The Specific gravity of solid particles is the ratio of mass of given volume of solids to the mass of an equal volume of water at 40C . It is represented by “G”. There are many methods available to determine the specific gravity of solids but here we are discussing about the density bottle method.
Specific Gravity of Solids
For solids, specific gravity is an important parameter. If we consider a soil mix, different particle in that mix has different specific gravity value. The specific gravity of whole mix is the average specific gravity of all solid particles present in that mix. For most of the soils, specific gravity lies in the range of 2.65 to 2.80. It has no units. Below table gives the average specific gravity values of different soils.
|Soil Type||Specific Gravity|
|Gravel||2.65 – 2.68|
|Sand||2.65 – 2.68|
|Silty sands||2.66 – 2.70|
|Silt||2.66 – 2.70|
|Inorganic soil||2.68 – 2.80|
Apparatus required to determine the specific gravity of solids using density bottle method are
- Density bottle of 50 ml capacity
- Digital balance of accuracy 0.001g
- vacuum desiccator
- Vacuum pump
- Constant temperature water bath (27 0C)
Test Procedure to determine specific gravity of solids using density bottle consists following steps.
- Firstly clean the density bottle and put it in an oven at a temperature of 105 0C to 100 0C for drying. After drying, put it in the desiccator to cool down.
- Now the density bottle along with stopper is weighed using balance to an accuracy of 0.001 gm. Note down this reading as “M1”
- Take 5 to 10 g of oven dried sample in the density bottle and weigh the bottle along with stopper and dry sample. Note this reading as “M2”.
- Now add de-aired distilled water to the soil in the density bottle up to the soil level and shake gently to mix soil and water.
- Now remove the stopper of density bottle and place it in vacuum desiccator and connect the vacuum pump.
- The air entrapped in the soil is expelled by applying vacuum pressure of 55 cm of mercury for about one hour in vacuum desiccator.
- After that, remove the lid and stir the soil using spatula. The soil adhere to the spatula is washed into the bottle with air free distilled water. Again apply vacuum pressure for some time which is stooped when there is no more air evolved from the specimen.
- The entrapped air can also be removed by heating in the absence of vacuum desiccator.
- Remove the bottle from the desiccator and add more distilled water until the bottle is full. Insert the stopper.
- To attain the constant temperature through the bottle, immerse it into the water bath for one hour.
- Takeout the bottle from water bath after attaining constant temperature and clean and dry the outside using smooth cloth.
- Now the bottle is weighed which is the total mass of bottle, soil and water. Note down this as “M3”.
- In the final step, empty the bottle wash it and refill it with only distilled water. Now also place it in water bath for one hour to maintain same temperature during experiment.
- Now weight the bottle with full of distilled water along with stopper which is “M4”.
- Now repeat the same procedure for three times and take the average reading of three observations as final result.
Observations and Calculations
|Mass of empty density bottle (M1)|
|Mass of Mass of bottle dry soil (M2)|
|Mass of bottle, soil and water (M3)|
|Mass of bottle filled with water (M4)|
|Specific gravity of solids|
|Average specific gravity (G)|
The specific gravity of solid particles is the ratio of the mass density of solids to that water. It is determined in the laboratory using the relation
Where M1 = mass of empty bottle
M2 = mass of the bottle and dry soil
M3 = mass of bottle, soil and water
M4 = mass of bottle filled with water only.
Specific gravity of the given sample = ________.