3). 7. Clean the pycnometer by washing thoroughly. 8. Fill the cleaned pycnometer completely with water up to its top with cap screw on. 9. Weigh the pycnometer after drying it on the outside thoroughly (W4). 10. Repeat the procedure for three samples and obtain the average value of specific gravity.
Observation and Tabulation
Sample Number W1 in gms W2 in gms W3 in gms W4 in gms Specific Gravity G 1 2 3
Calculation
Determine the specific gravity of soil grains (G) using the following equation Where W1 = Empty weight of pycnometer. W2 = Weight of pycnometer + oven dry soil W3 = Weight of pycnometer + oven dry soil+ water W4 = Weight of pycnometer + water
Result and Discussion
Thus the specific gravity of soil is obtained as____________ and Soil type is _____________