# Which statement is not true regarding specific gravity?

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Which statement is not true regarding specific gravity?
1. 50 ml density bottle is useful for all types of soil
2. Kerosene is used in density bottles
3. 500ml flask is used only for fine grained soils
4. Pycnometer is used only for coarse-grained soil

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Correct Answer - Option 3 : 500ml flask is used only for fine grained soils

Concept:

Specific Gravity:

Specific gravity can be defined as the ratio of the weight of a given volume of soil solids at a given temperature to the weight of the equal volume of distilled water at that temperature. It can be written as G = $\dfrac{\gamma_s}{\gamma_w}$

1. Density bottle method:

• The specific gravity of solid particles can be determined in a laboratory using a density bottle fitted with a stopper having a hole.
• The density bottle of 50 ml capacity is generally used [ IS:2720 (part III) 1980].

2. Pycnometer method:

• Pycnometer method is used to determine specific gravity and water content both.
• This method is suitable for cohesionless soils.
• A pycnometer is a glass jar of 1-liter capacity that is fitted at its top by a conical cap made of brass.
• It has a screw-type cover and there is a small hole at its apex of 6 mm in diameter

Explanation:

• Density bottle method can be used for every type of soil, and it is the most accurate one.
• Flask and pycnometer are used for coarse-grained soil.
• Distilled water is used in the pycnometer test and kerosene is used for the density bottle method. When kerosene is used, its specific gravity is determined accurately by a separate test.